HP97 battery pack rebuild

[Dieter]

(02-11-2016 03:08 PM)rprosperi Wrote:  I guess my basic point was that yes, NiMH cells, which are generally known to be of higher capacity and often self-discharge better, will work fine, but the charge time is often much longer (due simply to charger being designed for older, lower capacity cells), which may be undesirable, depending on how the anticipated use/charge cycles will be. As such, I should have just said it that way.

Charging times are roughly proportional to the charged capacity. What was the value for the original NiCds in the late Seventies? 1000 mAh? 1200? A current NiMH-cell offers twice or three times as much. If you want to take advantage of this, the charging time simply is 2x or 3x the original time. Of course can also charge NiMHs the way you did in the Seventies – and you'll get the same operating time as back then. So there is no specific disadvantage of NiMHs. With NiMHs you can only win in that they allow much longer calculator operation – after a proportionally longer charge.

(02-11-2016 03:08 PM)rprosperi Wrote:  I am frankly surprised it is only in the range you calculate; subjectively it has seemed longer than that, but this is on other devices.

Well, twice or three times the capacity simply means a doubled or tripled charging time. It's really that simple. ;-)

Dieter