question

chapelier avatar image
chapelier asked

Multiplus ii 5000 not inverting 4000w

I have a 14kw array charging a 33kw bmw battery with a 450/100 mppt , 1 60 amp mppt and a 100 amp mppt.


at the moment in testing everything is working as expected . I’m about to add a second multiplus ii 5000 in parallel but I’m first of all trying to figure out the low output of the multiplus ii and trying to see if I have missed something in my settings.

I’m running ess and I can’t see anything that would limit the output but it seems when the voltage of my battery is at the lower end the output is lower . My battery is a 12s and my bms will cut off if cell voltage goes high or low

I have the ess configured to stop discharging at 41v and stop charging at 49v

Output of the multiplus appears to be limited to around 3500w until the battery is 47-48v when the output can go as high as 4200w

my cell voltage settings are conservative and the battery is fully able to discharge 8kw right down to the 41v limit I have set


any idea why my output is not 4kw ?

Multiplus-II
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4 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Low voltage means higher amps for the same power and the electronics have a amp limit. Because of that you will get less power at low voltages.

If I remember correctly it was explained somewhere in this video:

https://youtu.be/4SXtGIx0x5w

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chapelier avatar image chapelier commented ·

Thanks for the link. I understand now.

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tozz avatar image
tozz answered ·

Yeah, the specifications on the MultiPlus seem to be a bit exaggerated. My discharge seems to be limited to +/- 3800W as well, even with full batteries at 56V (48V system)

This isn't too weird actually, if you look at the amps. 56V x 70A = 3920W. So 3800W actually seems to be okay, especially if you add some conversion losses.

I must admit I didn't look at the specs too much, I just bought the biggest MultiPlus there is, expecting it to do 5000W, since it has 5000 in it's name.

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chapelier avatar image chapelier commented ·

Ha yeah , a bit the same , saw 5000 and assumed. I’m actually doing a little better than you . My battery range is 41v to 49v fully charged. I have now paralleled 2 and I did see 8500w inverted today at one point in the VRM app , I’ll look at the screen tomorrow and see what amps I’m getting but that’s more what I was hoping for

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Elimac avatar image
Elimac answered ·

Besides what has been said, we also have to account for 2 other considerations:

1. Apparent power (Real+Reactive) and not Real Power. Specifications are for Apparent Power (Volts * Current) measured in VA and not the real Power measured in Watts. Here real means not reactive. If the installation power factor is not "1" (unity means there is no reactive power) then the VA will be different than the "Watts". It's impossible for the manufacturer to know the power factor of each installation, hence specifications are for apparent power, in VA and not Watts.

2. Temperature derate. When the inverter gets hot, its ability to output power will be hindered. Typically, the Multiplus will be limited by temperature after some time of operation, even if the ventilation kicks in.


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kevgermany avatar image kevgermany ♦♦ commented ·

Yes, and the 4000/5000 numbers are based on a typical 80% power factor.

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gpwengineer avatar image
gpwengineer answered ·

I still prefer the Multiplus 1st generation. I think the quality is better.

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