12v to 24v step up split charge relay

[holly_brown96]

Hi, just looking for a bit of advice. I have a portable power station battery. I have 3 100w solar panels but in winter, it's not producing the power I need so I want to fit a voltage sensitive split charge relay to my van to power the van as I drive. The best way to do this I have found is to install a 12v to 24v step up converter along with the split charge relay as it needs to trick my power station into thinking 24v solar panels have been attached otherwise it will only delivery 12v to my solar input and less wattage. My power station is 2000w and accepts 500w, 11.5-50v and 20a through the solar input. My van battery will be changed soon to a 70ah and my alternator is 140a. Would this system work:

This split charge relay kit which uses 7awg cables, 60a fuses and split charge relay is 140a: https://www.amazon.co.uk/gp/product/B0D17CL4RS/?tag=mhf04-21

This is the 12v to 24v step up converter: https://www.amazon.co.uk/gp/product/B09F3J45FW/?tag=mhf04-21

After the 12v to 24v converter, add one of these 60a fuses to the cable: https://www.amazon.co.uk/gp/product/B0BSGC8CKC/?tag=mhf04-21

And then this 10awg cable to go from the fuse holder after the 12v to 24v converter to then plug into my battery: https://www.amazon.co.uk/gp/product/B0CZ68Z8GG/?tag=mhf04-21

Would that all work or should I change some things? I have attached a photo of the system. Thanks

 

[Dellmassive]

The cost of all that, to might be best going for the dedicated 12v fast charger.

Also the cheap step up converters are very lossy and run hot.... The best one to get is the Victron Orion 12/24 or 12/36 or 12/48

They are all doing them now. Ecoflow, Bluetti, Anker etc etc.

 

[TallPaul_S]

Was literally about to say it'd surely be easier/more efficient to install a proper 24v (or higher) DC-DC charger.

 

[holly_brown96]

The ones from those companies seem to be pretty expensive and that doesn't seem to include the wiring and fuses etc. The set up I had would be around £97 whereas the bluetti charger one is £250 and I don't think that comes with the cables and fuses. I would rather make it safe so if that's the best option then I suppose it's better to buy expensive once instead of cheap twice (or more times)

 

[n10n]

Hi, just looking for a bit of advice. I have a portable power station battery. I have 3 100w solar panels but in winter, it's not producing the power I need so I want to fit a voltage sensitive split charge relay to my van to power the van as I drive. The best way to do this I have found is to install a 12v to 24v step up converter along with the split charge relay as it needs to trick my power station into thinking 24v solar panels have been attached otherwise it will only delivery 12v to my solar input and less wattage. My power station is 2000w and accepts 500w, 11.5-50v and 20a through the solar input. My van battery will be changed soon to a 70ah and my alternator is 140a. Would this system work:

This split charge relay kit which uses 7awg cables, 60a fuses and split charge relay is 140a: https://www.amazon.co.uk/gp/product/B0D17CL4RS/?tag=mhf04-21

This is the 12v to 24v step up converter: https://www.amazon.co.uk/gp/product/B09F3J45FW/?tag=mhf04-21

After the 12v to 24v converter, add one of these 60a fuses to the cable: https://www.amazon.co.uk/gp/product/B0BSGC8CKC/?tag=mhf04-21

And then this 10awg cable to go from the fuse holder after the 12v to 24v converter to then plug into my battery: https://www.amazon.co.uk/gp/product/B0CZ68Z8GG/?tag=mhf04-21

Would that all work or should I change some things? I have attached a photo of the system. Thanks

View attachment 270436

Irrespective of whether step-up converter or a dc-dc would be used shouldn't the fuse on 24V side be max 1/2 of that on 12V side?

P=UI so the amperes drop when voltage rises for the same amount of power. Some is lost in conversion so you would actually get <1/2 current on the 24V side.
Also 60A fuse is too large to protect 10AWG wire.

 

[TallPaul_S]

I don't think I'd be happy having a cheap chinese voltage converter in my van, personally.

Does your power bank have charging profiles via the solar input? guessing it does, hence no MPPT or the like to control the charging profile and stages, so you wouldn't technically need all that a DC-DC provides as part of it is done by the battery bank.

If all you need is a converter, at least look for a reputable brand - yes a Victron unit may be £90 more but if it doesn't burn your van down it's probably worth it...

Victron Energy Orion 12/24-20 DC-DC Converter IP20 - ORI122420020

Victron Energy Orion 12/24-20 Dc/dc Converter - Not Isolated

www.visionmarine.co.uk

 

[holly_brown96]

The cheaper one would be 480w so higher than the victron one which is 360w which was why I was leaning more towards that, and because of the price. The battery I have is this: Aferiy 2001A 2000W 1997Wh LiFePO4 Portable Power Station 624000mAh UPS Pure Sine | eBay It has a built in mttp. It only has solar input and AC charging but having the 12v to 24v step up allows the charging via driving. This guy has the same battery brand as me just the newer version and was how I learned I could charge this way:

I don't think I'd be happy having a cheap chinese voltage converter in my van, personally.

