hyperion balancer - how should it do? (longer ...)

[phibes]

Hi there,

im pretty new into the rc-hobby and i just bought my first decent charger, a hyperion 720. Currently i have a 3s 4500mAh-battery which is in a bad condition and i use this one to play with the charger to learn its functions.
Today i discharged the battery with a cautious current of 2A. I was surprised that the discharge stopped when one cell got below 3V (i thought the charger uses the balancer to discharge all the cells to 3V but it didnt happen).
So after the discharge-process stopped i started the balancer manually and recorded this:



so my questions are: what can and should the balancer do? can it only discharge single cells or can it charge a single cell from the pack?
When i started the balancer the cells had the following voltages: 3.1V (red line, the worst cell from the pack), 3.38V (blue, cell in medicore condition) and 3.6V (green, the best cell from the pack).
Since i started the balancing right after the discharge, i suppose the red cell was recovering some voltage by itself since it seems charging. After 5mins it seems that the red cell really gets charged. After 20mins the red cell 'overtook' the other 2 cells and it takes another 25mins(!) for the charger to realise that it has to discharge the red cell in order to actually balance the pack. This is what puzzles me.
It takes the charger a long time to react on what is actually happeing there. The decisions what cell to charge/recharge should be taken more frequently. It seems to me that the whole balancing-process takes way to much time ...
But maybe it does everthing the righ way and its me not understanding it ...
what do you think?

[ClodMaxx]

just curious: why are you discharging a lipo in anything other than a vehicle? lipos don't need to be discharged....that's why they're balanced when charging.

[phibes]

just wanted to check out the functions as i never had such an advanced charger ...

[lincpimp]

I do not have a 720i, but I do have a pair of 610i chargers. I also never discharge lipos (never really found a need) but always charge them in balance mode.

I have noticed that the charger does not really balance much in the cc (constant current) portion of the charge, unless the cells are way out. If the cells are way out the balancer communicates with the charger, and the charger lowers the amp rating of the charge to allow the balancer time to draw the higher voltage cells down.

Keep in mind the charger charges the entire pack in series, and the balancer applys a load to the higer voltage cells to bring the voltage down to match the lower voltae cells. While it would be better to charge each cell individually (I have a charger that does this) the small gauge wires on the balancing harness will only handle about 2 amps, so it takes a while with the larger packs.

Packs that are way out of balance will take a while to charge on the hyperion chargers, no way around that. The balancer can only bleed off so much voltage (300mv, IIRC), so the balancing process will take a while.