June 10, 20242 yr if anybody can shed any light or assist with advice in any way, that would be very much appreciated. 3kva Axpert-type inverter 24v battery bank Incoming pv voltage ~44v Inverter works. When PV is connected, it registers 24v and starts charging. When charging, every few seconds, it shows it charges at a volt or two less, gradually down to the voltage of te battery bank. Operating voltage range correct at 30 – 32 vdc Max v 60vdc Everything within specs. Once inverter has stopped charging and PV disconnected, there is still 24v between combiner box and inverter as if the inverter is powering backwards towards the combiner box. Individually tested strings and they're all good. What could possibly be the problem? If there's any help out there, we'd be most grateful!
June 11, 20242 yr 15 hours ago, Jeanne said: Incoming pv voltage ~44v So that's the open circuit voltage, where the solar cells are at about 0.6V each. So you have (a) 72 cell panel(s). Perfectly normal. 15 hours ago, Jeanne said: When charging, every few seconds, it shows it charges at a volt or two less, gradually down to the voltage of te battery bank. Does the solar power go up when this happens? It may be that as the panels heat up, the voltage goes down, and the Maximum Power Point voltage goes down. But for a typical panel, the MPP is roughly 0.5V per cell, or around 36V total. Presumably your battery won't go over about 29V. 15 hours ago, Jeanne said: Once inverter has stopped charging and PV disconnected, there is still 24v between combiner box and inverter as if the inverter is powering backwards towards the combiner box. That could be normal. It just means that your solar charger's buck transistors are leaking enough to couple battery voltage back from the battery. A 48V model would use a relay to prevent any leakage from the battery to the solar charger electronics at night; I don't know if 24V models do this. The other thing is that there are large capacitors at the input of the solar charger. They may take a few minutes to discharge. Is that voltage still present 10 minutes after disconnecting from the panels? Are you getting roughly 70% (now that it's winter) of your panels' nominal power rating near noon if there is sufficient need (battery not nearly full or sufficient load)? If not, you may have a hardware issue with your solar charger board. If so, these can be repaired or replaced, but first let's see answers to the above questions.
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