Two MPPTs connected to the same bus bars (big chunk of copper bus bars) - smaller 150/35 and bigger 250/85. Real battery voltage in the system is 54.50V, both the MPPTs set to 55.2 V absorbtion and 54.4 V float. Smaller MPPT reads voltage ok and is in bulk charging. But the 250/85A charger see 1 volt higher voltage and is in absorbtion phase… Checked voltage on its terminals (Fluke 1587 multimeter, calibrated) and it is 54,51 V. Cables are sound, voltage drop on the cables are up to 60 mV. Terminals are cool, no heat up observed. The other side of the cables are firm as well - no heat up. What is going on? Any ideas?
Today morning both the chargers are in bulk mode and 250/85 (device name “MPPT duza ladowarka”) is pumping 53 A while 150/35 (device name “MPPT mala ladowarka”) is pumping 12 A. At the same time 250/85 sees 55,23V while smaller one 54,18V:
Voltage drop on cables between MPPTs and main bus bar is 94mV for 250/85 and 14mV for 150/35. So their battery voltage readings should be off by 80mV only…
Any ideas? This is becoming annoying as most of the day half of my roof is not producing energy due to this irrelevant voltage reading by SmartSolar 250/85…
You’ve covered pretty all angles with the measurements and they look OK.
In this case it’s probably a calibration issue on the 250/85 MPPT…
Change it, if you can. The MPPT, I mean…
This is the answer l like the least;P;P Yes i can as it is quite new but now i need to provo to Victron it is not working as intended. Will try and report back.
looks like you have a very hot spot on the B+ terminal:
I would have a look at correcting this, re-terminate the wire, and use a ferrule.
Might not affect the Voltage readings much, but will enhance reliability…
