[wjdennis]

NihaoMike, that is exactly how I charge my Li-ion cells each night. It is a constant current 30A until the first cell reaches 4.2V. Then the charger gets turned down to 2A and shunt regulators hold all cells from going over 4.2V. When every cell reaches 4.2V, I turn off the charger.

So for the first 80% of the charge cycle, it is constant current.

But back to my original question. While driving and having one pack supply current to the other, I'm not really talking about charging the cells. It's just that Pack A would supply a constant 70A to Pack B.

During flat driving, Pack B would be supplying 30A and Pack A 70A.

When going uphill, Pack A would continue to supply 70A, but Pack B would supply whatever additional current was needed, say 120A.

When going downhill, Pack A would continue to supply the 70A and add a little energy back into Pack B.

But neither pack would be "charging". Both packs would be using up their energy during the drive, with Pack A occasionally shuttling a little of its energy into Pack B during downhill driving.

dcb, if you're reading this thread, I'd like to hear more about why you think lithium is inefficient when using constant current as I've described. I've certainly never heard that before.

Thanks.

Bill