[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.
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 &
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
and follow the instructions there.
More information about the time-nuts