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wedgehog avatar image
wedgehog asked

Can I feed a Multiplus-II with another inverter

Hi, May sound a bit silly, but I am trying to just use the internal charger of the Multiplus to charge some Lipo's. I don't want to pay for the electricity so I have some charged batteries of a different type and another, different make of Inverter, so I connected the AC input of the multi to this inverter, but the Multi just will not accept the 230v ac input and keeps going into overload, well there is nothing on the multiplus outputs yet.
I have tried selecting weak Ac, I tried limiting shore current to as low as 10 amps, Also limited the internal charger to 10 amps, makes not difference. I checked the box for accepting a widw frequency range and checked the low and high cut off voltages. I can't find a reason.
Any ideas anyone

cascading inverters
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gabius avatar image gabius commented ·

You can check the YouTube channel « offgridgarage » he did this but with two Victron product, maybe it will help you.

https://youtu.be/SsTkgoN6ENM?si=C5v23dTJXbF7o4jl

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vicens avatar image vicens commented ·

quita la funcion SAI

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derrick thomas avatar image
derrick thomas answered ·

This is not a victron approved or recommended installation method, but it has been done successfully by many. If you are using a cheap Chinese inverter or a modified sine inverter the multi may not like the dirty power. If you can connect to a PC through an MK3 with ve.configure it might give an indication of what's going on.

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wedgehog avatar image
wedgehog answered ·
Hi Derrick, It's definitely a cheap Chinese Inverter, and I have to say I also wondered that, Yes there is a Cerbo GX in the system and I have been monitoring everything, but it doesn't give much of a clue as as soon as I select charger only, it's almost instant that it goes into overload, if you leave it until it recovers it just goes into overload again

Bob


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derrick thomas avatar image derrick thomas commented ·

Cerbo is not going to show you what's going on. If you connect with a MK3 to a PC using ve.config it might give you the reason for the ac input rejection.

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wedgehog avatar image wedgehog derrick thomas commented ·

I haven't got a Mk3. But I have just ordered one,




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wedgehog avatar image wedgehog commented ·
Hi Derrick, Well I got the MK3 today, connected it all up and had a look, I could see it was loading the Chinese inverter when it started so I did a few tests, the following results have me at a loss.


First I tried limiting the charging current to 5 amps. no change
then I limited the line current to 5 Amps still loaded it.
I unticked the charger box in the Multiplus-II so the charger was off, also the mains output of the Multiplus-II is not connected to anything at the moment. Same result.

How can the Multiplus-II be loading the Chinese Inverter to the point it won't connect when it's internal charger is disconnected and the Multiplus-II inverter is not connected to anything? Yes I know there will be internal capacitors to charge up, but the amount of times now I have allowed it to re cycle those must be charged.

I loaded the Chinese inverter with a heat gun to stabalise it, no change.
I connected a 3KW fan heater to the Chinese Inverter and it ran it no problem
It is a 15KW Inverter, well! they claim it is. Added an electric drill still no problem.

So the Multiplus will not connect to it with no load and no charger, I can see on the computer display the incoming ac drops from 230 to around 170 when the muti comes on and I don't see why it should be loading that much with the above conditions.

Just for tests sake I connected the Multiplus to a generator and it connects fine and when I turn on the charger I was able to increase the charge up to 70 amps no problem and it was all very stable, but again, Initially when I connected to the Generator, which is a 10KW machine, with the Multi connected to nothing and the charger off, I heard a large load go on the Generator?.

Confused now. Bob


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derrick thomas avatar image derrick thomas wedgehog commented ·

If it is a modified sine and not a pure sine, the multi probably does not like the wave form. Also, with most modified sine inverters (especially the cheaper ones) the neutral and ground will not be bonded, and often times you will not get full voltage from line to neutral or line to ground, but part voltage from line to neutral and the rest of the voltage from line to ground. Does the cheap inverter have a built in transfer switch? If so, can you try swapping position? Feed the multi into the Chinese inverter and see if that works?

With charger off and no loads connected to the multi, it should not be loading the generator. Have you tried enabling dynamic current limiter and power sharing?

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wedgehog avatar image wedgehog derrick thomas commented ·

Thanks for that information Derrick, No it hasn't got a transfer switch. I don't understand the "Feed the multi into the Chinese inverter and see if that works?"
The Chinese Inverter only takes DC input 24v.
With everything you are saying above and the fact the Multi. Works with a Generator, I guess it's not going to happen.
Yes I tried Dynamic Current limiter, and Weak A/c. Bob

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wedgehog avatar image wedgehog wedgehog commented ·

The Chinese Inverter is this one, it says it's pure sin wave.
Oh! and it was £577 so I wouldn't say that cheap

https://www.amazon.co.uk/gp/product/B09DCZDLBL/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1


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