Victron Multiplus (surprisingly) couldn't handle this

[Madcodger]

Hi all,

I've been a Victron fan since day one, and am still happy that I bought it for my small (1.26 KW) "shed" system. But I was surprised (OK, disappointed) to find that my 3000 KVA Multiplus wimped out today as I tried to use it with a small (5-ton) electric (hydraulic) log splitter. The system was drawing just over 100 W of AC and the sun was bright. Batteries (three 24V 100 AH Amperetime in parallel, with 1/0 AWG cables) were at 100% SOC. Battery assist was turned on but there as no AC (shore power) running into the Multiplus. I plugged the log splitter into a 20A circuit about 12 wire feet away from the panel, and fired up the splitter. It sounded strained, and in about 3 seconds the Multiplus overload tripped. It reset itself perhaps 20-30 seconds later, so I tried again. No joy. This happened 4-5 times before I wheeled the splitter to the garage, plugged it into a 20A AC circuit, and it worked. To experiment, I then tried it with a 25 foot 12 Ga extension cord, then a 25 ft 14 ga, and finally a 50 ft 14 ga. cord, to see if that made a difference and caused it to fail. It worked fine. Wheeled it back to the shed, tried it on the Multiplus again, and no-go. At least I know the overload protection works well...

One of the main reasons I bought Victron was the low frequency transformer, and its (alleged) ability to handle surge loads.I still think Victron is great equipment, but I have to say, this did not help its case as I ponder whether to buy Victron or EG4 for the new house. I'm certainly not suggesting EG4 would be better. But it sure is a lot less expensive, and the low frequency inverter didn't help at all today. The new house will have a Grundfos SQ well pump, so this splitter might be the biggest thing I use there other than the Mig welder. I do wonder if this could have been a battery issue, but I'm skeptical, as the internal BMS didn't kick in. Instead, it was the Multiplus overload protection. Maybe I'll connect shore power in a few days and see if that makes a difference. But right now, I'm a little bit disappointed.

 

[Mattb4]

You got me curious. I have a 12-ton 120vAC electric splitter. I plugged in into a living room outlet powered by a PowMr 3kW and about 12kWh battery (fully charged and the PV was not adding). It had not been run since last Autumn so it would be a good test. Started without any issue I could spot though I could not see the surge on the AIO due to distance away. Running current was ~700w at pump idle. Split a small chunk just to give it a test and it worked fine.

 

[Checkthisout]

Log into the multiplus and see what battery voltage is at the moment of shutoff.

It's definitely possible it can't handle it but I would make sure it's not a battery side voltage drop issue first.

My bench testing shows a 3000 delivering 2400 watts constant and able to hold 2800 for 30 seconds before tripping on overload.

Edit. Remember that's KVa.

Log splitter motor is a reactive power Flux capacitor!

 

[Hedges]

Mine neither.

High Frequency Inverter battery current waveform

In the interest of science ;) I have captured waveforms drawn by a high frequency inverter from the battery. This could give some insight to how a BMS might react. About 25 years ago I found myself with idle hands and some money ($800?) burning a hole in my pocket. I wandered into Quement...

diysolarforum.com

Maybe a $350 Easy-start would let the inverter start the $350 log splitter.

 

[AntronX]

You may have too much voltage drop on DC side. At 6kVa surge your multiplus will try to pull 330A from battery. At 24V battery voltage DC cable/fuses/braker may drop it too much.

 

[shopman]

I'd be willing to bet the electric motor on your splitter has a capacitor or two in circuit. A separate start and run cap. Check each one to be sure they're within spec because if they aren't, that can create a situation where it will draw excessive current. It would run fine on grid in this situation but may be enough extra draw to trip your inverter.

 

[740GLE]

How are the batteries wired? Bus bars? Cross
wired?

Care to post a picture?

 

[sunsurfer]

So you never mention how much surge your drawing vs rating for the inverter and like others have said, what was input volts at the time. You could have a bad inverter.

 

[SoakedUp]

My multiplus is only about 75% efficient which was a big surprise from their 95% stated efficiency. When AC out reads 1000w my shunt reads about 1350w being drawn from the battery bank on the VRM.

 

[Checkthisout]

My multiplus is only about 75% efficient which was a big surprise from their 95% stated efficiency. When AC out reads 1000w my shunt reads about 1350w being drawn from the battery bank on the VRM.

That's just not possible.

That means the MP is dumping 600 watts of heat at full load.

 

[Hedges]

I wonder if SmartShunt reads RMS current, or Mean average current?
I think Mean is what is needed when calculating power from a roughly stable voltage source.
With high ripple, I think RMS is up to 11% higher. Which would explain half the discrepancy.

Can you add an RC filter to output of shunt, see how that affects the reading?

https://www.victronenergy.com/upload/documents/Datasheet-SmartShunt-EN.pdf

 

[SoakedUp]

That's just not possible.

