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oldjohnny

Using Battery With lower AH.

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Moved this from a previous post on flat batteries.

 

I have been given an almost new exide battery with 80AH and 800A.  My current not very well Bosch unit is 100AH 800A.  What, if any problems would this produce?  The car is used sparingly and seldom at night nowdays due to my sheltering from the plague.

 

Also, are coding and registering a new battery two different procedures?

Edited by oldjohnny
addition.

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Yes two seperate procedures. My understa ding is that coding is used when installing a different type ie going from 100a to 80a.
So if you replaced like for like (and all other owners did as well and nobody changed the coding) no coding required.

Registering is everytime you put a new battery in, even if the same type as it resets the IBC which will have been charging a very old battery at a lower rate.

If you dont reg a new battery the car will likely not charge it fully as it still thinks its got a 7 Yr old bat in etc.

I'm sure most will have their own view but in my opinion going down to a 80a will be OK, but not as good.

For instance when full charged (and still in good health) will start the car no problem (800cca not changed) but if your use was frequent, short drive cycles mostly from cold with lights, heater, seat heaters, CD playing and heated steering wheel on (as a worst case scenerio) you much more likely to end up with a flat battery as you only started out with 4/5's of the original batteries capacity.

Of course a decent run would fully recharge the 80 amp hour capacity so if you mainly do over say 15miles from a cold start with little draw on power from auxiliaries, you will be fine.

As you are not using the car much at present an 80a (having less capacity) will go flat quicker sat on your driveway. So unless you are going to make sure you use the car at least say once a week for a decent run or have a trickle charger on the go the small battery will let you down sooner.

BTW, just because this 80amp battery is nearly new/not had much use it doesn't mean it is necessarily in good health (ie ability to hold a good charge/actually put out 800cca) as I'm my experience the main reason a 12v Lead acid battery fails is due to it being flat (
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Many thanks.

 

Exide battery is reading 12.5 and current Bosch unit is 12.1.   Also just noticed the  Exide is an AGM type.  As the car is very old now I am tempted to fit this, register it and see what the outcome is. 

 

Talk about the big bang theory!:blink:

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Given you already have it, I would do exactly the same. You will need to code for 80a (assuming car is currently coded for 100) as well as registering. 

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3 hours ago, sarahMtony said:

Given you already have it, I would do exactly the same. You will need to code for 80a (assuming car is currently coded for 100) as well as registering. 

Yep, code then register.

Edited by GoNz0

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Just a thought.  In an earlier post on this, dirtydirtydiesel commented that it needs coded otherwise the ibs will overcharge it thinking it is still 100ah.  I have had this car nearly three years now and there is no ibs present.  The previous owner seems to remember it being removed for some reason.  This means the battery has been on the go for about 5 - 6 years and is only now on the wane.  So with no ibs will the 80ah unit still be overcharged?

 

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Without the ibs it's being overcharged some of the time anyway,

If you've been happy with it for the last 5 -  6 year's  go for it.

You say it was virtually free anyway, just don't moan at me if it fails mid winter ;-)

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It's impossible for the car to know it's 100ah as it isn't an option. 90 or 110 are the options for standard and 90ah AGM is the biggest for AGM

Someone put the wrong battery in so until you check what the car thinks it has you will be in the dark.

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Dropping from 100 to 80 could cause an issue in the winter. The battery would have 20% less ah available for starting the car. In the winter cold months there is more load on the battery when starting the car due to a colder engine and colder oil. In the cold there may be a need for more "turning power" from the battery.

I had a starting issue with my 03 VW Transporter in the winter. When cold it turned over very slowly. When I bought it it had a new battery. The dealer had gone cheap and put a 90ah battery in when it should have been a 110ah

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Many thanks for all the advice.  My soloution is as follows.  Her indoors has a c class merc estate and upon checking under the bonnet I can see that the nearly new battery I have been given is exactly the same.  As it hasn't been changed in donkeys then thats where it will go now.  I can then hopefully get her to pay half the price of a 'proper' spec one for my 530d!  :twisted:

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45 minutes ago, duncan-uk said:

Is that how it works in your house? My wife thinks the pixies do this kind of domestic admin! :lol::rolleyes:

Same here, she thinks her car is magic and doesn't need fuel either!!

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It's a two way thing in our house.  She buys the parts for the two cars and where possible I fit them for free.

 

 

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Here is an interesting oem clip.  Turns out my original battery was  61216901817,  110 ah.  The statement on the BMW oem page is to replace this, if discontinued with 61217604822 which is 90 ah.  Does the statement that a job order revision is not necessary mean that there is no need to re-code it?

Screenshot_2020-10-19 RealOEM com - Online BMW Parts Catalog.png

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5 hours ago, oldjohnny said:

Here is an interesting oem clip.  Turns out my original battery was  61216901817,  110 ah.  The statement on the BMW oem page is to replace this, if discontinued with 61217604822 which is 90 ah.  Does the statement that a job order revision is not necessary mean that there is no need to re-code it?

Screenshot_2020-10-19 RealOEM com - Online BMW Parts Catalog.png

It's telling you to use 384 but it's an awful page to read in my opinion. They would never tell you to replace a 110 with a 90...

Put your OE number in realoems part cruncher and it tells you it's superceded by 384...

 

 

Screenshot_20201019_161336_com.android.chrome.jpg

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Cheers for that S.

 

I am rubbish at reading those things.  At least I know exactly what to buy now and it will be interesting to see if the original coding and registration are still the same as I have a notion they have never been changed.

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Thanks Gonzo.

 

I had noticed this when trying to get my cars original battery spec.  I was speaking to the original owner about another matter and mentioned this to him.  He told me that almost six years ago now the battery was continually draining.  His indy disconnected the ibs, put in the current 100ah unit and neither coded or registered anything, so all those years later makes me think I will simply replace and hope for a similar result.

 

 

 

Screenshot_2020-10-20 RealOEM com - Online BMW Parts Catalog.png

Edited by oldjohnny
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