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using Victron Multiplus Compact to balance generator load spike

RudyGreene

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Jan 12, 2023
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Tennessee
I have a portable PA system that I run off a Honda 3000i inverter generator. When measured with a Kill-a-Watt, the total PA system draws 5-7A continuously, but the load spikes as high as 12.5A for a fraction of a second repeatedly during some songs (primarily because of the subwoofers). This causes the generator AC output voltage to drop as the engine struggles to spin up faster.

The Victron Multiplus Compact (12/2000/80-120V) seems to be a potential solution. My plan would be to set the "AC input current limit" to 7A (the upper limit of the normal continuous load) which in combination with the PowerAssist feature should force any momentary power spikes to supplement from the Victron inverter. Does this seem like a workable configuration?

Victron recommends a minimum battery bank of 350Ah, but I already know I would only draw a maximum of 7.5A/900W (AC) from the Multiplus inverter. Since my load spike range is known, can I instead use a much smaller battery? I'd like to use a tiny 12V 35Ah AGM if possible. I haven't bought everything yet so I'm open to other solutions as well.
 
I would think it would work - I don’t know about a 35ah battery??? what about a cheap 100ah lithium battery - probably about the same weight as that 35ah battery- just costs more. (But a lot less than the Multiplus.
 
I would think it would work - I don’t know about a 35ah battery??? what about a cheap 100ah lithium battery - probably about the same weight as that 35ah battery- just costs more. (But a lot less than the Multiplus.
Most UPS batteries are AGM so I assumed that chemistry was better suited for brief, high-amp loads. Do you think lithium would work just as well?
 
Most UPS batteries are AGM so I assumed that chemistry was better suited for brief, high-amp loads. Do you think lithium would work just as well?

Idea sounds viable to me , AGM and LiFePo4 should both work equally as well for what you're doing
 
I bought a Multiplus Compact so I'm ready to start wiring this up and testing my plan. But I'm still a little unclear how to properly ground this system since it's not a typical usage scenario. There is a grounding point on the Multiplus, but the Victron manual says it's an alternative for when the AC input isn't grounded. My generator is unbonded, but I can add a bonding plug so that neutral/ground are bonded at the power source. Then connect the grounding point on the generator to a ground rod. Does that sound correct?

I've illustrated my plan so it's easier to understand:

Multiplus Compact Wiring Diagram.png
 
I finished wiring my Multiplus and power panel today then tested it out with the PA gear. Worked great and ran the sound system no problem for a 2 hour show using only a 35Ah AGM battery as the backup battery.

The only thing that was strange is the charger went into "Storage" mode after about an hour which reduced the battery voltage to the 12V-13V range for remainder of the show. The Multiplus manual says the charger enters Storage mode after no discharge for 24 hours. But I've only had the Multiplus running for maybe 3-4 hours prior to top off the battery. Plus once it was in Storage mode, I started getting repeated "Low Battery" warning from the app as the voltage occasionally dipped into the low 12s. What else might have triggered it going into storage mode?

I watched from VictronConnect and saw loads as high as 50A coming off the battery for less than a second when there was very loud beats going to the subs. The assist would kick on about 5-10 times per minute. I don't want to mess with what's working, but is there any better battery settings I should consider given my usage scenario?
 
I am glad the 35ah battery worked!

You can turn off the storage mode and there may even be a few other settings that would be better to be changed in your use case.

There are settings where you can adjust all the settings. If you have a GX device attached (CCGX or Cerbo), you can change the settings and upload them that way. There is also an adapter MK3 to USB that you can connect the Multiplus to a laptop and change the settings there. There is also a Bluetooth adapter then you can change most of the settings on your phone - read the manual about everything you can change.
 
I have the MK3-USB, but I only changed the AC input current and the charging amps from the default. I'll turn off storage and see if that helps keep the voltage higher.

I made a second thread over in the battery subcategory to see if I could get more specific input on the best battery and charging settings given this scenario.
 
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