24 Volt Wiring Diagram Review and Questions

[willystyle]

I'll probably stick with wiring my 24-12 Orion to the OEM converter due to cost..

Changing the starter on the onan sounds like a very difficult process although it does sound like the best solution.

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"After doing a quick search, it seems like the best solution is to install 2 100ah batteries to start your Generator. The good news is that you can use these two batteries to supplement the power for your coach, all you have to do is install a simple on/off switch on your DC/DC Converter and these batteries will feed power to your coach. You can even automate this switchover by using the capabilities built into your (Victron) battery Monitor."

I dont fully understand the concept of using 2 12v 100ah batteries in combination with the 24v bank to power the coach? could you explain this further?
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[SolarPoweredRV]

I'll probably stick with wiring my 24-12 Orion to the OEM converter due to cost..

Changing the starter on the onan sounds like a very difficult process although it does sound like the best solution.

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"After doing a quick search, it seems like the best solution is to install 2 100ah batteries to start your Generator. The good news is that you can use these two batteries to supplement the power for your coach, all you have to do is install a simple on/off switch on your DC/DC Converter and these batteries will feed power to your coach. You can even automate this switchover by using the capabilities built into your (Victron) battery Monitor."

I dont fully understand the concept of using 2 12v 100ah batteries in combination with the 24v bank to power the coach? could you explain this further?
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First, to avoid any confusion, the two 12v batteries are wired into the same place as the OEM 12v batteries, these batteries are wired in as 12v batteries and not 24v.

The 24v to 12v DC-DC Converter is wired to accept a simple on/off switch. The DC-DC Converter will maintain the front batteries at a constant 13.2 volts using power from the 24v battery bank. If you see that your 24v battery is getting close to 0% you can switch the DC-DC Converter off and the two 12v batteries will then supply energy to the coach (sort of like back feeding). However, if these batteries become depleted, you may not be able to start the generator (you should be fine using up to 50% of these batteries before you risk not being able to start the Generator).

By utilizing the relay functions of the Victron battery monitor it is possible to automate this switchover based on the 24v batteries state of charge, probably not worth doing as I would count the energy in the two 12v batteries to be for emergency use. It is just good to know this would be available if you ever need it.

[sgprice]

Hey everyone,

Some background... I have pretty limited experience with electrical work.

I travel the country doing contracts for the US Forest Service. To reduce fuel costs I try to get my 5th wheel (2021 Grand Design Momentum 397th) as close to job sites as possible. This often means long-term boondocking without any shore power for 80% of the year. For now we use a generator for most of our power needs. My goal is to eventually put ~2000 watts of solar on the roof to supplement our power supply. For now however, I'll be installing everything but the panels and associated wiring.

Questions,

I have an onboard onan generator which needs 12v and ~350 cca to start. Since I'm going 24 volts I think I'll have to keep the current 12v interstate I have installed and use a 24-12 DC-DC charger (victron) is this the only route I can take? what would the advantages/disadvantages of this method vs. a 110v trickle charger. can I use the stock converter charger? Haven't determined wire or fuse size for that yet.

Is my single 200ah 24v battery enough to power this system for a month or 2 before I order the other 3?

I've sized the wires extra large as a safety precaution and as I add to the system/modify it I don't want to worry about it. Are there negatives other than cost/workability when looking at wire size?

I have a Lippert One Control system that I assume runs on 12VDC. I'm wondering if anyone has any experience wiring that system into a 24 volt bank. Any tips? what to look out for?

If y'all could please take a look at my diagram and give me some advice on improvements I could make and any errors there may be.

Hey willystyle,

This maybe too late for your needs, but in case you would like a detailed wiring diagram for what looks like the set up you want using a 2v battery bank and 24v VE Multiplus 2x120 24v with other VE components (and is what David - SolarPoweredRV is laying out is his replies), I found a great dowload for $10 at Explorist.Life - https://shop.explorist.life/shop/all...iring-diagram/

Cheers,

Steve

[houlster]

Late to this, but just as advice or suggestions for future readers:

Keep your coach 12v batteries & DC system in place. Let the batteries handle the surge amps for running jacks, slides, etc. There are also, potentially a *lot* of things running on 12v in an RV. Just keep the OEM 12v system in place. Use a 24->12 converter to keep the 12v bank always charged. No reason to remove the OEM converter/charger if you have a breaker you can just turn it off. That also gives you a backup to 12v charging in case you need it and have shore/generator power available.

12v vs 24v won't save you any size or space for the batteries. You're planning on Amperitime/LITime. The 24v, 200ah battery is the same size as the 12v, 400ah. Same battery, just wired differently internally. Def do 24v if you can. It has the substantial benefit of cutting the amperage in the DC system in half. You can use lighter wire that's cheaper & easier to work with than that required of an equivalent 12v system.

