Renogy Solar performance comparison

So I’ve been having trouble keeping my battery charged in the winter here in Central BC (short days, low sun). In a thought that maybe it was my ‘salvaged’ gel battery from work that was the issue. I pulled the trigger on a Renogy Lithium heated battery, a new Wonderer controller, and BT monitor.

This afternoon after installing it, I see that I’m only getting about 4W out of my Renogy 100W flexible panel on the roof of the rig. So at that I’m only getting .4A of charging which is barely enough to make a dent.

Does anyone else have this similar setup? How is it performing? I wonder if I have a bum panel. The whole purpose of getting the heated battery was to help in perform in the cold. But it needs 4A charging in order to activate. I don’t see that happening the way things are right now. I need at least 54W coming out of that panel in order to get the required 4A at a 13.5V float voltage (+/- cable loss)

I have had no issues with my renology gear. Dont know how to answer your question perfectly as I dont know what the cloud cover was like or the direction of your panel (laying flat on the roof at a higher latitude means that tour angle to the sun is even worse). Also what size wire did you run from your panel to your mppt? How long is the run of that wire… so many variables

Oh and my renology 100w flex panel on my truck puts out 17w in my garage with the garage lights on.

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Holy shit, 17W from you light in your garage. Jesus; I’d say there must be something wrong with my panel then. The panel was in the shade, somewhat and currently flat on the truck. Maybe tomorrow I’ll check it in direct sun. I’m using standard Solar cabling which I believe is 10AWG, I’d hazard to guess it’s less than 15’ from the roof to the back right corner of the rig. I also didn’t check today to see if it had some ice build up on it. But it did the same thing on the weekend, and couldn’t rely on it as the power source for my diesel heater.

I may have to stick with carrying an extra 100aH battery I have on long trips.

did you check the open voltage on the panel?

Yeah I’m pretty sure it was 24v…but I can’t remember if that was my old panel. Maybe I’ll check it again tomorrow. I just checked the spec sheet and it should be 22.5V So I’m going to confirm that. Is it safe to say if it’s below that that I have some bad cells?

You might have some bad cells. I also run a cheap automatic battery isolator so my battery charges when I drive… figure use both to be safe

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Yeah I looked into that, unfortunately because I’m rocking a Lithium battery it is not advised to connect it to the alternator. I’m hoping I don’t have some bad cells, the panel is siliconed and VHB taped to the roof :unamused:

I’m kinda bummed because I thought this expensive battery was going to be the solution to my dilemma. But at the end of the day, batteries don’t like sub -20C temps regardless of makeup. I’m thinking I may get a Nico 5A charger to set up for shore connection when I’m at home to keep the battery happy.

You could also run a DC to DC charger and have it switched on with keyed on power.

I went cheap and used a small rv tank heater on my battery to keep its lead acid self happy


Yeah I really thought I’d have this dialed; but I don’t think it’s going to make much of a difference from the salvaged Gel battery I had. Only time will tell I suppose. I’ll get a chance to test it out next weekend. But I will definitely be bringing an extra battery. If I remember tomorrow I’ll look into putting some insulation around that battery now that there’s more room in my compartment. That should help hold the heat in.

I was just looking at DC to DC’s with built in MPPT. That’s the route I should’ve gone, but I cheaped out on the controller and just got the PCM 30A. But it’s all speculation until I get some sun on that panel.

I have the 30amp PWM wanderer controller, 50ah Renogy LiFePO4 battery, and 175watt renogy panel. It seems to pull at least 35-40 watts even on cloudy winter days.


That’s a very similar setup, except have 100W panel and 100aH battery. I’m really going to have to dig into this tomorrow. It’s looking like I might have a bum panel. Would you think scraping ice off it would damage it?

I have had flexible panels still work well following a lot of physical abuse, but have settled on using rigid panels partly for their longevity.

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I hope to have a similar set-up done here in a few days, will report back. 100w flex + 100ah lithium as well

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Google shade affects on solar panels. Each panel is configured differently but a lot of the less expensive panels don’t have many bypass diodes to handle partial shading. If shade was hitting your panel there is a chance that it was essentially preventing any energy from going to the panel. I have 4x 100W panels, 2x 170 Ah lithium batteries, MPPT solar, and DC to DC. I knew about the problems caused by shading going into my design (MS in Computer Engineering) so I connected my system with two parallel circuits of two panels each to increase my odds of getting a charge when one of the lines was shaded.

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Thank you so much for the insight. I discovered this this morning. When I was driving around at one point the panel was putting out 14w in the sun. Turned a corner and, whammo, it went away. So that’s totally what’s happening. I’ll be looking into a dc to dc system in the near future.

Where do you have all the room for those panels? I’m thinking of adding one more panel. The funny thing is I need the power mostly in the winter when the sun is low. In the summer don’t need as much power.

You can see my solar setup here. Four panels basically take up the entire roof with enough room to spare on one side for skis.

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@PNW Now you really got me thinking. It seems from my reading that adding DC to DC capabilities is not as easy as plug and play. Because I have a Wonderer controller, I realize I should’ve spent the extra bucks and just got the proper DC to DC MPPT controller.

Where I’m still scratching my head is, if you build your own system. Do you need a way to switch between Solar, and Truck charge? Or is it ok to run both systems ( I know the DC to DC system will only turn on when 12V is keyed on)

What I’m thinking of adding to my setup is a 20A DC to DC charger from Renogy, using a 50A Terminal fuse, 50A breaker to feed the unit, then a 40A ANL fuse to the battery system.

The battery performed as expected yesterday at the ski hill with the kids running the heater for 5 hours (diesel). Today will be the test to see if the 100W panel can bring the battery back from 12.3 to full charge. If it doesn’t then I definitely need to look at a secondary charging option.

It should be totally fine to run both systems, no need to switch between truck and solar charge they will do it on their own. I run both systems at the same time with no issues as neither one of the systems will overcharge my battery so if one is putting out more juice than the other the lower one just reads it as a charged battery and doesn’t push any power to the battery.

as for fuses I run a 100A for my direct charge system with the alternator and a 20A breaker to protect my MPPT. after that it all goes to the fuse box of doom to run everything else. Not sure that you would need to fuse after your charge controllers to protect that battery but I am not running lithium so it may need it.