Solar charging a battery while using it

Hi I recently built a drone and I am trying to incorporate a solar panel such that I can charge the battery while it is being used while flying.

I found this mppt but I was wondering how I can wire my lipo battery such that it is being charged and used at the same time.

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Just split the line from the battery into two - one connecting to the charger and the second one to the ESC’s or power distribution board, if you have one.

More info on manufacturers website:
(Also important to pick correct version)

Something like this will work if you don’t want to solder something yourself.!USD!4.99!4.49!!!4.99!!%402101ec1f16957753379571544eaa34!65101707112!sea!US!0!AB&curPageLogUid=kSIXMSFBr1TR

You’ve posted in the Copter section, so if you do have a copter that would make adding any sort of panel and charger counter-productive due to the weight. You get longer flight times by improving efficiency = better parts, better design, better tuning, minimise weight.
Large sized copters would use some form of petrol powered generator (or similar) to keep batteries charged during flight, and that is not cheap or easy.
An RC Glider needs about 3m wingspan for solar cells, and a manned glider needs about a 22m wingspan.

You might be able to make a charging landing pad though, so when the copter lands it starts automatically recharging. Solar cells could complement or feed a normal charger to minimise power usage from the grid.

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I read at many sources that a LiPo cannot be ‘charged’ and ‘discharged’ at the same time. And it makes sense that since current can only flow in one direction in case of DC, either the battery charges or discharges.
As discussed here, your solar cells must provide power greater than that required by the load so that the excess power can be used to charge the battery.

correct me if I am wrong.
I would like to do more research on this topic as it can help in increasing the total flight time significantly.


It is just like an off grid solar power system,…which I happen to have and have installed a number of.
Yes, you can’t have both charge and discharge at the same time. The way it works is:

  • If the solar panels produce more electricity than what is needed, then the excess will charge the battery
  • If the solar panels produce less than what is used, than the rest of electricity (electrical current) required to power the drone (or other devices) the remaining electricity is taken from the battery. So this means the battery should last longer as only a reduced amount is taken from the battery
  • If the solar panel(s) don’t produce any electricity (i.e. cloudy day) then all power is taken from the battery.

Remember: Electricity takes the path of least resistance

The same can be said about water. → Imagine an old fashioned water powered flour mill - powered from a river or creek. If you now would attach a large water storage tank or dam to the water stream you would essentially have the same effect.
…If more water than is required to run the flour mill is available, the tank (or dam) will fill up. If less water than required is available some water will come out of the tank (or dam) to help power the mill.
In a drought whereby there may be no water in the stream, all remaining water will flow out of the tank (dam) until empty. At this stage of course the flour mill stop working.

So there will be some out there talking about the resistance of the load compared to that of the battery ,…yada,yada,…but this doesn’t change the basic principle just like a few rocks in the water stream wouldn’t greatly impact on the example with the old fashioned flour mill.

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Okay, Understood :+1:
Its clear now