Victron Multiplus (surprisingly) couldn't handle this

[Checkthisout]

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.

Yeah, it should start it. It's going to be hard to measure a voltage droop from the batteries that is that short in duration.

I would make sure all the batteries are on and outputting.

Also, load test the MP with a couple space heaters and check all your connections etc.

It should be able to hold about 2400 watts constant.

 

[740GLE]

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!

The number of times people have poor wiring as the main cause issues has always been quite high. I was just curious.

While you do have what seems to be a standard set up with adequate wiring the next thing I’d look at is battery voltages and SOC, and voltages on the MP terminals.

How are you tracking SOC? Just off voltage or do you have a shunt? If the voltages were around 27-27.5v when you tested, id say yeah you found the limitations of the MPII.

 

[Checkthisout]

The number of times people have poor wiring as the main cause issues has always been quite high. I was just curious.

While you do have what seems to be a standard set up with adequate wiring the next thing I’d look at is battery voltages and SOC, and voltages on the MP terminals.

How are you tracking SOC? Just off voltage or do you have a shunt? If the voltages were around 27-27.5v when you tested, id say yeah you found the limitations of the MPII.

It's important to load test any system at full throttle after setup, at least I think it is.

A 1/2 hour at full load to see both what it's limitations are as well to go around and feel the connections for heat/high resistance.

The only bad crimp in my system was a Windynation cable off Amazon. Fuse holders are sensitive to proper washer placement and of course proper torque on all this stuff.

 

[Q-Dog]

It's important to load test any system at full throttle after setup, at least I think it is.

A 1/2 hour at full load to see both what it's limitations are as well to go around and feel the connections for heat/high resistance.

The only bad crimp in my system was a Windynation cable off Amazon. Fuse holders are sensitive to proper washer placement and of course proper torque on all this stuff.

I was so paranoid about everything I installed that I did a stress test after any change to the system. I only found minor issues and feel pretty confident in what the system can do. Still, mistakes happen.

A few days ago I decided to plug in a couple of heaters to burn some power. Normally I run one of them on low and we stay under the 2400 watts continuous rating even if both kick on. While I was doing this the wife put the kettle on ... over 3200 watts coming from the Multiplus 3000 and the overload light started flashing. This made me wonder how long it could sustain a minor overload, so, when she was done I put both heaters on high and waited. After about 30 seconds I heard a pop and things went dark. OK. Checked the inverter and it was still running? WTH? Check the breaker panel and one circuit is tripped. I had accidently plugged both heaters into the same circuit ... just over 3000 watts through a 15 amp breaker. Everything worked as it should and I still don't know how much and how long I can overload the MultiPlus.

 

[Checkthisout]

I was so paranoid about everything I installed that I did a stress test after any change to the system. I only found minor issues and feel pretty confident in what the system can do. Still, mistakes happen.

A few days ago I decided to plug in a couple of heaters to burn some power. Normally I run one of them on low and we stay under the 2400 watts continuous rating even if both kick on. While I was doing this the wife put the kettle on ... over 3200 watts coming from the Multiplus 3000 and the overload light started flashing. This made me wonder how long it could sustain a minor overload, so, when she was done I put both heaters on high and waited. After about 30 seconds I heard a pop and things went dark. OK. Checked the inverter and it was still running? WTH? Check the breaker panel and one circuit is tripped. I had accidently plugged both heaters into the same circuit ... just over 3000 watts through a 15 amp breaker. Everything worked as it should and I still don't know how much and how long I can overload the MultiPlus.

2 space heaters, one on high and the other half on. Exactly how I tested my 3k multiplus and self-assembled battery setup!

Literally the exact same outcome as you!

 

[Hedges]

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!

Although, if a single soft-start which had learned on one motor could start a number of tools, this could be considered an enhancement of the inverter system. Could let it run other pumps, compressors, saws etc. without straining to start.

Would a 3-phase plug with its extra pin be sufficient to bring out the starting winding, allowing either Easy-Start or just hard wired adapter cord to be used?

 

[Checkthisout]

Although, if a single soft-start which had learned on one motor could start a number of tools, this could be considered an enhancement of the inverter system. Could let it run other pumps, compressors, saws etc. without straining to start.

Would a 3-phase plug with its extra pin be sufficient to bring out the starting winding, allowing either Easy-Start or just hard wired adapter cord to be used?

For the cost of the soft starts, you can just buy another inverter to parallel.

 

[Madcodger]

How are you tracking SOC?

Victron SmartShunt.

And, for those who commented about running heaters, etc., those are good ideas. I've had a heater and coffee maker both running on this system, and with other things running watched watts on VRM climb over 3300 without tripping the overload. I think this is just a very high surge motor that the combo of batteries and inverter can't handle. Everything else looks fine and works fine, but what I've learned is that a low frequency inverter doesn't solve all the problems I thought it would. Do they have an advantage? Yes. But that advantage isn't as big as I thought it was, in real world use (e.g., it can't make up for things like batteries not being able to supply enough voltage, which is likely a factor here despite being otherwise healthy, charged batteries). I can't think of anything else I use that's likely to trip this except the Mig welder, and I can run that from the garage, with AC. Anyway, was a good test.

 

[DIYrich]

If you have 3 24v 100ah batteries, each with its own 1/0 wire to the busbar, then they should easily be able to deliver 7,200 watts (100 Amps from each battery).

