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I am charging multiple batteries in parallel using a solar panel. The batteries are not meant to be used together and their voltages might be different when connected for charging. Another issue is that the panel might not be providing any voltage. So I have been using Schottky diodes to prevent one battery from discharging into another. Can I make this more efficient by using N-channel MOSFETs as shown in the diagram below? Is there a better setup?

If a battery tries to discharge, then the comparator should switch off the MOSFET. The body diode won't conduct either. If there's no input voltage then the result is the same.

If the panel is supplying enough voltage, the body diode will enable charging and then the MOSFET should turn on and the current should then use the conductance channel giving a very low voltage drop.

enter image description here

PS: Some sort of blocking mechanism is necessary. I have a panel for charging my phones and 18650's. It outputs more power than required by any single one of them. So I want to parallel charge them. I wired multiple female USB connectors in parallel. Panel output varies depending on time of day and cloud cover and I have noticed some time blocks where some of them are discharging while others are charging.

previous wrong circuit

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    \$\begingroup\$ Randomly charging lithium batteries off a PV panel doesn´t sound like a good idea. You really need some sort of charge controller designed for those batteries. At the very least, you´re going to reduce their lifetime. At worst, produce a bad fire. \$\endgroup\$
    – F. Bloggs
    Aug 2, 2016 at 20:58
  • \$\begingroup\$ There was a mistake earlier. I have edited it and also made it clear that the batteries are being controlled and protected. In my case, its the phones which take care of this. \$\endgroup\$
    – user683
    Aug 3, 2016 at 9:16

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You need overcharge and overdischarge protection. Btw. you have mistake in your circuit. Inverting input must be connected to solar panel, and non-inverting to battery. So it would make what you expect.

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  • \$\begingroup\$ Yes, I edited the diagram. \$\endgroup\$
    – user683
    Aug 3, 2016 at 9:18

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