How to wire AC side of Victron Multiplus

[Tia Bu]

Thinking of doing LifePO4 conversion. We often charge our batteries while cruising using our 5.5KW generator and 40 amp Charles charger. That charger has a lithium setting, so we could continue using it, but it seems so darn slow in the new lithium world!

After much searching, it seems a Victron Multiplus might be the fastest and most economical charger for a new 400ah 12v lithium bank? It seems to have a "charge only" switch, so I could use it that way.

But the inverter function seems nice. Trouble is, I can't conceptualize how to wire it into my current AC panel.

I have two 30 amp shore power inputs. And I have the 5.5 kw generator input (50 amp.) My panel allows me to switch between shore power and the generator. But it prevents both inputs being open at the same time.

I suppose I could wire the Victron in the line between the generator and the panel. That would let me charge the batteries when the generator is running. When the generator is off, and we're away from shore power, the inverter would power the AC panel, as long as we have the panel "generator" switch on.

But that would mean we'd have no charger available when we're on shore power, right?

Is that even a big deal with lithium? We would have solar to keep the batteries topped off at the dock.

Is there another way to wire this up that would make more sense?

[smac999]

Inverter chargers are not simple to wire correctly. and even harder if you nave 2 shore lines going to a single shore / gen transfer switch. As only one shore line can go through the multiplus and the 2 shore netreals must stay separated on board. As well as the inverter output neutral. .

I would suggest having someone come to the boat and make a plan for you. As it will vary greatly with exactly what you have existing.

The multi needs to go after the switch so both charge. Otherwise it would be silly.

[rslifkin]

You can always make a sub panel. So the existing sources feed the main panel for anything you don't want powered through the inverter. This will also feed to the inverter input. Then the inverter output powers the new sub panel and whatever loads you connect to it. The inverter has a built in transfer switch so when shore or generator power is available to the input it will be passed through to the output (even in charger only mode). In "on" mode it will pass through and charge, but when the input power is removed it will switch to powering the output side from the inverter.

[s/v Jedi]

Originally Posted by Tia Bu

Thinking of doing LifePO4 conversion. We often charge our batteries while cruising using our 5.5KW generator and 40 amp Charles charger. That charger has a lithium setting, so we could continue using it, but it seems so darn slow in the new lithium world!

After much searching, it seems a Victron Multiplus might be the fastest and most economical charger for a new 400ah 12v lithium bank? It seems to have a "charge only" switch, so I could use it that way.

But the inverter function seems nice. Trouble is, I can't conceptualize how to wire it into my current AC panel.

I have two 30 amp shore power inputs. And I have the 5.5 kw generator input (50 amp.) My panel allows me to switch between shore power and the generator. But it prevents both inputs being open at the same time.

I suppose I could wire the Victron in the line between the generator and the panel. That would let me charge the batteries when the generator is running. When the generator is off, and we're away from shore power, the inverter would power the AC panel, as long as we have the panel "generator" switch on.

But that would mean we'd have no charger available when we're on shore power, right?

Is that even a big deal with lithium? We would have solar to keep the batteries topped off at the dock.

Is there another way to wire this up that would make more sense?

Of course. Why two shore power cords? Is one for A/C ?

[Tia Bu]

It came that way. I think originally the two AC units needed two shore power cords. But with new AC units, you can run the boat fine at the dock with just one 30 amp cord.

[Tia Bu]

You can parallel the two AC buses with the current panel. I always parallel them if running the generator. And parallel them if at a dock with one 30 amp connection.

[Dockhead]

Originally Posted by Tia Bu

Thinking of doing LifePO4 conversion. We often charge our batteries while cruising using our 5.5KW generator and 40 amp Charles charger. That charger has a lithium setting, so we could continue using it, but it seems so darn slow in the new lithium world!

After much searching, it seems a Victron Multiplus might be the fastest and most economical charger for a new 400ah 12v lithium bank? It seems to have a "charge only" switch, so I could use it that way.

But the inverter function seems nice. Trouble is, I can't conceptualize how to wire it into my current AC panel.

I have two 30 amp shore power inputs. And I have the 5.5 kw generator input (50 amp.) My panel allows me to switch between shore power and the generator. But it prevents both inputs being open at the same time.

I suppose I could wire the Victron in the line between the generator and the panel. That would let me charge the batteries when the generator is running. When the generator is off, and we're away from shore power, the inverter would power the AC panel, as long as we have the panel "generator" switch on.

