Sailplane Power Supply

I just redid my panel and have used individual three-way on-off-on toggle switches together with a DIY MOSFET circuit to enable switching each instrument between battery A or B in flight.

The circuit itself needs a few components (2 N-channel MOSFETs, 2 capacitors and 4 resistors per channel) to facilitate switching in-flight without dropout, but they're all surface mount and the overall circuit isn't much bigger than the simple bus bar it replaced:

http://i.imgur.com/gGsPTU2.jpg

The benefit over running everything off a single battery at a time is that each battery should hold up better with the lower current required from each individual battery, but on a long flight I could separate "priority" and "nice to have" instruments onto separate batteries if power gets low, and I don't need to decide what the configuration might be in advance.

The capacitors on the MOSFET gates give about 2-3 seconds switching time when toggling from battery A to B or vice versa through the "off" position, ensuring flight loggers etc continue to work.

I've also added a simple "always on" channel with a couple of diodes for the gear up warning.

I didn't even know it was possible to have so many complicated solutions to simple problem. My battery1/battery2 toggle switch is clearly from stoneage.

On Thursday, February 2, 2017 at 12:38:26 PM UTC-8, krasw wrote:
I didn't even know it was possible to have so many complicated solutions to simple problem. My battery1/battery2 toggle switch is clearly from stoneage.

Moi aussi.
Jim

Re working my DG 400 electrical system. Adding 2 batteries for instruments only and keeping main batts for ships power only.

I have pulled all of the positive wires off everything that is not motor related. At present there is one main ground buss.

Some of the instruments already have breakers and positive wires from the breaker to the instrument and negative to the ground buss.

Would I create any problem using this common ground buss for the instruments already on it as well as the new instruments. All instruments will be supplied by two LiFePo4 batts. The ships chemistry is lead acid and with my current plan they would both share the same ground buss.

I will be using two separate switches for the new batteries that are pull to unlock SPST.

Thanks

Kevin
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