HELP - why would fridge flatten van battery?

[The_Lad]

You could disconnect the negative from the leisure battery and check that the fridge doesn’t work just to be 100% sure what they have told you is true

 

[Deaky]

Sorry to jump on this thread but @Deaky I have a bm6 on my battery, should I remove the negative of that from the battery and attach it to the body? If so is there one close to the battery?

The draw from a BM 6 will be negligible, don’t worry about it

 

[Deaky]

So from what I'm reading here I can conclude that:-
- I have a crap battery that needs to be replaced.
- I have 2 black wires coming off my battery negative terminal that need to be moved to a body ground.
- I still don't have any reason why the fridge would have flattened the battery, even though everything points to that being the only reason why it flattened overnight. The installer has confirmed it is wired to the LB only.

I'll do the battery and earthing changes and see where we are, unless there are any other suggestions??
Cheers.

The fridge didn’t flatten the battery. On your drive home, all the charge taken from your starter battery by the Orion to charge your leisure battery has not been replaced by the alternator because the black -ve of the Orion is before the shunt and not after it.

 

[RedPete66]

Just a final question (hopefully) on this. I've seen install videos showing the negative wire feeding Orion Isolated DC-DC charger run direct to the negative starter battery terminal rather than chassis earth. Isn't that what I have and why is that a problem?

 

[Howzat]

@Deaky has explained it in the above post. DC charger earth to chassis, not starter, because of the shunt on the starter battery. The only wire from the starter battery to the DC charger should be the posi.

 

[n10n]

Think in terms of water to make abstract electricity simpler. Battery is your water tank and shunt is a water meter. If you steal water bypassing the meter the maintenance guy is not aware that your tank should be filled and you will run out.

 

[RedPete66]

Think in terms of water to make abstract electricity simpler. Battery is your water tank and shunt is a water meter. If you steal water bypassing the meter the maintenance guy is not aware that your tank should be filled and you will run out.

Love that, thanks. Just confused why I appeared to have my DC-DC neg connected to the battery and then am seeing install vids showing same. I think I get it finally.

 

[n10n]

Love that, thanks. Just confused why I appeared to have my DC-DC neg connected to the battery and then am seeing install vids showing same. I think I get it finally.

Battery management is still kinda new thing. And different vehicles might have different systems, they’re not going to make videos for all possible scenarios.

 

[RedPete66]

OK, so new battery and moving earthing cables to body certainly have stabilised things. Starter battery seems to be holding nicely. I have some concern about the rate of decline in the SoC of the leisure battery whilst stood doing nothing. Do these traces look normal or is it dropping too low? I did run the Leisure battery down to zero SoC. cheers.

 

[n10n]

OK, so new battery and moving earthing cables to body certainly have stabilised things. Starter battery seems to be holding nicely. I have some concern about the rate of decline in the SoC of the leisure battery whilst stood doing nothing. Do these traces look normal or is it dropping too low? I did run the Leisure battery down to zero SoC. cheers.

View attachment 202553

SoC is really just a coarse estimate based on battery voltage, not be stared too much. So in the graph, 100% SoC is shown during charging but it doesn’t mean the battery is really topped up.

Give your leisure battery a good 24h charge with a 5-10A maintenance charger and see how it holds after that. Once the charger is removed, it should hold pretty steady at 12.7-12.9V for days/weeks if you don’t have anything consuming.

Batteries don’t like being drained to completely empty and especially AGM batteries can be damaged, so running to 0 SoC definitely was not good. But do the charging first before jumping to conclusions.

 

[RedPete66]

Understood, thanks @n10n