question

wsupaul avatar image
wsupaul asked

MPPT 100/30 not charging batteries, low current

screenshot-20220504-121616.pngscreenshot-20220504-121649.pnglolscreenshot-20220504-121424.pngHi All,

I have three 100 W panels controlled with an MPPT 100/30. My battery pack is two LiFePO4 200 AH batteries. The system says that it is in bulk charging mode but even after a full day of sun the batteries report no change in charge. There is nearly no load on the system. I can confirm this by the fact that for a week of heavy rains I had my camper covered, and hence getting no sun, over wich period the charge also did not change. If I plug into shore power the batteries change very quickly to 100%. Thanks for any help you can offer.

MPPT Controllersbattery charging
screenshot-20220504-121424.png (119.2 KiB)
screenshot-20220504-121649.png (134.9 KiB)
screenshot-20220504-121616.png (157.1 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
kevgermany avatar image
kevgermany answered ·

Assuming the shunt and MPPT are wired correctly, it's saying the battery is discharging. The shunt only sees current through the battery.

Total power from solar looks reasonable. So the power from solar is going elsewhere before it gets to the battery. I'd guess you left something switched on. Or is permanently on and you're unaware. You'll have to trace what is drawing current. Current clamp meter to the rescue. Or pull fuses one at a time and see which ones allow the battery to get full solar input.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

wsupaul avatar image wsupaul commented ·

screenshot-20220507-152043.pngThanks so much for your response. So now I'm very confused. Before I posted this I left my panels in the full sun for a full day and the percentage charge never moved from 86% (see spike in history screenshot). After that sunny day I covered my trailer again for some big rains (I have a small leak that I need to address so I've been covering her during rains). And then this morning, in preparation for responding to you, I checked the charge and now it's at 100%. This doesn't make sense to me. As you can see there is a small amount of charging occuring even through the cover but it's minor and doesn't compare to the sunny day (which gave no percentage change to the batteries). Also I notice that the solar is still in bulk mode even though the batteries are supposedly now at 100%. Thanks, paul.screenshot-20220507-152021.png

0 Likes 0 ·
screenshot-20220507-152021.png (140.3 KiB)
screenshot-20220507-152043.png (135.0 KiB)
kevgermany avatar image
kevgermany answered ·

Full charge is identified when charged voltage is reached/exceeded and tail current drops to/the set level for the set length of time. You can check the settings on your unit. At this point it resets SOC to 100%. Guessing that covering the panels, but they're still charging a touch triggered a false 100% setting.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

wsupaul avatar image wsupaul commented ·
Oh interesting! Good to know. I'm still confused by why the batteries were not charged over that first full day of sun when I made my original post (and in fact didn't change in percentage at all). The batteries only show a 2W draw but the panels are collecting at a rate approaching 100 times that. It seems to me that I should have seen some percentage increase over that day.
0 Likes 0 ·