Re: Still possible to be an idiot even though you drive a hybrid
Yeah when the meter shows full, the batteries are only at about 80% actual capacity. Same for zero bars, about 20% is really left.
Actually I never heard that fully discharging NiMH batteries was bad for them (unless you leave them discharged for a while, then they tend to short out, because the self-repairing membranes expend charge in the self-repair process). I have read a lot on NiMH tech and not seen that one before.
The problem may be that NiMH batteries tend to have slightly different capacities, thus when the first battery goes empty, the others will still force current through it. That can cause what is called cell reversal, effectively creating a dead cell in the pack. Don't know how many dead cells it takes before the computer will declare a dead pack. Likely that is what they are trying to avoid. We have heard that the HCH cells are capacity matched, presumably reducing the variation enough to where 20% reserve is a wide safety margin, allowing for the long warranties they provide.
Overcharging is a different story, that is always bad, especially at high charge rates. Older smart chargers used to back off their charge rate for the last 20% of charge which took as long as the other 80% did (new ones use a technique called constant pulse charging which mostly eliminates the need for the back-off). The HCH doesn't have the luxury of slow charging the last 20%, and I don't think constant pulse scales to the massive amperages the HCH uses, so it just quits at around 80% full. A pretty decent compromise aimed at maximizing battery life.
Maybe that unravels the mystery a bit?
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