question

nbezanson avatar image

AC input current limit setting is very different from where it actually limits.

Got a Quattro 12/5000/220-2x100 120V running firmware 2733430. (Same system as in this old post.) Since then, I've beefed up the shoreline to a true 20A circuit, and adjusted the input limit to 20A accordingly.

Sometimes the system will happily draw 19.8A from the shore, and sometimes it'll limit itself at 11.6A and go into PowerAssist for my roughly-2kW load.

Here's the weird thing: If I increment the input current limit just a little, the actual power drawn from the shore increases dramatically. Here's my observational data:

Current limit set in VEConfigure Actual current drawn Load and status
20A 11.6A 2kw, PowerAssist assisting
21A 12.6A 2kw, PowerAssist assisting
21.5A 20.2A 2kw, battery charging
22A 20.7A 2kw, battery charging
30A 27A 2kw, battery charging


AC input voltage is roughly 108-112V in all cases.

So why the huge jump in actual current, for a tiny bump in the set limit? It's not correlated with input voltage, and I can't identify anything this behavior is correlated with. I've tried setting WeakAC and it had no effect on the behavior either way. Shore power is 60Hz grid AC, so it's not like a generator is lagging its frequency or anything. What else should I be checking?

For the moment, I'm leaving it at 21.5A to keep the battery from draining while on shore power, even though it slightly overdraws the circuit's nominal rating, the breaker doesn't actually trip until a bit higher than that. ;)


MultiPlus Quattro Inverter Chargercurrent limit
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3 Answers
Johannes Boonstra (Victron Energy Staff) avatar image

Hello, The Ac input current is measuring the current on the AC input and controls this with PowerControl (charging the charge current to avoid AC input overload) or PowerAssist (adding energy from the battery to the AC power). Its starts regulating at app 80% of the setpoint at the normal setting. And starts regulating at 20% (at start) when dynamic current limiter is switched in).

This is done to avoid being on the edge of the current an incoming fuse could blow.

Beside this, depending on the load (cap/inductive) there can be a variation. Also a voltage change under load can create the current to change, and therefore also the controlling of AC input.

Lastely, depending on the model (pass through current) there is an error in measuring (app 1-2A). This is can be in wattage in your case roughly a 120-240 Watt error.

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Hello Johannes - when using the Multiplus with grid and loads connected to AC IN (such that the connection is bi-directional), is it possible to disable the PowerControl function, such that the Multiplus charger is not regulated?

I have MultiPlus II and with the settings I am running am limited to 50A draw on 100A grid connection as 50AMPs is the maximum I am currently able to set the AC Current Limit.

Colin59 avatar image

Another few experiences on input current limit: My system uses 2 paralleled 48/3000 quattros with dynamic loading & UPS selected, battery is 380 Ah ( 48v Lithium Chevrolet Volt batteries), running no assistants and virtual switch not selected. I had a remote Color control 15.5 A current limit set (minimum I can set -which should be 31A summed limit) on a 30 A shore power.

Starting with battery at 80% I started one AC running (~ 500 watts fan and ~1850 watts when compressor is running) plus had an intermittent refrigerator (~500 watts) and hot water heater (~1500 watt peak) loads. On initial starting power assist mode started with a AC load of about 3000 watts and shore power draw dropped from 2000 to 1500 watts, I came back a few hours later and found the battery discharged to ~42% and found the shore power draw had reduced to u 958 watts with just the AC running (AC load 1622 watts) plus 161W DC load, shore power was ~ 123V. In order to get the inverter to increase the shore power draw and change from assisting to bulk mode I gradually increased the current limit by 2 A at a time, I had to go over 40A (in parallel =80A limit) for it to switch to bulk, after that I monitored AC draw and had to gradually ramp down the current limit to ~ 18A which limited the shore power to ~ 3300 watts. This appears to demonstrate what can happen with power assist when the dynamic loading setting causing an undesirable effect where shore power could have handled the loads, initially and certainly after the how water was heated, but didn't. With the current limit at 18 A (36A for 2 in parallel) the shore power stays ~ 3300 watts - under 3600 watts and the inverters don't go into assist mode normally...

On a separate occasion I found the inverter in power assist mode 2985W ac load 186w DC load, solar at 2039 watts, battery at 81% with the shore power showing -510 watts, maybe due to the shore power voltage being lower than normal, but I didn't know the system would backfeed at all?

I am camped at a state park with no wifi, but my data will be uploaded later via VRM.

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Hi @Colin59

With a parallel setup, you don't have to divide the current limit setting, the system does that for you, so a 30A limit = 2x 15A (for double inverters) and 30A max on the input.

Why would you use the dynamic current limiter? this is only meant for variable speed generators, so they have the chance to speed up when the load gets higher.

A low grid voltage does also limit the current as you have noticed, depending on settings it will reduce current to not go under the minimum voltage setting.

Colin59 avatar image Colin59 Daniël Boekel (Victron Energy Staff) ♦♦ ·

Daniel,

l used dynamic loading since victron documents said to do so for inverter generators, which my Onan 7500 QD is..., though it is larger than the 2000 watt Hondas that are also inverter type, and thanks for the clarification....current limit with units in parallel wasn't clear from the posts, or Victron online documentation. Today I had to increase that current limit to 36 Amps to get the Quattro to switch fron assisting to bulk for an AC load of 2200 watts, I did connect so my data should show up on VRM again. I will change the configuration file to remove the dynamic loading and see if that puts the power assist at a more reasonable level.

Regards

Colin Barfoot


Colin59 avatar image Colin59 Daniël Boekel (Victron Energy Staff) ♦♦ ·

Daniel, l have done lots more monitoring and looking for answers and still have more issues. Following my previous report but now with dynamic loading off, I have continued to have the same issues, with minimal load and the battery in float with 2x 300 quattros in parallel and plugged into 30A shore power (30A currentlimit set), e.g. should supply approximately 3600 watts at 120V supply voltage, shore supplies and the quattros stay in float. If I introduce an AC run about 1700 watts, and the load goes over 2400 watts for more than a minute or so the mode changes to assist. Also similarly if in bulk charging , can go from shore supply of 3000W at 115v to going into assist where shore doesn't go aboue 1600watts . It gets stuck in assist mode until the current limit is increased to 40A with the same loads, still less than 3600W. For example of bulk version, see my VRM on Sept 21, 1913h, then 2020 assisting , 2021 bulk with current limit increased to 40A. ( raised 2A at a time from 30A).

Regards Colin.


Hi @Colin59

You have to look at the Current, and looking at the graphs, the system does well: at 40A input current limit it sticks to 37A nicely.

I would worry about the battery temperature btw.


nightcrawler avatar image

I have experienced the same issue with my 12/3000. I also have another scenario that is similar in its effect. When I set the current limit to 13 amps with a load of 15 amps it will only draw about 9-10 amps from shore and assist the rest.

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I am also having the same Issue with 2 x 8000 quattros.

have reported it but still get no answers.


Ie I have to set it at 80 amps to get a assist at 63 amps

very confusing for the customers