Now i belive that the solar ihave will be more than enough, however i have been thinking about a Durite vsr to top up the leisure batteries. The query i have is the lorry is 24v and the battery bank is 48v so can i fit the VSR to lorry batteries and then to a step up transformer to get the 48v for the leisure batteries? anyone know if this will work and is safe?
Need help with an electrickery idea
- Thread starter Bagofsand
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pappajohn
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I'm at a loss here.... Why do you need 48v leisure voltage?
There can't be much runs on 48v....water pump, fridge/boiler electronics etc
There can't be much runs on 48v....water pump, fridge/boiler electronics etc
Lenny HB
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Agree with John what's with the 48v?
On normal installations VSR are best avoided if you have solar charging the batteries.
On normal installations VSR are best avoided if you have solar charging the batteries.
pappajohn
LIFE MEMBER
I assume you have 4 x 12v batteries.
If they are wired in series that will be 48v but for leisure purposes they are wired in parallel.... Pos post of each battery connected together (Pos to Pos) and likewise for Neg post.
Series is wired Pos of 1st battery to Neg on next battery then the same to the 3rd and 4th battery.... IE daisy chained.
I've heard of 24v appliances but never 48v.
If the solar does charge at 48v you must have 4 panels also wired Pos to neg
If they are wired in series that will be 48v but for leisure purposes they are wired in parallel.... Pos post of each battery connected together (Pos to Pos) and likewise for Neg post.
Series is wired Pos of 1st battery to Neg on next battery then the same to the 3rd and 4th battery.... IE daisy chained.
I've heard of 24v appliances but never 48v.
If the solar does charge at 48v you must have 4 panels also wired Pos to neg
I believe 48 volt solar systems are used quite extensively for cabins static caravans buildings etc. you can buy complete kits if required.
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48v Off-grid Solar Systems and Kits. Includes Batteries
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pappajohn
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That's all well and good for a solar system...... But what's going to run off 48v.... Fridge, heater, boiler, water pump, TV, radio etcI believe 48 volt solar systems are used quite extensively for cabins static caravans buildings etc. you can buy complete kits if required.
48v Off-grid Solar Systems and Kits. Includes Batteries
Buy Complete 48v Off-grid Solar Kits from Sunstore Solar. Everything you need to setup and off-grid system. Easy to Install. 5 Year Solar Panel Warranty.
Inverters John, the solar system powers a 48 volt battery bank to supply power to an inverter that powers all the 240 volt kit.
pappajohn
LIFE MEMBER
Yes, but why use a 48v solar array and controller anyway.
4 x 12v batteries in series restricts amps to whatever one battery is... 110ah maybe.
4 x 12v in parallel.... 480amps (assuming 110ah)
Then use a 12v inverter.
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I don't profess to know why, only that it is common practise for static installations.
pappajohn
LIFE MEMBER
Agreed, but this isnt static.
It seems a convoluted and expensive way to get 230v
Short answer no. There is no transformer for DC power but step up DC-DC converters. Transformers only for AC power. What you need from the 24v starter to 48v house bank, is a Orion 24-48v converter, or a more nifty DC buck boost converter. Victron has few of these examples. My choice would be their isolated buck boost, pricey but good.
Have you got your 48v inverter and solar controller yet? What you got?
My house is off grid on 48v system with a 5kva multiplus 2, tree solar chargers and 8,8kwp array. Need any help with the 48v system, fire away. Used to do them for a living.
You will be surprised, 48v is standard off grid. The 12v is limited in power delivery.
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cmcardle75
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Higher voltages are generally more electrically efficient. 12V is only used for small systems for this reason. Reducing amps saves waste. However, as you say, it isn't ideal for systems where you want 12V devices. You have to run everything off the inverter.
cmcardle75
LIFE MEMBER
The VSR is only suitable for charging where the starter battery has similar voltage to the leisure battery, the alternator is not smart, and the chemistries are compatible. To run a 48V array (assuming Lithium here?) from a 24V will require a DC-DC B2B charger. The 24V>48V requirement will not be the easiest to source. If you draw a blank, you may need a 24V>230VAC inverter of sufficient power driven off the alternator that drives a suitable 48V charger. The two stage process will waste some power, but not that much and may be easier to find.
There are various 24-48v dc dc converters, you certainly don’t want triple conversion. Otherwise you kill the advantage of 48v, and stay at 24v for both. Plenty of 24v gear, almost anything what’s on 12v you can get it on 24v. The 48v is more for AC power, and only few niche items like water heater, pump and fridge. A steca 48v fridge is 1200-1400 quid special order. The people that run on 48v, is purely for high power AC appliances, like in a dwelling.
I don't know if this will work exactly, but there are solutions available. A VSR plus a step-up DC-DC converter won't be a very good battery charger. I have a 48V battery, with a Sterling BB124870 Battery-to-battery charger which is a proper 3-stage battery charger rather then just a 48V power supply. It takes 12V 70A from the alternator and converts it to a variable voltage suitable for charging the 48V battery. Unfortunately Sterling don't seem to do a 24V to 48V version, but other manufacturers may do this.
48V is a good option if you want an inverter of more than 2400W, ie 100A from the battery. The main downside is that in a motorhome, most of the leisure devices are 12V. At the moment I have a single 100Ah 12V battery which supplies these loads, but I have a 48V to 12V 25A DC-DC converter which I intend to fit instead of the 12V battery at some time in the future.
You don’t combine a vsr with a dc converter. You just set the converter at 55,2-55,4v on the output, and you’re done. The 3 stage will have to be done by ehu or solar. The alternator is there to help you out bring it up but saturated by other means. If 48v side is Li, it doesn’t have to be 3 stage anyways. I think OP will reconsider, personally a 24v house battery makes sense with a 12v converter for few small items. Keep all power hungry at 24v.
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I think you're right about the converter, but I think the OP wants the converter to turn on only when the 24V battery is being charged from the alternator. A VSR is one solution, but has its problems in a complex system like this. If for example the solar charges the 24V battery, it will turn on the VSR, which is not what you want. It's better to use a standard relay, triggered by the ignition (or ideally a D+ signal) so that it only comes on when the engine is running.
It's the same amount of energy storage either way. Series: 48V 110Ah = 5280 watt-hours of energy.
Parallel: 12V 440Ah = 5280 watt-hours of energy.
For the inverter, 3000W at 12V is 250A, 3000W at 48V is 62.5A. A 3k inverter is common in domestic off-grid, as is 5k.
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