V60 Auxiliary battery not charging

[muffking]

Following on from one of the many 'Start/Stop not working' threads I have replaced my auxiliary battery only to find that the real cause of the problem and the constant 'Battery Low' message is that there is no charge going to the auxiliary battery at all.

I heave measured power to the battery with it disconnected and there is no voltage going to the battery cable at all. I have also checked all fuses in the box near the main battery and under the glove box.

Does anyone have any other ideas or places I can check i.e. a 3rd fuse box, before I get the car booked in.

[Rooster]

The auxiliary battery is switched off when the ignition is switched off,

The low battery warnings are more likely to be the main batteries state of charge that has dropped,

If the SoC drops below 72% then the stop/start won't work and depending when the battery monitoring system was last reset then it still might be taking the calculation from when the battery was new,

The little backup battery actually has very little to do with the stop/start apart from providing an aid to the main battery as most calculations are taken from the main battery first hence the little wires either side of the big battery,

It might just need the main battery charging and the BMS system reseting

[muffking]

Thanks for the reply.
The thing that's pointing me towards the auxiliary battery is that when you go into the Drive menu and select Stop/Start it says that it's not available as the battery is charging, but when I disconnect the positive lead to the auxiliary battery and measure the voltage there is 0V.

I'll try manually charging the main battery to see what difference it makes next time I use the car.

[IainG]

Hi

The thing that's pointing me towards the auxiliary battery is that when you go into the Drive menu and select Stop/Start it says that it's not available as the battery is charging, but when I disconnect the positive lead to the auxiliary battery and measure the voltage there is 0V.

Some charging systems will switch off when it detects no battery so not allways an indication of a problem.

The best way is to monitor the voltage on the aux battery and see if it rises when the engine is running, there might be certain parameters to be met before that happens, ie main battery charged etc etc, depends on the set up.

Iain

[muffking]

Finally fixed it!

You were spot on about the car choosing not to charge the Aux battery as it was the main battery that was below par. I bought myself a new multimeter as my old one was reading high, but as the MyCar menu kept telling me that the battery was on charge and that's why Stop/Start was disabled. I ended up measuring the main battery which I found was reading low 12's in the morning, but high 12's after a run, so I suspected that the main battery was losing some of its charge overnight, although not enough to stop the car from starting ok.

Looks like I may have wasted £25 on changing the Auxiliary battery, but someone local had a spare brand new Bosch S4 main battery which I got for £40, so it all worked out in the end

[RoyMacDonald]

I take it you know the auxiliary battery is only to run the cars systems like air con and radio to take the strain off the main battery? It's the main battery that starts the car including during stop start. If the main battery is low on power stop start will be turned off as you have found.

[GMcL]

Originally Posted by muffking

Finally fixed it!
...
Looks like I may have wasted £25 on changing the Auxiliary battery, but someone local had a spare brand new Bosch S4 main battery which I got for £40, so it all worked out in the end

How far is your daily commute? I swapped batteries on my car last year. I use Bluetooth connectivity for Tune-In radio every journey. I also have two cameras permanently live. Previously my commute was 20 miles/day c. 25 minutes each way. This was not enough to keep the battery topped up and I'd get a Low Battery ! warning every 8-10 weeks with the new battery. I now commute 50 miles/day, no more battery messages.

[igmox]

Originally Posted by muffking

Looks like I may have wasted £25 on changing the Auxiliary battery, but someone local had a spare brand new Bosch S4 main battery which I got for £40, so it all worked out in the end

my guess is that Bosch S4 does not qualify for V60 with start-stop.

my battery died last week and after some research in the owner's manual, i figured out that the main battery is required to be AGM type.

start-stop and regenerative braking are said to need higher amounts of energy transfer to/from the battery, so you may want to have a look at the user's manual for the correct type.

[muffking]

Originally Posted by RoyMacDonald

I take it you know the auxiliary battery is only to run the cars systems like air con and radio to take the strain off the main battery? It's the main battery that starts the car including during stop start. If the main battery is low on power stop start will be turned off as you have found.

Yeah that's what I figured in the end. It was the fact that the main battery was never above the charge threshold to allow Stop/Start to enable and the car to switch to charging the auxiliary battery.

Originally Posted by GMcL

How far is your daily commute? I swapped batteries on my car last year. I use Bluetooth connectivity for Tune-In radio every journey. I also have two cameras permanently live. Previously my commute was 20 miles/day c. 25 minutes each way. This was not enough to keep the battery topped up and I'd get a Low Battery ! warning every 8-10 weeks with the new battery. I now commute 50 miles/day, no more battery messages.

I did some very long runs when checking the voltage, but it was never enough to enable Stop/Start. And when I metered the battery voltage each morning it was much lower than after a run.

Originally Posted by igmox

my guess is that Bosch S4 does not qualify for V60 with start-stop.

my battery died last week and after some research in the owner's manual, i figured out that the main battery is required to be AGM type.

start-stop and regenerative braking are said to need higher amounts of energy transfer to/from the battery, so you may want to have a look at the user's manual for the correct type.

Good point, I'm aware the battery should be an AGM, but neglected to check what type the Bosch S4 is. Next stop, Google....

[muffking]

Originally Posted by igmox

my guess is that Bosch S4 does not qualify for V60 with start-stop.

my battery died last week and after some research in the owner's manual, i figured out that the main battery is required to be AGM type.

start-stop and regenerative braking are said to need higher amounts of energy transfer to/from the battery, so you may want to have a look at the user's manual for the correct type.

Not sure what to make of this.
According to Bosch the S4 is a Flooded battery. Only the S6 AGM is Absorbent Glass Mat. https://www.boschautoparts.com/docum...b-9bd088a9a626

However, according to http://vonwentzel.net/Battery/01.Type/index.html Flooded & AGM may be interchangeable?