12/200 bms

DIY
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1

G’day all. So I’m new to all things lithium and victron including this site. I have just installed two victron 160 ah batteries into my camper with a 12/200 BMS and a 100/30 MPPT solar regulator. At first everything seems to be working fine, but I noticed that there is full battery’s voltage at the alternator/ starter battery terminal on the BMS when the is no connection to the starter battery. Correct me if I’m wrong but this can’t be right as the BMS is supposed to act as a battery protect for the starter battery. Any thoughts is the BMS cactus?

2

You will have to draw us a diagram of the way you have set your system up.
In general, its typical to have a dcdc between the alternator and the house battery, so that the alt doesn’t get burnt out, and tge house battery doesn’t get over charged.
The bms only acts as a battery protect for its own battery

3

Thanks RP,
Yep understand that and the old system I had did have a dcdc charger in it, the only reason I went away from using one this time is that the product manual that came with the BMS read as if a dcdc charger was not necessary. I have basically wired up my system as per the diagram below only I’m not using a Multiplus.

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4

Do you only have residual voltage or can you light a bulb ?

5

Actually have more voltage at that point than what each of the batteries are showing. 13.7+volts

6

You may not understand the previous question, yes the system does have reverse current protection, but these devices are not perfect blockers of reverse current, they may allow a few milliamp though which nothing connected can be read as a voltage because a voltmeter only passes a few microamp. Hence connect a 12V bulb, that could allow a lot more current to flow, if it does not light reverse current is not flowing to any extent. A lot of people have a blind spot for leakage current.

7

Morning all,
So I did the light bulb test and you are correct there is not enough current there to power a standard 12v globe, although there was enough to power a small festoon type led, if that means anything :man_shrugging:. With that said is it safe to say that this small current leakage is nothing to be worried about?