#62293  by WoodyZ
 Sat Oct 12, 2013 12:25 pm
I have one cell on my 60 a/hr pack which always goes high on charging but settles back down when standing or when a brief load is applied. I have yet to use my hybrid system in the wild so am unsure yet whether I need to build in any more battery management componentry or not.
 #62444  by newPowr
 Tue Oct 15, 2013 11:13 am
[quote][/quote]Out of interest, the system was supplied by New Powr, who made some posts on another lithium thread earlier this year.

Thanks Dene, happy to help

If anyone is still doubtful about the importance of fitting a proper BMS with load balancing and cut-offs I hope the attached picture will set them straight. Only good news in it is the cells failed in a safe mode with no fire, explosion, leakage of toxic fumes (please note that our cells don't contain yytrium which is mildly toxic) or other catastrophic event some fear unwarrantedly. The battery is a clear write write off however and I can tell you the owner wishes he didn't think saving pennies whilst risking pounds is the way to go. Make sure you are not making the same mistake or, if you already did, get in touch so we can help you fix it.


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 #62445  by WoodyZ
 Tue Oct 15, 2013 11:33 am
What specific conditions caused that failure?
 #62456  by newPowr
 Tue Oct 15, 2013 1:23 pm
Couple of years running without BMS leading to significant differences in cells SOC and ultimately pushing one (to start with) outside of the normal operating range. With no BMS there was nothing to alert the user to it and the whole pack ultimately failed. A common misconception is that if cell rest voltages are roughly the same the state of charge is roughly the same but with lithium that's not the case (flip side of having a very flat voltage curve, guess people see only what they like to :)
Measure the cell voltages under charge and discharge conditions and you will know better (I think I saw a post here where somebody mentioned a cell going over voltage when charging and then "coming right"? With no BMS? Good luck with that!)
 #62458  by mattn
 Tue Oct 15, 2013 1:39 pm
Frankly the last few posts scare me off Lithium batteries. All the advantages mount to zip if you come home to a pile of ashes or worse, were home when it happens...... With lead, all you need is a fuse.

Is it people taking shortcuts to save $$$ really the only cause of these kinds of problems. How often is a typical Motorhome/Caravan install likely to fail dangerously? How typical is Lithium battery installation below a "safe" standard? Does a BMS completely eliminate these problems?
 #62459  by Justintime
 Tue Oct 15, 2013 1:44 pm
Your comments well noted Matt. However, it would be wrong to also state that lead acid batteries themselves are immune from such meltdowns.

Cheers, Dene
 #62460  by WoodyZ
 Tue Oct 15, 2013 1:45 pm
Another good question is - What chemistry was that battery?

All Lithium batteries are not created equal.
 #62461  by newPowr
 Tue Oct 15, 2013 1:58 pm
No need to get scared or exaggerate the risk (even in an un-managed situation the effects were well contained and there was no health or safety risk. Only thing that was affected here was the back pocket). A BMS would have definitely prevented that and this is why every serious company out there insists on fitting them.
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