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Discussion Starter #1
I wanted to hear your opinion on a strong battery (one with a high Amper) can cause damage to an alternator or even other parts in the engine.
The reason I ask is because I am hearing a squealing noise from the engine, which might be related to the drive belt, but I read somewhere that it could also be from the alternator.
I changed the battery in my car for 2 months ago and replaced it with a 70 Ah, and the previous one was a 42 Ah. I was wondering if this difference on the battery power could make an alternator to force work more than it should do, and cause this noise?
 

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No, it won't.

Squealing is almost always the serpentine belt trying to turn a pulley that's started to seize. The best way to find the suspect pulley is to pull the tensioner forward enough to slip the belt off, then turn each pulley by hand until you find one that makes grinding noises or is hard to turn.

You can also try a stethoscope to each pulley as it's running, but you have to be very careful not to get fingers, hair, sleeves (or other bits that you want to keep) caught in the belt.
 

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LOWER amp battery forces alt to work more not the reverse.
 

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Discussion Starter #4
Leora thanks for the tip, I think there are 3 pulleys around the belt and do you think in this way you mentioned its possible to check every three of them, I think I have easy access to one pulley.

Thanks amc49 :)
 

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Ah is not a power rating but a measure of capacity. As long as the voltage is within limits, you will not damage anything. In theory, 70Ah will operate a given load 66% longer than 42Ah but will also take longer to fully charge when depleted. The previous battery could have lost it's charging efficiency (i.e. high internal resistance) and thus the charging load on the alternator would have been minimal. With a new battery, the charging system is back to normal and demanding more current from the alternator, which also means more stress on the drive belt. When was the last time the belt was changed ?
 

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I'm not familiar with the UK version of the Focus (and you don't specify which year you have), but on mine I can access all the pulleys either from up top or underneath. Your experience may differ, obviously. Newer models tend to have more plastic covers over things, so if yours has this you'll have to take a few bolts out for access. It shouldn't be overly time-consuming, though.

Generally once it's squealing, it's telling you that it needs attention or it will strand you on the side of the road soon.

It could just be that the belt is old and worn, but my money is on one of the pulleys...idler, tensioner, alternator, power steering, water pump, AC compressor. Some don't squeal first, they just seize suddenly (then like my idler, tear apart), so you're fortunate to get some warning.
 
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