24v to 48v B2B - Is there such a thing?
- Thread starter Wissel
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Abacist
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Can you not introduce a transformer/regulator to make the voltage change and so keep to a standard 24 volt B2B if you cannot find what you want?
They appear to be available if you Google it.
They appear to be available if you Google it.
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This is listed as a voltage converter, but the data sheet suggests that it can also be set up as a charger suitable for LiFePO4.
If you need more power, a Canadian product sold by an American distributor with a slightly dodgy looking website. I couldn't see who made it though.
If all else fails, you could use a 24v inverter to power a 48v battery charger.
If you need more power, a Canadian product sold by an American distributor with a slightly dodgy looking website. I couldn't see who made it though.
If all else fails, you could use a 24v inverter to power a 48v battery charger.
Difficult to find, I think. I could only find one 12V to 48V charger, from Sterling, but I think they don't do a 24V to 48V charger. Maybe something like this one will do:
DC input 24V volt to 48 volt DC/DC battery charger for lead acid and lithium batteries (common negative) 1500 Watts peak Robust, marine, heavy duty from PowerStream.
1400W 24V to 48V DC-DC voltage boost converters for use in 24 volt heavy duty, marine, military and industrial systems.
www.powerstream.com
There are plenty of converters just no chargers as I understand the problem
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https://vanjunkies.co.uk/products/s...7t91K8awmzknZC0xH7IgN_6tNyraLNLhoCQJUQAvD_BwE
Seems to do what is required. Probably worth contacting Sterling direct if you can before committing.
Seems to do what is required. Probably worth contacting Sterling direct if you can before committing.
That's the one I have, 12V to 48V. It's not 24V to 48V unfortunately.
Are you trying to use a domestic battery bank in a truck based mh? Would you perhaps be better with a 48v alternator and then step down to 24v for the Engine chassis requirements?
Quite a few solar regs are apparently ok at 48v
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Wissel
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I'm thinking of building a 15kW 48v battery.
I can build this for about £2.5k. This works out at £165 per kW. My preferred battery choice works out at £320 per kW. Not a small difference.
The system in the van will be to power our workshop as well - hence the battery size. The van will have a 1.2kW solar array and the unit another 4-5kW (initially). There will also be a 3kW Honda genny in the system for emergency charge and to combine with the Multiplus 5k if I need to run high draw tools (will give me a maximum of around 6.4kW continuous draw).
The upsides to a 48v system are 1 x BMS, 48v Multiplus a little cheaper, cabling cheaper. The downsides are the issue with B2B (there is a product available that I trust, but it's around £1700 + import fees) and the van MPPT would be quite a bit more expensive (would have to run the panels in series to get the voltage).
The other option is to run the van and workshop @24v.
I'd need a second BMS, so the battery cost would rise £150-£200. The 24v Multiplus would be about £130 extra. But, I can use 24v-24v Victron B2B's and the MPPT's work out about £300-£400 less.
Not doing it yet, so I'll give it more thought
Also considering a second 48v alternator as you suggest. Lots to think about
I'm not getting where the Mh/van fits in this arrangement? Is it not just adding complication? Without knowing the intimate details - Wouldnt fitting a few 400w ground/roof mounted panels give a better result wkthout the limitations of what will fit on your mh.I'm thinking of building a 15kW 48v battery.
I can build this for about £2.5k. This works out at £165 per kW. My preferred battery choice works out at £320 per kW. Not a small difference.
The system in the van will be to power our workshop as well - hence the battery size. The van will have a 1.2kW solar array and the unit another 4-5kW (initially). There will also be a 3kW Honda genny in the system for emergency charge and to combine with the Multiplus 5k if I need to run high draw tools (will give me a maximum of around 6.4kW continuous draw).
The upsides to a 48v system are 1 x BMS, 48v Multiplus a little cheaper, cabling cheaper. The downsides are the issue with B2B (there is a product available that I trust, but it's around £1700 + import fees) and the van MPPT would be quite a bit more expensive (would have to run the panels in series to get the voltage).
The other option is to run the van and workshop @24v.
I'd need a second BMS, so the battery cost would rise £150-£200. The 24v Multiplus would be about £130 extra. But, I can use 24v-24v Victron B2B's and the MPPT's work out about £300-£400 less.
