Can I disable Victron Multiplus 12/3000/120 Bypass?

DIY
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1

Hello,

Is there a way to activate only the charging on a Multiplus, yet have all external mains/shore power go to charging only, rather than let it try to service the leisure AC circuit? In short, to separate them and operate them completely independently? I would like the Multiplus to both invert, but also charge at the same time…

We are liveaboards on our sailboat, and we have 12.8Kw of DC (5 Victron SuperPack 200Ah batteries) and a Multiplus 12/3000/120.

I can run an AC dive compressor off it once in a while, and we live easily day to day with our 2650W of solar topping us up every day by noon. We’re in the tropics…

The problem I have is every once in a while, when its been cloudy for several days, we break out the noisy 2000W portable gas generator to aid in charging. If the Instant Pot, or kettle, etc is turned on, the circuit first tries to shunt all of the AC load directly to the generator, understandably, as it’s considered an ‘unlimited’ mains/shore power. However, this causes a surge in the RPM of the generator’s governor and often trips it offline.

I would like the mains input to be dedicated to the charger, to not power the AC circuit on our boat, and have all AC come from the inverter only. In 5 years with this setup, we’ve plugged in to shore power less than 3 times, so it’s not a loss of function for us. So, when an external AC source is connected, it can only be used by the Multiplus for charging, even when switched to inverter/charger.

Is this not possible, not a good idea, or is there a setting I’m missing in VE Configure? Is it a wiring issue on our boat? Perhaps at 7A on the shore currently limiter, it’s too high?

Thank you.

2

Drop your input current limit so the inverter power assists instead.

What it means though with the lower input current limit, is if the load is high on the output you will be discharging rather than charging.

Current limit is 2000 x 0.8 ÷ ACV (ac voltage used in the system) for the max load on the generator assuming it is in good service condition. It should be around 13A, but go lower if it is still struggling.

The other option is dynamic current limiter.
More ideas from the FAQ

3

This is great, thank you.

I thought it might be something like this, and I possibly hadn’t dialed back the input current limit enough. I’m likely trying too hard to keep the maximum charge up and perhaps didn’t leave enough room for varying loads to let Power Assist kick in.

Perhaps I should have gone with a divorced inverter/charger setup, but for the amount of times this is a ‘problem’ for me, I can certainly work around it, and I prefer the all-in-one solution of the Mutiplus overall.

Next cloudy period I’ll give it a try and experiment more.

5

Hi there,

I see your comment about running your AC dive compressor from a 3000w inverter. I am struggling with mine (also 3000w but 240V). The dive compressor is 2.2kw.

Thats a link to my question on victron community.

Thanks for any information,

Rob

6

Hi Rob,

I’ve had good success running our Bauer Jr 2 with a 220VAC motor on the MultiPlus 12/3000/120. I think the key is to use a 3phase motor coupled with a Variable Frequency Drive.

The VFD can convert the 2phase from the MultiPlus to 3phase, and is a more efficient motor. The bonus of the VFD, to my mind, is that it also operates like a ‘slow start’. The motor can start from about 10RPM (estimated) and ramps up to full speed in about ten seconds, by varying the Hz. This is all programmable in the VFD. I also have set the max Hz to around 42. This means the motor runs a bit slower, and the tank takes about 40mins to fill, but it’s easier on the MultiPlus and my 2650W of solar can almost keep up.

Don’t start the Bauer with the pressure lines closed, of course. It starts compressing using about 1500W, and climbs to 1900W when the tank is approaching full.

Have a look for a video from Outer Passage called ‘Electric SCUBA Dive Compressor Onboard a Small Sailboat’. He explains it all very well and closely mirrors what I’ve done.

Rereading your post, I wonder if you couldn’t just use a VFD for the soft start feature? I don’t know if you could just pass the 2phase through and modify only the Hz, perhaps something to consider. This might allow you to use your existing motor. YMMV.

Dave

7

Dave,

Many thanks for your detailed reply, exactly what I was looking for. When you get around to it would you please be able to send a photo of your motor nameplate and the VFD you are using. I will also watch the video you have recommended (haven’t done so yet). My motor is single phase and I’m on a 230v system. I will look into your suggestion about trying the VFD as a soft start on my existing motor.

What are your thoughts on using something like this on my single phase motor? https://docs.rs-online.com/e6e0/0900766b8002c42b.pdf

My direct email is svchieftain@gmail.com.

Thanks again, this will soon be a very important project for me, just finished a 19 Month refit and of course other gremlins are in need of killing off first!

Rob