[RE-wrenches] Older iCel System Lithium Ion Batteries (Steve Higgins)

[Tom Ruscitti]

Some of my non-solar consulting involves test engineering for lithium 
ion materials development. I'm no expert but I do get to work with folks 
developing and testing cells and sit in on industry training and 
conferences now and then. I would discourage trying the jump start 
described here without direct guidance from the cell / battery 
manufacturer and a properly operating BMS. Li-ion batteries can be much 
less tolerant to over-charge and over-discharge than the lead acid we're 
used to working with in the solar business. Li-ion batteries require a 
strictly enforced minimum cutoff voltage. For example, the discharge 
cutoff for one recent client's battery is spec'd at 2.5V per cell. There 
can be damage to the anode If voltage falls below that. Also, if you try 
the jump-start on compromised packs with no BMS, different cells will 
charge at different rates due to differing internal resistance (one 
function of BMS is cell balancing). Over-charging can result in 
permanent capacity loss and also electrode damage. Depending on the 
chemistry this sort of damage can increase the risk of thermal events. 
I've heard that some BMS will prevent recharging if the minimum cell 
voltage limit has been busted, but no first hand experience myself. If 
you do a web search on "lithium ion damage over discharge" you'll see 
plenty of discussion. I tried to find specs on the iCel system but 
didn't find anything useful.

be careful,

Tom

-- 
Tom Ruscitti
Senior Engineer

Taitem Engineering, PC
110 S. Albany Street, Ithaca, NY 14850
Mobile: (607) 220-7022
www.taitem.com