Adding 24V Multiplus to Schaudt WA+EBL setup

[ian27]

I have a Carado, existing 12V setup is as per this diagram, all under the front seats (apart from the fridge!)

I've measured the WA121545 and its a bit disappointing, I get 40A, which is only 20A into the battery with the fridge running. so , I may replace the WA121545 with an orion XS.

I've also been looking at the EBL31 and am beginning to not see the point of it. I'm not using its mains charger as it doesn't do lithium properly (AC side not in the above drawing but I have a Victron Bluesmart in place at the moment, this may change). Its not doing the fridge relay or the B2B relay in my vehicle, its not doing solar, and there are too few outputs that are on the "always on" side of the panel master switch (e.g. the fridge and the b2b relay are on the switched side) for my needs. so it may be simpler just to replace it with a simple 12v distribution board and I gain some space.

I intend to add a 24V battery and inverter to serve AC loads, together with solar and B2B charging. 12V loads will still be served from the existing 12V battery. The changes I intend to make are as below.


12V:

• change the fuse on the 12v lithium leisure from 50A blade inline to 50A MRBF on the terminal for improved safety
• Add shunt so it can be measured
• orion XS 12-12 to replace the WA, so I have better efficiency and proper control
• add a simple DC distributor in parallel to the EBL, then debate whether to remove EBL or not...

24V
add a complete 24V system (a little further back in the vehicle, but not in the garage, due to weight). I don't wish to add inverter/solar etc to the 12v , and wish to use 24v for the reasons of cable + fuse sizing, inverter size and efficiency, solar sizing, etc.

questions / debate:
1. the chassis ground point as is , comes from on the starter battery -ve . Do I need to take the -ve of my 2nd -ve bus bar serving the 24v kit to the starter battery -ve, or the 1st busbar? Does it need to be in 50mm ? Do I need to increase cable size all the way back to the starter?
I think yes because of the flow between 24v battery and inverter can in worst case situation go this way, but appreciate a sanity check, if the work is needed or not.
2. The 12-24V B2B: at this time I will not be able to run both this and 12-12 B2B in parallel as I have not enough on the alternator side (its configured for 50A, both cabling and fuses from battery to alternator). Debating whether to wire B2B's in parallel and use remote on/off switches so as to only ever run one at once, or to wire effectively in series i.e. connect the 12-24 B2B to the leisure side of the 12-12 b2b. thus using the 12v leisure as a buffer and guaranteeing never to overload the alternator side. Use GX and BMV monitoring SOC to decide when to switch 12-24 B2B on or not. If I do this it changes where the "vehicle side" supply to the 12-24V b2b comes from of course.

ta for any help
Ian

 

[LostInSpace]

Sounds like a lot of work, for debatable gain. and future confusion.

Why do you nneed a 12 volt system and a 24 volt system?

 

[mikash]

I would do parallel B2B's definitely. Series is just more losses for same cost. Even if you can't run both at full blast (50A input), you have the option to adjust the split to fit your needs, remotely at 1A resolution or with a button to halve power.

 

[Lenny HB]

Unless you are going to change the whole habitation electrics to 24v I don't see the point of having a 24v Multiplus just for the sake of saving a bit of cable it makes it unnecessarily complicated.

Changing the Schaudt B2B for the Orion XS will only gain you 5 amps however it is a much better unit that works better with Lithium.
I had a Schaudt 25 B2B fitted as standard and lost 15 amps to the fridge so I swapped it for a Orion XS. I have now wired the Schaudt unit back in with a switch in the D+ so I can manually switch it on when I need more charging.

 

[eddie]

The most important question is why?

So much work for questionable gain

The only 100% reliable way of charging a 2nd 24 VDC system is with a dedicated secondary 24 VDC alternator

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[Sewdhull]

You may as well parallel the B2Bs if the units don't mind being paralleled as it will save all that stress on the 12v system.

Im unsure why you want 12v and 24v, if you are running a fridge only as it seems, go 24v save some complexity and use a 24v 12v converter for that esp if you are looking at a compressor fridge later when you could choose 240v to run it if you wanted to.

