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| Simple voltage cutoff schematic for solar charger, any tips? |
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| Psi:
--- Quote from: Zero999 on April 29, 2022, 06:46:26 am ---I've used that circuit before, in the same application and it works. Yes, D1 can be removed, if you can guarantee the solar panel won't be connected backwards. How much current can the solar cell produce? If it's >1A, use a larger diode, as the LM317 might not current limit until 2.2A. I would also recommend adding a 33V zener diode across U1. I had problems with the LM317 failing, which I put down to lighting strikes and the zener fixed it. Obviously it doesn't protect against a direct strike, but it will suppress shot spikes, capacitively or inductively coupled from a nearby strike. I thought you wanted to vary the battery voltage, depending on the temperature? You could make part of R1 or R2 a thermistor. --- End quote --- Panel is only 18V 350mA, so no problems spec'ing the diodes. My currently design includes a 36V TVS diode on the battery side to handle any spikes. However I do wonder if that maybe better located between INPUT and OUTPUT, since ADJ to OUTPUT is kind of current limited due to the divider resistors. |
| Zero999:
--- Quote from: Psi on April 29, 2022, 09:14:17 pm ---My currently design includes a 36V TVS diode on the battery side to handle any spikes, so should be fine. --- End quote --- That's no good. The battery doesn't need any protection. It's the LM317 which needs protecting against spikes. |
| Psi:
--- Quote from: Zero999 on April 29, 2022, 09:23:56 pm --- --- Quote from: Psi on April 29, 2022, 09:14:17 pm ---My currently design includes a 36V TVS diode on the battery side to handle any spikes, so should be fine. --- End quote --- That's no good. The battery doesn't need any protection. It's the LM317 which needs protecting against spikes. --- End quote --- yeah, you're right. Thinking about it more i agree. Needs to be between input and output. |
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