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pizote avatar image
pizote asked

Multiplus Compact 12/2000 tripping below 2000 watts

I have a brand new MultiPlus Compact 12/2000. I currently have it hooked up to two Type 34AGM batteries and a 165AMP alternator (will be installing two 170Ah LiFePO batteries tomorrow). I also have 800w solar array, but let's leave that out for now.

Hooked up to it, I have a Dometic Brisk II AC unit.

Current behavior is that the inverter trips into fault mode when the compressor kicks in. Here's the supporting data that I have and which has me scratching my head:

On 110vac shore power, the following occurs:
Off-High fan - no compressor - max amp pull is 3.8amps

Off-On compressor - max amp pull is 43amps, but settles down at 7.6-8amps

I installed a hard start capacitor on the AC unit and this is what I get now:

On 110vac shore power:

Off-High fan - no compressor - max amp pull is around the same 3.8amps
Off-On compressor - 20.32amp

Here's the problem:

When I run from the inverter - no shore power, the source is the two Type 34 batteries and the 165amp alternator, the inverter trips into fault mode at 12.38amps.

According to my calculations, that's just shy of 1400watts. Even if it did get higher, to the 20.32amps I get on shore power, that would be 2235 watts. The Compact 12/2000 has a sustained wattage rating of 2000watts, but can spike up to 4000w. Both of the numbers I am getting are within the spike and well below the rating of 2000w for the 12.38amp trip.

All wiring to/from inverter, batteries and alternator are 2/0 and the longest run is 10'.

What am I missing here?

inverter current draw
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klim8skeptic avatar image klim8skeptic ♦ commented ·

'When I run from the inverter - no shore power, the source is the two Type 34 batteries and the 165amp alternator, the inverter trips into fault mode at 12.38amps."

I suspect the batteries are way to small (60ah each?), and the alternator is not fast enough to pick up the slack.

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2 Answers
ben avatar image
ben answered ·

You will see different results with the new LFP batteries, I think.

Your DC side likely can't meet the surge demand.

If you do still see it with the LFP batteries installed, there are more things to try. Come back and let us know.

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pizote avatar image
pizote answered ·

Thank you Ben and klim for your answers. Indeed, after I installed the two LiFePo batteries, the AC unit would then power up properly. I would get DC current spikes to about 280 amp but then goes back down to 70amps running the compressor. That's sufficient for me to run it off my alternator and solar going down the road (I have a combined amp input of about 180-200 amps - not including the batteries - which should not be drawn from.

I will be adding an additional 200amp alternator to the engine so I won't be pulling from the factory alternator.

Thanks again...

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ben avatar image ben ♦ commented ·

Glad to hear you got it working!

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