Fuses and relay - what are they for?

[XEG12]

In my 2021 Marco Polo I have under the left seat, to the left of the leisure battery a block of spade fuses (mostly 50A) and a relay.

I had a problem with car and leisure batteries being totally flattened and we reckon the charging relay was stuck closed, but something else must have gone.
My local installers found that the relay mentioned above had no power and the front of the 50 fuses was blown.
They replaced the fuse and there weas then power to the relay. For now they disconnected the leisure battery negative terminal.

Given that the blown fuse might have something to do with the flat batteries does anyone know what that relay is for? I wondered about the electric roof but that has not been touched for 3 months (yes I need to open it to air it and check but first the charging relay is getting replaced with a DC to DC charger - small steps).

 

[Van Diesel]

fuse diagrams are in the manual i think...or the mbac manual.

 

[MarioF]

I think you'll find that the relay is there to isolate the leisure battery from the other battery, it's only powered when charging the leisure battery.
If your dc-dc charger handles isolation then you'll have to bypass that relay.

 

[XEG12]

I think you'll find that the relay is there to isolate the leisure battery from the other battery, it's only powered when charging the leisure battery.
If your dc-dc charger handles isolation then you'll have to bypass that relay.

Afraid it's not that relay - we watched the aux battery display on the MBUX show 60A (yes really - VERY dead battery!) going in while the relay I am enquiring about had no power to it (the fuse had not been replaced).

The relay you mention is in front of the battery - and yes my installers have just disconnected that while fitting a DC-DC charger today.

The relay I am enquiring about- I wonder if it is the poptop roof? Mine is electric and I can't think of anything else which might require a relay and 50A fuse. Anyway it worked today when I got home.

 

[MarioF]

Just out of curiosity, what kit did you install?
I take it you went lithium.

 

[XEG12]

Just out of curiosity, what kit did you install?
I take it you went lithium.

I am getting a lithium battery at the end of the month, along with an inverter so no more need for my battery pack (this is stage 2)

The DC-DC charger is a Votronic 50A device.

The Lithium battery will be a 180 Ah one, can't remember the manufacturer - note they had to measure to the millimeter as there is so little space available under the seat, and they also had to fit the DC-DC charger under the right hand seat (once trims are removed there is plenty of space to route thick cables between the seats).

The inverter will also be a Votronic device. I settled for the 600W as I do not need more, and it not only has a removable front panel which can be fitted below the RCD but it also can be mounted under the bottom right drawer.
I ordered the version of this unit which senses shore power and if available turns off the inverter, and also has an auto option to only turn on the inverter if it senses a certain power requirement.

 

[Van Diesel]

I am getting a lithium battery at the end of the month, along with an inverter so no more need for my battery pack (this is stage 2)

The DC-DC charger is a Votronic 50A device.

The Lithium battery will be a 180 Ah one, can't remember the manufacturer - note they had to measure to the millimeter as there is so little space available under the seat, and they also had to fit the DC-DC charger under the right hand seat (once trims are removed there is plenty of space to route thick cables between the seats).

The inverter will also be a Votronic device. I settled for the 600W as I do not need more, and it not only has a removable front panel which can be fitted below the RCD but it also can be mounted under the bottom right drawer.
I ordered the version of this unit which senses shore power and if available turns off the inverter, and also has an auto option to only turn on the inverter if it senses a certain power requirement.

sounds wonderfull... could you pls post the items so i can maybe get something similar.
my real problem with power is the stereo which runs off the primary batteri.

so i would like a 180ah. and be able to switch the mains maybe. D

 

[MarioF]

I am getting a lithium battery at the end of the month, along with an inverter so no more need for my battery pack (this is stage 2)

The DC-DC charger is a Votronic 50A device.

The Lithium battery will be a 180 Ah one, can't remember the manufacturer - note they had to measure to the millimeter as there is so little space available under the seat, and they also had to fit the DC-DC charger under the right hand seat (once trims are removed there is plenty of space to route thick cables between the seats).

The inverter will also be a Votronic device. I settled for the 600W as I do not need more, and it not only has a removable front panel which can be fitted below the RCD but it also can be mounted under the bottom right drawer.
I ordered the version of this unit which senses shore power and if available turns off the inverter, and also has an auto option to only turn on the inverter if it senses a certain power requirement.

Wow 180Ah, that's almost double mine! You'll have power to spare.
Give us some snapshots when you're all done.

 

[MarioF]

sounds wonderfull... could you pls post the items so i can maybe get something similar.
my real problem with power is the stereo which runs off the primary batteri.

so i would like a 180ah. and be able to switch the mains maybe. D

Van Diesel, this is my install: https://www.marcopoloownersclub.com/threads/orion-tr-smart-dc-dc-charger.1396/post-16702