But that would mean we'd have no charger available when we're on shore power, right?

Is that even a big deal with lithium? We would have solar to keep the batteries topped off at the dock.

Is there another way to wire this up that would make more sense?

The manual is your friend here.


The Multiplus is designed to have all the shorepower running through it. I wired mine so that the input of the Multiplus is connected to the output of the generator/shore transfer switch, and the output of the Multiplus is connected to the AC distribution panel.


I think that's how you want to do it. So the changeover switch on your power controls what goes INTO the Multiplus.

[Tia Bu]

That makes a lotta sense. Thanks so much!

[s/v Jedi]

Originally Posted by Tia Bu

It came that way. I think originally the two AC units needed two shore power cords. But with new AC units, you can run the boat fine at the dock with just one 30 amp cord.

Originally Posted by Tia Bu

You can parallel the two AC buses with the current panel. I always parallel them if running the generator. And parallel them if at a dock with one 30 amp connection.

I see, this is a dangerous installation that you need to fix. When you parallel the two shore power feeds, but the pedestal outlets come from different hot conductors, i.e. L1 and L2 instead of both L1 or both L2, which is common, then you create a short circuit.

This is not how the boat was originally wired. I recommend to completely remove one shore power inlet, keeping the other one, then wiring that inlet and the generator output to a manual rotary transfer switch and the output of that switch to the Multiplus. Alternatively you can skip the manual transfer switch and buy a Quattro which has two inputs and an internal automatic transfer switch.

I also recommend to install an isolation transformer for safety of boat and crew.

[rslifkin]

Originally Posted by s/v Jedi

I see, this is a dangerous installation that you need to fix. When you parallel the two shore power feeds, but the pedestal outlets come from different hot conductors, i.e. L1 and L2 instead of both L1 or both L2, which is common, then you create a short circuit.

This is not how the boat was originally wired. I recommend to completely remove one shore power inlet, keeping the other one, then wiring that inlet and the generator output to a manual rotary transfer switch and the output of that switch to the Multiplus. Alternatively you can skip the manual transfer switch and buy a Quattro which has two inputs and an internal automatic transfer switch.

I also recommend to install an isolation transformer for safety of boat and crew.

Most "parallel" setups I've seen with 2 inlets simply feed both sides of the panel from one of the inlets and leave the other inlet disconnected and doing nothing (for exactly the reason you described). Basically it's a selector switch for whether panel 2 gets power from inlet 1 or 2.

[Tia Bu]

Originally Posted by rslifkin

Most "parallel" setups I've seen with 2 inlets simply feed both sides of the panel from one of the inlets and leave the other inlet disconnected and doing nothing (for exactly the reason you described). Basically it's a selector switch for whether panel 2 gets power from inlet 1 or 2.

Yes. That's how it's set up. You can't parallel the two buses without disconnecting the second shore power inlet.

[Tia Bu]

This is our current AC panel. Hope you can see the upload. I'll have to look at the back side of it when I get to the boat, but I think I may be able to take the Victron "AC in" from the Shore 1 and Generator switches (which can't both be on at the same time.) Then I can connect the Victron "AC out" to the Bus 1 input, (removing the current connection from there to Shore 1 and the generator, of course.)

Does that sound right?

[s/v Jedi]

Originally Posted by Tia Bu

This is our current AC panel. Hope you can see the upload. I'll have to look at the back side of it when I get to the boat, but I think I may be able to take the Victron "AC in" from the Shore 1 and Generator switches (which can't both be on at the same time.) Then I can connect the Victron "AC out" to the Bus 1 input, (removing the current connection from there to Shore 1 and the generator, of course.)

Does that sound right?

Exactly. The two breakers replace the rotary transfer switch

[smac999]

Originally Posted by rslifkin

Most "parallel" setups I've seen with 2 inlets simply feed both sides of the panel from one of the inlets and leave the other inlet disconnected and doing nothing (for exactly the reason you described). Basically it's a selector switch for whether panel 2 gets power from inlet 1 or 2.

That’s called transfer. Sending 1 line to the other side of the panel so both halves share 1 input . Not Parellel. Parellel would have 2 30a cords forming a single 60a feed on the boat. But that now blows elci / gfci dock breakers which is becoming more common.

For example look at Bluesea 8498.

[smac999]

Originally Posted by Tia Bu

That makes a lotta sense. Thanks so much!

It makes sense with a single shore cord. Yours is more complicated.