Installed 100|50 blue solar MPPT four months ago between 2 * 250W solar panels and 4 * 12V 105Ah LiFePO batteries on my canal boat. Also have Victron Smart Shunt in the system. Happily living off PV for that period, MPPT functioning as usual until today.
About 1pm while on boat, checked Victron apps and MPPT was in off status during full sun when I’ve been reading 350W from panels on most days. No charge going into batteries.
Voltage across solar input cables was 70V. (Well above the 5V above batter voltage required for MPPT to switch on)
Batteries reading 91% full from the BMS and just over that from Smart shunt.
All connections and fuses from MPPT to batteries appear good.
Noticed firware and app updates needed on devices. Installed all updates. Checked settings were as before. Still MPPT was off status
Post-firmware MPPT went to absorption status while Shunt was showing 100+W going into batteries
MPPT then went to off status again.
Placed heavy load on batteries to drain them to 86%.
Reset MPPT - disconnected MPPT from solar and batteries, left for 5 minutes, reconnected in reverse order as I’ve seen recommended in this community.
MPPT still off status
Disconnected and reconneted Smart shunt.
Checked voltage across MPPT solar terminals which was 13.2V (less than 5V over battery required to turn MPPT on) but voltage across incoming solar cables nearly 70V
MPPT still off and no charge going into batteries.
My conclusion is that there’s something wrong with the MPPT but if there are any troubleshooting steps or mistakes I’ve made then I’d be grateful for feedback.
You don’t say if you have a Cerbo or other GX device ? Do your batteries have a BMS which communicates to the MPPT anyhow?
IF the MPPT is in stand alone mode, (Not controlled by the BMS) then it may well have an internal problem, such as a blown fuse.
As you updated the firmware in the MPPT, you must have Victron connect to communicate with the MPPT. Does this show the correct battery and Solar voltages?
Hi. Thanks for the reply.
There are no other devices connected. Smart Shunt and Blue Solar mppt only. Battery BMS doesn’t communicate with victron devices. The Smart Shunt is showing battery voltage ok.Victron VE direct showing solar voltage at 13.24 volts and battery at 13.28 (image attached)
Did you click on the " why is the controller off" sentence to see why it was off, this is on the status page.
The unit says 13.2V input with pv connected. Use the multimeter to test the pv voltage on the terminal screws of the mppt. If that is 13.2V, then you have a broken supply, if it is 70V then there is an internal failure in the mppt.
Hi. Thanks for the reply.
yes I looked at ‘why is the controller off’. None of the issues around faulty wiring or no PV available apply. Multimeter across incoming solar +ve and -ve wires shows 70V but when conencted to MPPT solar input terminals the multimeter reading is 13.2V across those terminals, hence my conclusion that it’s the MPPT at fault. Also took a multimeter reading across MPPT battery terminals which showed 14.2V (different to MPPT VE direct reading of 13.28V).
My thoughts are for defective panel(s) or cabling up to MPPT.
Try to measure the current on panles cable while connected to MPPT.
It is a huge voltage drop that, if panels and cablig are correct, would have to dissipate the energy somewhere like MPPT, cables etc.
A faulty MPPT is not impossbile but really improbable, if used within datasheet limits.
Pictures of MPPT cabling and panles label might also help.
Voltage (V) is one part of power formula, the other part is current (A).
Real measurements are made under reasonable load.
If panels are in series, you can wire 4 pieces of 21W car bulbs in series and test it on bare panel cables.
Measuring the voltage and current, under load, will also help a lot.
For 2x250W panels, usable power in perfect sunlight might be around 400-450W. Considering the 13.2 voltage measured at MPPT panel input, will give ~30A of current, probably half if your panels are in series.
Quite some energy to dissipate as heat. Cables, panels or MPPT must get really hot.
Others have replied, high resistance joint, when open circuit or on multimeter no current flow so you get voltage, when mppt connected current flows, high resistance contact develops 60V loss. Absolute classic case and 90+% of the problems on here with solar not working.
