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Jared Wellman avatar image
Jared Wellman asked

Power Assist Boost Factor and overloading MutiPlus

I have a 12/3000/120 MultiPlus and I'm trying to understand some Overload issues that I'm experiencing and wondering if the Boost Factor is potentially causing the issue.

Setup is as follows:
Input Limit: 30A
Power Assist: Enabled
Boost Factor: 2.0
UPS: Disabled
Input Power: 4500W Inverter Generator (3800W running)

I've noticed when a large load comes online that the MP will overload and disconnect. I also get an error from my EMS that the voltage has gone "out of spec" (sadly it doesn't tell me which way). What is interesting is that the load is under the 30A input limit and can easily be handled by the generator alone. I'm wondering if the MultiPlus is "preparing" to power assist approximately 7200W (Boost Factor * Input Limit) and causing the overload itself?

If I set the MP to "Charger Only" the Generator can handle these loads just fine. So it seems to be something specific to Power Assist causing the issue. I do plan on turning down the Input Current and running this same test to see if Power Assist successfully assists without disconnecting but I haven't ran this test yet.

Should I lower the Boost Factor down to 1 (or maybe even lower) to stay within the 3000W that the MP can provide? Is there anyway to configure this so that it is not reliant on the input limit? For instance if I'm connected to 15A power I would want a higher boost factor.

Thank you!
Jared

MultiPlus Quattro Inverter Chargerpowerassist
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3 Answers
Jared Wellman avatar image
Jared Wellman answered ·

So answering this myself.

Basically "Yes". The MultiPlus was actually overloading itself because of the Boost Factor.

I set the input current to 15A with the generator connected and started both AC units no problem with the MultiPlus happily filling the gap:
1624314400150.png

However I will primarily be on 30 or 50A power so the main goal was to figure this out when on a 30A circuit. After finally understanding what the boost factor does it was pretty apparently that setting it to `2.0` and having the input be 30A was almost certainly causing the MultiPlus to overload. 2nd post explains it: https://community.victronenergy.com/questions/2162/multiplus-boostfactor.html

Basically the `boost factor` is how much power the MP will prepare when Power Assist is engaged. So with a boost factor of 2 and an input of 30A, this is 60A of power...or 7200W, which is substantially more than the MultiPlus 12/3000/120 I have is capable of. Thus any load over the 30A input limit would send the MultiPlus into an overload situation when it tried to "spin up" that much power.

I ended up setting the Boost Factor to 0.8 since
(Input Limit) * (Boost Factor) * (AC Voltage) = MP Boost Wattage Requirement
so
30A * 0.8 * 120 = 2880W

1624315719356.png


So this will work for 30A but will likely not be adequate for 15A input limit. Honestly I feel that the "Boost Factor" is a poor way of setting this up. Ideally the MP should handle this internally without the need for configuration and it seems very odd that it is related to the input current. If the MP can supply 3000W then it should prepare 3000W for the Power Assist operation. Or maybe I'm just missing why this has to be related to the Input Current? It's also very frustrating as if I move to a location with 15A power or run off of a smaller generator that I now have to reconfigure the MultiPlus.

Jared


1624314400150.png (224.4 KiB)
1624315719356.png (221.2 KiB)
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pop avatar image pop commented ·
What's the actual *total* power output of this MP model boosting the AC shore power via the PowerAssist mode? Is it the rated 3000W maximum output, or is it 3000W added to the input power?


I think you're the first person to answer this question for me, albeit indirectly. The total output power is limited by the MP output rating, in this case, 3000W. PowerAssist does not *add* 3000W additional power AC input shore power. I was hoping that I could use the MP to boost, say a 2000W AC power input and *additional* 3000W, to 5000W total. But this doesn't appear the be the case. The inverter can only handle *up to* 3000W when the AC input shore power is less than 3000W.


So, the PowerAssist boost factor is a multiplier factor applied to the AC input current, but is limited to the maximum rated power output of the MP inverter model? And if that total current exceeds the inverter's rating, the inverter will shut down with an error.

