Your imagination required…

[frizzuti]

170A over 25mm2 and 30mm2 on a 4.5m run still shows a volt drop.


Using this calculator, it shows using a 70mm2 is recommended for that run. (12.2v 170A 4.5m)

Voltage Drop Calculator | 12 Volt Planet Cable Calculator

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Cable Calculator for Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator

www.12voltplanet.co.uk

.


View attachment 296376View attachment 296377

I don’t think I’ll draw 170A, that’s just the capacity of a 25mm2 cable.

So my load current draws calculate as follows:

- Inverter 67A (that’s 800W/12V)
- 12V circuits add to around 21A
- B2B DC-DC upto 60A
Total 148A

But is my load calculation correct? Should I be including the DC-DC load as this is from SB to LB and nothing to do with the inverter?? If so then that reduces to 81A and so from the calculator a 35mm2 cable is in limits - also considering that the calculator accounts for a return cable length (so effectively doubling the 4.5m) opposed to using the van body as the return.

 

[frizzuti]

I don’t think I’ll draw 170A, that’s just the capacity of a 25mm2 cable.

So my load current draws calculate as follows:

- Inverter 67A (that’s 800W/12V)
- 12V circuits add to around 21A
- B2B DC-DC upto 60A
Total 148A

But is my load calculation correct? Should I be including the DC-DC load as this is from SB to LB and nothing to do with the inverter?? If so then that reduces to 81A and so from the calculator a 35mm2 cable is in limits - also considering that the calculator accounts for a return cable length (so effectively doubling the 4.5m) opposed to using the van body as the return.

That’s should say 88A load draw…

 

[Dellmassive]

Not quite..

The b2b link is 60A from SB to LB. So 16mm2 or 25mm2 for that cable link

The LB to multiplus is 70A so 25mm2 or 35mm2 for that cable link. And same for NEG.

12v circuits from LB will be from seperate fuse box.. ie 2.5mm2 10A feed.

 

[Dellmassive]

Take a look at mine....


Post in thread 'Dellmassive`s Camper Van Adventure' Dellmassive`s Camper Van Adventure


.

 

[frizzuti]

Take a look at mine....


Post in thread 'Dellmassive`s Camper Van Adventure' Dellmassive`s Camper Van Adventure


.

Oh wow, that’s some neat set-up! I dream of the space you have - oh well.

Now I know why people pay other very knowledgeable people to do this stuff - my head is starting to hurt. But….i persevere…

Thanks very EVERYTHING, really! So with the correct load draw fig whilst a 25mm2 cable will be ok, I’m gonna go with 35mm2 for good measure.

When you say ground the inverter as close as possible, ie keep the cable as short as possible - would this suffice in the photo, to the ground point or make a new one at the holes even closer?

Same for LB NEG - I see you’ve ground to the seat base bolts - nice . I was going to go back to the chassis ground point 606 in 2nd photo - thoughts?

Your +ve fuse block (1x MEGA and 4x MIDI) does this have to be a certain rating? I don’t mean the fuses themselves I mean the connecting plate inside?

 

[frizzuti]

Also… main LB POS fuse - I was going to use the isolated part of the +ve bus bar in photo but I don’t need all 6 of the others fuse positions and it’s quite big to fit next to the LB in seat base. So then thought of the fuse holder youve used (also in photo) but then I’d need to remove part of the plate to isolate it as it then connects to my isolator switch, otherwise it would short circuit the switch. Then I had a thought to simplify things by using a MRBF terminal fuse and can use the mega-mini fuse holder without needing to modify.

So MRBF would need to be below 240A, as that’s the total capacity of a 35mm2 cable but at least high enough for any surge currents, so 200A would be ok or down to 175A?

 

[Dellmassive]

Use the D pillar earth stud, or create a new one on the frame .

Where is your LB going?... Under driver's seat?.. there is a stud there. But I cut mine off to fit in the Roamer 230SB.

35mm2 is a good upgrade.

Mega/midi fusebox, yes. They are rated for the MAX through put in Amps... Higher ones have thicker bars inside...

 

[Dellmassive]

Also… main LB POS fuse - I was going to use the isolated part of the +ve bus bar in photo but I don’t need all 6 of the others fuse positions and it’s quite big to fit next to the LB in seat base. So then thought of the fuse holder youve used (also in photo) but then I’d need to remove part of the plate to isolate it as it then connects to my isolator switch, otherwise it would short circuit the switch. Then I had a thought to simplify things by using a MRBF terminal fuse and can use the mega-mini fuse holder without needing to modify.

So MRBF would need to be below 240A, as that’s the total capacity of a 35mm2 cable but at least high enough for any surge currents, so 200A would be ok or down to 175A?

View attachment 296388

View attachment 296389

Sound like a plan.

Cube fuse, --> isolator --> midi fuse box

Fuse rating to protect the cable, so 175A max, but you can drop down to 150A, 100A , 80A . Work out your max draw from the loads, then add 20% and fuse at that per cable... But stay below the max rate for the individual cable.

 

[frizzuti]

Use the D pillar earth stud, or create a new one on the frame .

Where is your LB going?... Under driver's seat?.. there is a stud there. But I cut mine off to fit in the Roamer 230SB.

35mm2 is a good upgrade.

Mega/midi fusebox, yes. They are rated for the MAX through put in Amps... Higher ones have thicker bars inside...

Got it! Yes LB under dvr seat. Like you I needed to cut that ground nut out to fit 230A fogstar. So is the other one I mentioned ok or too far away?