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Inverter tripping fuse

elewis33

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Feb 13, 2020
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I built my own little solar power pack https://diysolarforum.com/threads/diy-solar-power-pack.8847/ and recently added a 12 volt fuse panel to it. So as you can imagine the primary 12 volt positive comes into the fuse panel and I have a single fuse for the 12 volt outlets (one cigarette outlet and one dual USB charge port).

Prior to adding the fuse panel I could plug my 300 watt inverter into the cigarette outlet and it would run with no problem. I put a 10 amp fuse on the line that connects to the power ports and as soon as I plugged the inverter in (even with the inverter turned off) it blew the fuse. Ok, so I bumped the fuse up to 15 amp and same thing, the fuse blew as soon as I plugged in the inverter.

I'm hesitant to just keep bumping up the fuse size so wondering how (if?) I can find out what size fuse I should have on this circuit to keep things safe and make sure the inverter works?
 
Sounds like the inverter (or something else in the wiring) has a dead short with the changes, test it with an ohm meter. Then follow the circuit back looking for the short.

Check the math too, 300 watts / 12 volts = 25 amps (but when everything is off, no amps should be flowing (suppose it could be the capacitors in the inverter charging)). Be sure the wiring is rated for > 25 amps.
 
Last edited:
Your inverter may have had a melt down in connector. They often have fuses and springs etc..
Cigarette lighter outlets are typically rated 10A. You can find some 15A marine outlets. Fine for my 120W inverter.
At 300W / 12v = 25A. Any added voltage drop will increase the current to deliver 300W. I suggest a different connector.
anderson pole chassis mount
XT90 pig tails.
ATC fuse holder
 
Your inverter may have had a melt down in connector. They often have fuses and springs etc..
Cigarette lighter outlets are typically rated 10A. You can find some 15A marine outlets. Fine for my 120W inverter.
At 300W / 12v = 25A. Any added voltage drop will increase the current to deliver 300W. I suggest a different connector.
anderson pole chassis mount
XT90 pig tails.
ATC fuse holder
I have an ATC fuse on the main positive (and it also blew at one point) going to the fuse block and I just matched the fuse to the size of the only fuse I have on the fuse block right now. I'll bump that up to a 25 Amp and do the same on the fuse block size.

I do like the idea putting that inverter connection on a different/separate connector with a properly sized fuse of it's own.

Thanks for the reply and suggestions. Very much appreciated!

Earl
 
Sound like the inverter (or something else in the wiring) has a dead short with the changes, test it with an ohm meter. Then follow the circuit back looking for the short.

Check the math too, 300 watts / 12 volts = 25 amps (but when everything is off, no amps should be flowing (suppose it could be the capacitors in the inverter charging)). Be sure the wiring is rated for > 25 amps.
Excellent suggestions. Thanks so much. I'll have to learn more about reading/using my multimeter and see what's what. Thank you!
 
BTW: Is the polarity on the cigarette socket correct? Seems like your problems started after a rewire.
 
BTW: Is the polarity on the cigarette socket correct? Seems like your problems started after a rewire.
Bingo! I should have thought to check this. Thanks so much. Now 20 amp fuses are working just fine. Maybe a little undersized but better than going the other way.
Thanks everyone!
 
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