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kirby avatar image kirby pop commented ·

I was hoping that I could use the MP to boost, say a 2000W AC power input and *additional* 3000W, to 5000W total. But this doesn't appear the be the case. The inverter can only handle *up to* 3000W when the AC input shore power is less than 3000W.

Sorry, I didn't understand you, or you are a bit wrong.

I have MultiPlus 5000/48/70-100.

That means, inverter:

  1. 5000: is able to generate power 5000VA (~20A current for 220/230 VAC)
  2. 48: works with 48V batteries
  3. 70: can provide 70A DC charge current.
  4. 100: current passthrough value, up to 100A could be handled on AC input.

Now about PowerAssist feature. This inverter is able to get any power from input (but up to 100A, or 22 kW) and... add all power to this amount.

At the end it would be up to 120A.

The weakest 3000VA model with 16A-passthrough shall be able provide up to ~5-5.5 kW.

I tested a 5.5kW generator today. As it still shall be on idle working for some time, we decided to use it a bit, in low load.

I've set 8A for input to have load up to ~1kW for battery charging. In the same time, when the deep water pump started working, the generator got a spike (!) up to 2kW and the inverter switched to PowerAssist.
By the way, it's assisted on L1 line.

But I'd like to figure out, if I set Boost Factor to 1.0, would the inverter get spikes much lower (I don't know, maybe up to 10-20% from input current)?

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JohnC avatar image JohnC ♦ kirby commented ·
Hi @kirby

The trouble with gensets is that they don't handle 'spikes' well. This may not be noticeable when the load is applied directly to the genset, the spike's end result of an instantaneous sag in V and/or Hz can often just mean a cough and all rolls on. But the Multi knows when the genset output goes through it. It will reject the input if outside specs and take over itself. And it's own spike handling capacity is far greater than it's continuous rating.

Try ticking Dynamic Current Limiter, which which will buffer/delay instant load increases on the genset, and the Multi should pick those up in the meantime with Power Assist (seconds). Also tick the Wide Input Frequency Range so the rejection parameters are eased.

In your case I'd leave the Boost Factor alone.



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kirby avatar image kirby JohnC ♦ commented ·

Yeah, thanks for this note. I'll try it next time.

The same is advised for Weak AC (probably worth to use them both):

Weak AC


Strong distortion of the input voltage can result in the charger hardly operating or not operating at all. If WeakAC is set, the charger will also accept a strongly distorted voltage, at the cost of greater distortion of the input current.

Recommendation: Turn WeakAC on if the charger is hardly charging or not charging at all (which is quite rare!). Also turn on the dynamic current limiter simultaneously, and reduce the maximum charging current to prevent overloading the generator if necessary.

Note: when WeakAC is on, the maximum charge current is reduced by approximately 20%.

Not adjustable with DIP switches.

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JohnC avatar image JohnC ♦ kirby commented ·
@kirby

Best treat WeakAC as a last resort thing. It comes with some downsides, not necessarily serious, but better without. And if you really need to use it then there may be something else wrong.

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kirby avatar image kirby JohnC ♦ commented ·

@JohnC , thanks for this point.. Hm..

It comes with some downsides, not necessarily serious, but better without.

Do you have any certainties about that?..

What's my shore power problem is that's a low voltage, that's my another riddle to solve =).

1671809652053.png

After blackouts, it's hard to charge batteries first hour or two.

I was thinking to use Weak AC for that case.

Probably, it worth to raise this in a separated post...

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JohnC avatar image JohnC ♦ kirby commented ·

@kirby

WeakAC applies a Power Factor 'penalty'. This definitely reduces the Multi's charge capability, and I found that reduction much worse than the 20% suggested in the literature. And if you have a keen ear you may even notice inductive ac loads 'groaning' a little. Coupled with that low V of yours, a nasty mix for ac loads on the end of it.

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Mike Dorsett avatar image
Mike Dorsett answered ·

good to have some detail on how this behaves.

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Paul B avatar image
Paul B answered ·

What you may find is that you are going over the MAX passthrough limit there are two versions a 16amp pass through and a 50amp passthrough versions of the multiplus 3000

if the load goes over the max figure that multiplus will disconnect the gen

Some motors have very large startup currents that push the amps over the max limits

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