For me, id have everything 24v in the back and go for 240v, perhaps 2 inverters to keep cable sizes down although put them close to the batteries and it probably doesnt matter.

 

[ian27]

why:
1. keep the 12v system active so that everything that works on 12v (all the usual motorhome stuff, the way it was built in the factory) works as it does today. If the 24vDC/230vAC part misbehaves - all the old 12v stuff still works: resilience.

2. I haven't drawn them on the diagram to avoid overcomplicating it even more, but I did state in the blurb, the purpose of the inverter is for significant AC loads. Having looked into the available batteries on the market, inverter, cable, fuse sizing, read a lot of stuff on here and other forums it seems so much more sensible to build the inverter setup on 24v. I did think about 48v, but I suspect I would not be able to fit enough solar for that to work properly, plus the voltage means more care on components choice . The 24v part is only to run the inverter, not the hab.

3. if I was to do a 12v for the inverter then I would still have to have two separated 12v systems because I can't easily parallel a new battery with the existing one: the existing one is a small one and relative old so would not want to buy another identical. So I'd have to buy two. Plus the physical separation (one under seat, one in cupboard part way back) would make parallel cabling challenging. so I end up with a smaller 12v system at the front and a separate larger 12v system further back for the inverter. In which case the 2nd system might as well be 24v - more efficient, cheaper, lighter. The number of people on here and other forums who have said "I wish I'd not done 12v for my inverter wish I'd gone 24".

 

[ian27]

The most important question is why?

So much work for questionable gain

The only 100% reliable way of charging a 2nd 24 VDC system is with a dedicated secondary 24 VDC alternator

surely a 12-24 B2B would also be reliable? as reliable as a 12-12 B2B charging a 12vDC system, anyway?

 

[ian27]

You may as well parallel the B2Bs if the units don't mind being paralleled as it will save all that stress on the 12v system.

Im unsure why you want 12v and 24v, if you are running a fridge only as it seems, go 24v save some complexity and use a 24v 12v converter for that esp if you are looking at a compressor fridge later when you could choose 240v to run it if you wanted to.

For me, id have everything 24v in the back and go for 240v, perhaps 2 inverters to keep cable sizes down although put them close to the batteries and it probably doesnt matter.

The 12v loads are already there in the vehicle, not going to change those , want 12v always there for the basic stuff - lights , water pump etc.

I am afraid I don't understand your explanation in the second part.

 

[ian27]

I would do parallel B2B's definitely. Series is just more losses for same cost. Even if you can't run both at full blast (50A input), you have the option to adjust the split to fit your needs, remotely at 1A resolution or with a button to halve power.

thanks. The tunability by 1A and "half power" makes sense.

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[ian27]

. I have now wired the Schaudt unit back in with a switch in the D+ so I can manually switch it on when I need more charging.

do you have a bigger setup than me (50A) on the alternator side?

 

[eddie]

surely a 12-24 B2B would also be reliable? as reliable as a 12-12 B2B charging a 12vDC system, anyway?

No, step up - step down equipment has always been inherently un reliable

Given the small margins your working on there is absolutely no point doing it, that I can see, but, I’ll ask what is the major advantage as you see it?

 

[ian27]

No, step up - step down equipment has always been inherently un reliable

Given the small margins your working on there is absolutely no point doing it, that I can see, but, I’ll ask what is the major advantage as you see it?

advantage / reasons why - as per post #7

 

[eddie]

advantage / reasons why - as per post #7

Yes I read that. They are not reasons, saying loads of people on here, although honestly I can't recall reading that, even if they have done/did, that is not the advantage. Perhaps you have read about people converting their own van and have bought a larger van that has 24 VDC chassis electrics? That would make sense

You will make loads of extra stress for yourself an gain nothing

Your not starting from scratch your adding to an existing 12 volt system

I spent thirty odd years installing all of this stuff, exclusively on motorhomes and RV's and am trying to advise not wind you up

24 volt on higher amperage equipment, and on much longer wiring runs there is an advantage. On a medium sized European factory converted motorhome there is no advantage that could be discerned, additional costs and you build in a higher failure rate.