If you have 1/0 wire from the busbar to the inverter, then that may be your problem. It may be rated for 150 amps in conduit, and 285 amps as open air battery wire.

 

[Madcodger]

If you have 3 24v 100ah batteries, each with its own 1/0 wire to the busbar, then they should easily be able to deliver 7,200 watts (100 Amps from each battery).

If you have 1/0 wire from the busbar to the inverter, then that may be your problem. It may be rated for 150 amps in conduit, and 285 amps as open air battery wire.

1/0 to the inverter, in open air. Holy cow, larger than 1/0 and it's gonna look like a pipe running into the inverter! Basically, this was a test, so no need to go beyond 1/0 for normal use, I think, as cables never even get warm. I'd hoped it would work as using the splitter at that location, without a big extension cord running out from the garage, would be handy. But it's not essential and we still don't know what happens with shore power. Always learning, aren't we? Thanks for the input.

 

[Q-Dog]

1/0 to the inverter, in open air. Holy cow, larger than 1/0 and it's gonna look like a pipe running into the inverter! Basically, this was a test, so no need to go beyond 1/0 for normal use, I think, as cables never even get warm. I'd hoped it would work as using the splitter at that location, without a big extension cord running out from the garage, would be handy. But it's not essential and we still don't know what happens with shore power. Always learning, aren't we? Thanks for the input.

Victron does recommend 2/0 for full capacity. If you don't want to run a larger conductor you can add another 1/0. Just make it indentical to the first one.

 

[Madcodger]

Victron does recommend 2/0 for full capacity. If you don't want to run a larger conductor you can add another 1/0. Just make it indentical to the first one.

Is it OK to have 1/0 connecting each battery to the bus bar, if I go to 2/0 between bus bar and inverter? I used an online calculator (can't remember which one) and was pretty sure I went one size up as I wasn't really concerned about cost. BTW, just noticed in history that I got a momentary high voltage alert (28.92) associated with these overloads. Batteries trying to recover? Interesting.

 

[Q-Dog]

Rereading post #31 I see it might be confusing.

Size wise, your conductors from the batteries to the bus bar are fine. (I use 2AWG from batteries to bus bar.) Your connection from the bus bar to the inverter could be bigger.

 

[justinm001]

View attachment 198499

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.

Victron posts effeciency numbers at specific watts.
Power loss and efficiency as a function of load

As an example let us look at the Phoenix Inverter 24/3000 or MultiPlus 24/3000/70 (both
products have the same inverter). These products use high frequency switching to
generate a sinewave, which is then transformed to the required output voltage by two
toroidal transformers. Toroidal transformers have a higher efficiency and less no load
losses than the more common E-core transformers.
The measured efficiency curve is shown below:
Output power (W) Dissipation (W) Efficiency (%)
0 20 0
10 20 33,3
20 20 50,0
30 20 59,9
50 20 71,3
100 21 83,0
200 22 90,1
400 28 93,5
800 52 93,9
1600 148 91,5
2500 333 88,3
3000 470 86,5
4000 820 83,0
5000 1270 79,

https://community.victronenergy.com/storage/attachments/21928-output-rating-operating-temperature-and-efficiency.pdf

 

[Hedges]

Wow, I was going to fault them for poor 80% efficiency at full load. Then I remembered the graph was shown in red up there - that is 5000W from a 3kVA inverter. At 2500W output, 90% efficient. Peak at 800W of 93.9%

Derating of wire wouldn't affect surge capability, only resistance would. So long as not too long, shouldn't be a problem.
Fuses and breakers in battery cable could starve it.

I would guess the primary issue is the motor itself, some seem to need more current to start than others.

 

[Mattb4]

...

I would guess the primary issue is the motor itself, some seem to need more current to start than others.

Quality of Chinese made non branded motors is not the best. From the steel used in the laminations to the amount of insulation and coatings. Nor can you trust the ratings such as claimed horsepower. Likely this motor does not list either FLA or SFA in its specifications.

There was a lot of stories circulating on HF 1/2 hp water pumps that would trip out inverters that ought to have ran them based on specs.

 

[740GLE]

Victron SmartShunt.

And, for those who commented about running heaters, etc., those are good ideas. I've had a heater and coffee maker both running on this system, and with other things running watched watts on VRM climb over 3300 without tripping the overload. I think this is just a very high surge motor that the combo of batteries and inverter can't handle. Everything else looks fine and works fine, but what I've learned is that a low frequency inverter doesn't solve all the problems I thought it would. Do they have an advantage? Yes. But that advantage isn't as big as I thought it was, in real world use (e.g., it can't make up for things like batteries not being able to supply enough voltage, which is likely a factor here despite being otherwise healthy, charged batteries). I can't think of anything else I use that's likely to trip this except the Mig welder, and I can run that from the garage, with AC. Anyway, was a good test.

Seems like you have a quality set up, you just found the limitations under a hard test.

I’d have to think if you swapped out the 3k for a 5k it might run it.

I have to imagine if you had a HF inverter you’d prob need a 7-8k rated for that inrush.

 

[sunsurfer]

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.

Don't forget, most ratings on anything is while going down hill with a tail wind. Your mileage may vary, etc......

 

[740GLE]

Victron uses creative words, it’s “max efficiency is 95%” which is a much lower than rated output. Sadly that max efficiency is prob more closer to idle or <500w.

 

[ricardocello]

Deleted, my comment already covered above.