Bms Cut Off

[Bessy765]

Should the BMS cut off the Lithium leisure battery when the voltage is low and if so what voltage. Looked at mine this morning showed 0 volts everything dead?

 

[Jimbohorlicks]

How did it get that low ? Probably knackered now if its 0 volts. Thought they held at 13 + volts even at 1 amp. Never heard of a lithium at 0 volts before.

 

[cyberyacht]

I think a BMS does cut off when voltage drops below a threshold. Usually something like 10.8. Forgotten how one goes about waking it up again.

 

[funflair]

Where are you reading the voltage? if it's the van system does it see the battery when the BMS has cut off?

 

[Jimbohorlicks]

Being curious I checked the internet and there are lots of videos on reawaking s lithium battery.
Basically you require to connect another 12 v battery to it in parallel to wake it up. Can be a lead battery. It allows the lithium BMS to let a trickle charge in and to show as 12 v on a meter so a charger can start to charge it up.

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[peterc10]

Should the BMS cut off the Lithium leisure battery when the voltage is low and if so what voltage. Looked at mine this morning showed 0 volts everything dead?

If the BMS cuts off the battery when it's low it will probably show zero because it is cut off. Put some charge in via solars, if not on EHU, and then you need to find out why it dropped.

 

[Wissel]

Which battery is it?

It's probably just got low and switched itself off, in which case it will be fine, that's what the BMS should do.

Most LiFePO4's will restart once they are being charged and get to a certain threshold, say 5% charge.

Some need some kind of manual reset, although I've not used one that isn't automatic myself, I have seen posts on this.

 

[cmcardle75]

Should the BMS cut off the Lithium leisure battery when the voltage is low and if so what voltage. Looked at mine this morning showed 0 volts everything dead?

Yes. And it has. What voltage would depend on the BMS or its settings.

Typically, to wake it back up, you'll need to apply a certain voltage, although there could be some manual shennanigans.

 

[Ranger]

We have let our KS Energy batteries get down to cut off a couple of times as suggested by KS at which point they show 0 volts and just turned the charger on and they wake up at some point. Another point with KS batteries, if you don't use any power in the van for so many hours they go to sleep and show something like 9.7 volts on the meter but wake up when anything draws power except an led light does not draw enough power to start it.

 

[Bessy765]

I left the air con on running from the inverter on Sunday no ehu forgot about it until yesterday morning. This was the power curve from 2 x 100 Lithium. The display was blank, no power at all. Plugged in the ehu set incoming 240 to 16 amps, within three or four mins system came back to life and read batteries at 100 % but took a further 6 hours showing 57 amps to fully charge 200 amps of battery until it dropped down to a few amps. Am I reading it wrong. I should add that our van is kept in a garage so gets no benefit from our 700 watts of solar panels.

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[Wissel]

It's likely that the reason it showed 100% so quickly was because the cells needed balancing. The full charge should have done this.

Sounds like the BMS did it's job and that should be the end of it

Which air-con do you run? How long can it run, purely from your batteries?

 

[Bessy765]

It’s a Dometic freshjet 2200. Set at 20c will run for most of the day in full sun with 700 watts of solar. Up to three hours safely on its own from fully charged batteries (200 amps lithium) when in France with temps around 28 to 30 we made good use of it. Got a few strange looks when using it to cool the van down prior to turning in for the night on aires with no EHU available.
i think the trick is not to try and turn the van 7.5 A Class into a fridge we set it about 10c lower than the current temp during the day.