I'm interested in buying a new charger but I'm a little confused on what the best way to track lipo battery pack performance over time is.
I know some just do it by feel...aka if you car gets slower then buy a new pack but I'm a bit more OCD than that.
I'm wondering if the best way to track pack performance over the long term is with a charger that can graph and log while it charges but maybe thats pointless too as it seems to me that the best way to measure battery performance is while it's being discharged, not charged. Am I correct in that thinking?
So do I buy a charger that can graph/log while discharging to an external load like a 30 amp resister pack?
I was leaning towards a Revolectrix PowerLab 6....is that a good charger for this, is there a better one?

Thanks.

The internal resistance of each battery cell is a decent way to keep track of the performance of a battery, many chargers can measure this while a pack is being charged but the resistance will also influence the batteries performance during discharge.

If just monitoring the IR is the best way to know if my packs are getting old and need to be replaced then I guess that makes finding a new charger significantly easier.

Something like this? battgo
Unfortunately it's not available for most packs

Powelab 8x2 touch. Has the Revo tags for each battery. Tracks each better, cycles, ir, etc.

I was looking at the PowerLab 8 touch but was told to steer away from it due to a flaw in it's design that causes it to fail charging when the amps start to get even a little bit high.