tcollatz avatar image
tcollatz asked

SmartSolar MPPT issues?

Hi all,

I’ve been browsing the forums here for a bit searching for an answer to my dilemma, but haven’t found it quite yet. I suspect this is due to me not understanding the issue quite well enough so not searching properly. Therefore, sorry in advance if I’m asking a question that’s been answered a million times already.

That said, I’m wondering if I have an issue with my SmartSolar 100/50 MPPT controller. This is installed on my RV along with 3 100 watt flexible solar panels (2 HQST and 1 Renogy with very similar specs). About a month ago I installed the Renogy panel. Prior the that installation (in April in WI) I was pulling in between 150 and 190 watts on a nice sunny day with just the 2 HQST panels. Once I installed the third panel I generally do not pull any higher than 150 watts, often less than 100 on cloudless days around noon. I’ve been searching for answers for a while, so my tests are about a month old now, but I haven’t seen any improvement and not found answers so I finally decided to ask for help.

The first test I did was the obvious one. Things worked good before installing the 3rd panel and so I reverted back to my 2 panel setup. No improvement, I was pulling less than 50 watts. I tried each panel individually and got the same results. I tested voltage and current at each panel with a multimeter and was getting about 19.5 volts and close to 5 amps per panel, yet when reconnected to the MPPT (via circuit breaker) I would see the input voltage drop to between 14 and 16 and pull in less than half the rated output of the panels. I tested the wires down to within about a foot of the MPPT with the breaker off and was at about the same voltage as at the panels. I also did a test removing the breaker and directly connecting the wires to the MPPT and had the same results.

Some other stats/info: I have 400ah of AIMS LifePo4 batteries (2 200ah 12v wired in parallel). Batteries were around 60% SOC at the time of the tests according to my Victron BMV 712. I currently have two panels wired on one 10awg run about 5 feet to a junction box, one panel on its own 10awg run to the junction box (tested all these wires and they were good). Have a 6awg run from roof to MPPT, about 7’ run. From MPPT it’s tied into a bus bar with 6awg about 1’ run, and from there about 10’ of 4/0 to the batteries. MPPT was set manually to lifepo4 recommendations I found from Victron, but I also recently switched it to the lifepo4 preset that I believe is a recent update. I tried resetting by disconnecting all power. Reconnected to battery first then panels. No change.

My next step will be to try wiring the panels in series to see if that makes a difference, but I don’t see why it would when I was having success previously with panels in parallel. Does anyone have any idea what might be wrong? Perhaps an issue with the controller? Or am I getting something wrong in my setup? I’m still fairly new to this stuff, so it’s definitely possible I’ve screwed something up.

Thanks in advance for any help you all can give.


MPPT Controllers
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1 Answer
JohnC avatar image
JohnC answered ·

Hi Tim. Unless you've spent at least a little time tuning the BMV for a reliable SOC, don't count on it in a troubleshooting situation. Just go back to plain-vanilla Voltage. If V is satisfied, then the mppt will back off regardless.

That said, your 3x '12V'? panels will work better in series connection anyway in poor light. Up to a total Voc of 100/ that your unit allows (leave a fair margin). Yours may spec ~22V, so well under.

Of course if the charge V isn't playing ball, then there may be more involved..

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tcollatz avatar image tcollatz commented ·

Thanks for the response John, and for pointing out some info I missed.

I did spend some time setting up the BMV712, and I believe it to be reasonably accurate. I’ve attached the setting in case your interested as well as the settings for the MPPT. I also tested in a way that I thought would rule out the possibility of the issue being that SOC was much higher than I thought. I kicked on the AC to get a big draw on the batteries and there was no change in charge current.

I will definitely give a series set up a shot and see what results I get once the weather cooperates again (doesn’t happen too often in WI). And, you are correct, they are ~22v solar panels, sorry I missed that stat.

Any ideas on other tests I can run or things I should check?

Again, thanks much for your insights I truly do appreciate it.

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