Battery replacement
 

Looking at replacing (main) battery on my 2015.5 V60 - recurring "Low Battery Charge" warning at first start-up - starts OK and warning does not recur until car has stood, unused, for a day or two. Between dealer and net look-up I see the following possibilities:

1. Dealer: $300 for another "genuine Volvo" (junk) battery + $200 for VIDAS connect to "reset"
2. DIY (or battery shop) replacement - shut car down, wait 15 minutes for everything to shut off completely - proceed in normal fashion
3. As (2) above but after the battery is disconnected (both sides) touch + and - cables to presumably eliminate any stored charge.

Any comments/relevant experiences?
Thanks

Whatever you do, the BMS does need to be reset. Should be included with replacement at the dealer. A battery installed runs $275 to $400 or so where I work, depending on the battery. That includes BMS reset.

BMS? what is it? what does it do?

Further to the above - dug through my files:

Main battery replaced (warranty) 10/18 - "Start/Stop" not working

Main battery declared "dead" by dealer (would not fully charge) 11/20 no warranty offered - battery only 25 months old $300 replacement + $200 BMS reset!

Duracell Platinum AGM battery from Batteries + Bulbs - $219 - 10% + free installation 48 month total warranty

???????????????

BMS is the Battery Monitor Sensor.

If the dealer forgot to reset it when the first battery was replaced, that could be why it failed in 25 months.

If you want, ask them for a printout of the CEM parameter displaying "Time since BMS last reset". It shows how many days ago the BMS was last reset. Then do the math and if it wasn't done when they did the battery under warranty, you have a leg to stand on in arguing for them to replace it for free.

Thanks - according to the dealer, the diagnosis of failure was based on failing to respond to an external charger attached for several hours, not the BMS report. Would a BMS "error" interfere with an external charger?

No. If the BMS was not reset it effects how the car charges the battery.

Cure or Crash?
 

What is described below is an experiment - the results are not in so it should not be taken as advice, suggestion etc.

Three things came together:

1 As described above, my battery was pronounced moribund by the dealer November. Although the "Low Battery Charge" usually comes on, the car has started reliably since despite the fact that it is typically driven about 3 times a week and never for more than 30 minutes at any one time.

2 The above post by ES6T suggests that an "unreset" BMS could affect charging

3 I found a BMS reset hack on the internet: Ignition on (car not running), headlamps on low, press fog lamp switch 5X, press emergency flashers 3X (it would be interesting to know how this was found - hardly the sort of thing one stumbles into!)

Nothing untoward happened. Three days in, the car starts normally - but no "Low Battery Charge" warning.

So - either I fixed it or one of these days I will be unpleasantly surprised by a "click" instead of start.

Will report any significant observations

I've seen that, have no idea where it came from and have not tested it at work, though I've been meaning to. It's certainly not a listes procedure in VIDA.

But I can say with certainty that the reset matters.

I've had cars come in with aftermarket batteries installed elsewhere complaining of a low battery light. First thing I do is check to see how long ago the BMS was last reset. Its usually never been reset. The State of Charge could be around 50% and then simply resetting it causes it to jump to 75% or so.

So I recharge it overnight and reset it in the morning. Haven't had one come back.

Customers then realize they didn't really save money by having someone else replace their battery for less when they have to pay me to do that.