My Dad has a Smart MPPT that is not charging properly anymore.
His MPPT stopped charging properly last winter and it is unclear why.
There is a 5W charge going in even when in bulk and when the battery is low. What could be the problem?
The setup is in a boat and had 2 100W solar panels connected paralel and on a flat plane. The MPPT is connected to a lead battery of 3 years old.
The MPPT never charges more than 14W, with more othen then not 5W. During a day this comes to 70Wh of charge.
The MPPT does register the panels as expected as there is a V max of ±18 Vdc.
When disconnecting the solar panels and checking their Voc this comes to ±18Vdc for both and should be 21 Vdc according to the manual. This is with full sun and warm (24°).
Even when connecting only one ther is still no charge.
I am now looking in to the option that it is the battery as I can not think of a way that the MPPT got damaged.
Also the battery seems to take some charge as the voltage rises. There is never an absorbsion phase (the onse seen is from disconnecting).
I will change the battery either way but would like to check if there are other things at play.
Could you please help me out with finding the problem?
Below some sceenshots of the system during sunny days.
Your panels would be better wired in series, they really are at the lower acceptable voltage range and so!e deterioration may have occurred dropping them too low. Are these flexible panels, lower quality low price flexible panels on boats often do not have a long life.
If the battery was limiting charging it would be at 14.4V or whatever your absorption voltage is.
You may have a failing panel(s) or a poor connector, loose wiring to a device, poor breaker etc causing voltage drop but this normally reduces the panel voltage to the battery voltage.
These are Sunbeam flexible panels of 2 years old. I would not expect any problems with them.
They are in paralel because of shade therefore I do not think a gain can be made with wiring to series. 1 panel is always in the shade when the other is not due to the setup of the boat.
I will look into having a poor connector but as the victron and my multimeter give the same Voc I do not think this is the problem.
I will run the checklist tomorrow! Thanks for the recommendation.
The panels may be fine, but age of panel has absolutely no correlation with probability of a connector fault. In fact, the past fault statistics suggest that a fault on a newish array will almost certainly turn out to be a connector fault given the reliability of modern panels.
As you suggest, putting them in series would likely lead to lower overall production. You are right on the bottom edge of the viable solution area because of the combination of a 12v battery and a not-much-more-than-12v panel, given the requirement for the panel to produce 5v more than the battery voltage to start, and 1v more to keep charging, but given it worked before, bad connectors is very very likely. For a large array where Voc >>> Vbat, you can afford to have a lot of losses before the system is noticeably broken - with your system, the smallest drop in voltage will lead to a large drop in power produced.
Unless i’ve misunderstood the test you did, you are thinking about this incorrectly - the fact that the MM and the SCC give the same Voc just means that either the SCC voltage sense is working AND the MM is working, or that both the SCC and the MM are incorrect by the same amount (unlikely).
To know what is actually happening in the voltage drop over the cables & connectors, you need either your commissioning sheet (where you recorded the Voc in full sun when the panels were installed), or the panels spec and some guess work. One of those two gives you the expected Voc, and if measured Voc is less you can start to binary troubleshoot.
Unless you have put the MM probes on each panel’s + and - connectors, and compared to the spec sheet Voc, the SCC’s Voc tells you nothing about the amount of voltage drop in the 2-to-1 connector or the panel’s connectors.
I would put money on the fact that if this system worked previously, but yield is now near zero, its either the panels themselves or the connectors and cables, not the SCC that is at fault.
