question

lorettaboy avatar image

Looking for advice on my planned setup!

Hey everyone. My current setup is 6x40W Coleman solar panels, using 2 cheap Coleman charge controllers, connected to 2 Trojan T105 6V golf cart batteries.

My new plan is to add a 100W solar panel to my system, along with the Victron SmartSolar MPPT 100/20 charge controller to replace the cheap Coleman units. I believe this will put me at about 19.6A. Does anybody see any issues with this new setup?

I'm also wondering about wiring this all up to the charge controller. My current setup uses SAE Y branch connectors. Any advice is appreciated!

mppt smart solarsolar sizing
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4 Answers
randy-putnam avatar image
randy-putnam answered ·

I would consider a 100/30 MPPT. I think you may be at the limit of what the 100/20 can do.. I’m running 2 170W panels, wired in parallel for 340W into a Victron Smart 100/30 and out to a 200AH house bank of 2 Battle Born 100AH LFPs. The Trojans are really good LA batteries but how old are they? Whatever you decide an MPPT controller will be more efficient than the cheaper PWM controller. And mono panels will be more efficient than polycrystalline panels.. Don’t know what you’re using this for (RV, Van, Boat, etc). More info would help.. Oh, and I’d get better connectors than SAE ones.

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Thanks Randy; i'll take your 100/30 recommendation into consideration.

I'm using this setup on a 25 foot travel trailer. We boondock for most of the summer. My Trojans are only a year old, and are my second set. I couldn't determine whether my panels are poly or mono, but they are blue in color: Coleman 40- Watts, 12 Volt Crystalline Solar Panel with Stand. Includes 7 Amp Charge Controller. Weatherproof. Portable. (Silver): Amazon.ca: Patio, Lawn & Garden

Unfortunately the panels came with the SAE connectors, so I don't think they can be changed. I'm also considering adding an inverter to my setup, but not sure it's worth the added cost and setup. My fallback for 120 is a honda generator.

Got it. I went to the Amazon site. You have 6 of these? Hooked up in parallel? (Pos-pos, neg-neg) If you’re thinking about adding panels there are a lot of choices. If you want to mount them on the trailer then I’d go with monocyrstalline panels. They come in various sizes and wattages. You can check their power profiles on line (wattage, amps, etc) and that will help you decide on the size and kind of controller to get. I prefer the fixed, aluminum framed panels. There a zillion you-tubes on installing panels and controllers on RVs so you’ll get plenty of resources to go by. And the manufacturers of many have good tech help via their websites. Just don’t go down too many rabbit holes because theyre out there..

marky01 avatar image
marky01 answered ·

I would suggest you look at the MPPT size calculator on the Victron website, you can input Victron solar panels or use custom figures in there, it will give you a better idea of what will work together

https://www.victronenergy.com/mppt-calculator

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dazey77 avatar image
dazey77 answered ·

I can't believe no-one else is pointing this out so perhaps I am missing something in what you say.

You can't hook a 100w panel up to a controller with 6x40w panels. You have to have a balanced solar input with all the panels the same.

You would be best off using two controllers, one for the new 100w panel and another for the coleman string.

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DeVo Tyler avatar image
DeVo Tyler answered ·

What all are you trying to run? Have you done a power audit?and what are the specs on your panels

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