On 2 Dec 2018 at 9:04, Harold Hallikainen wrote:

> This now reminds me of a shunt regulator I did to equalize a series
> string of lead acid batteries in an electric car. There I used a PIC
> to PWM a transistor that switched a power resistor on and off. The PIC
> also drove an opto isolated open collector bus with the battery
> voltage, battery current (sensed the voltage across the negative lead
> going to the next lower battery), temperature, bypass current, etc.=20
>=20
> I suggest using power resistors as the load, as they are cheaper per
> watt than power transistors. I also don't really like the variable
> resistance of using an incandescent lamp as the lad. I did, however,
> use an incandescent lamp as a current regulator to charge the
> batteries. The charger consisted of three SCRs acting as switched
> rectifiers (to turn off the charger at the end of charge) from a 3
> phase wye service. These drove the incandescent lamp to the positive
> side of the battery string. The incandescent lamp was bright at the
> start of charge and dim at the end of charge.=20

Thanks Harold. I'm not sure power resistors are so cheap, just looking arou=
nd at=20
some 100W and 200W parts. Will do some better costing comparisons when I ha=
ve=20
narrowed a couple of circuit options. A lamp (or a number of lamps) is cert=
ainly=20
somewhat attractive... with a risk of a blown lamp causing loss of voltage =
regulation,=20
but on the other hand high power dissipation in a small device, little or n=
o heatsink=20
required, and inherent power indication~!

--=20
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