I recently chose to replace an older PWM controller with a Victron MPPT 75/15 charge controller, and yesterday I hooked them up to my fully charged battery bank (12.85 V before starting). I followed the instructions, that say that I was to hook up the cables in this order:
- Hook up the load
- Hook up the batteries
- Hook up the PV
Nothing happened on 1, but some leds flashed for a second or so when I connected the batteries. After that, it has seemed dead :-/ I disconnected the various cables to see if it happened again, but they all remained "dead" (no light). Yesterday was overcast/grey, so was getting 16.5-17V from the PV cables (two panels of 140W total max), and I wonder if this is the reason? The manual says it needs Vbat + 5V to start, and I guess that means it would need a minimum of 12.85+5=17.85V from the PV cables to get a starting power? Am I right in understanding this "Vbat+5V" terminology? The system is in a remote location, 3 hours from my home, so I am not able to hang around for sunshine to appear to verify ... Just had to leave and hope for the best :-/
One indication that something was happening is that the initial voltage of the batteries (same reading from the battery terminals as on the screws on the controller) increased after connecting them to the controller, from 12.85V to 13.2V, after a little while. This indicates they were being charged, but I do not understand how, if the controller was inactive/powered off. The LED overview in the manual did not show what "all leds off" indicated, so I assume that would imply a non-functional state.
I read some threads on the same topic for this controller, but could not really glean much info from them (conclusion: hw error).
Points where I have deviated from the manual
- Did not connect a earth/ground wire, basically because I have no idea how to do that when I did not find any diagram or specific terminal marked "GND" or something
- Connected everything while the controller was not yet mounted. The manual says it should be mounted vertically, which I did after connecting everything, but I cannot see how/why this should matter.
Debugging info:
- Voltage reading from BATT screws on controller: 12.85V
- Voltage reading from LOAD screws on controller: 12.85V
- Voltage reading from PV screws on controller: 16.8V
- 4 Concorde Sun Xtender 2580 batteries in parallel connected to bus bar
- Charge controller connected to 100A busbar (one per polarity)
- All battery cables of equal length (1m) and terminated with cable lugs or similar.
- Sufficient cable thickness. 10mm2 for batteries, 6mm2 to load, 35mm2 to PV (long length).
