Multiplus not utilizing generator input current

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jenseinarjohansen asked Dec 28, '23

Multiplus not utilizing generator input current

Hey.

I have 6600w Huyndai Diesel generator and a setup of two Multiplus 12/3000/120-16 in parallel setup.

I have set up the multis with an input current limit in veconfigue at 16amp each, with dynamic current limiter active, accept wide input frequency, and weak ac input.

The problem i´m having is that I can´t get the multis to draw more than about 3000w from the generator for charging, but if there is load on the ac output the multis will draw from the genset(maybe its not the multis drawing, but the effect is the same). For example; 3000w for charging from the genset, and 1500w load will draw 4500w from the genset.

If i disable the weak ac the multis will disconnect from the genset above 18-19 amp input. As far as i can tell the output voltage from genset is between 220v and 230v, but the frequency is at about 49hz - maybe the problem is with the frequency?

My generator is quite simple, it will shutdown if voltage, frequency og load is off range. If I try to draw to much, it will shut down - there is no function that reduces output current, it just shuts down... the problem is that its not the genset that is disconnecting/shutting down its the multis... I have tried readin other posts that seem similar without finding a good answer for my issue.

Does anybody know how sensitive the mutis are to the input frequency? or any other ideas to why i cant seem to get the multis to utilize the full charging current of the genset?

Generator multiplus in parallel charge current limit

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Answer 1 · 2023-12-28T21:15:06Z

Justin Cook answered · Dec 28, 2023 at 09:15 PM

3000w of AC = roughly 208A of charge current at 14.4vDC so there doesn't seem to be much of an issue here? Two Multis in parallel can charge at 240A if they've been set appropriately, and if the batteries will accept that high of a charge rate, but you're already well within range. Are you sure you've set your Multis to the maximum charge rate of 120A each, and that your batteries will accept that high of a charge current?

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Answer 2 · 2024-01-10T21:10:55Z

jenseinarjohansen answered · Jan 10 at 09:10 PM

Thanks ;-)

It seems to me that I’m not coming close to the 240a mark on dc. The batteries are rated for 100a each(6 of them), so I was thinking that shouldn’t be the bottle neck…

I was thinking that the multis decided themselves about the charging current based on internal temp, battery temp, charging profile and so on.

To me it seems they’re holding back a bit… but if I disable weak ac and or dcl, they attempt at drawing higher current from the generator, but drop out - probably due to some characteristic of the generator frequency/current or something… I was hoping someone new how the multis react to for example a little to low hz, though still within the “extended” range 45-65hz

Thanks again ;-)

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Alexandra ♦ commented · Jan 11 at 10:11 AM

So they are drawing a current that leaves the generator voltage frequency fairly stable.

The inverters do not like sudden changes in frequency. So you are on pin there if the generator is prone to that.

The other thing is gensets are derated the higher you are above sea level and then don't like to be loaded above 80% anyway

80% of 6.6 is 5.2kw max at sea level.

If you are 1000ft above sea then 80% again. 4200w. There are other factors. Like state of service and settings. Has it ever worked that hard?

You will find the rating isn't what it says on the box.

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Answer 3 · 2024-01-11T06:58:28Z

kevgermany answered · Jan 11 at 06:58 AM

Are these LFP batteries? If so, are they using a BMS to control a GX and the multis?

If lead, how close to charged are they? Internal resistance in them will limit charging current.

What happens if a single multi is turned off? Will it then charge at a higher rate than it did when both were charging?

What's ambient temperature where the multis are and do they have adequate ventilation. They will reduce output if loads are too high. Are the fans running in the multis?

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