question

underkwang avatar image
underkwang asked

MPPT load output turning on and off

I have a basic solar setup consisting of a panel, battery, MPPT 100/20, fridge, lights and so on. The appliances are connected to the load output of the MPPT. Everything works perfectly unless the fridge overheats because of external heat. In this case the fridge will protect itself by shutting down and blinking its light in a cycle of 4 sec on and 1 sec off. For some reason this cycling will cause all the other appliances to go on and off in the same cycle. The load current is oscillating between zero and only a few amps according to the Victron app. What could be behind this phenomenon?

MPPT SmartSolar
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
Trina avatar image
Trina answered ·

= Brown out! Your housebank is too small!

How much current start up does the fridge need? They usually use significantly more to get the compressor started (dropping back down to less amps after a bit) and it sounds like you are having the dreaded "Brown outs" -it's taking everything down with it as it tries to start up again!


Solutions:

1. Have no other loads on when this happens (or figure out exactly what else could be on while the fridge compressor pulls all those amps to get back on task)

2. Increase your battery bank size to handle the increased load of the fridge compressor with the other things you want to keep using whenever this happens (and maybe solar PV increase as well).


There is also a way to have everything else shut off with a relay while the fridge gets back started up if IF space constraints are an issue vs. battery bank increase, but that's a more complex issue. Might be able to use the relay function on the bmv battery monitor depending on your setup.

Really you are too close to margins and over max when the fridge gets too warm and needs to pull more amps.



1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

underkwang avatar image underkwang commented ·

Thank you for the reply, but I don't think the problem is in the battery bank. The battery bank is definitely large enough.

However I studied the subject a bit and I think I know what's the problem. The fridge has a capacitor, and when the fridge goes into the safe mode during overheating, it's charging and discharging the capacitor. This cycling draws more amps than the MPPT can handle. As I said before, when looking this cycling in the Victron app, the load current is oscillating between zero and only a few amps. The actual number is actually much higher because the current spike is too fast for the app to display.

My solutions: 1) Making sure the air ventilation around the fridge is sufficient enough to avoid the overheating problem in the first place. 2) Disconnecting the fridge from the load output and connecting it straight to the battery.

0 Likes 0 ·