Not doing it yet, so I'll give it more thought
Also considering a second 48v alternator as you suggest. Lots to think about
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You can use a Orion dc-dc and you can get one or many in parallel from victron. There’s a misconception that a fixed voltage can’t charge lfp, wrong. I use a a Orion converter as a b2b set at 13.65v. Multiply that by 4, set the output for 48v and you are good to go. I use mine since 2019 with no issues, even victron manual says it can be used as a charger, or power supply.
Best price for lfp self build is fogstar, for what you said, including bums and breaker/fuse comes less than 2300 now.
Best price for lfp self build is fogstar, for what you said, including bums and breaker/fuse comes less than 2300 now.
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I think this is the way to go.
I think I would set the output voltage to 56.8V (14.2 x 4) on a 24V-48V DC-DC Converter.
Wissel, you said the MPPT would be more expensive? Not sure about that one
Remember that you can use a "lower" rated controller than that for a 24V and especially a 12V system. You say you are looking at a 1200W PV array on the van? You are not far off being able to use a little Victron 100/20 MPPT SmartSolar. For most folk, that has a rating of 290W, but for you, that will be 1160W as the power rating is determined by the voltages and output current.Before you make a decision on the 48V Multiplus, have a check on the Victron Community site. It is not a version of the product I have taken a great deal of notice as very unlikely to ever get involved with 48V setups, but I have a recollection that some folk have issues with the 48V Multipluses and what they can set the charge voltages to? Like I said, I didn't take a lot of notice of the issue but I certainly remember some dicussions on voltage levels on 48V setups....
eddie
LIFE MEMBER
I do love you, but Christ your making life difficult for yourself.I'm thinking of building a 15kW 48v battery.
I can build this for about £2.5k. This works out at £165 per kW. My preferred battery choice works out at £320 per kW. Not a small difference.
The system in the van will be to power our workshop as well - hence the battery size. The van will have a 1.2kW solar array and the unit another 4-5kW (initially). There will also be a 3kW Honda genny in the system for emergency charge and to combine with the Multiplus 5k if I need to run high draw tools (will give me a maximum of around 6.4kW continuous draw).
The upsides to a 48v system are 1 x BMS, 48v Multiplus a little cheaper, cabling cheaper. The downsides are the issue with B2B (there is a product available that I trust, but it's around £1700 + import fees) and the van MPPT would be quite a bit more expensive (would have to run the panels in series to get the voltage).
The other option is to run the van and workshop @24v.
I'd need a second BMS, so the battery cost would rise £150-£200. The 24v Multiplus would be about £130 extra. But, I can use 24v-24v Victron B2B's and the MPPT's work out about £300-£400 less.
Not doing it yet, so I'll give it more thought
Also considering a second 48v alternator as you suggest. Lots to think about
Your ability to get an ‘off the shelf’ workaround in an emergency will be non existent and frankly your making the Van virtually unsaleable in the future due to the unnecessary technical complexity done for no real reason other than ’you can.
It would be of interest to a handful of nerds who wouldn‘t actually buy it, just want to tell you that ‘They’d do it another way’ before pushing their spectacles (repaired with a 3D printed ‘fix’ up their moustacheod nose, whilst hitching up their Rohan trousers above their sandals (with socks obviously) and walking back to their home build which after 17 years is nearly finished!
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makes a fair bit of sense.I do love you, but Christ your making life difficult for yourself.
Your ability to get an ‘off the shelf’ workaround in an emergency will be non existent and frankly your making the Van virtually unsaleable in the future due to the unnecessary technical complexity done for no real reason other than ’you can.
It would be of interest to a handful of nerds who wouldn‘t actually buy it, just want to tell you that ‘They’d do it another way’ before pushing their spectacles (repaired with a 3D printed ‘fix’ up their moustacheod nose, whilst hitching up their Rohan trousers above their sandals (with socks obviously) and walking back to their home build which after 17 years is nearly finished!
24V systems are relatively common with bigger setups and are well catered for with supporting products.
48V 'mobile' systems are few and far between.
I would certainly find your setup interesting, but I wouldn't 'do it that way' myself and wouldn't see a 48V setup as an asset. Guess I must be one of Eddies nerds
(except I don't know what Rohan trousers are 
)
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Wissel
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Thanks for that HoovieI think this is the way to go.
I think I would set the output voltage to 56.8V (14.2 x 4) on a 24V-48V DC-DC Converter.
