MPPT beeping – did it overheat?

[benmason]

I’ve recently added new solar to an existing system on my sailboat. Today one of the new MPPT charge controllers started beeping loudly and derated itself for a few minutes. As this happened we also lost AC power briefly, as if the inverter reset itself.

I’m thinking that perhaps the charge controller overheated but I don’t see how that would cause the inverter to reset, unless it caused a voltage spike through the busbar they’re both grounded too. The data shows that this all happened at the exact moment the system went into absorption mode.

System details
1 x legacy 100|50 BlueSolar charge controller
2 x 100|50 SmartSolar charge controllers
1 x 75|15 SmartSolar charge controller
Multiplus II 12v | 3000w inverter charger
Cerbo GX
SmartShunt

It’s on a boat in florida as it was midday with most hatches closed so it was warm (>30*C) where the charge controllers are.

The charge controller that beeped and derated itself covers the hole in the wall that all the cables run into, so lots of cables are running through the very bottom of the heat sink. Some cables are also running through the far left and far right heatsink columns, for neatness. So I’m wondering if the presence of the cables could have reduced the MPPTs ability to keep itself cool? Also, could the lack of a wall behind the unit actually reduce the airflow through the heatsink? (Does the wall help the heatsink columns work like chimneys?)

If this is an overheat issue, is it because of the cables? That would seem overly sensitive. Both 100|50s were very warm to touch at that point, but not worryingly hot. I can put a 12v fan behind the device but it didn’t feel much hotter than the one above it so I’m worried about both in that case.

And then what caused the AC power to turn off for a second? All these devices are grounded to the same bus bar as the inverter. Could that have received a voltage spike and protected itself?

Thanks in advance!

[pwfarnell]

The point where absorption starts is the point with coincident max output volts and amps. But also looking at your PV output, not long after it had reached peak power and heat soaked for a while.

The cooling is not ideal, I can not categorically state that the cables etc are an issue but it is quite a bad idea to do this. The heat sink is designed to have large enough channels to get enough air through. Added to this, the cables generate heat from resistance and are rated for duty in free air or ducts, but not in heated ducts. Poor installation on both fronts. Get your cables out in the open.

In terms of the inverter, the sudden loss of a supply of power to the DC system will have caused a voltage dip, no idea how large or what else happened in response. You could look at the SmartShunt voltage on VRM but this normally misses fast transients.

[benmason]

The voltage dip makes total sense and I can see it in the DC data too.

I’ll pull other mppt the cables out too.

Thanks for the response.

[benmason]

I removed the wires from the heatsink but the alarm went off again today.

It hasn’t for the last few days while pointing a fan at the unit.

Today I raan it without the fan after removing the wires from the heatsink. The alarm went off just now, and the heatsink was showing a temp of just 37C / 100F.

It makes me think that the unit is faulty, given that the fan seemed to stop the issue for a few days, so temp is the likely cause. But yet the unit seemed to trigger overheating behaviour when it’s not actually too hot. I took a reading of 42C on the heatsink an hour before the alarm went off.

Any thoughts? I’ve submitted a support request with Victron.