Inverter kicks out when microwave is started

[racatk]

I have a Victron multiplus 3000, 3 Battle Born batteries, Victron BMV battery monitor. I have a GE 1000w microwave. Sometimes it works fine, most of the time it instantly shows low battery warning and runs for less than 20 seconds before the inverter shuts off. I have about 9ft of 4/0 Ga. wire between batteries and inverter.

 

[DonTom]

Welcome! I see that is your first message.

First measure the DC voltage under load right on the battery, on the wires to the inverter.

Then measure the DC at the inverter input under load.

Watch them both for at least 20 seconds.

-Don- Okeechobee, FL

 

[silversport]

first question, how old are the Battle Borns?

 

[racatk]

first question, how old are the Battle Borns?

6 months

 

[racatk]

Welcome! I see that is your first message.

First measure the DC voltage under load right on the battery, on the wires to the inverter.

Then measure the DC at the inverter input under load.

Watch them both for at least 20 seconds.

-Don- Okeechobee, FL

By under load do you mean with the microwave or something lighter

 

[racatk]

By under load do you mean with the microwave or something lighter.

Yes this is my first post and I am a bit challenged when it comes to my Solar system. Everything else works fine and batteries stay above 70%.

 

[DonTom]

By under load do you mean with the microwave or something lighter

The best would be to find something to cook and put it in the MW. Something that will take a few minutes and then do your testing.

-Don- Okeechobee, FL

 

[DonTom]

6 months

Lith batteries? How many AH?

-Don- Okeechobee, FL

 

[racatk]

100ah each.
I'll give it a shot.

 

[DonTom]

A large cup of water in the MW oven will be a good thing to test with. Use a large MW safe cup, of course.

-Don- Okeechobee, FL

 

[Gary RV_Wizard]

It seems evident that the amp load of the microwave is high enough that the batteries cannot maintain an adequate voltage to the inverter, causing the inverter to shut down. Not really surprising, since a 1000W (output) microwave typically draws north of 1500W to produce that much cooking power. 1500W @ 12.0v is 125A plus the inverter loss (10%-20%?), so roughly 150 amps. That's will cause a substantial voltage drop and I'm confident that the DC voltage measurement will show that. The question is why. It sounds as though the batteries can handle the load at full charge, but at anything less than 100% the voltage drops within a few seconds.

Since the 4/0 wire from battery to inverter is adequate, my guess is that the wiring between the three batteries is either too small or the connections at the battery terminals are poor, causing excessive power loss at those points.

 

[creativepart]

What settings do you have on your Victron Inverter for LVCO? When the microwave starts heating it will draw a lot of amps and the batteries will temporarily sag and the voltage will drop. If you've set the LVCO for something too high then, yeah, it will cut off just like you've set it to do.

I have a Magnum inverter. I set the LVCO for 12.1v because I was thinking that to reach that voltage my batteries would be at 50% state of charge. But even with the batteries at 100% SOC the jolt from the microwave starting dropped my battery voltage down to 12.1v "momentarily" and this caused the inverter to shut down.

So, check your settings. Battery voltage can sag upon large demand. It's temporary and the voltage will soon bounce back.

 

[Bobtop46]

Use the gas stove to cook with. Don't use the microwave while boondocking.

 

[Gary RV_Wizard]

There is a minimum DC voltage required for the inverter to produce acceptable AC voltage and frequency, regardless of any LVCO setting. It will shut down if the DC voltage does not meet the minimum requirement. It's typically around 11.5v.

 

[Isaac-1]

My gut feeling is you have a connection point problem along the way, what sort of fuse are you using, and is anything along the wiring path getting warm?

 

[DonTom]

Use the gas stove to cook with. Don't use the microwave while boondocking.

I use my MW oven in both my RVs often when boondocked with no issues at all.

I changed my L-A batteries to a 300AH lith battery in my old RV.

I did this, to this new RV I am now in.

-Don- Okeechobee, FL

 

[SeilerBird]

How are the three batteries wired? If not like this then it is part of the problem:

 

[John From Detroit]

Ok with three Battle Born (I assume 100 AH if you did not state) LI batteries. and a 3,000 watt inverter... and the batteries reasonably charged (With LIs that is just about any charge at all

The suspect list
Connections (12volt side of inverter) Dirty
Cables (12 volt side of inverter) too small or too long or both.
Cables 12 volt side. Tape the negative and positive cables side by side (or use a wire loom) so they are like "Zip Cord" (2 wire lamp cords) .

As others have said measure voltage at the batteries.. Might want to measure at the inverter under a lesser load (The meter likely won't react fast enough with Microwave) say 750 watts of space heater (LOW) if it holds check for voltage drop in the 12 volt leads.

 

[8Muddypaws]

We had a similar problem even when plugged in. We dealt with it for years and finally figured out it was the microwave drawing many more amps than it was supposed to.

Replacing the microwave fixed the problem.

 

[racatk]

It seems evident that the amp load of the microwave is high enough that the batteries cannot maintain an adequate voltage to the inverter, causing the inverter to shut down. Not really surprising, since a 1000W (output) microwave typically draws north of 1500W to produce that much cooking power. 1500W @ 12.0v is 125A plus the inverter loss (10%-20%?), so roughly 150 amps. That's will cause a substantial voltage drop and I'm confident that the DC voltage measurement will show that. The question is why. It sounds as though the batteries can handle the load at full charge, but at anything less than 100% the voltage drops within a few seconds.

Since the 4/0 wire from battery to inverter is adequate, my guess is that the wiring between the three batteries is either too small or the connections at the battery terminals are poor, causing excessive power loss at those points.

Wire connecting batteries is also 4/0 and connections are tight.