12v to 24v step up split charge relay

[holly_brown96]

The connector was swapped for an xt90 cable as the original had an issue so it was sent to get repaired and swapped from the Anderson to xt90. The cable for the solar is 10awg which is 5.26mm2. Does that sound like a better size?

 

[TallPaul_S]

The connector was swapped for an xt90 cable as the original had an issue so it was sent to get repaired and swapped from the Anderson to xt90. The cable for the solar is 10awg which is 5.26mm2. Does that sound like a better size?

Yeah that'll be fine.

Just one other thing you'll need to be aware of using a split charge system, is that when the van stops charging the SB when it gets to 80%, it'll stop providing 13.3v+ volts and so the split charge will also stop, meaning you might find on a long drive that your power bank has stopped being charged. You might be able to get around this by turning on the headlights or something to force the alternator the charge the SB. That's the downside to a split charge, with a proper DC-DC charger it'll draw from the SB/alternator for as long as it needs to.

 

[holly_brown96]

Ah ok, is there a way to stop that with a different system instead of a split charge?

 

[holly_brown96]

Sorry, just realised you said I can do that with a DC-DC charger. I thought the charger and converter was the same thing. The highest 12/24 charger I can find is the victron 15a one. I would lose 120w because the converter would supply 480w but if that would be the better option because it would continuously charge the battery then I would go with that. So it would install the same way, right? Would this set up work?

 

[TallPaul_S]

Sorry, just realised you said I can do that with a DC-DC charger. I thought the charger and converter was the same thing. The highest 12/24 charger I can find is the victron 15a one. I would lose 120w because the converter would supply 480w but if that would be the better option because it would continuously charge the battery then I would go with that. So it would install the same way, right? Would this set up work?
View attachment 270710

If you went for this, you wouldn't need the split charge relay at all, the DC-DC replaces this.

You'd need to set the DC-DC as a power supply in the settings which will then provide a set voltage and so would act the same as a converter in that respect.


There is another DC-DC charger coming out which can do 12-24v and vice versa, the Orion XS 1400 - however the launch isn't confirmed yet not is the price. This would be the most future proof system though as it'll charge 24v and 12v systems from a 12v alternator. So if you did ever swap to a normal LB set up you wouldn't need to replace this.

Victron Orion XS 1400 12/24 DC-DC Charger Converter Victron Orion XS 1400 12/24 DC-DC

Price to be confirmed Launch in 2025 Bluetooth Equipment Converter Charger Nominal Charging Current: 50 A Adjustable Input Voltage: 9-35 V Adjustable Output Voltage: 10-35 V Protection Class: IP65

fvcomponentes.com

 

[holly_brown96]

Ah ok, so no split charge relay. This is the system I think will work:

I looked into that new charger coming out and it seems way more powerful than what I would need and is predicted to cost a lot more too. It would be good if I was going to expand my power in the future but I'm not planning to for this van. Maybe something to think about if I build out another van though!

I have found a company that sells everything I need: Victron 12/24 15a, red and black cable for the switch, red and black cable for the 12v side, 16mm terminal lugs, 6mm2 terminal lugs, busbar for the 2 negatives coming from the 24v side, on/off switch, midi fuse holder for the 12v side, 20a blade fuse, 60a midi fuse, Cable for 24v side with fuse and xt90 attached already. I will just cut off the SAE side of the cable and attach to charger/busbar.
All in all, I think this will be a pretty good system. I need to take my van to the garage to get a new battery fitted so might just take all this stuff and get them to fit it for me while I'm there.
Just want to say, thanks so much for all your help! I couldn't have figured all this stuff out without you! I felt like my brain was rotting doing all the research and nothing made sense but you made sense of all it for me so thank you so much!

 

[holly_brown96]

I had written on a different forum a few weeks ago but no one replied. Someone just has now replied and they are telling me to change the 16mm2 cables to 25mm2 to avoid voltage drop. I then spoke to the company 12 volt planet and they are suggesting 10mm2 cables and 30a fuses. Do you think it would be best sticking to the 16mm2 cables?

 

[TallPaul_S]

I had written on a different forum a few weeks ago but no one replied. Someone just has now replied and they are telling me to change the 16mm2 cables to 25mm2 to avoid voltage drop. I then spoke to the company 12 volt planet and they are suggesting 10mm2 cables and 30a fuses. Do you think it would be best sticking to the 16mm2 cables?

I'm presuming you mean the SB to DC-DC wiring - 6AWG/16mm² wire is the recommended wire for a Victron Orion XS 50a for runs below 5m, so it's plenty for a 15a DC-DC. 10mm² would be enough.

25mm² is complete overkill.

If in doubt, check the Victron manual, that will give the recommend wiring sizes.

 

[n10n]

I had written on a different forum a few weeks ago but no one replied. Someone just has now replied and they are telling me to change the 16mm2 cables to 25mm2 to avoid voltage drop. I then spoke to the company 12 volt planet and they are suggesting 10mm2 cables and 30a fuses. Do you think it would be best sticking to the 16mm2 cables?