That means the MP is dumping 600 watts of heat at full load.

Yea I don’t really get it. Nothing gets more than slightly warm as far as cables and connections. It’s a Multiplus 2k so my max continuous is 1600w. So at 75% efficiency at max load I’m dumping 400w somewhere. I try not to sustain more than 1200w loads for too long being a 12v system. I do get closer to 85% efficiency with loads between 100-300w.

 

[Hedges]

What kind of loads?
What is their power factor? (affects efficiency of inverter)

 

[SoakedUp]

What kind of loads?
What is their power factor? (affects efficiency of inverter)

Mostly inductive loads. AC, fans, Fridge, microwave. I thought that was the issue so I tested with a couple different purely resistive loads like radiant heater, heat gun, electric water kettle. Same results.

 

[Madcodger]

Hi all. Well, the little log splitter is back in the garage and given that it is snowing now and a workday, we'll need to wait on further scientific experiments (i.e., I'll check the voltage drop as that sounds plausible, and I suspect that's the culprit). I can confirm that I saw a single spike to 3293 watts using the 1 sec reading of an Emporia Vue, after plugging it into AC and writing my original post. Everything else (adding filters and tearing things down to check them) is probably not going to happen given that I can just plug the splitter into AC, and all works fine for my normal use of the inverter. I was just disappointed, and surprised, as I thought the low frequency transformer wouldn't blink. At least with 300 AH of 24V batteries, I was wrong.

Will be interesting to see what happens on shore power, and now I want to try the splitter plugged into a little 4500 watt generator to see what happens, but it's out in a storage shed, so science must wait for now. I'm also curious about the Mig welder, but that means rewiring the pig tail and getting it out to the shed, with those little wheels the stand has. Maybe not, unless boredom kicks in one Saturday, which seems unlikely given all there is to do here.

BTW, the batteries are connected to a bus bar with equal length (25 inch) 1/0, factory-crimped cables cables, and equal length 1/0 cables (36-inch as I recall) running to the inverter, and all connections are tight. And no, I'm not going to go snap pics, because I don't need to diagnose anything - I'm just reporting my experience here. Also, the soft start suggestion (tongue-in-cheek, I assume) was funny, as I thought the same thing - I can solve this for more than double the money!

 

[Madcodger]

You got me curious. I have a 12-ton 120vAC electric splitter. I plugged in into a living room outlet powered by a PowMr 3kW and about 12kWh battery (fully charged and the PV was not adding). It had not been run since last Autumn so it would be a good test. Started without any issue I could spot though I could not see the surge on the AIO due to distance away. Running current was ~700w at pump idle. Split a small chunk just to give it a test and it worked fine.

Thanks, @Mattb4 . I wonder now if it's my batteries, or just the surge load of my cheap Harbor Freight splitter, or the fact that the shed has just a 24 V system. Do you have a 48V system?

 

[Q-Dog]

Its been a while so I don't remember all the details of how I ultimately came to it, but I have the same Multiplus and I used 2/0 for the main connection to the inverter. After studying a few charts it was the smallest wire I felt could do the job with low enough losses, especially since Victron recommends to fuse the 24 volt MultiPlus 3000 with a 300 amp fuse.

 

[Checkthisout]

Thanks, @Mattb4 . I wonder now if it's my batteries, or just the surge load of my cheap Harbor Freight splitter, or the fact that the shed has just a 24 V system. Do you have a 48V system?

I basically concluded during my own testing that the MP 3000 can supply the needs of a normal 20 amp household circuit.

2400 watts constant with headroom to surge to 6000 for starting inductive loads.

Is the logsplitter unable to start or just unable to split wood?

 

[Madcodger]

I basically concluded during my own testing that the MP 3000 can supply the needs of a normal 20 amp household circuit.

2400 watts constant with headroom to surge to 6000 for starting inductive loads.

Is the logsplitter unable to start or just unable to split wood?

Unable to start. I suspect that if it got past the surge it would be fine. The issue might be, as others have noted, the voltage drop from the batteries. But I'd say three 24V 100AH Amperetime batteries, properly wired with 2/0 cables, is a reasonable, somewhat typical installation for a small, off grid building with loads typically between 100-150 watts and just occasional need for a "big load", like this small log splitter. So, whether it's the inverter or, perhaps even more likely, the batteries behind it, this was "no joy" situation that having a low-frequency inverter didn't resolve. Still to be seen... What happens on shore power, with the same inverter.

 

[Mattb4]

Thanks, @Mattb4 . I wonder now if it's my batteries, or just the surge load of my cheap Harbor Freight splitter, or the fact that the shed has just a 24 V system. Do you have a 48V system?

I run 24vDC. If I was to guess it would be the Harbor Freight motor though it could be the hydraulic pump/valve on it has a higher pressure bypass set on it than mine. Higher bypass pressure would cause the motor to strain when starting. My splitter has a Leeson motor on it which is a very good quality one.