Yes, that one battery (24v, 200ah) will run things, just not for very long if you're planning on running AC with it. It is the mininum AH suggested for the 24/3000/70.

Wires need to be sized for the amps the inverter(s) can draw. Plan wire size based on your future inverter power rather than battery bank size. Per Victron (at 5m or less length), that's 1/0 for a single 3000va inverter on 24v. 2/0 or 2x 1/0 if it's 12v. If you're planning on 2x 3000va inverters, it depends on how you wire them to the bank. If you wire each one to the bank separately, then use those same size wires on each inverter. If you're going to run one set of wires from the bank to a union to where your inverters are, anywhere you have power for both inverters in the same wire, you'd increase that wire size. 2/0 for 24v or 2x 2/0 for 12v.

For example, for my 24v setup, I run one set of 2/0 cables from the bank to a Lynx distributor. Then from the Lynx to each inverter is just 1/0. For 12v, I'd need probably 4/0 & 2/0, respectively. This is all based on Victron spec. I think it's a pretty safe / conservitive spec. Just look at the amps in a wire when specing cables for your DC system.

The 12/3000/120 is 120 amps
The 24/3000/70 is 70 amps.
Up to maybe 100'ish amps from a solar controller.

If they're all wired direct to battery bank, that's a lot of smaller wires (and fuses for each). Or if using a Lynx, smaller wires to the Lynx and a much bigger set Lynx <-> batteries.


If you have an OEM inverter installed (soley) to run the fridge, there's no real reason to remove it. Let it power the fridge if it's wired to just the one plug the fridge uses (this seems to be the norm). You'll end up with triple redundancy. Shore/generator, 24v inverters, 12v OEM inverter. If there's power anywhere in the coach, it'll keep the fridge going.

[houlster]

After doing a quick search, it seems like the best solution is to install 2 100ah batteries to start your Generator. The good news is that you can use these two batteries to supplement the power for your coach, all you have to do is install a simple on/off switch on your DC/DC Converter and these batteries will feed power to your coach. You can even automate this switchover by using the capabilities built into your (Victron) battery Monitor.

Hey was wondering if you could expand on this. Are you saying that your 24/12 DC-DC converter works bi-directional? That the 24V will charge the 12v through the converter... But if you shut the converter off it'll work in reverse and the 12v bank can then charge the 24v bank instead? What model is it?

I have a victron Orion 24/12 70 set up in this same configuration, but I can't find anything that indicates it'll work in reverse if shut off, but I did have a weird issue show up on my Cerbo GX panel one time where the 24V DC loads were fluctuating between low positive & negative numbers. I thought it a bit weird but found later that the bypass plug for the switch on the Orion was loose (turning the converter off) around the same time. It looked like the 12v bank was charging the 24v bank, but I didn't think it'd work that way. Now I'm wondering...

[SolarPoweredRV]

Hey was wondering if you could expand on this. Are you saying that your 24/12 DC-DC converter works bi-directional? That the 24V will charge the 12v through the converter... But if you shut the converter off it'll work in reverse and the 12v bank can then charge the 24v bank instead? What model is it?

I have a victron Orion 24/12 70 set up in this same configuration, but I can't find anything that indicates it'll work in reverse if shut off, but I did have a weird issue show up on my Cerbo GX panel one time where the 24V DC loads were fluctuating between low positive & negative numbers. I thought it a bit weird but found later that the bypass plug for the switch on the Orion was loose (turning the converter off) around the same time. It looked like the 12v bank was charging the 24v bank, but I didn't think it'd work that way. Now I'm wondering...

In this configuration, the Orion 24v to 12v DC-DC Converter charges up the 12v batteries that are used to start the Generator to whatever voltage the Converter is set to (usually 13.1 or 13.2). Consequently, the 12v batteries would never get to 100% SOC. However, that doesn't matter as long as they can start the Generator when needed.

Where the "backup stored power" comes into play is when your 24v battery bank goes dead. Your 12v battery bank can supply power to your 12v devices simply because the batteries are wired into the 12v circuit.

Here is how it works in my coach...

I have two 10ah (yes that is 10ah) LiFePo4 batteries in my front hold to provide "surge" power for the motors in my slide and hydraulic system. These batteries are wired into the system exactly as the OEM batteries were. When I installed my Orion 24v to 12v, DC-DC Converter, I simply disconnected the OEM Converter and attached my DC-DC Converter to the same wires. So, the new LiFePo4 batteries are charged in exactly the same way as the OEM batteries were. Consequently, if my 24v batteries go dead, the 12v batteries can supply power to the 12v devices inside the coach in exactly the same way it did when the coach was built. I even left the battery disconnect switch in place.

In my case, 20ah does not provide me with any meaningful "backup" power, however, in the case above, where there are 2, 100ah batteries installed, that is useful "backup" energy storage.