My setup is that the 2 NNW strings export through the battery so there is continuous export in daylight if the batteries are full.. both MPPTs used to do this but the smaller one has changed over time. Hence my question is my MPPT failing? It seems that it is gradually charging in fewer and fewer instances.
I now understand. Do the smaller and larger MPPTs have similar settings? Same firmware?
You could also try switching the two chargers between the two arrays to see what happens then.
Of course, these are basics but I canāt think of a solution.
This may be blindingly obvious, but it took me a whileā¦ Iāve had a somewhat similar ongoing problem on my sailboat. At mid-day, just as solar power is approaching maximum, one (or sometimes both) of my MPPTās stopped charging. Since I have no āgridā this left me with half-charged batteries at the end of the day. Iām not sure I can see it in the data posted above. But the clue in my case was a discrepancy in the battery voltage as measured by the MPPT and as measured by the battery monitor. The culprit was one or more poor connections in the cabling between the MPPTs and the battery bank. Everything looks fine in the morning. But, per Ohm, with unexpected resistance, as current increases, voltage increases unexpectedly. And it doesnāt take much R: a bit of corrosion, a misplaced washer, etc. The MPPT thinks that the battery is charged and shuts off. The battery begs to differ.
On the sailboat, my entire system gets shaken vigorously, from time to time, and the cabling gets put to the test. I cleaned all the connections, simplified the system as much as possible, and increased the wire gauge to one size beyond reasonable, which solved most of the problem. Slightly bumping up the āabsorption voltageā setting in the MPPT solved the rest. The biggest culprit, I think, is a ācheapā busbar I used as the charging bus. It seems to loosen over time for no reason. So Iāve accepted that I need to throw some money at it. This month, Iām purging all the old stuff and putting in a new Lynx system.
This has probably all been hashed out better elsewhere, but Iām rarely afraid to state the obvious.
Thank you @toddster ill check that tomorrow.
That will be my next course of action after checking all the connections as @toddster suggests.
Thanks