AGM battery lifespan

[Gutoneto]

Hi,

How long should an AGM battery last? I installed a new about 3 years ago and I think my battery started to die.

If I leave the car parked for a day or so the car starts to turn on heavily and the lights dimes a lot, if I drive around everything works fine when I need to start the car again.

It only started to happen few weeks ago but it's getting worse.

If that's the case, which brand you guys recommend? The current one is a SuperCharge (MF66HSS).

Thanks!

PS.: Yes, the battery has been coded correctly. The car knows that it's an AGM battery and Start/Stop has been disabled all this time.

[MIG]

My original Varta EFB lasted 12 years, AGM is meant to have a longer lifespan again.

The SuperCharge one you have has a 36-month warranty, so maybe get the battery checked and if it fails, claim the warranty?

Also might not be the battery causing the issue if you have a parasitic draw on the system, the battery may be draining over the course of the day, do you have a dashcam or something that could be draining the system?

[Lucas_R]

The original AGM battery in my SQ5 is from 2015 and has done 98,000km and still going. I do put it on a CTEK battery maintainer every few weeks though.

When I had my Mk7 GTI it had the same Supercharge battery as you have. It was near new when I bought the car, and when I sold the car 2.5 years later it was still going strong. But I also put the CTEK battery maintainer on this battery every few weeks.

Given the extensive mods on your car, id say its likely that something is draining the battery.

[Gutoneto]

My original Varta EFB lasted 12 years, AGM is meant to have a longer lifespan again.

The SuperCharge one you have has a 36-month warranty, so maybe get the battery checked and if it fails, claim the warranty?

Also might not be the battery causing the issue if you have a parasitic draw on the system, the battery may be draining over the course of the day, do you have a dashcam or something that could be draining the system?

I'll take the car to a SuperCharge distributor tomorrow to get it tested.

The funny thing is that I never had this problem before and studently started couple to few weeks ago.

[Gutoneto]

The original AGM battery in my SQ5 is from 2015 and has done 98,000km and still going. I do put it on a CTEK battery maintainer every few weeks though.

When I had my Mk7 GTI it had the same Supercharge battery as you have. It was near new when I bought the car, and when I sold the car 2.5 years later it was still going strong. But I also put the CTEK battery maintainer on this battery every few weeks.

Given the extensive mods on your car, id say its likely that something is draining the battery.

That's a weird issue, and haven't done any mods/retrofit for a long time.

Few months ago the car was parked for few weeks without been started and when I started worked flowless. Something happened lately...

[Hillbilly]

That's a weird issue, and haven't done any mods/retrofit for a long time.

Few months ago the car was parked for few weeks without been started and when I started worked flawless. Something happened lately...

Yep sure has It is dieing My original Passat battery only lasted 4 1/2 years but then it sat more than it got driven

[gregozedobe]

Unfortunately recent (Mk7 and later) Golfs don't fully charge the main battery (VW trying to get the best possible "official" CO2 and fuel consumption figures). The end result is that batteries don't last as long as older VWs used to. 3 years isn't too bad, particularly for a car that isn't driven frequently. Heavy stop/start traffic also prevents batteries from being fully charged.

You could get your battery tested with a proper load tester (they are a bit like a 12V toaster) to see what current it can actually deliver, and replace it if it is on the way out.

[DV52]

@gutneto: Hi.

When you say " I installed a new about 3 years ago" - did you replace like-with-like? Or, the question asked another way - was this car factory fitted with an AGM battery, or with a EFB battery?

And perhaps the even more critical question to ask is: when you installed the new battery "about 3 years ago" - did you tell the car's Energy Management System (EMS) about the change by re-coding the Gateway module with the new battery's details ?

Don

@gregozedobe:Hi. Yes, 101% correct!!

But and with absolutely no offense intended - how does the EMS charging regime in mk7s/7.5s (which as you correctly say reserves 20% of the battery's capacity for regenerative braking) affect battery longevity (AGM and EFB battery technologies don't have a memory problem AFAIK)? What have I missed?

Don

[doc_777]

Moat "battery problems" don't originate with the battery - they are usually caused by other issues. Generally issues with the charging system or with parasitic drain. Spending some time (and money) with an auto electrician might be useful in this situation. They should be quickly able to identify issues with the charging system, or hopefully help work out if there are parasitic drains on the system when the vehicle is shut down.

[gregozedobe]

@gregozedobe:Hi. Yes, 101% correct!!

But and with absolutely no offense intended - how does the EMS charging regime in mk7s/7.5s (which as you correctly say reserves 20% of the battery's capacity for regenerative braking) affect battery longevity (AGM and EFB battery technologies don't have a memory problem AFAIK)? What have I missed?

Don

G'day Don,

I don't think it is a memory issue, simply that all lead acid batteries (of any kind) last better if kept fully charged. The problem with the newer VW EMS/BMS strategy is that it deliberately keeps the battery at less than full charge (eg my R consistently keeps its battery around 13.3V most of the time, whereas my 2008 Octavia usually runs around 14.7V).

This "undercharged" situation gets worse if there are any other factors reducing the level of charge further (eg car not driven for a week or two, driven in heavy traffic with auto stop/start enabled, using the car to charge phones etc, parasitic drain from dashcams, immobilisers/alarms, non-OEM infotainment etc). This is probably where a lot of the reduction in battery life happens, especially if the battery gets completely discharged as a result (this damages the plates so they now have less capacity).

The end result is a battery that spends a lot of time at less than 100% charge and I believe this is what reduces its lifespan compared with a battery that is usually kept fully charged. IMO these days I see a lot more reports of batteries in newer VWs being replaced at 3-5 years (or less) compared with the (older) cars that people previously had (that were presumably subject to similar driving regimes) where batteries tended to last 5-8 years (sometimes more).

It makes sense to me, anyway.

BTW, Thanks for all your helpful posts on coding (here and other sites too).