MPPT head scratcher

[Sea Change]

We have three 450w bifacial panels, each going to its own MPPT.

I recently noticed that we weren't getting as much power as we should, and I found that one of the MPPTs was only putting 10w in to the battery. The others were up at about 250w.

I've eliminated the panel and the cable run, and I took the opportunity to swap out the MPPT itself for a spare brand new Victron that I had in stock.

I've noticed that the MPPT is sensing a much higher battery voltage than every other device. It's seeing about 14.2v, and going straight in to absorption mode. The other two MPPTs and the two BMSs are reporting around 13.8v.

The three MPPTs are all wired identically, or nearly so. The one that's playing up goes through a maxi fuse and the others use breakers instead (this was just due to what I had on hand at the time). I can't see how on earth the different fuse could account for the difference, and the BMSs agree with the two well behaved MPPTs anyway.

Any suggestions? I could do a bit more fault finding, swapping wires around, but it's tea break time and I thought I'd pick the collective brains off the forum first.

 

[Baggywrinkle]

We have three 450w bifacial panels, each going to its own MPPT.

I recently noticed that we weren't getting as much power as we should, and I found that one of the MPPTs was only putting 10w in to the battery. The others were up at about 250w.

I've eliminated the panel and the cable run, and I took the opportunity to swap out the MPPT itself for a spare brand new Victron that I had in stock.

I've noticed that the MPPT is sensing a much higher battery voltage than every other device. It's seeing about 14.2v, and going straight in to absorption mode. The other two MPPTs and the two BMSs are reporting around 13.8v.

The three MPPTs are all wired identically, or nearly so. The one that's playing up goes through a maxi fuse and the others use breakers instead (this was just due to what I had on hand at the time). I can't see how on earth the different fuse could account for the difference, and the BMSs agree with the two well behaved MPPTs anyway.

Any suggestions? I could do a bit more fault finding, swapping wires around, but it's tea break time and I thought I'd pick the collective brains off the forum first.

I have 2 MPPTs going in parallel to the same battery bank, each has 2x 315W Bifacial panels in series. (There are 4 in total) ... I set up a Victron Smartshunt as the provider of battery voltage for the MPPTs (Bluetooth network) so they don't use their own sensed values (they were about 0.1V difference).

The two MPPTs seem to be working in sync with each other, showing a total for all panels as well as their own individual output. The charging is also coordinated.

One usually produces more than the other but this is due to angles, shading and sun.

They go to Zero output if shore power is connected and the batteries are 100%

Perhaps see if you can set up a master source for battery voltage and feed it to all MPPTs with VE Smart Networking?

https://www.victronenergy.com/uploa...tworking/20723-VE_Smart_Networking-pdf-en.pdf

 

[noelex]

The first thing to try is a hard reset on the controller that is reporting the wrong voltage.

To do this, disconnect from both the solar panel and the battery, wait a few minutes, then reconnect.

Disconnect from solar first, then the battery, and when reconnecting, battery first, then the solar panel input.

 

[chris-s]

Have you measured the voltages yourself? We had a faulty breaker that caused the charger to read a lower voltage that affected its behaviour. Different kit than yourself, but similar issue.

 

[Sea Change]

Have you measured the voltages yourself? We had a faulty breaker that caused the charger to read a lower voltage that affected its behaviour. Different kit than yourself, but similar issue.

My meter is playing up a bit so I don't really trust it. Need to get a better one... preferably with all the digits on the screen working!

 

[KompetentKrew]

I've eliminated the panel and the cable run, and I took the opportunity to swap out the MPPT itself for a spare brand new Victron that I had in stock.

…

The three MPPTs are all wired identically, or nearly so. The one that's playing up goes through a maxi fuse and the others use breakers instead (this was just due to what I had on hand at the time).

What happened when you swapped out the MPPT with the other Victron?

Did the fault stay with the MPPT or with the fuse?

I had a voltage drop fault that took ages for me to track down, and was caused by corrosion on the fuse blade and holder (I had to replace both in the end).

 

[lustyd]

If they’re Victron doesn’t the voltage usually come from the shunt anyway? Assuming you have one? May be worth describing the whole system.