Any ideas?
My MPPT 75/15 does not charge battery, showing the solar voltage always about 0.5 V below battery voltage. This is independent of sun exposure. Wiring has been double checked.
I would appreciate any suggestions.
This is somewhat normal. The PV voltage will raise to battery voltage when theres not enough sun, for example early morning. Once the the panels produce enough power the voltage will raise, and at battery voltage +5V the MPPT will start to work. Heres an example how this looks, yellow is battery, blue is PV
If it never goes above bat voltage +5V then the PV array is too small, not configured correctly or something is damaged
Hi Chrigu,
Thank you for your quick and detailed the response.
My problem is, that even in brightest daylight the measured voltage of the panel connected is nearly never higher than the battery voltage. Open terminals of the panels show more the 20 V, going down to battery voltage if connected. Is there any easy way to check the panel itself?
Main question would be, if the measured 20V open circuit voltage is actually what the panel is rated for. If so, then it might just not be enough.
If the battery is at 13.0V then a PV voltage of 18.0V should be enough to start the charging/tracking process.
But its also possible that the panel, or the cabling/connectors, are damaged. Has it ever worked before, so this issue is a sudden change, or is this a new install?
If you know the exact panel type, or can get access to the nameplate on the back of it, then you know for certain if those 20V are good or not.
You can also test the shortcircuit current if you have a meter capable of measuring DC current. This Isc should then again be close to what the rating says.
(With a bit of lee way, since ratings are lab results, not real world)
You are absolutely right!
Tomorrow I will check current output, I did now manage to put a tiny camera underneath my panel and got a first glimpse of the type label.
It’s 100 W panel from a not more existing manufacturer providing just 17,5 V nominal and 21,2 V open circuit - way to low for a MPPT.
I think, I should replace the panel with a better one …
Thanks for your help and best regards,
Andreas
1 Like
Hi,
To have this conversation finished, I’ll tell you the final solution. Today I did replace the panel with a Renogy Anti Shadow panel.
Even with a very cloudy sky, I’m getting about 40 Watts and 39 V. everything is now working perfectly fine. the MPPT hasn’t been the problem, but the old panel.
Have a nice weekend!
This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.