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Morning guys,

 

I need a quick bit of help / advice please.

 

My E38 750 has a 700CCA battery in it and its supposed to have 850 - 900CCA. I can buy a battery from Halfords that will fit it no problem but my question......

 

Can I fit the 700CCA battery in my 525 E34? the voltage is the same and she should only take the Amps needed????

 

Any help would be appreciated

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As far as I understand it, CCA is a bit of an outdated measure of battery performance. You are right in thinking the car will only pull the amps it needs, which should be no more than ~3-400 under normal starting conditions.

 

So long as it's around or above 80Ah (measure of total energy capacity rather than peak current) it will be fine for use in the E34.

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3 years after I bought my 525i I discovered it'd been soldiering on quite effectively with a 540CCA / 60aH battery. 

 

I think you really want 72aH minimum although I decided to put a big type 019 100aH battery in.

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Thats what im going to do put the 700CCA 100Ah battery from the E38 into the E34 and a 900CCA 100ah battery i the E38

 

 

 

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Ive always personally bought the biggest battery I could fit when it comes to cars....

You really aint gona notice a few kgs extra in an E34 especially being where the battery is loctated under the rear seats.

On my 540i I went with a Varta type 019 100Ah 830cca jobbie. It does fit quite nicely and never had any issues firing up that big V8 since I fitted it.

May I also sugest Tayna battieries in Wales. I have no affiliation with the company what so ever, but have always received great customer service with them and they can usually beat any like for like quote when it comes to car batteries.

Sent from my GT-I9195 using Tapatalk

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Just to add, if the car gets used sporadically / for short trips which will tend to leave the battery consistently undercharged, the bigger the better to help mitigate the effects of self-discharge and sulfation.

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@TomGC   Yes this is another issue, because the car has a tracker it tends to drain the battery over several weeks (6),  3 in the winter months.

 

This was the reason of putting the 700CCA 100Ah battery into the E34 and having a new higher 900CCA 100ah battery in the E38.

 

With this in mind it may last longer once laid up including over the winter months ???

 

If I'm wrong please do say so and I will leave the E34 alone and upgrade the battery in the E38 instead (sluggish start), but I though I could "recycle" the battery into the E34.....

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Yes the 100Ah will last longer in the E34, it makes sense to fit the biggest one you can in the car that gets used least often. If you can though, fit a float (not trickle) charger to avoid ever draining the battery too much.

 

Lead acid batteries aren't designed to be left undercharged (this is how they permanently lose most of their capacity). The plates corrode whenever the voltage is lower than when fully charged (12.8v), the longer they are left corroded the less capacity the battery will retain. Ideally they should be charged fully, immediately after any discharge.

 

The gel-type (called AGM or VRLA) batteries handle deep / consistent discharge much better than liquid types, as they are less susceptible to corrosion on the plates. But they are expensive and not necessary if you can keep the battery charged.

 

If the battery in the E38 is old and has had a life of being undercharged, this is a more likely reason for sluggish starting than the rating being too low. The tracker in the E34 probably kills the battery so quickly because the battery has consistently been drained by the tracker. It's a vicious circle.

 

Nothing wrong with using an old one even if it is a bit short of breath, but if you can't float charge the one in the E34 then an AGM might be a good purchase.

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