Hey everyone! I have a solar setup that includes two 100Ah lithium batteries wired in parallel, a 100W Go Power flexible solar panel, a Go Power GP-PWM-30-UL PWM controller, and a Victron 75/15 Smart MPPT controller. I'm curious if I can connect both controllers to my setup, and if they should be wired in parallel. I upgraded to the Victron controller because I was hoping for better performance, especially in less-than-ideal weather, but when I tested it on a cloudy day, it didn't seem to charge the batteries. The voltage from the solar panel was showing around 15-16V at that time. Is it correct to assume that the cloudy conditions might be causing the poor performance? I'm looking to compare the output of both controllers, but I'll only connect them temporarily unless there's a good reason to keep both hooked up.
2 Answers
You’re right to question that setup! With your setup, those 100Ah batteries can handle a 100W panel, but connecting both a PWM and an MPPT controller simultaneously can confuse the MPPT. It won't burn out, but it likely won’t perform optimally—or might not pull in much at all. Generally, PWM controllers are less efficient with lithium batteries, which is why the Victron is a solid upgrade. It’s suspicious that you’re not getting any charge on cloudy days, but it could be an issue with how the two controllers are interacting, or simply the weather not allowing enough sunlight to hit the panel. If you're just testing, you might be okay, but ideally, you should pick one controller to avoid potential issues.
I would definitely recommend against using both at the same time for long periods. The potential for confusion between the two controllers can lead to inaccurate readings and possibly cause issues for your MPPT controller. If you’re looking for efficiency, the Victron really shines in less-than-perfect conditions compared to PWM. As for the cloudy day—yeah, that’s likely the culprit with low charge effectiveness. Try testing each controller independently to truly see their performance if you want accurate comparisons!
Thanks for the advice! I'll stick to testing one at a time then and see how both perform individually.
Gotcha! So if I want reliable data, I should stick with just one during tests? Just using the Victron should help me see how it really performs, right?