Does your power bank have charging profiles via the solar input? guessing it does, hence no MPPT or the like to control the charging profile and stages, so you wouldn't technically need all that a DC-DC provides as part of it is done by the battery bank.

If all you need is a converter, at least look for a reputable brand - yes a Victron unit may be £90 more but if it doesn't burn your van down it's probably worth it...

Victron Energy Orion 12/24-20 DC-DC Converter IP20 - ORI122420020

Victron Energy Orion 12/24-20 Dc/dc Converter - Not Isolated

www.visionmarine.co.uk

 

[holly_brown96]

Irrespective of whether step-up converter or a dc-dc would be used shouldn't the fuse on 24V side be max 1/2 of that on 12V side?

P=UI so the amperes drop when voltage rises for the same amount of power. Some is lost in conversion so you would actually get <1/2 current on the 24V side.
Also 60A fuse is too large to protect 10AWG wire.

Honestly you are probably right. I'm not gonna lie, I haven't done anything like this before. I did some small electrical work inside my van but it was pretty much just a case of buying things with plugs already attached and plugging them into my power station. I was going to take the van to an auto electrics company to fit the split charge relay and 12v to 24v converter but everything seems to be adding up the price and I like learning new things so I wanted to do it myself. I just made up that diagram quickly this morning and didn't think about the fuse coming from the 24v side

 

[holly_brown96]

Just realised that the bluetti charger 1 is 560w which would be too high for my solar input on my battery. Do you know what that Victron is? I agree I would rather pay more than have cheap stuff. I didn't realise there were many other options like this one

I don't think I'd be happy having a cheap chinese voltage converter in my van, personally.

Does your power bank have charging profiles via the solar input? guessing it does, hence no MPPT or the like to control the charging profile and stages, so you wouldn't technically need all that a DC-DC provides as part of it is done by the battery bank.

If all you need is a converter, at least look for a reputable brand - yes a Victron unit may be £90 more but if it doesn't burn your van down it's probably worth it...

Victron Energy Orion 12/24-20 DC-DC Converter IP20 - ORI122420020

Victron Energy Orion 12/24-20 Dc/dc Converter - Not Isolated

www.visionmarine.co.uk

 

[TallPaul_S]

The victron one can do 20a continuous at 24v which is 480w, with a peak of 30a.

There's a few amp options in the drop down list. Here's the datasheet for them, I'd look at the 12/24-20. - https://www.victronenergy.com/uploa...DC-converters-high-power,-non-isolated-EN.pdf

That one also has a remote on off so you can use an engine run signal wire (if you can get one installed and coded) to trigger the converter rather than relying on voltage sensing or a split relay. So you'd eliminate the need for a split relay. Or you could fit a low power switch on the dash to turn it on when needed.

 

[holly_brown96]

The victron one can do 20a continuous at 24v which is 480w, with a peak of 30a.

There's a few amp options in the drop down list. Here's the datasheet for them, I'd look at the 12/24-20. - https://www.victronenergy.com/uploa...DC-converters-high-power,-non-isolated-EN.pdf

That one also has a remote on off so you can use an engine run signal wire (if you can get one installed and coded) to trigger the converter rather than relying on voltage sensing or a split relay. So you'd eliminate the need for a split relay. Or you could fit a low power switch on the dash to turn it on when needed.

I am planning on going up into the scottish highlands so my worry with installing a switch is that I forgot to turn it off and drain my van battery and I end up stuck in the middle of nowhere with no phone signal. If I wanted it to automatically charge and stop charging when I stop driving, is the only option with that the coded run signal wire or could I install the voltage sensing split charge relay too? Would it essentially be the same set up as in my first message but with the victron 12/24 instead of the cheaper one?

 

[TallPaul_S]

I am planning on going up into the scottish highlands so my worry with installing a switch is that I forgot to turn it off and drain my van battery and I end up stuck in the middle of nowhere with no phone signal. If I wanted it to automatically charge and stop charging when I stop driving, is the only option with that the coded run signal wire or could I install the voltage sensing split charge relay too? Would it essentially be the same set up as in my first message but with the victron 12/24 instead of the cheaper one?

Yes you could - as you've seen you have the risk of this as that Victron converter will run from 8v upwards so it'll drain your starter battery if not switched off.

You could run a full power VSR as per the original idea, or you could use the remote on off which is very low amps, with a low amp VSR (with manual switch if they exist), which would then switch on or off the converter when the engine is running and the volts are over 13.2v (or whatever you set it at). You'd then have a switch to control the VSR so if the power bank isn't connected you can turn off the converter completely.

The engine run signal is the cleanest option, I had a factory fitted LB in my van so use this on my Victron XS 50a and it works flawlessly. You can fit a simple inline 12v switch to this if you didn't want it to activate all the time.

 

[holly_brown96]

Yes you could - as you've seen you have the risk of this as that Victron converter will run from 8v upwards so it'll drain your starter battery if not switched off.

