Microwave Tripping Inverter: Wiring, BMS, or System Mismatch?

[shadowman114488]

Seeking opinions for an issue I am having.
My fiver has 400W of solar, an inverter, and a LiFePo4 battery. The solar and the inverter were factory installed. See the photo for the specs, from the owners manuals, of the relevant components.

I wired my microwave into the inverted circuit of my rig so I could use it while boondocking. I tapped into the wire for the television to do that. The microwave is an inverter model so it has just one start-up surge - not multiple start-up surges like a non-inverter micro has as it pulses while operating.

My problem is that I cannot use the micro on 100% power without the inverter shutting down after just a few seconds. Then I have to restart the inverter to regain AC power. The best I seem able to use the microwave at - and keep it running - is 80%.

And, yes, the problem persists whether the television is on or off.

I have friends with similar systems - some with even less robust systems - who have also rewired their micros and who do not have this problem. They can all use their micros at 100% power with no problems.

Lots of smarter people on this forum about electricity than me. I am hoping someone may have an idea about why my system is not working as well as it should (IMO and in my friends opinions)

 

[Aussieguy]

I would start by looking at the 12v wiring to the inverter

Inverter supplied wire is often cheap crap that fails at high amp loads

Use multi meter to measure the volts as you start up the microwave
If volts dip below 12v start looking at better wire and connections

Welding cable is often used which is way better than some of the cheap copper clad aluminum

You also want good pure copper zinc plated lugs that have good flat surface area

——-
Next is to look at your battery bank
Do you have multiple batteries in parallel? … ensure the cables are up to the job too

 

[pgandw]

From your stat sheet, looks to me like your battery BMS is inadequate for the load. BMS will only pass 100amps continuous. Microwave needs 1200W for full power. That equates to 10amps @120V, 100 amps @ 12V. Add in inverter loss (at least 10%) and the probability for failure (tripping the BMS) goes up.

Your microwave is more powerful than most - mine are either 1100 or 1000 watts. Your battery BMS are marginal for the load. You need a battery with a 150 amp BMS.

Fred W

 

[Bob K4TAX]

You need the services of a qualified RV technician to do what you are asking. One with an in-depth knowledge of RV DC power systems.

The inverter needs to be located physically close to the battery and connected by at least #2 AWG or larger copper welding cables between the inverter and battery. The shorter lengths the better. Then you need to decide how you want to use the 120 volt output of the inverter. Power just the microwave, which will require dedicated wiring from the inverter to the microwave.

I can assure you that " I tapped into the wire for the television to do that." is absolutely the WRONG way to do it, as it could be unsafe, be it 12 volts DC or 120 volts AC.

As others have stated, your present BMS is not adequate for your objective.

Bob

 

[shadowman114488]

Late breaking update.
Turns out there is an updated BMS available for my battery that allows 50% more continuous amp discharge.
I installed it and no longer have a problem using the microwave at 100%.
Thanks to all who responded.

 

[TacomaJoe]

Late breaking update.
Turns out there is an updated BMS available for my battery that allows 50% more continuous amp discharge.
I installed it and no longer have a problem using the microwave at 100%.
Thanks to all who responded.

What battery do you have? Nice to be able to update the BMS. On my trailer I know the microwave pulls over 100A but I have 3 batteries in parallel so the individual BMS current is under 50A.