How to go from 12V to 24V system in RV

[Ceefiveceefive]

Greetings!

I am remodeling my Class A RV to include completely re-doing the coach electrical.

I would like to switch to a 24V system instead of going back to the 12V that it was originally.

What are the steps involved?

I will be installing solar with my remodel.
I would like to build batteries like Mr. Prowse has shown on Youtube.

Right now I am still on the tear-down stage. What should I be planning?

 

[jasonhc73]

24V system so you can have battery storage, so you can ultimately use 120V appliances?

24V DC stuff is not very common. But 120VAC stuff is just normal everyday stuff.

Consider it a house, and wire it like that.

Your "grid supply power" is your solar and battery packs. 24V inverted into 120VAC (or even 240V for split/dual legs)

I would not mess with any of the "chassis" wirings that most likely are all 12VDC for automotive stuff.

Some "light" reading to go through:

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf
https://www.victronenergy.com/upload/documents/BatteryCables.pdf
https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

 

[Ceefiveceefive]

24V system so you can have battery storage, so you can ultimately use 120V appliances?

Yes. I will get the whole setup to include an inverter so I can run AC appliances.
I also will still want to power some DC items too, so I am thinking I'll need a converter to go from 24V to 12V?

24V DC stuff is not very common. But 120VAC stuff is just normal everyday stuff.

Can I use the same solar panels for a 24V as I would have for 12V system?

Consider it a house, and wire it like that.

Your "grid supply power" is your solar and battery packs. 24V inverted into 120VAC (or even 240V for split/dual legs)

The 240VAC - is that comparable to the 50Amp on an RV? My coach electrical is 50Amp.

I would not mess with any of the "chassis" wirings that most likely are all 12VDC

Agreed! Not touching the chassis system except to add maybe charging capability of the alternator to the coach batteries, etc.

 

[jasonhc73]

If you are going to redo all the wiring.
I think the most important thing you can do is think about the systems as two separate systems.

The coach, and the "Off-Grid" house (that happens to ride around on the coach).

The critical point though is that you never mix the grounds. 12VDC ground is nothing at all like 120VAC ground.

In order for AC to work, it must have "line" and "Neutral". In order for DC to work, it must have Positive and Negative. As long as you understand a circuit, and never ever mix the AC and the DC or try to ground the AC to the chassis, you will be fine.

Wills book is probably the best way to go with this.

Charging the batteries can be done from the alternator or the solar panels.

Look through all these posts:

Vehicle Mounted Systems

RV's, Vans, