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From section 414-00.............

'The smallest possible set value for the generator voltage is 12.2 volts, while the maximum charging voltage can be anywhere between 14.5 and 14.9 volts. However, when the battery is in a refresh phase, the voltage may occasionally reach up to 15.2 volts. These refresh phases are required when the battery charge status is 80% over long periods of time, which increases the risk of sulfation in the battery cells.'

Two things there.............one, the volts can go as low as 12.2 but that is a VALUE only, meaning the system has ability to do it but that does not mean it goes there normally. Number two..........look at the last sentence there, that is a clear indicator that the battery is NOT maintained at 80%, the norm is HIGHER than that. The system itself knows that 80% is too low to keep the battery at.
 

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"the BMS was reporting the battery at 80% state of charge when it clearly wasn't" - In my opinion, the lack of correlation in SoC values may be the result of either an incorrect initialisation when the battery was replaced or a problem with recalibration. I may be shooting in the dark here but the 80% needs a reference, i.e. 80% of what ? It seems that the BMS has an incorrect value that it is comparing the actual SoC with. Does a new battery need to be fully charged before the BMS is reset so the SoC reference will be set to the upper threshold ? Has the BMS the right conditions in order to recalibrate. Quoting from the manual -

Battery State of Charge

During the drive cycle the Electrical Energy Management software will adjust the initial battery state of charge by monitoring the charge and discharge current and adjusting the state of charge up during charging, and down during discharge. During rest periods (key off with no electrical loads) when the vehicle enters sleep mode, the battery voltage is sampled to recalibrate the State of Charge. The Battery monitoring sensor automatically executes this recalibration anytime the vehicle enters sleep mode and when the total vehicle current draw is below 300mA. It takes 4 to 6 hours in the sleep mode to recalibrate the battery state of charge to high accuracy. If the system draw does not allow the battery state of charge recalibration over the previous 7 to 10 days the State of Charge quality factor will change to flag this and some Electrical Energy Management Functions which rely on the accuracy of the battery state of charge may be temporarily turned off until a recalibration takes place.

NOTE: Any devices left attached to the power socket that draw in excess of 200mA (or less depending on other battery loads) will prevent a battery monitoring sensor to recalibrate the battery state of charge.


Given all these variables, if I were you, I would start from the beginning. Remove the battery, charge it to the full extent possible, install, ensure no electrical loads are on, reset BMS, etc.
 

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Discussion Starter #23
From section 414-00.............

'The smallest possible set value for the generator voltage is 12.2 volts, while the maximum charging voltage can be anywhere between 14.5 and 14.9 volts. However, when the battery is in a refresh phase, the voltage may occasionally reach up to 15.2 volts. These refresh phases are required when the battery charge status is 80% over long periods of time, which increases the risk of sulfation in the battery cells.'

Two things there.............one, the volts can go as low as 12.2 but that is a VALUE only, meaning the system has ability to do it but that does not mean it goes there normally. Number two..........look at the last sentence there, that is a clear indicator that the battery is NOT maintained at 80%, the norm is HIGHER than that. The system itself knows that 80% is too low to keep the battery at.
I don't understand your insistence on being argumentative and pedantic, but your interpretation of that quote is not quite correct. Under normal conditions, the system will NOT charge the battery past 80% as has been explained multiple times. The PDF linked in post #2 of this thread also demonstrates this clearly in the illustration on page 2.

By*comparison,*Smart*Regenerative*Charging*uses*the*information*from*the*battery*monitoring sensor*to*maintain*the*battery*at*a*calibrated*state*of*charge*(approx.*80%)*at*all*times.*This
means*that*the*battery*has*a*certain*amount*of*extra*charging*capacity*at*all*times.
If*the*battery*monitoring*sensor*detects*that*the*charge*status*is*above*the*calibrated*value
(approx.*80%),*then*the*generator*charging*voltage*is*reduced*in*order*to*discharge*the
battery
.*If*the*opposite*occurs*and*too*low*a*value*is*detected,*the*charging*value*is*increased
in*order*to*return*the*battery*to*the*calibrated*value.
However, if the system knows that the battery has been at this 80% level for extended periods without receiving an extra charge through regenerative charging, it will go through an increased voltage phase to maintain the battery.

With all due respect, and while I do appreciate you taking the time to post, I'm not really after a lecture on the operation or benefits of the smart charging system. If you don't agree with the implementation, that's one to take up with Ford's engineers. I doubt they'll agree, mind.

"the BMS was reporting the battery at 80% state of charge when it clearly wasn't" - In my opinion, the lack of correlation in SoC values may be the result of either an incorrect initialisation when the battery was replaced or a problem with recalibration. I may be shooting in the dark here but the 80% needs a reference, i.e. 80% of what ? It seems that the BMS has an incorrect value that it is comparing the actual SoC with. Does a new battery need to be fully charged before the BMS is reset so the SoC reference will be set to the upper threshold ? Has the BMS the right conditions in order to recalibrate. Quoting from the manual -

(snip)
The battery was fully charged and a BMS reset performed, check for parasitic drain, etc. This was evidenced by the battery age displaying correctly in Forscan.

However for whatever reason, whether that's the self-test, putting the battery on a mains charger myself or some combination, the system seems to be correctly interpreting this 80% value now.
 

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Glad to hear that you've made some headway. Like I said, I've never diagnosed a system like this before but when one's dealing with non-absolute values like 80%, it's always good to know the absolute of 100% so measured values can be compared accurately especially when a 1% can make the difference between charging and shedding.

At least to me this is not yet clear, i.e. is the 100% determined by the system once you reset the BMS (in which case it could be off the designed optimal value if the battery is undercharged) or is it a preset parameter ? If it is the first case and a non-fully charged battery is installed, would the system reduce the SoC by a further 20% on BMS reset to meet the charging threshold criteria, with the result that it maintains a SoC which is too low and causes shedding ?

BTW, there's a well written article here on smart charging -

https://www.motor.com/magazinepdfs/042010_09.pdf
 

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Discussion Starter #25 (Edited)
I'm not 100% sure on how the system determines SoC, but as far as I know it bases it on both temperature-compensated resting voltage during those idle calibration periods, battery age, and in the shorter term (e.g. when driving) based on current measurements to/from the battery.

The battery was fully charged upon installation although that isn't mentioned as a requirement, but I agree it would make sense (to me) that the system would keep some sort of record of the highest recorded long-idle voltage of the battery as some sort of reference point. A single idle voltage measurement wouldn't be a very good indication of state of charge, as there's likely to be some variance between batteries as manufactured anyway, and again with age - I understand that's why it records battery age and stresses it should not be reset with an aged battery.

Just to elaborate on that point, the old battery was 'full' at about 12.4v, in that no amount of charging would raise it above that, but a new battery would be closer to 12.8v, and batteries aren't all going to age predictably so knowing age alone isn't really enough. I didn't check what the system thought the SoC was in the older battery.

There are a few other data points the system could potentially use if it has some way of interpreting them. For example, I guess the system could monitor voltage/current under heavy loads like cranking, charge current under various voltages (an empty battery will accept a charge far more readily than a full one). Also, to speed up acquisition of a 'full' reference voltage after a reset, the system could revert to a 'normal' alternator until resting voltage levels off which would indicate a full charge.

Maybe they use more, maybe less, just thinking of what could be useful data to use in such a system! And to be clear I'm not suggesting it actually does any of the above.

I'll have a read of that pdf, cheers!
 

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You guys can talk 80% charge all day long...........after working on hundreds of car electrical systems it becomes clear that only keeping a battery at 80% is a problem whether or not Ford or anybody else thinks so. It means the whole idea of starting with a FULLY charged battery is silly based on 80% and typical Ford engineer bullsh-t. All that is is a quick starting reference point as the system has to figure out over and over until battery is dead where the new daily SOC is. One could stick the numeration of 12.86 volts (the ideal laboratory voltage of millions of batteries in ideal conditions with proper specific gravity and temp) into the software but NO, the dealer has to do magic there to get more of your money.

Reality will be what it will and the above clearly shows exactly what I'm talking about with different Ford sections not even agreeing with each other, the entire language becomes useless garbage at that point. I've already given a surmised reason why they do it and tied to more service work in the future and what Ford does on countless occasions. The parts of the system are getting cheaper and this entire lower charging thing is an attempt to make cheaper parts last longer while complicating things enough to drive more dealer work into the doors. Only what Ford has been doing for the last 20 years now and it can be pointed out in countless examples over and over and why I have dropped them to never buy another again.Their service manuals have largely dropped from world leading content to much lower intelligence pandering stuff and the english used is often shoddy as well as the proofreading.

Utterly stupid statements like this from post #22........

'During the drive cycle the Electrical Energy Management software will adjust the initial battery state of charge by monitoring the charge and discharge current and adjusting the state of charge up during charging, and DOWN DURING DISCHARGE.'

WHY??? Anybody with a lick of sense knows that discharge provides its' OWN lowering of initial state of charge without any need for software to do so. And WHY again would the system lower charging when the load is highest and the need is for more at that point? Unless the system is strained by temperature ( a key point figuring in what I said above) that is the WRONG thing to do. I strongly suspect that what actually goes there is that the system begins to charge more to then discharge battery at a lesser rate and more correct but too much english there to swallow all at once.

The linked .pdf in post #24 as well does NOT refer to 80% as anything other than a LOWEST limit, note the mentioning of 'GREATER than 80% charging' in more than one place! The optimum charge will be between 80% and 100% and where it has been for 75 years. The english is implied but crystal clear for those that look.

Sticking with 80% as a go-to point I feel is a massive mistake in understanding how these systems work. It should be considered the LOW point, NOT the middle.

You guys read and interpret what you will, I'll be working on these likely with zero issues too.

I'll leave you alone to figure it out, some of us learned long ago to rip through Ford manuals and tear out big chunks of them to discard as worthless many long years ago. The first VCT systems taught me that back in the late '90s, the utterly stupid explanation of how they timed to give even the Ford techs massive timing belt fits when they couldn't get rid of error codes. It took Ford many years to crawl away from the infantile explanations of how to time them and only after going to double VCT so multiplied the huge numbers of errors that they were forced to add timing marks for the VCT cylinders themselves and what they should have been doing all along for their own service guys. DUMB, DUMB, DUMB. I simply combined a couple of pieces of info from 100 pages away in the manual from the timing procedure to the actual procedure to revise it to 100% perfect timing and using only one more step to do it.

The people who write those service manuals are no smarter than anybody else and often now it becomes obvious they are less. One has to be pedantic these days, nobody can pretty much tell you anything right any longer and you are on your own to figure out what is real and what is not. Reality and what works in it all day long and every day is all I focus on.
 

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Discussion Starter #27
Again you're just posting an unproductive rant which has nothing to do with what I was asking. You've posted demonstrably incorrect information several times and now you're banging on about how you're right and how everybody else, Ford electrical engineers included, must be wrong. When proved wrong, you just criticise the materials or facts which invalidate your statements. I'm frankly not interested in how many systems you have or haven't worked on - facts are facts plain and simple.

You can't just 'stick 12.86v' into the system - not all batteries will present the same resting voltage at 100%, particularly when aged. Older batteries may not go above 12.4v when fully charged; they may not be at full manufactured capacity and cannot retain further charging, but will still function fine as a starter battery. And as you said yourself, 'under ideal conditions' - an engine bay is not ideal conditions nor a consistent temperature. Specific gravity isn't really a practical data point under the bonnet of a vehicle.

Ford are far from the only company to implement such smart charging systems believe it or not, particularly with tightening environmental regulations pushing engineers to reduce wasted energy where possible. It has absolutely nothing to do with making parts cheaper - the alternator, regulator, and battery are typically more expensive and built to higher specifications on a smart charge system vs a 'dumb' system for obvious reasons.

The system, as I understand it (and backed up by observations), will not leave the battery at 80% over extended periods of time; the engineers will obviously understand the chemistry of the batteries in use and have this designed into the system e.g. through the occasional higher voltage charges if full charges have not occurred through regeneration for example.
However, when the battery is in
a refresh phase, the voltage may occasionally reach up to 15.2 volts. These refresh phases are required when the battery
charge status is 80% over long periods of time, which increases the risk of sulfation in the battery cells.
WRT post 22, it sounds quite straightforward to me. By monitoring the current flow to/from the battery in real time, the system can keep track of the *remaining* SoC of the battery. It would be pretty useless to stick with the initial SoC after the battery has been charging/discharging, or to rely on load voltages. It doesn't mean it's shorting out the battery to dump charge under load or something!

Provided the battery SoC is at ~80% the alternator will usually, through voltage regulation, meet the vehicle's electrical demands and therefore a roughly zero battery charge/discharge current (something else I've both measured and observed through diagnostics software). If regenerative charging pushes the SoC above this level, then the system will back off on alternator current and allow the battery to pickup the surplus until it drops back to 80% or so, therefore removing load on the alternator and reducing engine load. Remember, this is energy which was recovered essentially for free by recovering energy by slowing the vehicle (kinetic>electrical>chemical); energy which would have otherwise simply ended up as heat in the brakes. Were the battery maintained at 100%, the regenerative charging system wouldn't be able to store this energy for later use by the vehicle's electrical systems.

Plenty of documentation lists 80% as the 'calibrated state of charge'. That's even demonstrated clearly in the illustration. Of course, it's not a rigid value in practice and the charge is allowed to vary in normal usage, but that's the point at which the system aims to maintain the battery under normal conditions outside of opportunistic regenerative charging or battery 'refresh'. You don't have to infer anything from the text in Ford's own documentation, it's quite simple what is happening. And once again, backed up by my own measurements. Coincidence? I think not. The following explanation is quite straightforward.

If*the*battery*monitoring*sensor*detects*that*the*charge*status*is*above*the*calibrated*value
(approx.*80%),*then*the*generator*charging*voltage*is*reduced*in*order*to*discharge*the
battery
.*If*the*opposite*occurs*and*too*low*a*value*is*detected,*the*charging*value*is*increased
in*order*to*return*the*battery*to*the*calibrated*value.
 

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Hi ExSpark,

I have very recently purchased a 2017 Focus TDCi and after a week of driving it with Start/Stop being "not available", set about investigating why.

Your original post describe pretty much the findings in my case also (low battery volts @12.2V) - and I don't think we are alone in this situation.

Anyway, your post comments in this thread are the best I've come across so far, so I wondered if you ever managed to resolve your issue?

I should explain that I am, professionally, a technical person, with some understanding of electronics and battery technology and management, although not in the automotive industry/trade.

FYI, the car's battery was too flat at the dealership to start it when I went to view and had to be jumped (with a portable recharger). The battery itself is original, as far as I can tell, being a Ford/Varta EFB type. All my research thus far suggests EFB types are little more than lead-acid batteries with a few enhancements to improve repeated cranking/cycling e.g. for Start/Stop. So as far as I can determine, they still have the same basic characteristics of a normal lead-acid... And that, to me, means that a nominal resting voltage @12.2V is bad news, likely leading to reduced life and possibly even capacity.

FYI I completely recharged the battery overnight, and it seemed to hold it's Voc for a while thereafter, suggesting the battery is still OK-ish. But no sooner did I drive with it - @20miles cross-country to work - it dropped back to 12.2V. The alternator/charge system does appear to be working as I can see the Battery voltage on the dash diagnostics screen peaking up @14.1V. I've also confirmed this using a proper voltmeter/DVM (which actually reads a consistant 0.3-0.4V higher than the dash).

I appreciate its now 2 years since your last post, but I would very appreciative if you could share what, if any, resolution/improvement/change you were able to make in your case.

Thanks in advance,

FFLu
 

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Discussion Starter #29
Hi FFLu,

I'm not sure if I can provide much in the way of help with your issue, but could it possibly be a damaged battery if it's been left in a discharged state for a long time? The fact it was too flat to start suggests this may be the case, it doesn't take too long for a deeply charged battery to become permanently damaged i.e. unrecoverable capacity, even though it may still work to start the vehicle after charging.

I think my original battery had either a worn cell or some permanent sulphation as it would not hold what I would consider a 'proper' full charge voltage as described earlier, even after I left it on a long trickle charge at a higher voltage (removed from car obviously) after replacing it, just to see if I could recover it as a spare. The new battery recovered auto start-stop functionality immediately. When I tested the old battery on one of those electronic battery testers used by mechanics, it said something like 'good - recharge' even though it was fully charged.

As I think I mentioned earlier, through some research and my own experimentation I found the Focus's charging system intentionally holds the battery at around 80% SoC to allow for opportunistic regenerative charging when braking etc. I'm not sure if all vehicles are the same but in mine, you can notice this if you e.g. have the air con blowing - upon slowing or going downhill with no throttle input you hear the fan speed increase. If I remember correctly, it apparently also periodically applies a higher charge voltage to the battery in order to combat sulphation which would otherwise be a potential problem for a lead acid battery not getting a regular full charge.

Also yeah, I don't think I found a standard definition of EFB other than what the name implies, it's an enhanced version of a standard flooded lead acid battery, intended to have better cycle life etc for start-stop vehicles where both the frequent starting and use of accessories when stopped would put greater demand on the battery vs a 'standard' vehicle. But chemically I think they're pretty much the same, maybe just more substantial electrodes, construction, etc.

I can't recall exact voltages but even after my attempted recovery of the original battery, I think it was resting at something like 12.5V or 12.6V. That's obviously off-load i.e. not connected to vehicle which will always draw a small amount*. A fully charged battery should be 12.8V+. The 0.2V difference may seem pedantic to those unaware of the implications of it, but it's obviously significant in what it says about the state of charge, or condition of the battery.

*A note about testing on-vehicle voltage. Something else I found in the process of this testing, when you first pop the bonnet, the vehicle may be drawing something like 2A from the battery which will pull down the voltage. After a while (maybe 30 mins?) of being left alone, the vehicle enters a sort of lower power mode which was something closer to 30mA if memory serves correctly. Obviously be careful of vehicle security before testing this, but in my case I locked the car with the bonnet still open and left it like that for a while.

Personally, I now try to give the battery a periodic top-up with a mains-powered charger as it's easy enough for me to do. Obviously that charge is quickly used up by the vehicle but a periodic full charge can't hurt in terms of preventing permanent sulphation. This may be overkill depending on vehicle usage though, and more relevant for short journeys or infrequent use.

Also beware if you do remove the battery, some vehicles may need things like radio codes. Mine didn't but always worth checking first. Also it may reset certain vehicle parameters like learned ECU engine parameters, so the vehicle may drive weirdly for a while afterwards. I think the manual warns about this, and if I remember correctly recommends a certain driving style afterwards while it re-learns. All worth considering and checking before proceeding with a battery replacement, too.

Hope some of that was useful, and feel free to message me!

Thanks
 

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Hi again,

First off, thanks for taking the time and trouble to reply - and so much info too!

Secondly, well done for remembering so much info from 2 years ago!
:)

You wrote:
I can't recall exact voltages but even after my attempted recovery of the original battery, I think it was resting at something like 12.5V or 12.6V. That's obviously off-load i.e. not connected to vehicle which will always draw a small amount*.

In your original post you wrote:
...today the battery is now back to 12.2v despite fully charging it again last weekend...

This is exactly what I am seeing, with a battery that's barely 2years old (similar age of yours at that time, maybe?).

[FYI a chap at work has recently purchased the exact same model and age as me, and when we check his battery yesterday it too was ~12.2V. This seems like a systematic problem to me - possibly/probably associate with Ford's unusual (??) 80% SoC Smart Charging strategy].

You also wrote:
A fully charged battery should be 12.8V+. The 0.2V difference [from 12.6] may seem pedantic to those unaware of the implications of it, but it's obviously significant in what it says about the state of charge, or condition of the battery.

I understand and agree entirely! Info I have seen suggests every 0.1V represents approx 10% capacity, with 12.6V representing ~80% SoC, typically (for lead acid). So 12.2V suggests ~40% SoC!

The 2017 Focus I now own has its original Varta 75Ah EFB battery, which looks decent enough quality, so its frustrating to think it might already be going bad. (My previous '03 Focus had the original battery for its entire 17yr life. Non-Smart charging though!)

Anyway, can I assume that in your case, replacing your battery for a new one, gave a lasting improvement in the resting/offload voltage, from ~12.2V towards the 12.6-12.8V range?

You've written lots of very useful info - thank you - but for now, I'd appreciate any comment re the bolded question above. I need to try and unravel whether I do have a dying battery, or there's something else wrong, or its just a systematic side-effect of Ford's Smart Charge strategy.

Thanks again,

FFLu
 

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Discussion Starter #31
Regarding the voltage discrepancy vs original post, in my original post the battery was still in the vehicle. The 12.5V or 12.6V reading was with it out of the vehicle and after an attempted recharge (at higher than usual charge voltage), just to be clear on that.

Do you have any indication of how long the vehicle may have been sitting unused, or e.g. at a dealership with people playing with electronics etc with engine off? The 80% thing may not provide the best starting point for such a situation but any battery will likely sustain damage from sitting at a very low SoC for a long time. Plus, whereas other vehicles may not show signs of this damage for some time (the old battery still started my car just fine, though your diesel may be more demanding on the battery when starting?) the start-stop function in this type of vehicle seems particularly sensitive to battery condition, and won't shut off the engine with a degraded but otherwise still-working battery. I think this was probably the case with mine to be honest.

I'm not too sure what the in-car voltage is for my car at the moment but I'll try to check for you tomorrow if I remember.
 

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Regarding the voltage discrepancy vs original post, in my original post the battery was still in the vehicle. The 12.5V or 12.6V reading was with it out of the vehicle and after an attempted recharge (at higher than usual charge voltage), just to be clear on that.
Understood, thanks for clarifying.

Its difficult to be sure how inaccurate in-car/situ battery voltage readings might be.

If we consider my 75Ah battery, at 80% SoC, it would be reasonable to expect to park it for, say 2wks (e.g. long holiday) and still be able to start it thereafter, so say down to 30% SoC remaining. Hence a SoC change from 60Ah to 30Ah, over 14 days, is <90mA in-situ idle drain [that aligns reasonably well with your earlier recollection of ~30mA].

Now for a 75Ah battery in reasonable condition, I would not expect this relatively light loading to affect the Voc reading significantly... Which is why I have trusted the in-car/situ readings so far (but I could be wrong).

The problem right now is Xmas is imminent so its not a good time for me to be extracting/messing with batteries in cars (although I could just try disconnecting the positive post - maybe),

Do you have any indication of how long the vehicle may have been sitting unused, or e.g. at a dealership with people playing with electronics etc with engine off? The 80% thing may not provide the best starting point for such a situation but any battery will likely sustain damage from sitting at a very low SoC for a long time. Plus, whereas other vehicles may not show signs of this damage for some time (the old battery still started my car just fine, though your diesel may be more demanding on the battery when starting?) the start-stop function in this type of vehicle seems particularly sensitive to battery condition, and won't shut off the engine with a degraded but otherwise still-working battery. I think this was probably the case with mine to be honest.
The salesperson (who was actually quite amiable) seemed uncertain but suggested the car may not have been driven properly for some 2-4wks. So I agree with you that with enough people playing with the electronics, the battery could have been overly discharged. There was just enough juice in it to light the dash, but that's all... And I also agree with you that it might not take much time in an overly discharged state for a battery to permanently lose capacity.

Noted about the diesel being more demanding on battery, but in any case after my first whole week of driving - I do approx 40miles/day round trip, cross-country - the S/S still said "unavailable". It was only after an overnight battery charge (in-situ) that it recovered.

I'm not too sure what the in-car voltage is for my car at the moment but I'll try to check for you tomorrow if I remember.
I'd be very interested to know, if you are able to check it. (I presume you are familiar with the dashboard diagnostics method, although a direct reading across the battery is obviously going to be more accurate, if you have access to a DVM/voltmeter).

Coming in this morning, I could again see reasonable charging activity (including regenerative events - downhill, coasting etc - similar to your observations) but the battery still ended up at 11.7V by the time I arrived. Even allowing for the 0.4V offset error I already determined, that's still only 12.1V at the battery terminals... And that simply goes against all known good practice I've ever learned about regarding standard lead-acid batteries. It definitely suggests (to me) that the battery is distinctly under-capacity, maybe through ageing, and/or inappropriate charging/maintenance.

The 80% SoC strategy may have some merits, but I suspect that (similar to Coulomb Counting with Li-Ion technology) unless the system can confirm/check the 0% and 100% points periodically (which is totally impractical for a car battery in-situ!), it is notoriously difficult to maintain a desired mid-point otherwise.

Anyway, for now at any rate, the car seems to be cranking OK, and S/S has remained "available" since last w/e (although I don't actually use/need S/S much).

My real concern is that the actual State of Health (SoH) and/or SoC of the battery is unknown/incorrect, and that one cold morning, or after a holiday airport parking etc I'll will let me down.

(Bit of a frustrated rant - apologies)
:)

FFLu
 

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Discussion Starter #33
No reason to apologise, I find it interesting if nothing else!

I'm not 100% sure on that 30mA but the value sticks out. It may have been lower but I'd have to check again to be sure. I just used a clamp ammeter over the negative cable linking battery to body for the measurements, so no need to disconnect battery to test that (and no risk of blowing multimeter fuses if the car suddenly draws a few amps when you're on the mA range!)

I did run a couple of quick measurements at the cigarette lighter a few minutes ago. I can't say they're necessarily representative as I've done mostly very short journeys the past couple of days but with the engine running, after an initial spike up to over 15V, the voltage stabilises at around 12.5V - in the past I've had an OBD system connected to the vehicle and it appears to be keeping the current in/out of the battery at close to zero in this state i.e. to maintain at that ~80%.

Immediately after switching off the engine, when the interior lights come on and with the radio etc still working, voltage drops to 12.1V, but it's obviously not an ideal measurement because it's still on-load and likely won't settle to a useful measurement voltage for a while afterwards. I didn't get around to doing a long-idle measurement today, but either way it's probably still not too reliable as a comparison point.

A point of note, these vehicles have a battery monitoring system on the negative side of the battery, effectively Coulomb counting like you say - it's basically a current clamp linked to the vehicle's ECU for measurements. I think it mentions this in the manual, and says you shouldn't connect anything directly to the negative terminal and therefore bypassing the BMS as it would invalidate the stored state of charge.

Obviously, disconnecting any battery terminal risks resetting the ECU/radio/clocks/etc, so be careful of that unless you're prepared to deal with what happens. I think automatic transmissions in particular may behave strangely after a battery replacement where power is not maintained.

Likewise, it does seem to go against good practice for maintaining a lead acid battery in good health, hence why I do occasionally give the battery a full charge.

I didn't bother with the dashboard voltage reading, like you found it reads very low vs battery terminal voltage. The voltage present at the cigarette lighter socket seems fine but obviously you have to be careful to not short anything out if using probes. Also beware of some of those cheap+nasty cigarette lighter voltmeters as they can also be horribly inaccurate!

Overall, I'd say it's relatively difficult to get a good idea of battery health from resting on-vehicle voltage, but the fact your car has resumed Stop-Start could be a good sign - mine would not do that even after being on charge, and the post-charge voltage was still quite low. It might just be something worth monitoring, and if you're lucky it might have recovered OK. The original battery on mine was a Ford-branded one (manufactured by Johnson Controls) which I've since replaced with a Yuasa. A word of warning though - it's fairly awkward to replace if you end up doing it in future!
 

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No reason to apologise, I find it interesting if nothing else!
Cheers
:)

I'm not 100% sure on that 30mA but the value sticks out. It may have been lower but I'd have to check again to be sure. I just used a clamp ammeter over the negative cable linking battery to body for the measurements, so no need to disconnect battery to test that (and no risk of blowing multimeter fuses if the car suddenly draws a few amps when you're on the mA range!)
Good technique, but regrettably I dont own a current clamp.

I havent actually tried to measue the idle battery current directly (my earlier 90mA figure was purely a calculated, hypothetical value), but after I'd had the battery on charge overnight last w/e, I then used my DMM in series with the charger to meausure the residual charge current, and that was <200mA. That seems a pretty decent figure (to me) for a 75Ah lead-acid, suggestive that the battery is not entirely shot yet...

I did run a couple of quick measurements at the cigarette lighter a few minutes ago. I can't say they're necessarily representative as I've done mostly very short journeys the past couple of days but with the engine running, after an initial spike up to over 15V, the voltage stabilises at around 12.5V - in the past I've had an OBD system connected to the vehicle and it appears to be keeping the current in/out of the battery at close to zero in this state i.e. to maintain at that ~80%.
Thanks for doing that.

I've used the 12V power port and noted similar voltage activity. What's daft though is that the voltage does generally seem higher with greater loading e.g. heater, headlights etc, and altho this is to be expected, it actually means that the battery is getting a higher voltage (hence presumably charging more) than with no loading.

By the way, I might invest in an OBD device myself. Can you recommend a decent but inexpensive one? Someone on another site recommended this ELM327 device - suspiciously inexpensive, but the guys seems to be an accepted expert...

Immediately after switching off the engine, when the interior lights come on and with the radio etc still working, voltage drops to 12.1V, but it's obviously not an ideal measurement because it's still on-load and likely won't settle to a useful measurement voltage for a while afterwards. I didn't get around to doing a long-idle measurement today, but either way it's probably still not too reliable as a comparison point.
I'm a little surprised to note your 12.1V low, but of course without knowing tha associated load current, its difficult to assess what that says about the battery SoC/SoH.


A point of note, these vehicles have a battery monitoring system on the negative side of the battery, effectively Coulomb counting like you say - it's basically a current clamp linked to the vehicle's ECU for measurements. I think it mentions this in the manual, and says you shouldn't connect anything directly to the negative terminal and therefore bypassing the BMS as it would invalidate the stored state of charge.
I became properly aware of the current sensor whilst re-reading a bit of the owners manual last night.

Of course, it makes sence that such a device is in place, although I still dont understand how the Smart system can determine a mid point (e.g. 80% SoC) without knowing where 0% and 100% are.

Interesting that you should mention about bypassing this sensor, as I had an idea about exactly doing that very thing to try and fool the system into thinking a fully charged (100% SoC) battery is still at 80% Soc. Problem is that the sensor is not accessible without removing the battery...

Obviously, disconnecting any battery terminal risks resetting the ECU/radio/clocks/etc, so be careful of that unless you're prepared to deal with what happens. I think automatic transmissions in particular may behave strangely after a battery replacement where power is not maintained.
Your warning is noted - thanks.

Likewise, it does seem to go against good practice for maintaining a lead acid battery in good health, hence why I do occasionally give the battery a full charge.
I applaud you for doing this, but it offends my sensibilities that I might have to. What's the point of technology if it creates work!

I didn't bother with the dashboard voltage reading, like you found it reads very low vs battery terminal voltage. The voltage present at the cigarette lighter socket seems fine but obviously you have to be careful to not short anything out if using probes. Also beware of some of those cheap+nasty cigarette lighter voltmeters as they can also be horribly inaccurate!
I'm using the 12V power port with a special lead I've made up to my DVM. Its safe and appears to give readings near identical to staright across the battery terms.

Overall, I'd say it's relatively difficult to get a good idea of battery health from resting on-vehicle voltage, but the fact your car has resumed Stop-Start could be a good sign - mine would not do that even after being on charge, and the post-charge voltage was still quite low. It might just be something worth monitoring, and if you're lucky it might have recovered OK. The original battery on mine was a Ford-branded one (manufactured by Johnson Controls) which I've since replaced with a Yuasa. A word of warning though - it's fairly awkward to replace if you end up doing it in future!
Agreed about assessing SoH in-situ.

What's the issues with replacing the battery, aside the fact that it looks pretty crammed in?

I checked the idle voltage again shortly after returning home this eve, and it does appear to have improved a bit (~0.2V maybe) from last w/e. Better still I could see the voltage increasing (slowly) for quite a few minutes after completely locking the car. Its similar to the voltage "bounce-back" one observes from a good battery after a heavy load is removed.

This eve, I've elected once again to charge it overnight, albeit without bypassing the current sensor. Afterwards, tomorrow, I'm going to try a so called Battery Reset (simple button sequence on the dash) and see what the consequences are...

I want to explore all reasonable DIY avenues before approaching Ford to try negotiating a replacement battery under warranty...

Thanks for your emails to date. Its been useful for me to bounce a few thoughts off of somebody like-minded.

Cheers for now,

FFLu
 

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I have a cheap USB ELM327 clone which seems to work OK for me, and I use the software forscan on a laptop. I understand they're generally less temperamental than the wireless ones, and based on the experience of a friend with a Bluetooth one, I can believe it. I would be wary of using any discs supplied with this sort of device too (potential for malware etc), you shouldn't need to install the drivers manually anyway. Also, as always with stuff like this, the risk is your own given there are some potentially dodgy devices out there, and you can break stuff if you're not careful.

With regard to resetting the BMS, I would not recommend doing this as the system 'learns' the battery's capabilities, along with battery age etc. I'm not too sure how it uses this information but it's inadvisable to do. On the other hand, it's important you do this after actually replacing a battery so it knows a new battery has been installed.

As for fooling the sensor, I don't think it would make much difference - I believe, amongst other methods, the system also monitors resting battery voltage. Plus I think the system intentionally fully-charges the battery periodically anyway, and it obviously wouldn't then go to 120%.

Yes, the voltage will recover a while after the car has been locked, both because the car enters a sort of sleep mode, and because the battery voltage itself will recover some time after being loaded.

I wouldn't worry too much about it now - it's possible the battery was only mildly sulphated and recoverable - a few full charges would help. Keep an eye on how it goes, see if you notice any sluggish starts etc. or if stop-start stops functioning again. And I wouldn't become too concerned with on-load battery voltage either, it's weird but seems 'normal' for these vehicles, and probably loads more besides. And if it's no inconvenience for you, it wouldn't hurt to give it the odd decent charge as a sort of preventative maintenance.

As for physically replacing the battery, yes it's just awkward because of location. You have to partially un-clip the battery compartment and get the (heavy) battery out, at an angle, at arm's length. I saw some places recommending removing the air box which is in front of the battery (on mine anyway), but I didn't find that to be necessary. It was a tight fit though, and you do have to tip the batteries with that method so have to be aware of potential battery spills (both to skin and car parts), especially if the battery is physically damaged.
 

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Quick update, after a bit of motorway driving today, voltage was more like 12.7V after switching off but it had been close to 15V for much of the drive in this case. Not sure if SoC was a bit low beforehand or perhaps one of those desulphation charges. So a healthier voltage reading but you still have to consider load and surface charge.
 

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Hi, and thanks for the update, that's useful to know.

I charged my battery overnight [email protected] in situ. It started ~12v4 & ~6A reducing to <1A within 2hrs. By the morning the charger had peaked at its 14v7 limit & charge current was ~200mA. After 3hrs rest the battery terms had settled to ~12v7. At no point throughout did i trigger any of the car systems so this reading was as close to offload ("Voc") as should be possible in situ.

