On Thu, Jun 6, 2019 at 9:57 PM Tony Duell via cctalk <cctalk@classiccmp.org> wrote:
> HP were fond of using NiCds as shunt regulators at that time. The did > it in many of > their handheld calculators (HP20 series 'Woodstock', HP30 series > 'Spice', etc). In > those it wasn't normally a problem (the calculator electronics drew > enough current to > pull the voltage down) except in machines with 'continuous memory' > (battery backed > RAM). There, if the machine it turned _off_ the RAM is the only thing > drawing current > and it doesn't draw enough to pull the voltage down below the zapping > level. > The should have paralleled the battery with zener with a voltage somewhat above the normal battery charging voltage but below the abs max rating of the power supply pins of the chips. They saved maybe ten cents by omitting that.
