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Old 10-26-2021, 04:40 PM   #1
Join Date: Sep 2021
Posts: 54
Solar trickle charger questions

I have a sunsul 20 watt solar panel that was given to me as a gift when I purchased my new travel trailer. I have 2 12v batteries wired from the dealer in what I believe is called series? I have a picture attached of battery setup and solar system. My question is do I run the alligator clips from the solar to positive on one battery and negative to the other when wired like this? Or both positive and negative to same battery? I understand this little panel will not do much of anything for me but with a boondock trip coming up I figure I better take everything option I currently have.
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Old 10-26-2021, 04:52 PM   #2
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How my solar is hooked up, so it might be the same for yours.
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Old 10-26-2021, 05:51 PM   #3
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Either way will work. 20W solar panel pointed directly at the sun in the middle of summer might put out 1.4 amps. Probably not worth the trouble of hooking it up.
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Old 10-26-2021, 07:15 PM   #4
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Your two 12v batteries are connected in parallel not series or you would have 24volts.
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Old 10-26-2021, 07:25 PM   #5
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You would connect your solar panel clips to the positive and negative of the same battery, as said above they are wired in parallel, not series.

The amperage of that charger will do OK as a trickle charger to maintain the batteries when the RV is not in use and the battery cutoff switch is in the disconnect position, they won’t provide enough power to make much difference while boondocking.
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Old 10-27-2021, 03:18 PM   #6
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Your way will work

I had the exact same question, but only after I killed one of my batteries by hooking the positive lead to the same battery as my negative lead. Thanks to a helpful forum member, I hooked my 5W solar trickle charger by putting the positive lead to one battery and the negative to the other (after I purchased two new batteries because I killed the one doing it the "old" way). All I can say is wiring my batteries and trickle charger leads as you described worked...both batteries remained charged all summer, no problems. Your 20w trickle chargers certainly ought to provide enough charge to keep your batteries charged. Good luck.
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Old 10-27-2021, 09:43 PM   #7
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The simple answer is that the solar charger gets hooked up to the exact same posts that the cables going from the batterie to the RV are connected to. And the batteries are wired in parallel.
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Old 10-28-2021, 06:39 AM   #8
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DougW, I believe you are mistaken. NavyLCDR is correct. 20 watts is just a trickle charger. You could probably leave it hooked up in storage to keep your batteries charged, but charge controllers are so inexpensive it seems silly not to have one installed. Connected in series would be pos. to neg. You are pos. to pos. which is parallel, and correct. If you are very careful with power, you can probably go a few days without damaging your batteries. Get a Volt Ohm Meter (very inexpensive) so you can check your battery voltage. If you get below 12.1 volts you are damaging your batteries. Definitely hook up the solar. Every bit helps.
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