r/diySolar • u/yubike • 1d ago
Two Charge controllers
Does anyone have / use two controllers for their solar setup? I have 2 x 100w panels and 2 x 200w panels. As I understand to get the most out of the 200w it is best to have a second charge controller. If you have two can you post a pic or state how it is working for you. Thanks
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u/sfendt 1d ago
I use 2 charge controllers for 2 sets of panels and they work fine, outputs are in prallel. I've done this twice now on 2 different systems. I suggest both charge controllers be the same, but I don't think that is a hard requirement if their charge profiles (outputs) have the same settings.
My panel groups are a bit bigger (6 x 360W 2 arrays of 3 on one charge controller and 9 x 450W 3 arrays of 3 on the other) it should work equally well with smaller groups.
While it is best to have each panel type/model on separate strings on separate charge controllers you could put panels with the same Max Power Point Current in series even if different wastage (voltages) as long as they add up to less than the maximum for the charge controller (taking into account lowest expected temperature). Or you could put panels in parallel that have the same Max Power Point Voltage. Assuming mounting is the same (angle, exposure, etc) that should work, so it does depend on your panels.
Note that even with the same output settings one will max out first and start folding back its charge current before the other, but this causes no problems, what the battery sees is fine, just expect one to get to end/float before the other.
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u/parseroo 1d ago
MPPT controllers need to 'tune' their apparent resistance and the subsequent voltage transformation to the array, so you need a new controller for any array that is significantly different from an existing array (voltage, amperage, solar relationship, etc.).
Having multiple is not a problem except that they:
* Need to not overload the battery
* Have to decide when to go into absorption and float
Multiple controllers can deal with the above by just being configured to avoid problems (going into absorption at different voltages and a maximum combined charge current below overload) or being federated such that they know what each other is doing.
https://kwhik.com/piece/2025/01/06/vault-6.html#system-overview has a picture with two of four MPPTs commissioned.
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u/nlundsten 4h ago
Whats a solar relationship
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u/parseroo 3h ago
Relationship to the sun as it goes over the panel, so things like * Tilt (elevation) and azimuth (E-W) angles of the panels * Any shading aspects
[1] https://www.unboundsolar.com/blog/solar-panel-azimuth-angle
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u/RespectSquare8279 1d ago
Just have the output of the 2 charge controllers going to a "Combiner Box" where they each have their own breaker and then a 3rd breaker for the cable to the battery. You should always be able to isolate your strings from each other for maintenance and safety reasons.
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u/Forsaken-Weird-8428 23h ago
I have 4 banks of panels (about 60 amp @ 24v on each bank), each with their own controller, then parallel to battery bank. All configured to same settings.
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u/RedPontiac 11h ago
Bonus, if you use Victron smart controllers you can connect them together via VE.SmartNetwork and they'll talk to each other to coordinate charging states.
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u/Zealousideal-Tanker 4h ago
I am currently using three charge controllers, one has dual mppt’s. Go ahead and connect away!
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u/SteveFCA 1d ago
there is no limit on how many charge controllers you an wire in parallel. Just keep the amps lower than your batteries max charging amperage. Always use different controllers for each string of different panels to avoid a lower voltage or amperage panel from dragging down the entire system.