Recommendations for wiring multiple panels of different wattages

[tinyejp]

Hello, all! Long time lurker, first time poster.

I'm adding solar to my new (to me) TC, and am hoping to find some advice on a proper wiring scheme. I have two 80w panels that I used on my last rig, and recently found a deal on a pair of 100w panels that I'd like to add. My controller is a 30A Sunwhale MS2430N, an MPPT unit that specs say can handle up to 450w at 12v.

I'm on the fence about batteries. I need new ones, and while a dual 6v system is tempting for the longevity, I'm leaning toward a 100ah LiFePo4 from Lisuateli (sold on Amazon at a price of around $210 on sale right now!) for the weight savings. Reviews are mostly very positive, with some dissenters. Another would probably be added as funds allow, and while I doubt 360w will keep them full for extended periods, it should allow me to be out for a good while longer than my previous setup.

So how would you solar gurus wire up two sets of panels of different wattages to my controller? I've read a bunch about losses from mixing panels, but I'd like to use what I have. Selling the two 80s and buying another set of 100s might be the best and simplest idea, I suppose...

Thanks for your time and the great forum!

 

[tinyejp]

It occurred to me as an afterthought that my existing onboard charger may not play nice with lithium batteries. I am not at the TC at the moment, but it's a 2004 Arctic Fox 806, and I don't think lithium batteries were much of a thing way back then. More reading to do...

 

[TonyL]

You will also need to look at the charging system from your tow vehicle as lithium could damage wiring and alternator.

 

[tinyejp]

Good point that I had missed! Forgive my ignorance, but what exactly am I looking for? I'm in a 21 Ram 2500 at the moment, though that alone probably isn't enough information to comment on compatibility.

 

[HueyPilotVN]

I would suggest that you simply wire them in parallel as the difference between 80 and 100 watt panels is not that much.

I would also start with the convertor/charger that you have because the solar will help top off the batteries if the charger does not fully charge them.

I would also not bother with a DC to DC convertor right now for the truck alternator as you only have 100 AH Lithiums, and they also have Solar input.

You will have three sources of charging for the battery, and it is like using three water hoses to fill a swimming pool.

The 400 watt systems that I did put out about 33 to 36 amps, so your 360 watts should put out about 30 amps.

 

[Gary RV_Wizard]

Lithium batteries can and will accept charging at a very high amp rate if the charge level has been depleted, so there is the potential for overloading the tow vehicle's alternator or wiring. This can occur if you camped off-grid for a few days and ran the batteries down to maybe 20% of charge, then hooked up to the tow vehicle and started the engine. Most tow vehicle charge wiring is designed for only 20A-30A (and hopefully fused to that limit). And even a 160A alternator can be overwhelmed if 4 x 100AH lithium batteries suddenly try to suck big amps at the same time. I'd suggest an auto-resetting circuit breaker on the tow vehicle charge line and rated for at most 30A.

Your existing converter/charger won't be optimal for lithium but should work ok, probably reaching 90% of full charge over time. And your solar can probably top of the rest of the way.

 

[tinyejp]

Thanks for the recommendations, fellows! I'll put that in my back pocket and move forward. With the camper package on the Ram, it's running a single 220 amp alternator. I will add a breaker as per your suggestion.

As for panel wiring, I may just try a few different configurations and see what the output looks like from the charge controller. My limited experience with the old TC showed that this controller is far smarter than I am, and some real boots-on-the-ground testing may yield the most accurate data.

I appreciate your help!

 

[Gary RV_Wizard]

Your Ram surely has at least a fuse for the charging line to the trailer connector, but blowing a fuse is a nuisance so a breaker is a more convenient method.

 

[HueyPilotVN]

Here is a link to the ones that I usually use.

The fuse itself can be switched for a 30 amp if that is what you want.

You can use one of them on the input to your charge controller. In addition to a fuse function they also make a easy way to disconnect the panels.

Amazon.com

 

[solarman]

Hello, all! Long time lurker, first time poster.

I'm adding solar to my new (to me) TC, and am hoping to find some advice on a proper wiring scheme. I have two 80w panels that I used on my last rig, and recently found a deal on a pair of 100w panels that I'd like to add. My controller is a 30A Sunwhale MS2430N, an MPPT unit that specs say can handle up to 450w at 12v.

I'm on the fence about batteries. I need new ones, and while a dual 6v system is tempting for the longevity, I'm leaning toward a 100ah LiFePo4 from Lisuateli (sold on Amazon at a price of around $210 on sale right now!) for the weight savings. Reviews are mostly very positive, with some dissenters. Another would probably be added as funds allow, and while I doubt 360w will keep them full for extended periods, it should allow me to be out for a good while longer than my previous setup.

So how would you solar gurus wire up two sets of panels of different wattages to my controller? I've read a bunch about losses from mixing panels, but I'd like to use what I have. Selling the two 80s and buying another set of 100s might be the best and simplest idea, I suppose...

Thanks for your time and the great forum!

normally I would suggest not mixing different size panels, however, IF your panels are all 36 cell types ( known as 12 Volt panels ) then you can parallel them. do not series connect different wattage panels.

 

[Lou Schneider]

Identical panels or groups of panels are best, but slight mismatches in panel capacities aren't as much of a concern as combining grossly different panels.

Differences in voltage affect parallel connections, different currents affect series strings. In either case the critical parameter (voltage or current) of the lowest panel will pull the rest down to it's level, reducing the potential output from a MPPT controller. Not much of a concern if the difference is in the range of a few percent but significant if you're doing something like mixing 12 volt and 24 volt panels.

What are the specs of the panels you want to mix?

 

[tinyejp]

They are indeed all 12v panels, and the same number of cells. The 80s are just a bit narrower than the 100s. It sounds like parallel will be the ticket for this application!

 

[tinyejp]

Here is a thought:

What if I wired the 2 80's in series, and the two 100s in series, and then paralleled them together? It would essentially work like two 24v panels then, right? Would the controller work more efficiently with that?

I'm such a noob...

 

[tinyejp]

What are the specs of the panels you want to mix?

I'll have to check when I get back to the shop for the specs. I'll report back!

 

[solarman]

Here is a thought:

What if I wired the 2 80's in series, and the two 100s in series, and then paralleled them together? It would essentially work like two 24v panels then, right? Would the controller work more efficiently with that?

I'm such a noob...

yes, you could do that and it would work ok, but it's not going to be any more efficient than the parallel
setup.. in fact it would be worse if you had a little shading on one panel.. go with parallel...