Keep us posted--know it is supposedly a royal pain to get to and you'll probably need to reset the BMS when you are finished. And then it will be worthless in a year or two. I'm trying to forget I have one and maybe it will go away...a beta system on the 2015 for sure...

 

Judging by pictures of used batteries on eBay, the Volvo support battery is a BTX12 made by FIAMM. Apparently this is a motorcycle/ATV battery. While I don't have first hand experience replacing this battery yet, this might work:

https://shop.advanceautoparts.com/p...s-battery-group-size-btx12-bs-180-cca-tx12/16940010-P?searchTerm=btx 12 battery

I haven't found any independent listing that even acknowledges the existence of a support battery for our cars. Whatever you get, I'd make sure it is an AGM battery, and I wouldn't get a battery that requires you to add acid to activate it. You might want to remove the battery and take it to the battery store to match it up by size and ensure that the terminals will work with the car. Batteries Plus and Interstate might carry the battery and not know that it fits our cars. Advance's database says that this battery does not fit, but they have it in stock at my local store. I believe that most battery application databases cover only the starting battery, since that is what most cars have/need.

Depending on what the dealer is charging it might make sense to get the genuine Volvo part if you can't find an equivalent battery. You also might want to get your battery tested before you replace it, if you haven't done so already.

 

Our side of the pond seems to omit detailed info on the battery; however it looks like the specs are for LHD automatics with start stop:
Size in mm LWH 150×90×130
Capacity: 10AH
Minimum CCA: 170

I haven't found any independent listing that even acknowledges the existence of a support battery for our cars.

3rd party listings may not have caught up to the Drive-E batteries; I hope with enough demand they will start.

 

I found this YouTube video helpful because I experienced the exact same issue as the poster, i.e. Start/Stop Service Required light for months then 12V Battery Charge Default light.

Called a Volvo dealer and they have the battery - cost $242.

 

Called a Volvo dealer and they have the battery - cost $242.

FCP Euro has this battery in stock for $110 with free shipping and a lifetime warranty.

 

This is a 5 minute job.

The FCP Euro is the way to go. My part number in the car was 31358957; the other option (also works, same battery) is the one listed above, and the one I ordered too:
Volvo Auxiliary Battery (AGM)

• - SKU: VOL-30659531

 

This is a 5 minute job.

The FCP Euro is the way to go. My part number in the car was 31358957; the other option (also works, same battery) is the one listed above, and the one I ordered too:
Volvo Auxiliary Battery (AGM)

• - SKU: VOL-30659531

FCP Euro delivered the battery in one day. So, I just replaced the battery in 5 minutes. No more alerts for Start/Stop, no more 12V Battery Charge Default.

Pictures of batteries, top is the old one and bottom is the new one. Part numbers match what moosecar mentioned.

Thanks all. Could not have done this without this forum.