I have been struggling to maintain an equilibrium between my needed load drain and charging of single LFP battery with Victron 12/24V 50A SmartSolar MPPT 100/50 Bluetooth Solar Charge Controller as it reads higher voltages from my Renogy 12V 200Ah battery and thus turning into Absorption and Floating mode well before the battery gets properly charged.
And the sunnier the day, the bigger the discrepancy is. For example, today my multi-meter showed 11.89V whereas Victron MPPT showed 15V. If anyone knows a solution to this, kindly advise.
You recon this is wiring issue? I don’t have much of wiring though. It is just inverter to the battery and then from the battery to MPPT and from the charge controller to a single solar panel. Which part of this should be causing issue? My thought is that the MPPT controller does not read the voltage properly.
Nic; Get your multimeter, put the negative probe on the battery terminal, and then check from the MPPT down, i.e
The MPPT battery + terminal
The busbar + if you have one
The battery breaker terminal on the mppt side
The battery breaker terminal on the battery side
The battery positive.
Even with the 100/50 cranking, these voltages should all read within about 0.1v if you don’t have much wiring, your cables are the right guage, and connections are tight.
Now repeat with your positive probe on the battery positive terminal, and your negative probe on the negative versions of the list above.
This will rule in/out any cabling issues between mppt and battery.
@guystewart or other Victron staff might have empirical data or be able to comment on how much of an effect polishing your lugs makes (that’s not a euphemism) to voltage drop. I’ve seen installers recommend something like isopropyl alcohol (for removing grime/grease/skin oils) and then 1000 grit emery paper to get a near-mirror finish on lugs.
Thanks a lot for your thoughts and pieces of advice. After thoroughly inspecting my MPPT controller, I found out that the battery positive terminal has signs of burning and even melting, see a photo attached.
I have no idea what might have caused it, but it might be a clue to voltage discrepancies. I have reconnected all the wires after giving all breakers and connections a decent cleanup. When the sun rises again tomorrow I will be able to assess whether this MPPT will be doing its job properly again.
Overheating of a terminal occurs if the terminal has not been tightened up properly, has worked loose during operation (mainly an issue in RVs and boats) or the wrong wire with coarse strands has been used. The manual lists the type of wire to use, fine strand.
Nic: your situation adds +1 to the stats of systems where loose connections are the root cause.
Good catch, and this will be a memory that serves you well.
We send out a reminder to our customers around Nov (May for you northern hemi people) after a few cracking days, to retension their terminals.
