[time-nuts] Li-ion Batteries

EWKehren at aol.com EWKehren at aol.com
Mon Jan 23 06:47:47 EST 2017

The biggest mistake you can make if you plan to use them in series not to  
equalize them before use. They come in different state of charge. Maybe 
close if  from the same lot but not close enough and I do not count on the 
equalizer. I  start with a discharge to 2.5 V and charge two at a time in 
Parallel with a  holder that I modified. Set a power supply to 4.2 V precisely and 
charge all  batteries for that particular application with that setting.
Bert Kehren
In a message dated 1/23/2017 4:12:08 A.M. Eastern Standard Time,  
holrum at hotmail.com writes:

I built  a switched capacitor balancer.  It takes some time to balance a 
wildly  out-of-balance pack but does a great job of maintaining balance during 
 charging and discharge.  I run the balancer during pack charging and  
discharging.  I tried it charging an 8S LiFePO4 pack with 7 fully charged  cells 
and one fully discharged cell and it worked fine... no cells were  
over-volted during charging.

It does not waste energy/generate heat  like a resistive balancer.   An 
inductive balancer can handle higher  balance currents for very high capacity 
packs, but is also quite a bit more  complicated to do correctly.  Also built 
a processor-per-cell BMS using  ATTINY-85's.   I've used both on  4S32P / 
8S16P A123 packs and  ICR 18650 packs.

Those A123 cells can dump 200A (each!) into a short  circuit... you REALLY 
don't want to short a 32P A123 pack...  They are  also rather tolerant of 
abuse.  A friend made a video of charging one at  a 100C rate and it survived 
without exploding/melting.  I once bought  some that had been sitting fully 
charged for over 4 years and when tested  still retained over 80% of the 
charge.  A couple of charge/discharge  cycles and they performed like new.  I 
keep  4S1P packs in my cars  for jump starting.   There is a video of a guy 
in Canada staring his  car over 10 times in sub-zero weather using one.  The 
cells are 26650  size... are about the size of a D  cell.


> The BMS doesn't balance the  charge after charging (which consumes time & 
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