[stick_shift]

So some people have reported that replacing the aux battery fixes the start/stop - and indeed it does!

I followed this video:

I charged the new batt for about 20min prior to putting it in the car (12v, AGM type)

Steps:
1) Go to your Volvo dealer and buy the battery, I had mine price match online sites and got it for $90 + tax Part 30659531
2) Open the hood, take off two 8mm bolts that hold down the cover
3) Disconnect the two battery cables, held by 8mm bolts
4) Swap batteries
5) Assemble in reverse

Didn't do anything else, wife reported that start/stop was working fine when she went to work the next day!

Battery and box

Measured old battery voltage - it is indeed considered 'dead' (ie. below 12v)

 

[brabbit]

Just make sure you use insulated tools because removing first the negative will still allow shorts to chassis in the positive because of the other battery still being connected in the trunk, not like cars with a single battery.


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[Volvolic]

@stick_shift, can you comment on how long the start-stop keep on operating? I ask because my Aux and Main batteries were changed in the past year (on separate occasions). Although the start-stop worked flawlessly for a little while, there comes a time when the start-stop quits working again, and you're back to your old situation unless you take a cross-country road-trip, and the system starts working yet again until it doesn't.

If I were to place a bet, I would say an inherent system design flaw is to be blamed, and not the batteries.

 

[FusionRedXC60]

I agree the start stop support battery should be able to last longer. It basically is only used when starter is spinning. How many minutes a year could it be? There must be some design issue that it is not recharged properly.

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[stick_shift]

Can't comment on those who have ongoing problems with the SS. Our 2018 is about 3 years old now, that's about the expected lifespan of a battery. I consider it to be a wear item.

I'd hate to face dealer visits if the thing broke more often than that! (I wish I had one of the newer models where you can simply disable the SS...)

 

[Ultrarunner511]

Did have any battery error notices on the dash? I've read that codes may need to be erased/reset through VIDA.

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[Stickygreen]

I thought start stop could be disabled in all models. When did this feature start? I absolutely loathe auto SS

 

[stick_shift]

Did have any battery error notices on the dash? I've read that codes may need to be erased/reset through VIDA.

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We had the usual "SS needs service" message before the fix. One could clear it for the rest of the drive by pressing the center button on the RHS of the steering wheel.

The video I linked also says "If you still have a message after swapping the battery, you may need to visit a dealer to have them clear it via VIDA." There is supposedly some kind of calibration that must take place. I've seen some references claiming the vehicle must be driven for 20min after the battery install. Others have said the vehicle must be left to sleep overnight.

That's why I made sure to charge the new battery before installing it, figured it would give the whole system a fresh start. Did not go to dealer, did not use VIDA.

 

[FusionRedXC60]

Is there a battery monitoring sensor for the support battery as well? May need to reset the BMS after new battery is put in.

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[tanXC90]

Nice simple DIY stuff..thanks for sharing.

 

[stick_shift]

I thought start stop could be disabled in all models. When did this feature start? I absolutely loathe auto SS

We have a 2018 and it cannot be disabled except for current drive. I think the 'sticky' disable feature was added in 2019 (supposedly cannot be added to the older models for purely political reasons... would pay good money for a workaround.)

 

[Ultrarunner511]

We have a 2018 and it cannot be disabled except for current drive. I think the 'sticky' disable feature was added in 2019 (supposedly cannot be added to the older models for purely political reasons... would pay good money for a workaround.)

Yep. 2019's had the change. Disable once and never have to disable it again (one of the amazing things about the 2021). Our 2017? It gets really annoying.

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[Tech]

There is no BMS for the support battery. If it is just the support battery, any warnings should disappear without VIDA.

However, if the main battery is causing the problem, VIDA will likely be needed.

Also, I've seen some instances where a particular code could be stored and be difficult to clear, but I don't remember if these instances were for cars needing one or both batteries.

 

[Zahra]

I agree the start stop support battery should be able to last longer. It basically is only used when starter is spinning. How many minutes a year could it be? There must be some design issue that it is not recharged properly.

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Isn't the support battery (small capacity of 10Ah as can be seen in the picture of the OP) used to keep all
systems alive while the engine is off, and the main battery (high capacity in the trunk) used to power the starter?

 

[FusionRedXC60]

When engine is off, the big battery in trunk is keeping up everything. T5/T6 and old cars it is like this. T8 doesn't need to change to use the small battery only when engine is off.

The support battery is only needed when huge current is drained from the main big battery while starter is cranking. On old cars, this is the moment all the lights are dimmed when starter is cranking.

 

[Stickygreen]

Thank you! Didn’t realize there was a semi-permanent disable on any of the models...thought they all had to be disabled each time you start the vehicle. Looks like I have to find a cpo ‘19 model...

 

[Zahra]

When engine is off, the big battery in trunk is keeping up everything. T5/T6 and old cars it is like this. T8 doesn't need to change to use the small battery only when engine is off.

The support battery is only needed when huge current is drained from the main big battery while starter is cranking. On old cars, this is the moment all the lights are dimmed when starter is cranking.

Aha! 😀

 

[Fmfosnacht]

My dealer, Premier Volvo, quoted $340 to replace the battery. I ordered it from FCP Euro for $107, with lifetime warranty. They also wanted to charge me $60 for a battery test, despite the fact I told them it was needed. When I protested, they removed the charge.

And speaking of overcharging, ($ that is), Premier also quoted $1500 for rear pads and rotors and front rotors. I declined. I then bought the $1325 5 year maintenance plan from Michael at Steingold, who was extremely responsive despite the Nor’easter in RI. He applied the $200 discount for being a Swedespeed user for full brakes and rotors and 4 sets wiper blades for 1125. So I saved hundreds of dollars, have three sets of wiper blades left and a front set of pads left on my plan.

One more hint. My auxiliary battery was off gassing the horrible rotten egg smell. Be aware this is extremely toxic. Make sure to limit driving if you have this smell.

 

[PKvolvo]

Thanks to the OP for sharing this, I have a 2018 XC90 T6, I was getting the error message start/stop service required for the last 6 weeks or so, this week I got the error message "12 V Battery Charging fault Stop safely".

I tested the auxiliary battery with a voltmeter and got a reading of 3 volts, got a replacement battery from my Volvo dealer and installed it, problem solved, after I changed the battery I was still receiving the error message "start/stop service" but it cleared itself after about 24 hours.

During the time I was receiving the error message "start/stop service required" the Spotify app was taking a lot longer to connect, normally it would take about a minute for the music to start playing after getting in the car but it was taking double that the last few months, since I replaced the auxiliary battery Spotify is connecting in about a minute.

It looks like the auxiliary battery has an impact on other systems besides the start/stop?

 

[DNIX]

Just went through this myself. I own a 2018 Volvo XC90 Inscription. The Start/Stop service required message suddenly appeared one day out of nowhere. I ordered a new Volvo brand replacement battery from a website based out of Connecticut for around $110. Replacing the battery was simple, I watched the YouTube video noted at the beginning of these messages. I replaced the battery at around 6:00 p.m. At first after the replacement, the Start/Stop service required message DID NOT clear. However, when I woke up the next morning and drove to work at 7:00 a.m., the message had cleared. So, it appears that the message will clear by itself after the battery is replaced and the vehicle sits for awhile. I know that I probably saved hundreds by doing this myself.