Why didn't you make this an MPPT?

For low power solar charging of lithium ion's, its not necessarily a better way to charge. For information on why we did not design it as a true MPPT, read our design notes!


For large multi-watt solar arrays that are charging lead acid batteries, you will want to get an MPPT charger. For small cells, its not necessarily more efficient. For information on why we did not design it as a true MPPT, read our design notes!

What if my microcontroller also charges batteries?

This can in VERY RARE cases cause issues where the microcontroller tries to also charge the battery through the JST connector.

If you are using a microcontroller with charging circuitry, you should add a diode into the positive line (red wire) between the microcontroller JST connector and the board JST connector, oriented so that power can only flow into the microcontroller.

This will prevent the microcontroller from using its charging capabilities to send power to the board.

What solar panels can I use?

Use any rigid, flexible, monocrystal, polycrystal, etc panels with 6V to 10V rating (12 to 20 'cells') for the best performance

5.5V panels sometimes work, 6V to 9V is really the best!

Can I charge with a solar panel on my windowsill?
The charger will draw as much current as possible, but the efficiency of the panel will be much lower. Solar panels must not have any glass or shade to work efficiently, they must be outside, pointed as best as possible directly at the sun!
The Power Good or Charge LEDs are not on and the battery is not charging.

This is a fault condition detected by the charger.  Most often it is a battery problem or voltage input problem.  This can happen if the battery is allowed to discharge completely.   The protection circuits on some LiPo cells require the battery to be disconnected in order to reset the circuit after an over-discharge cutoff event.  Often just disconnecting and reconnecting the battery will allow it to charge again.

This guide was first published on Sep 16, 2020. It was last updated on Mar 27, 2024.

This page (FAQ) was last updated on Mar 08, 2024.

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