You could run a full power VSR as per the original idea, or you could use the remote on off which is very low amps, with a low amp VSR (with manual switch if they exist), which would then switch on or off the converter when the engine is running and the volts are over 13.2v (or whatever you set it at). You'd then have a switch to control the VSR so if the power bank isn't connected you can turn off the converter completely.

The engine run signal is the cleanest option, I had a factory fitted LB in my van so use this on my Victron XS 50a and it works flawlessly. You can fit a simple inline 12v switch to this if you didn't want it to activate all the time.

I am trying to simplify it as much as possible as I haven't fitted something like this before so I think fitting the remote on off may be more difficult? If I was to go with my original idea and buy that kit to do the split charge relay but rather than the cheap converter, have the victron one, would that mean that if I didn't want/need to charge my power station, that I could just unplug the cable from my power station and drive like normal and the power would just all go to my van battery? Or would that effect the victron converter negatively?

 

[TallPaul_S]

I am trying to simplify it as much as possible as I haven't fitted something like this before so I think fitting the remote on off may be more difficult? If I was to go with my original idea and buy that kit to do the split charge relay but rather than the cheap converter, have the victron one, would that mean that if I didn't want/need to charge my power station, that I could just unplug the cable from my power station and drive like normal and the power would just all go to my van battery? Or would that effect the victron converter negatively?

I'm not sure how the converter will handle having no load attached so what I'd do if you go with the std split relay, is add a basic 12v switch to the on off remote (it's a separate small circuit) to be able to manually turn it off and on.

The split relay will then provide voltage to the converter when the engine is running, and the separate switch will allow you to decide whether you want it running when the engine is on.

 

[holly_brown96]

I'm not sure how the converter will handle having no load attached so what I'd do if you go with the std split relay, is add a basic 12v switch to the on off remote (it's a separate small circuit) to be able to manually turn it off and on.

The split relay will then provide voltage to the converter when the engine is running, and the separate switch will allow you to decide whether you want it running when the engine is on.

Ah ok, sorry I misunderstood before but have done more research and realised that the vicron converter has a remote on off. I thought it was a whole separate thing I would have to buy and fit to a cable. The battery I have has a built in mttp so if I was to plug in every single time I drive, once the battery is fully charged, would that be ok to leave plugged in and converter would know to stop supplying power or would I still need to install the switch to turn it off?

 

[TallPaul_S]

Yes, that's basically what an MPPT does with a solar panel. A panel in full sun might be providing 300w of power (or more) to the MPPT, but if the battery is full it's the MPPT's job to regulate that to charge the battery safely.

Basically all you're doing is substituting a solar panel voltage and amps with volts and amps from the engine/starter battery. The MPPT doesn't know what's supplying the power, it just sees volts and amps.

For the remote:



Part 4 on the above, the remote is literally just a loop of small guage wire. With the loop complete it's powered on, therefore add a longer loop with a switch and you break that loop, meaning the converter can be powered off manually.

You could even attach a small 12v input which you plug into your power bank when you want to charge it which provides a small amount of power to the remote on the converter, which would mean the converter would only run when it's plugged into the MPPT input and the switch input.

 

[holly_brown96]

Ah ok, I think I understand it now. I have been watching some videos of others that have fit them too. So would I basically want the system to be like this?


For the switch, I asked chatgpt, it says I need a "single-pole, single-throw (SPST) switch that can handle the low current on the remote on/off circuit (usually <1A). This switch will control the signal sent to the remote on/off pins". Is this correct? Would it be this kind of switch that I need: 1A switch
When wiring, the positive wire will run from the remote/on off pin to one side of the switches terminal and then a negative wire will run from the other side of the remote to the other side of the switches terminal which would create the loop?
Am I right in thinking that if I install it like in the diagram above, that even if the switch is on, it wouldn't drain my vans battery and would only power the power station when the car is turned on? The switch is just to turn it off if I want to drive and not have it charge the battery?
Thanks so much for all your help! You are helping me so much!

 

[TallPaul_S]

In the above diagram, because you've got a constant connection from the SB to the converter, and the converter runs when the input is above 8v, it'd run your SB dead, if it was left switched on. The split charger relay stops this as it only connects the 2 sides when the voltage of the SB is over 13.3v or so (IE when the alternator is charging it).

With the split charge relay, if the engine is off the converter won't be powered at any time, regardless of switch position.

If the engine is on, the convert who only be on when the switch is on.

Everything else is good, for the switch any std 12v switch you'd use for lights etc while be fine.

For the cables though you will probably want to go bigger just to be able to fit the necessary terminals and connectors too the solar input (normally an mc4 connector). The converter has 6mm studs and there's no massive downside to going a bit bigger.

 

[holly_brown96]

Do you mean going bigger with all the cables or just the cables on the 24v side going from the converter to the battery? What size do you suggest?

 

[TallPaul_S]

Just the 24v side - I would check first what size the solar connector wiring on your power bank can take, 3/4mm² cable is pretty thin. It looks like an Anderson powerpole connection, with an mc4 connection and these tend to be 4mm² or 6mm². Just match whatever the cable size on the connector currently is, it'll be more than enough for the amps @ 24v.