Wissel, you said the MPPT would be more expensive? Not sure about that one
The reason for the MPPT's being more expensive, is I'd have to run the panels in series to get the voltage. I've put the panels into the Victron calculator (I know it goes a bit over the top, but prefer it that way) and on a 24v system I can run in parallel with a 100/50. Same panels on 48v (in series) means a 250/60 Tr.
Thanks for that, I'll check into it more before deciding
Tbh, I think I'm leaning towards a 24v setup. Keeps everything simple.
I do love you, but Christ your making life difficult for yourself.
Your ability to get an ‘off the shelf’ workaround in an emergency will be non existent and frankly your making the Van virtually unsaleable in the future due to the unnecessary technical complexity done for no real reason other than ’you can.
It would be of interest to a handful of nerds who wouldn‘t actually buy it, just want to tell you that ‘They’d do it another way’ before pushing their spectacles (repaired with a 3D printed ‘fix’ up their moustacheod nose, whilst hitching up their Rohan trousers above their sandals (with socks obviously) and walking back to their home build which after 17 years is nearly finished!
Liked that.Thing is, it isn't that complicated. Our workshop doesn't have mains power, so I need a reliable setup to power it and our van. Especially for the winter. If I just put a larger system in the Vario, I can power the unit from the van. Means I only need to buy one system.
Powering a building from a vehicle isn't unheard of. I've believe that EV's are now on the market with an outlet plug to act as house backup power if the grid goes down? I'm just eliminating the grid. As I don't have it
Having the genny in the loop makes sense as we could burn through 15kW in 4 days (workshop & van combined). A few really bad days of weather and we will need a way to charge.
Then, when we do go away, we have ample power on tap and can run aircon in the summer.
As far as the resale value of our van, it's going nowhere
I've kept my current van for 11 years and fully intend to do the same with the next. If circumstances changed and we were to sell it, the 15kW would probably be removed and a more usual size lithium installed.
Talking of my current van, when I first built it I fitted 400Ah of LA batteries and 2 x 100w solar panels. At the time, I was ridiculed online for this ridiculously OTT setup. A few years later and it's the norm.
Likewise, I fitted lithium over 5 years ago. I went with a 400Ah setup and 540w of solar. Again, ridiculed online (worse this time
). Now 400Ah isn't even seen as that big. Especially with fulltimers.Okay, 15Kw might be a bit OTT for most motorhomes, but it's quite small for a house system which is basically what I need. And who knows - maybe more people will want off-grid aircon in the future. Maybe it will catch on
(unlikely I agree).That's interesting to know
I was looking at the Mason kits on Fogster, just not sure about the BMS? Looking at getting EVE cells from them if I do go down this path.
Which BMS would you say is the best performer at the moment?
My fault for not making myself clear
The van will have 1.2kW on the roof, connected to one MPPT.
The workshop with have 4-5kW on the roof, connected to a second MPPT in the van. Like an EHU lead.
I need power for our workshop (no mains) and our van. Two separate systems seems OTT when I can just fit one to the van.
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While not disagreeing with eddievanbitz, the proposed system does make some kind of sense. A 4.5kW solar array and a 5kVA inverter is best supplied by 48V batteries, like most domestic storage supplies. And if you're going to have a super big battery, why not put it in the MH so you can use it while you are away, and plug it it when you are back home. It's a one-off, sure, but I'm sure a lot of people are thinking along those lines.
Agree with Autorouter, the 4.5kwp solar will benefit of being on 48v at 24v you will overwhelm any bms even with active balancer.
The seplos is ok but not excellent, lack of active balancer is making the charge at the top to bounce on-of allot. Specially with a big array. Increase voltage to 48v will minimise this, and active balancer is a most. Im a big fun of JK bms 200A and 2A active balancer. Run it at half dutty cycle 100A at 48v and you have a solid system. I went for 32 cells 2 JK bms and 2 multiplus 5kva for the house. Over the 3 months monitoring i had to turn voltage dow to 3.47vpc for daily cycling. I can get fully charged that low, with 8.8kwp array.
In your situation is pretty much half of my set up. I would stil strive to go 48v.
This is my battery set up, two sets of 16 cells with their own bms. I can dray 5kw of each pack, two in parallel its just easier on them.
