Starter battery SOC - BM2

[NicolasH]

For about a month I’ve been monitoring the starter battery with a BM2, as recommended on here, so that I know when I need to connect an external charger.

For context it’s a 2016 Euro 5 with Stop Start BM. It’s a campervan conversion and it doesn’t get used much this time of year.

The battery is an AGM Varta - is this likely to be the original battery?

As you can see from the graph and screen shot it generally says low power and sits around the 50% mark. So my question is, is this normal or does the battery need replacing?

Thanks. Nick

 

[Pete C]

That looks fine to me. Our van of the same age with original battery sits at about that voltage.
It easily lasts 4 weeks (if we leave it that long).
Batteries generally have some sort of date stamp on them, but it can be hard to find.

Pete

 

[NicolasH]

Thanks Pete, that’s good to know.

 

[Dellmassive]

as @Pete C says that trace looks normal.

its more about the voltage over time than the xx% reading.

so as long as the voltage stays above 12.1v you are all good.

if it drops below 11.99v then it needs a full charge.

Battery State Of Charge (SOC)​

Level %	Lead-Acid	Lithium Lifepo4
100%	13.00V	13.60V
90%	12.75V	13.40V
80%	12.50V	13.30V
70%	12.30V	13.20V
60%	12.15V	13.10V
50%	12.05V	13.00V
40%	11.95V	13.00V
30%	11.81V	12.90V
20%	11.66V	12.80V
10%	11.51V	12.00V
00%	10.50V	10.00V

FYI - you can tweek the battery settings an the BM2 settings page to adjust the XX% trigger points if you wanted.

ie create a custom profile and set 00% as 11.8v and 100% as 12.4% - and see how that works for you?

 

[NicolasH]

as @Pete C says that trace looks normal.

its more about the voltage over time than the xx% reading.

so as long as the voltage stays above 12.1v you are all good.

if it drops below 11.99v then it needs a full charge.




FYI - you can tweek the battery settings an the BM2 settings page to adjust the XX% trigger points if you wanted.

ie create a custom profile and set 00% as 11.8v and 100% as 12.4% - and see how that works for you?

Thanks @Dellmassive, that’s reassuring to know. I didn’t know about the custom profiles either so I’ll set that up.