I have 2 ev's in my shop now with Li -ion batteries and shunt
regulators . One pack of 90 100 ah cells now in the bed of my pick up
came from a car that only had the bms set up to shut off the charger
, so when a cell went bad the car could still be driven just not
charged ( batteries ranged from 0v to 2.50) when I got it) . I have
weeded out about 10 cells and can pull 60 ah from the cells that are
left. I did the slow charge after a full charge and have also
individually charged certain cells to get to this point ( first cycle
gave 12ah) . What I think may be happening is this . Some of the cells
have a different internal resistance which makes some cells voltage go
up faster that others when being charged ( The cells that have the
most voltage drop under load seen to go up in voltage faster when
being charged). I am thinking that the shunt regulators start
shunting current across these batteries first and that on every cycle
these cell don't get the same ah as the others . The regulators on
this car come on at 3.65 and stay on till the cell come down to 3.32v
, So I'm thinking that the week sells hit 3.65 first , start backing
off the charger while shunting 1/2 an amp and the good cells keep
soaking up the ah getting ahead , at some point charger shuts off and
every body drops back to 3.32v with the good cells having gotten more
ah then the week ones. I also noticed this same thing on the bike
that's here ( same kind of shunt regs) with a 48v pack that had 3 bad
cells . I now can kind of see why people are thinking that a shunt
reg my not be the best and something that shows batteries voltage of
every cell with lowest and highest cells controlling shut down along
with some way to individually charge/ shunt cells might be better. It
may well be that not much is needed until some kind of abuse has
happened and thin it becomes an on going balancing act that shunt
regulators can't really do .
Steve Clunn
--
Tomorrows Ride TODAY !
Visit our shop web page at: www.Greenshedconversions.com
_______________________________________________
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regulators . One pack of 90 100 ah cells now in the bed of my pick up
came from a car that only had the bms set up to shut off the charger
, so when a cell went bad the car could still be driven just not
charged ( batteries ranged from 0v to 2.50) when I got it) . I have
weeded out about 10 cells and can pull 60 ah from the cells that are
left. I did the slow charge after a full charge and have also
individually charged certain cells to get to this point ( first cycle
gave 12ah) . What I think may be happening is this . Some of the cells
have a different internal resistance which makes some cells voltage go
up faster that others when being charged ( The cells that have the
most voltage drop under load seen to go up in voltage faster when
being charged). I am thinking that the shunt regulators start
shunting current across these batteries first and that on every cycle
these cell don't get the same ah as the others . The regulators on
this car come on at 3.65 and stay on till the cell come down to 3.32v
, So I'm thinking that the week sells hit 3.65 first , start backing
off the charger while shunting 1/2 an amp and the good cells keep
soaking up the ah getting ahead , at some point charger shuts off and
every body drops back to 3.32v with the good cells having gotten more
ah then the week ones. I also noticed this same thing on the bike
that's here ( same kind of shunt regs) with a 48v pack that had 3 bad
cells . I now can kind of see why people are thinking that a shunt
reg my not be the best and something that shows batteries voltage of
every cell with lowest and highest cells controlling shut down along
with some way to individually charge/ shunt cells might be better. It
may well be that not much is needed until some kind of abuse has
happened and thin it becomes an on going balancing act that shunt
regulators can't really do .
Steve Clunn
--
Tomorrows Ride TODAY !
Visit our shop web page at: www.Greenshedconversions.com
_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
