On Mon, 28 Aug 2017 18:56:01 +0000
Jim H  wrote:

> On Wed, 23 Aug 2017 22:29:55 +0100, in
> , Folderol 
> wrote:
> 
> >
> >First off, charge voltage is inversely proportional to temperature, and one
of
> >the companies I contacted was kind enough to send me a schematic of a simple
> >compensated voltage regulator, with a thermister which had to be *in*
*Thermal*
> >*contact* with the battery under charge.  
> 
> 
> Would you care to share that schematic? Please?
> 
I'd be more than happy to, only that was a long time ago, and that along with
many other documents of the time have long since disappeared.

From memory there wasn't much to it. An op-amp driving a power transistor as an
emitter-follower, then a diode to protects against the battery feeding back
when the power was off. Control was from a high resistance feedback path from
the battery terminals (so negligable drain on the battery) and somewhere in
that
lot was the thermistor and a preset pot.

Current limiting was crude - just a resistor in series with the transistor
collector.

Not a lot of help I'm afraid :(

Hmmm, thinking a bit more. The thermistor and preset weren't directly in the
feedback but in the potential divider producing the reference voltage.

Actually it's remarkable what you remember once you actually start thinking
about things. One resister from the battery + to the inverting pin of the
op-amp. Something like 470k I think, and the same from there to the common
ground.
A resistor from a zenner reference to the non-inverting pin of the op-amp, then
resistor - preset - thermistor from there to ground. No idea what the values
were, nor what specific thermistor it was


-- 
W J G

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