New Victron Multiplus Installation - What to do with old converter?

[babyrocket]

I have a 2022 Grand Design Fifth Wheel and recently installed a new Victron Multiplus inverter/converter in the front compartment with 4 lithium batteries. I thought I needed to disconnect the old converter at the AC panel to prevent it from trying to charge the batteries along with the Multiplus, but when I unplugged it the whole DC panel lost power. Plugging it back in restored 12v power.

Should I just leave the converter plugged in, or is there another way to disconnect it without losing all 12v power?

Thanks in advance for any help!

Patrick

 

[Tecnodave]

Patrick...

The factory converter does two things,

1: when powered up it engages a relay which disconnects the coach DC power feed from the batteries and connects the coach DC buss to the power converter, it also connects the battery charging circuit in the converter to the batteries.

2: it converts AC to DC to power the coach

To get best results you need to do two things:

1: It is best to disable the converter from the AC feed as it is set for lead acid by disabling the AC input via the breaker (remove and cap the wire from the breaker)

2: Then you will need to change a DC wire that feeds the coach DC buss from the converter and connect it directly to the lithium battery bank. You will be bypassing the DC buss around the relay in the converter

most installations will have two DC wires coming into the converter, cut the input wire and the output wire and connect them together to bypass the relay.....if you are bold open the converter and change the wires at the relay but doing it externally is probably easier.

By this process you will be protecting your lithium investment.

 

[TAS CPA]

I have a 2022 Grand Design Fifth Wheel and recently installed a new Victron Multiplus inverter/converter in the front compartment with 4 lithium batteries. I thought I needed to disconnect the old converter at the AC panel to prevent it from trying to charge the batteries along with the Multiplus, but when I unplugged it the whole DC panel lost power. Plugging it back in restored 12v power.

Should I just leave the converter plugged in, or is there another way to disconnect it without losing all 12v power?

Thanks in advance for any help!

Patrick

As Tecnodave notes, when you remove the old converter you will need to run power from your new lithiums to the DC panel. Where you tie in will depend on what your DC distribution setup looks like at the batteries.

 

[AndyRonLI]

Can you explain that first statement about the relay? I don't have one on my rig

 

[babyrocket]

Patrick...

The factory converter does two things,

1: when powered up it engages a relay which disconnects the coach DC power feed from the batteries and connects the coach DC buss to the power converter, it also connects the battery charging circuit in the converter to the batteries.

2: it converts AC to DC to power the coach

To get best results you need to do two things:

1: It is best to disable the converter from the AC feed as it is set for lead acid by disabling the AC input via the breaker (remove and cap the wire from the breaker)

2: Then you will need to change a DC wire that feeds the coach DC buss from the converter and connect it directly to the lithium battery bank. You will be bypassing the DC buss around the relay in the converter

most installations will have two DC wires coming into the converter, cut the input wire and the output wire and connect them together to bypass the relay.....if you are bold open the converter and change the wires at the relay but doing it externally is probably easier.

By this process you will be protecting your lithium investment.

Many thanks for this. I'm attaching my wiring diagram to avoid any confusion. I think the problem is where I rerouted the positive and negative connections from the factory busbars near the old battery to the Lynx Distributor, effectively connecting them to the new battery bank. I now think that this only connected the "always on" circuits to the battery. I didn't change anything about how the converter is wired to the DC panel, and didn't realize that removing AC power to the converter would remove the power route from the batteries to the DC panel.

So in summary, I need to either remove and connect the incoming and outgoing DC power cables at the converter (thereby bypassing it), or run a new power cable from my battery bank (actually the Lynx Distributor) to the DC panel and disconnect the incoming DC power from the converter, correct? Is either way preferable?

 

[Tecnodave]

Patrick......

Which ever way is easier will work, you just need to disable the transfer relay. And remove power from the old converter as it is not needed for the upgrade to lithium batteries and will impress voltages too high for the lithium batteries


my high speed internet is down so at the moment I cannot review your document as my alternate internet access is dead slow

 

[TAS CPA]

Looks like you still need to feed the DC panel. For mine, needed wires from Lynx to DC panel, replacing the feed that used to come from the converter.

 

[babyrocket]

I now realize that this could be as simple as an open battery disconnect switch. I'm going to replace the key and confirm that this restores power to the DC panel. If so, I'll probably take it out of the loop since I have a much better disconnect in the front bay where the Victron equipment is.

I appreciate all the help!

 

[Tecnodave]

Can you explain that first statement about the relay? I don't have one on my rig

Some modern converters such as the IOTA do not have a relay, they are a true multistage battery charger and power source, the load side and the battery do not need to be seperated. If you power them up and they do not “see“ a battery in the circuit they come up as a regulated power supply, if they do see a battery they do come up as a multistage battery charger and will charge the battery and power the loads at the same time. The other design with the relay does have seperate outputs for battery charging which is very limited (3 amps maybe) and the regulated power output 35, 45 amps or more.

There are advantages of both types....

The units that have a relay will have a lower output voltage on the coach output which will not be affected by the higher voltages needed to charge the battery but are limited to maybe a 3 amp battery charge at maximum

Units such as the IOTA converters have a voltage sense function which will actually “see” the battery condition and will automatically select the correct mode and start in bulk charge, adsorb charge, or float charge depending on battery state of charge. The big advantage of this type is if you have seriously run down the batteries they will use the full amperage capability of the unit to bring the battery up to voltage....

Personally i use the IOTA brand units as they can and will correctly diagnosis the battery condition and be in the correct stage.......bulk, adsorb, or float....or in the case of no battery will come up as a regulated power supply at “float voltage” where the older units have only a trickle charge function.

If you go out and do dry camping away from the power grid and run your batteries very low the generator run time will be greatly reduced by the full output of the “IOTA” type of converter as opposed to the trickle charger found in the older units.

 

[babyrocket]

Turns out it was the old battery disconnect switch that I had left open. Dumb mistake but easy fix!

 

[fblevins1]

Turns out it was the old battery disconnect switch that I had left open. Dumb mistake but easy fix!

Welcome to my world. I need a lifetime of accomplishments to make up for the lifetime of shenanigans and mistakes. Looks like you have sweet rig so looks like you are on the plus side of that equation. Glad you got it all worked out.

 

[carlrx7]

I left my factory converter installed and just flipped the breaker.