OEM secondary battery and split charge relay are wired with 10mm2 wire and fused at 100A on starter battery end, 80A on secondary battery end. Since it's just a relay, there's no current limiting (charger) on OEM system. Of course bigger is better but 25mm2 would be complete waste.

 

[holly_brown96]

Yeh from the starter battery to the dc charger is what I meant. Would 16mm2 and lower than 60a fuse be best then just for complete security? Chatgbt has suggested about 8 different fuse ratings so is no help at this point. It said I should use a fuse size rated for the cable not the system?
I felt 25mm2 was overkill, not sure if the person on the other forum misunderstood the system I am building. Given bigger is better, 16mm2 would be better than 10mm2 and the way to go?

 

[n10n]

It said I should use a fuse size rated for the cable not the system?

And it's correct - fusing should be designed to protect the wiring

Given bigger is better, 16mm2 would be better than 10mm2 and the way to go?

Even 10mm2 is quite sufficient for your use case. However since you're doing the work anyway you can future proof and use thicker wire, this will make charger upgrades later easy. For reference I'm using the OEM 10mm2 cabling with Victron Orion XS 50A but have limited the charger output to 20A.

 

[TallPaul_S]

Yeh from the starter battery to the dc charger is what I meant. Would 16mm2 and lower than 60a fuse be best then just for complete security? Chatgbt has suggested about 8 different fuse ratings so is no help at this point. It said I should use a fuse size rated for the cable not the system?
I felt 25mm2 was overkill, not sure if the person on the other forum misunderstood the system I am building. Given bigger is better, 16mm2 would be better than 10mm2 and the way to go?

Chatgpt is partially correct, the fuse and wiring size are dependent on each other - the fuse is there to protect the wiring in the event of a short circuit, so the fuse needs to be below the wire rating, so if there's a massive surge through the wiring, the fuse pops, not the wiring!

I would use 16mm² then fuse as per the Victron recommended size, probably a 40a based on 15a at 24v being delivered by the Victron, so it'll pull 30a from the SB.

 

[TallPaul_S]

And it's correct - fusing should be designed to protect the wiring


Even 10mm2 is quite sufficient for your use case. However since you're doing the work anyway you can future proof and use thicker wire, this will make charger upgrades later easy. For reference I'm using the OEM 10mm2 cabling with Victron Orion XS 50A but have limited the charger output to 20A.

As above - also, I'm using a Victron 50a with the std oem 10mm² until it reaches my seat base and the 2nd fuse, I've had zero issues in 3000 miles.

Even 10mm² is good for 70a.

 

[holly_brown96]

I don't see myself changing the way I power my campervan as the power station I bought was pretty expensive but I suppose I don't know what could happen in the future, it could break and need replacing so I suppose futureproofing with 16mm2 is probably not a bad thing and won't cause any harm having thicker cables.
I found this manual online for the charger:

If this is correct then the input should be 16mm2 and 60A. It may end up being shorter than 5m as I haven't measured but even then having 16mm2 wont be a bad thing, right?

 

[TallPaul_S]

I don't see myself changing the way I power my campervan as the power station I bought was pretty expensive but I suppose I don't know what could happen in the future, it could break and need replacing so I suppose futureproofing with 16mm2 is probably not a bad thing and won't cause any harm having thicker cables.
I found this manual online for the charger:
View attachment 271208
If this is correct then the input should be 16mm2 and 60A. It may end up being shorter than 5m as I haven't measured but even then having 16mm2 wont be a bad thing, right?

Yeah all good, and just go with the Victron recommended sizing for fuses, so 60a on the engine side and 30a on the power bank side.

The only real downsides to going bigger with wiring is cost and trying to route a bigger cable through spaces.

 

[holly_brown96]

I am going to get cable conduit and have the cables go under my van rather than trying to feed them through my van I think (if all goes to plan) just because it would be easier and the cables will come into my van where the dc-dc charger is so will be neater too. Will paint the drilled metal entrance to the van to prevent rust and will use a rubber grommet and silicone to seal and protect the cable. The thicker cables aren't too badly priced on 12v planet website so may as well pay £10 more and get the thicker cables. Will change the fuse on the 24v side to 30a
Thanks so much for your help!

 

[holly_brown96]

Just realised they sell tinned copper cables instead so I will swap my cables for that kind

 

[holly_brown96]

Sorry, one last thing. On the Victron manual, for the switch it shows a yellow cable not red and black. Should I be using that instead? I can get a switch like this to use if that would work? Sorry for all the questions, just want to make sure I do this correctly

 

[TallPaul_S]

Sorry, one last thing. On the Victron manual, for the switch it shows a yellow cable not red and black. Should I be using that instead? I can get a switch like this to use if that would work? Sorry for all the questions, just want to make sure I do this correctly
View attachment 271257

Yeah that switch is fine - any small guage wire is find and any simple 2 pole, 12v switch is good.

 

[holly_brown96]

Perfect! Will buy everything now. Thanks so much for your help!