Hi, I have 3 solar panels in series total of 560 watt going into a 30 amp MPPT which goes into a lithium battery. When the battery gets above 13.2 volts it goes out of zinc with the MPPT. Over a short period the MPPT will start rising to about 13.8 volts but my battery will only be at 13.3 13. 4
volts. Once the MPPT goes into absorption it will not come out again. So I have replaced the MPPT, the battery, replaced all the fuses and the wiring to the battery. The solar gives the correct voltage at each solar panel and also at the MPPT. Has anyone come across this problem any ideas would be most helpful
When you have high current charging the battery you will get a voltage drop along your wiring. What gauge / area of cable do you have and what is the distance between the MPPT and the batteries. Dp you see the maximum charge current of 30A during this period.
Yes I have seen the max current, the run is less than 2 metres and I am using 10 mm2 cable, I am getting the same voltage at both ends. Thanks for taking the time to respond
The cable details predict about 0.2V drop at 30A, a bit more for connection losses, fuses, isolators to give 0.3V drop which matches your figures so you should be OK with that. Not sure what the issue is.
Voltage drop calculator
Thanks for getting back to me, the problem is that once the batteries get to about 13.2 v the mppt will read about 4 or 5 volts higher than the batteries, if the mppt goes into absorption mode it will stay in absorption mode no matter how low the batteries go. The mptt goes into absorption mode when my batteries reach about 13.5 volts. This has happened overnight.
Have you checked the voltage of the output terminals of the MPPT and the battery terminals when this happens.
Are you using a non Victron standalone lithium battery with built in BMS, if so does this have Bluetooth.
Often the cause of the voltage jumping up on an MPPT is the battery BMS shutting down charging and the MPPT being slow to respond. The BMS can shut down if the charge current is too high or if one cell is at a high voltage if the cells are unbalanced. Have you checked your battery from its app for balance and status.
Yes the voltage is fine when the mppt is Not in absorption or float, when in absorption everything seems to shut down and the mppt turns off completely. At first I thought it was either the wiring or fuses so I replaced all, then I thought it must be the mppt so I replaced it, then the only other thing was the batteries so I have replaced them.
Whilst writing this the batteries went into absorption with only 5 watts of power going in as it is 8 15 pm here and it blew the 100 amp fuse I had protecting the battery. Where is the mppt getting the voltage from if not the battery.
Many thanks for your help, it’s definitely driving me crazy.
The battery is the only source of enough power to blow a 100A fuse and normally only if something extremely high power turns on or goes short circuit.
Your symptoms are unusual and I am out of ideas especially as you have changed everything. You could capture screenshots of your mppt settings and the mppt status page, that might give a clue, but Internet diagnosis is hard for unusual cases.