I'm hopeful these are good signs and will continue to monitor "at rest" and recharge periodically to see what further recovery or change there may be.

My sense is that the battery HAS lost some capacity, but I'm not sure how and whether it can be recovered, or whether i need to replace it. The next week or two may tell.

I've also decided to take your advise and stop watching the charging activity too closely. For now, at any rate!...
 

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I really enjoyed reading this thread. Thanks a lot!

A month ago i got problems starting the car. I just heared a click at the first try when outside temperatures got below freezing. But it started at the second or third try.

I measured with voltmeter in the sigarette socket 12.03 V. And i locked the doors when i sat inside the car and waited for the calibrating sound of the needles in the gauges. When you hear this sound the current draw is at the lowest and the voltage rises to 12.15 V. So about 0.13 V more.

I have always turned off the start stop system. The voltage from the sigarette socket is very accurate compared to measuring directly at the battery poles. The voltmeter in the speedometer is inaccurate and shows 0,4 V less than my voltometer, just as you said.

But the last weeks i have tried to drive longer trips and started to use the start stop system. And now the voltage is 12.21 V.

A guy on a battery shop said that i should try to drain the battery a little and charge it up to get rid of sulfating. So i think that after i started to use the start stop to drain battery the voltage is getting better.

What was strange is that when i parked in a warm parking cellar 2 weeks ago, the resting voltage rised to 12,50 V.

I got a professional voltmeter connected all the time when driving and here is some info from the last week:
11,97 V to 12,08 V when i get in a cold car with the roof light on.
12,15 V to 12,21 V when locking doors and waiting for the speedometer needles calibrating sound.
10,13 V to 10,80 V when starting the car
15,08 V to 15,15 V the first few minutes of driving
14,87 V the first 20 minutes of driving
13,51 V after the 20 minutes of driving

This is with the lights on when driving.

Car is made february 2014. It was first time registrated 31 october 2014. It was a demo car for a Ford shop from october 2014 to may 2015 when i bought it. It had 2400 miles on it. So i belive the battery had a bad start and was drained as a demo car. So the battery will soon get 6 years old from when the car was manufactured. Today the car only has 56k miles on it.

I now have bought a new original ford battery 60 AH 590 CCA but i have not installed it yet because i want to see if my old battery gets better. The car starts fine now but resting voltage from 12,15 V to 12,21 V is not good.
 

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Discussion Starter #39
Interesting post, and it's another one which agrees with the observations we've made.

Before passing judgement on the idle voltage, be sure it's a true reading because of the considerations we've mentioned earlier. Firstly, the car tends to draw a fair amount of current from the battery unless it's been sitting for a while (you can check this with a clamp ammeter, if you have one, over the negative battery cable connecting to the chassis), also you have to give the battery long enough to 'rest', to settle to a stable voltage which would be useful for measurement.

Also, an observation I've recently made which I think you've referred to, is the system voltage is kept higher, more around 13.4V for me if I remember correctly, with the dipped beams switched on. Side lights alone don't seem to cause the same effect. Perhaps this is intentional so as to not allow the light output to dim too much, but it's one thing worth bearing in mind if you're observing higher system voltages lately (winter), and likely contributes to better battery condition.

If you're planning on keeping the new battery stored for any length of time, remember to keep an eye on voltage and keep it charged to avoid that getting sulphated too.

As for the old battery recovering, it's hard to say and each battery is likely a bit different - hard vs soft sulphation for example. My original battery didn't recover properly but it sounds like FFLu's might have done.
 

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Hi exsodius,

I concur with ExSpark's guidance.

Since he and I last spoke on this thread, I've managed to take readings of the battery current draw and was surprised at the findings. For example, simply unlocking the car, with no headlights, no heater, no SYNC display, no interior lights - just the dashboard and mandatory running lights - will easilly take 4-5Amps from the battery.

I can also confirm that these elevated levels of current will continue to be taken for quite some time (>5mins) after you've locked the car and walked away. I've no idea how long it takles for the current to minimise (got fed-up waiting for it) but it does eventually drop to <10mA on my car (when I returned >1hr later to check).

Finally, on my car at least, the charging voltage behaviour can be very strange, but one thing I've notice repeatedly now (and again aligns with ExSpark's observations) is that with enough loading e.g. headlights and heater on, it rarely drops below ~13.5V. Whereas with minimal loading, distinct intervals with the voltage drifting down to ~12.2V are easilly observed.

During my recent discussions with ExSpark I gave my battery 3 overnight charges to try and bring it back. At first the resting voltage seemed to recover to ~12.5V and all was well. But two days ago the Stop/Start started becoming unavailable again and I observed the resting voltage was back down ~12.2V. [Just to clarify, I measure resting voltage by leaving the car locked - in my garage - but with the bonnet popped. I then go back to it after >1hr and measure across the battery terminals. This avoids triggering the car electronics and hence maintains the lowest battery current loading].

ExSpark FYI - I've decided to take my car for a dealer checkup (hopefully under warrenty) in the NY, but if this is correct behaviour for the 80%SoC strategy, then in my vehicle at least, it seems to be permanently undercharging the battery...

FFLu
 
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