The seplos is ok but not excellent, lack of active balancer is making the charge at the top to bounce on-of allot. Specially with a big array. Increase voltage to 48v will minimise this, and active balancer is a most. Im a big fun of JK bms 200A and 2A active balancer. Run it at half dutty cycle 100A at 48v and you have a solid system. I went for 32 cells 2 JK bms and 2 multiplus 5kva for the house. Over the 3 months monitoring i had to turn voltage dow to 3.47vpc for daily cycling. I can get fully charged that low, with 8.8kwp array.
In your situation is pretty much half of my set up. I would stil strive to go 48v.
This is my battery set up, two sets of 16 cells with their own bms. I can dray 5kw of each pack, two in parallel its just easier on them.
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Wissel
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Wissel
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Looks like from the above comments, 48v is the way to go.
So back to the original issue, the B2B.
I think I’ll initially not bother with this as I rarely drive anyway. Besides, I doubt my existing alternator would be powerful enough to put any meaningful charge in.
If I change my mind in the future I think a dedicated second 48v alternator makes the most sense. But a decision for the future.
Thanks all for your help
So back to the original issue, the B2B.
I think I’ll initially not bother with this as I rarely drive anyway. Besides, I doubt my existing alternator would be powerful enough to put any meaningful charge in.
If I change my mind in the future I think a dedicated second 48v alternator makes the most sense. But a decision for the future.
Thanks all for your help
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Thanks for that Hoovie
The reason for the MPPT's being more expensive, is I'd have to run the panels in series to get the voltage. I've put the panels into the Victron calculator (I know it goes a bit over the top, but prefer it that way) and on a 24v system I can run in parallel with a 100/50. Same panels on 48v (in series) means a 250/60 Tr.
Thanks for that, I'll check into it more before deciding
I don't quite understand that, have to say.
Victron say that for the MPPT to start, the PV voltage must be >5V than the battery. Now I would guess they are referring to 12V systems, so for a 48V system, it needs to be >20V maybe?
Your 48V battery on full charge will be around 56V, so the PV will need to be around 76V?
In essence, you can run 1 "12V Panel" (which is really around 21V) on a 12V system for it to work. so if you can 4 x "12V Panels" (or 2 x 24V Panels) in series, that would work on a 48V system would it not? and the maximum PV voltage would be under 100V. So will be fine on a 100V MPPT Controller surely.
I had a go on the Victron Calculator and I think there is a bit of a quirk to it. The 12V panels are stated as having a voltage of >25V, so you can never have 4 12 V panels in series, or 2 24V panels in series either according to that. Which begs the question why is the 100/20 Solar Controller described as 48V capable, and in the datasheets has full specs and numbers when configured for a 48V setup?
I think they have added extra voltage to cover low temps and that has kicked the numbers just over the threshold, so a 100V controller is not really 48V capable despite there being settings for it
I mentioned the 100/20 Smart Solar as close to the array as I was basing it on the 1200W you mentioned. Is that 250/60 for the whole array including the workshop array?
I honestly think that if a 100/50 output is powerful enough to cope with the array on a 24V system, the 150/35 absolutely will be on a 48V system and will give you a safe margin on the PV voltage. The 150/35 run on a 48V battery has a greater power rating than the 100/50 on a 24V battery.
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Hoovie, as you discovered the 100/20 will struggle on a 48v bank in dull weather. From experience, the array vmp for 48v, needs to be at least 1.5 times of the nominal battery voltage. Close to 75vmp. That will put voc out of range on a 100v controller. The 150’s are best choice for 48v and 250v series if you have a far away array. I have both, a 150/85 for house and garage, and a 250/85 for the ground mount that’s a bit further in the garden. The 250 always starts sooner and finishes last, due to 180vmp compared to the 90vmp on the 150. But, the 250 is always runs hotter than the 150 due to more conversion work. Both very good controllers
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I remember your couple of Youtube videos with your Lithium Installation (Using the SmartBMS and the Yellow Winston Cells, If I remember correctly?)Talking of my current van, when I first built it I fitted 400Ah of LA batteries and 2 x 100w solar panels. At the time, I was ridiculed online for this ridiculously OTT setup. A few years later and it's the norm.
Likewise, I fitted lithium over 5 years ago. I went with a 400Ah setup and 540w of solar. Again, ridiculed online (worse this time
Anyone who ridiculed that build wouldn't have a clue. You did a superb job and the only thing wrong with it was that it made me very envious
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