For charging 7v NiCd from 4.8v:
We came up with a simple circuit to use the cheap DC/DC boost regulators to boost 4.8v solar panels to 7 volts for our NiCd charging.
http://aprs.org/psat/Cubesat-solar-boost-charger-bob-a.doc
You cannot just use the DC/DC boost regulator directly because it has a peak-starting-current which cannot be met with a solar panel. So we added a transistor load switch to hold off the load until after the regulator was started… Works like a champ at near 80% efficiency.
I’m sure there are lots of circuits and parts, but this little circuit more or less worked the first time, so we are going with it.
Bob, WB4APR
Linear has a whole bunch of useful ICs for these kinds of applications. Probably Analog Devices too. Example: http://www.linear.com/product/LTC 3105. Their µModules look quite useful too
It's not entirely clear from your paper how your test rig works. The typical, simplest way of testing PV regulators is to use a constant-current source in parallel with a diode string
A good idea though, only turning the charger on if there's enough voltage. That way the rest of the system can work even if there isn't enough light yet to enable charging. It seems too many sats die to these kinds of problems
/Tomas, SA2TMS
On Thu, 2016-02-25 at 13:27 -0500, Robert Bruninga wrote:
For charging 7v NiCd from 4.8v:
We came up with a simple circuit to use the cheap DC/DC boost regulators to boost 4.8v solar panels to 7 volts for our NiCd charging.
http://aprs.org/psat/Cubesat-solar-boost-charger-bob-a.doc
You cannot just use the DC/DC boost regulator directly because it has a peak-starting-current which cannot be met with a solar panel. So we added a transistor load switch to hold off the load until after the regulator was started… Works like a champ at near 80% efficiency.
I’m sure there are lots of circuits and parts, but this little circuit more or less worked the first time, so we are going with it.
Bob, WB4APR
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Robert Bruninga -
Tomas Härdin