Power assist hysteresis

I’m setting up my multiplus 12/3000-240v to assist my small 2.1Kva generator during peak loads.

I understand that the input current limit is actually 10% lower than the set limit so when set to 8A assist starts at 7.2A.

And that there is a minimum assist level of 1.6A for this multiplus model.

so the current draw from the ac input may drop during assisting if the load is only slightly above the limit.

I assume there is some hysteresis built in to stop this current drop from kicking the system out of assist and back in again repeatedly.

can anyone tell me what this hysteresis lower set point is for 12/3000-240 multiplus?

ie: how much load do I need to shed in order to drop out of assist.

Thanks.

Bob.

It should be any time the load drops back down under the 8 amp set.
Theres a few slight variations…

If you have dynamic current limit on it can also affect it a bit. So a few amps different. It also has a bit to do with the load type and power factor.

Thanks for your reply LX.

There appears to be some hysteresis so it has to drop somewhat below the 8A set current before it drops out of assist.

This makes sense as it prevents the system flip-flopping between assist and no assist when the power draw is around the set limit.

The “somewhat below” is the value I’m after.

Cheers.

Bob.

The somewhat is affected by install and load so i guess that a voyage of discovery you are on…

@bigbadbob76 this is an interesting concept because switching in and out of assist doesn’t strike me as a big problem. I wonder could you outline the reason for the enquiry as for me, the assist function is a linear application of the feature.

For instance, if the setpoint for assist is let’s say 10 amps and the current reaches 10.1 amps, the 0.1 amp component is provided by batteries. When it drops back to 10, that 0.1 amp part is now not supplied by batteries. That doesn’t seem to be an issue even if I it did rapidly switch in or out or have I missed something?

I don’t think the current draw from the generator does “reduce” during assist. In fact it stays exactly the same. The assist factor ( normally 2.0) is the maximum assist available. The current draw from the generator once it has reached its maximum stays at the maximum and does not fluctuate as assist cuts in and out.

AC input current limit. Set this to a safe value for your generator so the inverter doesn’t let the generator run overload. Dynamic current limiter if enabled, the MultiPlus will gradually allow the generator to supply more power; useful for small or slow-ramp gensets. Assist Current Boost Factor sets how much extra the inverter will inject during short surges. But this only affects the very short burst, not overall hysteresis. If your generator has a distorted waveform or weak AC input that is unstable this may help.

There is another thread that describes the threshold trigger a bit more form the spreadsheet.

Thanks guys.

Trevor- yes, an interesting concept, according to the spreadsheet on Victron pro my multi has a minimum assist level of 1.6A so when you go over the set point by say 0.1A it assists with 1.6A not 0.1A, so the current draw from the generator drops by 1.5A. the drop takes the generator draw below the setpoint which if there was no hysteresis would kick it back out of assist mode and it would cycle in and out constantly. as you draw more current the drop reduces to the point where if you try to draw more than 1.6A over the setpoint the drop reduces to zero, the generator draw stays at the set point and the multi provides the rest. cycling in and out of assist would be a problem as the multi would boost each time it goes into assist (see Alf’s comments) and draw a lot of un-necessary current from the battery.

Alf- yes, I see what you mean, the boost factor will also come into play as the multi initially assists with a higher current before it settles to the required level after a surge but still with a minimum assist of 1.6A. this boost factor makes the hysteresis more complicated. I have dynamic current limit and weak AC disabled.

Maybe I should just let it do it’s thing and not worry about it as it only affects the small rage from set point to 1.6A over set point, but I like to understand what’s happening.

LX- yes, that thread led me down this rabbit hole, haha.