Fun with MPPT - what's causing this?

RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
Curiosity overwhelms me... 8)

I just purchased some new panels and an Outback FlexMax 80 controller, to go with my new larger battery bank. Still waiting for the mounts to arrive, that should be tomorrow. (Looks like fun for the weekend!)

While waiting, I went ahead and hung the controller and wired in my old array - a truly stellar (heh) set of three Harbor Freight panels (the 45W "kit" they sell that has almost never provided more than 20W). The nifty part is that I immediately saw an improvement in charge rate from the old PWM controller I was using. Went from 1.5A into the batteries to a whopping 2A! :roll: Hey, it's cool to see it work!

But last night and tonight the controller is baffling me. It is now dark outside, but the controller still says it's in "MPPT Bulk" and putting 0.5A into the batteries! It shows the PV side at 46V (I wired them in series for the Outback) and 0.1A. Huh? Last night when I noticed this I first switched off the breaker for the solar panels (no change) then switched off the controller. When I turned it back on it tried to track, said "Low Light" and went to sleep. I'm sure that would happen again tonight if I did that, but maybe I'll just sit and watch it, see how long it goes...

Anyone know what might be causing this? Surely the controller doesn't have *that* large of a capacitor in it! :p It's been dark for at least an hour now...

The only parameter I changed in the controller is the minimum current before switching to sleep. It defaults to 0.6A, which this puny array dips below anytime it gets the least bit cloudy. I set it to 0.2A, the lowest setting.


  • halfcrazyhalfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: Fun with MPPT - what's causing this?

    this i s a known problem with the new outback controllers you may want to call outback.

    the work around is to put it in auto restart mode this will restart the controller every 2 hours i believe causing it to become unstuck. but also does a restart every 2 hours during the sunny times.
  • blackswan555blackswan555 Solar Expert Posts: 246 ✭✭
    Re: Fun with MPPT - what's causing this?

    May be worth a look

    Have a good one
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Fun with MPPT - what's causing this?

    Well, phooey... Just what I want, to possibly have to send a fresh-from-the-box item back to the factory!

    So far, I only have the "night power" problem, it has worked just fine during the day, and I did try raising the cutoff threshold back to 0.6A last night which let it shut down. Think I'll just go ahead and install the panels, then see how it does with them. The only reason I had reduced the minimum was because the HF panels are so small to begin with.

    I'll have to spend some time on that forum too, thanks for the link!
  • AntronXAntronX Solar Expert Posts: 462 ✭✭
    Re: Fun with MPPT - what's causing this?

    Mine does same thing. I have FM60 that i bought new 1 month ago. It usually goes to sleep fine. But 2 weeks ago, i noticed it sitting in MPPT Bulk mode at 8:00PM. Funny thing, that after i've read your post, i went to check my FM60 and there it was, stuck in MPPT mode at 8:20PM again! I have set auto restart mode 2. This problem seems intermittent in my case.
  • halfcrazyhalfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: Fun with MPPT - what's causing this?

    This problem is fairly common and it seems to pop up after a partly cloudy or dreary day. i have no idea why? If it has been a real sunny day it seems to be rare. give outback time they will get the kinks worked out. there will always be little bugs pop up on new product.

    I believe i noticed Crewzer saying there may be a new software upgrade coming real soon? For now setting it to auto restart or simply force a bulk charge after dark and it will go to sleep.
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Fun with MPPT - what's causing this?

    First day down with the new panels up. Two 135W Kyoceras. The controller worked perfectly, and went to sleep dutifully at dusk. Playing with settings while on the old panel the previous two nights, it appears my controller doesn't drop below 0.5A to the batteries while running as it gets dark. Putting the cutoff point to 0.6A makes it switch off. Once it's off, the meter shows 0A.

    Guess I'll see how it does over the next week. Today was nice and sunny, just some thin high clouds in the afternoon. We have a chance for storms tomorrow, with some other mostly cloudy days in the week to see if anything happens with weak-light days.

    As an aside, sweet - I went from 2A with the old HF panels to 17.5A / 250W at peak production! Nice... (And I'm already thinking about how soon I can get two more to fill the rack I installed...! :cool: :roll:
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Fun with MPPT - what's causing this?

    If your FM60 or 80 get's "struck" at night, try increasing the "snooze" setting by 0.2 A. I'll try to remember to keep you posted on firmware upgrades.

    Jim / crewzer
  • halfcrazyhalfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: Fun with MPPT - what's causing this?

    Any progress with the charging in the dark issue?
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