Community Forums

leadman · 06-07-2019, 08:54 PM

I currently have 5 Renogy 100 watt mono panels on our motorhome. I just bought 2 more from Renogy and want to also charge my boat battery with one of them. Sounds simple until I explain what I plan on doing after testing it first.
I want all 7 of the panels on the roof of the MH but want to separate out one panel at times to charge the boat battery which will be in the water tied to the shore. Could be up to 50' or more from the MH.
All the panels have separate wiring that meets up in a fuse panel near the current 60 amp controller. I want to put a 3 position toggle switch at the end of the last panel wire on the center terminal and run one wire from another switch terminal to the fuse panel which will hook it to the current controller in one switch position. The other switch terminal will run to an extension cord with a quick connect plug on the end. This will be full panel voltage until it get to the second 10 amp controller at the boat. This will then be connected to the boat battery to charge it.
I know there will be quite a bit of line loss but hope the full voltage of the panel will have enough voltage and amperage left to enable the controller to charge the battery.

The reason I want to do this is I already had surgery on one knee from and injury suffered when carrying a gas can down to the boat on the rocky shoreline and the batteries are getting heavier the older I get. I'm 67.

I have a connector at the MH I have been plugging a cord with alligator clips and charging the battery this way but this means carrying it up and down the incline to the shore.
Anyone ever do this? Or have opinions on my plan?

Chuck Q · 06-07-2019, 09:05 PM

I use a simple 120 watt portable that I use to charge the boat battery.
$149 Amazon, works great.

leadman · 06-07-2019, 09:16 PM

I could do that also but don't want to carry anything heavy or awkward up and down the bank. This is an Arizona reservoir so the shoreline is rocky and/or loose rotten granite. I also have severe arthritis and have had 10 hand surgeries with 3 missing joints. Thirty-five surgeries total so far.

I will finish up the fridge replacement in the MH tomorrow then will get out some wire and do some testing.

vsheetz · 06-07-2019, 09:58 PM

What you outlined is doable. Makes sence to me for your senario.

astrocamper · 06-08-2019, 09:30 AM

Use a voltage drop calculator to make sure you have enough voltage at the 10 amp controller. I just looked at the Renology site for their 100 watt panel.

VMP = 18.9 volts
IMP = 5.29 amps

I used a calculator to figure about 0.79 volts drop on 75 feet of 10 AWG wire. You should be fine with about 18 volts at your 10 amp controller. You could use a quality outdoor 10 AWG extension cable for the source of the wire. It should hold up to the rocks and UV.

leadman · 06-09-2019, 07:27 AM

I have used the drop charts before, Some where close, some not. I will do some hands on testing before I install anything in the coach.
Yesterday I got up at 4:30 a.m. to install the 2 new solar panels. First panel installed with no issues. When I turned the second panel over to install the brackets I saw that the potting material was very badly applied with at least 20 spots where there were depressions from too little material. Pockmarks if you will. I'm going to call Renogy Monday morning as they do not work weekends.
Always something with Chinese products!