Lithium BMS dead (1 Viewer)

[Gazz Kaz+Spag]

I have been away 4 months and have a few weeks left. I have a 400Ah winston cell which is 4x 3.2v cells. They use a Smart 123 BMS. Last night i was at about 12.7v. This morning i was at 8.7v. The BMS didnt kick in for some reason. I cant get charge in as the BMS is stopping it. One of the BMS on one cell still works. I have checked each cell and during the day a second BMS started working. I now have 2 not working as they are on each cell. I think the power is too low on the other 2 to allow a charge in ie not enough power to operate the BMS. I have spoken to manufacturer but i aint holding my breath. Any ideas. I thought about linking the one working to the one not ie 6v to see if they even out. No charge going in or load.
Thanks Gary

 

[pappajohn]

Not much help but you probably killed em anyway.
They will tolerate deep discharge on amps but I doubt they'll like 30% down on volts.

A regular lead acid only drops 0.5 volt at 50% discharge.... Yours are down 4 volts.

 

[Gazz Kaz+Spag]

So readings are now
2.86v
2.00v
3.07v
1.82v
The 1st and 3rd BMS is working but the 3rd wasnt this morning. One or some have definitely gone up in the last 6hours or stabilised.

 

[autorouter]

I thought about linking the one working to the one not

I presume you don't have access to a charger suitable for charging a single cell, so I suppose the next best thing is to use a good cell to try to revive the failed one. Best to wait until one of the cells is charged to at least 3.2 volts. Then disconnect all the cells from each other. Connect the good cell to the failed cell (in parallel, ie pos to pos, neg to neg). this may bring it up to a level where the BMS will regain control of it. But be careful. I'm not an expert on these things, so this may be dangerous for some reason I don't know about.

 

[pappajohn]

Main question is..... What caused them to discharge so low...
It must have been a massive load to drain 400ah to nothing overnight.

Be careful... Lithium are prone to fire and explosion when faulty.

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[Gazz Kaz+Spag]

Thanks autorouter thought about this but i would have done + to - not like you said. Cant charge any single cell as away and no 3.2v charger just onboard 12v. Another came to life but i tried to hook them all up but no joy. I need a 3.2v charger i think

 

[pappajohn]

+ to - would just give you a 6.4v battery.
+ to + would keep it at 3.2v but the amps would try to balance between the two cells until the equalled out.

 

[Gazz Kaz+Spag]

I was wild camping but even so 12.8 to less than 9 smh.....i dont know. Will try to add the 2 not working to the other higher 2. Lucky they are next to one another. Will sort some wire between the 2 cells. On EHU now so will try tomorrow. Ive some jump leads in the back will be messy but will join 2 cells. Thank you

 

[Gazz Kaz+Spag]

I can charge the starter battery with onboard charger. So i could use jump leads to the normal + and - and without the BMS not trickle charge but balance them ish ?. So glad i used credit card to buy cells and bms!

 

[pappajohn]

Be VERY careful.
There should be no sparking when you connect, if there is DON'T CONNECT.
Keep a watch on the battery temperatures, if they begin to get SLIGHTLY hot DISCONNECT.

Either of these scenarios could be one cell has shorted internally and connecting a good battery to it will introduce a short circuit to that battery too.

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[Gazz Kaz+Spag]

Ok thanks. The temp of all the cells is room temperature has been last 24hr

 

[pappajohn]

No, I mean when you connect them together.
A shorted battery will produce heat.

 

[Pausim]

Not sure this will help, different battery with built in 12v BMS but I found the idea of jump starting it interesting.

“For some issues, such as BMS protection against low voltage, your Relion Battery can be reenergized by applying (jumping) 12 volts to the terminals, much like jump starting a car battery, this can be easily done with jumper cables. If this does not work, it will need to be charged in parallel with another battery that has enough voltage at least 10 volts in a 12 volt battery, this allows the charger to detect a complete circuit. You can use any type of 12 volt battery. Connect your charger directly to a working 12 volt battery. Then, connect your Relion Battery in parallel (positive to positive, negative to negative) to the first battery. The Relion Battery’s BMS will reenergize, bringing the battery back up to its voltage prior to the BMS kicking in. After about 20 minutes, reconnect the charger directly to the Relion Battery, and the charging process will continue normally.”

 

[hilldweller]

Thanks autorouter thought about this but i would have done + to - not like you said.

They would have seen the result from the International Space Station.

You are playing with fire. If your luck runs out it will be more than a battery that you are replacing.

 

[pappajohn]

They would have seen the result from the International Space Station.

You are playing with fire. If your luck runs out it will be more than a battery that you are replacing.

Nah, the neutrons would just go round in circles Brian.
Out of one Pos into the other Neg, through the battery and out that Pos into the first Neg then through that battery then out the Pos and into the Neg and............ Ad infinitum



Don't try this at home folks ... You can't see neutrons without special goggles.

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[hilldweller]

Nah, the neutrons would just go round in circles Brian..

I'm sorry John, I'm taking this a bit more seriously. One mistake and this guy and his motorhome is toast. And not a hope in hell of making an insurance claim.

 

[pappajohn]

Makes a change for you Brian.

But i know what you mean.

 

[hilldweller]

Makes a change for you Brian.

But i know what you mean.

I know, sorry, I don't know what came over me.

I do have a terrible cold.

 

[Gazz Kaz+Spag]

Well this morning all the cells have gone up. Back at 11.25v currently. May be hope yet. Still no charge going in. Will leave them all fastened up as i did uncouple the worse cell. No load out and leave em a bit longer. Thanks all