Author Topic: AGM battery replacement  (Read 416 times)

Offline Catnapper

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AGM battery replacement
« on: 09 October 2021, 15:08 »
I've just changed my battery from EFB to a AGM.
All other specs the same.
Voltage now when running is 12.6V. Previous reading around 13-14v.
Any thoughts or is this right
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Offline Finglonga

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Re: AGM battery replacement
« Reply #1 on: 09 October 2021, 15:24 »
Have you coded it using VCDS or OBDEleven, as it must be coded to tell the charging system the type of battery.

Offline Catnapper

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Re: AGM battery replacement
« Reply #2 on: 09 October 2021, 15:29 »
Yep coded with carista. May try recoding it
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Offline mustard

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Re: AGM battery replacement
« Reply #3 on: 11 October 2021, 08:23 »
Mine is the same, coding will tell the system that it does not need to put as much charge into a new battery as an old one

Offline JamesR27

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Re: AGM battery replacement
« Reply #4 on: 11 October 2021, 10:20 »
I wonder if my battery has issues, it’s the original EFB but when the car is started is running 14.7v. When turned off it’s showing 11.2v.
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Offline clubsport

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Re: AGM battery replacement
« Reply #5 on: 11 October 2021, 10:57 »
I wonder if my battery has issues, it’s the original EFB but when the car is started is running 14.7v. When turned off it’s showing 11.2v.

A static battery showing 11.2v is too low, you need consistently above 12v to have confidence in the battery. As it gets colder, it is likely the 11.2v falls a bit and the car just won't have enough battery power to turn over and start.

The reason it shows 14.7V is that the healthy alternator is partly sending power back to charge the battery, the fact that the battery only holds 11.2v after receiving this top up charge suggests it's on the way out.
With winter coming, I would change the battery now, before it lets you down.

Offline Catnapper

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Re: AGM battery replacement
« Reply #6 on: 11 October 2021, 12:57 »
sorted...... recoded it as I didnt increase Ah from 69 to 70. Now reads 13.6v
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Offline JamesR27

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Re: AGM battery replacement
« Reply #7 on: 11 October 2021, 13:34 »
I wonder if my battery has issues, it’s the original EFB but when the car is started is running 14.7v. When turned off it’s showing 11.2v.

A static battery showing 11.2v is too low, you need consistently above 12v to have confidence in the battery. As it gets colder, it is likely the 11.2v falls a bit and the car just won't have enough battery power to turn over and start.

The reason it shows 14.7V is that the healthy alternator is partly sending power back to charge the battery, the fact that the battery only holds 11.2v after receiving this top up charge suggests it's on the way out.
With winter coming, I would change the battery now, before it lets you down.

Thanks Clubsport I suspected it was on its way out so been looking online to get a new battery. Was tempted with the Halfords one but they want £182 with £25 fitting. So looking to see how I can do the battery replacement coding myself.
MK 7.5 R Pure White, Pretoria Silver, DCC, Rear Camera.
Gone - MK 7 GTI Carbon Grey, Rear Camera, Service Pack.
Gone - MK 6 GTI  Reflex Silver, Monza Shadows, RCD 510, Rear Camera, Bluetooth, Tyre Pressure Sensor, Xenons Convenience pack, Service Pack :)
Gone - MK 5 GTI Reflex Silver, Monza II 18's, Luxury Pack, Mulitchanger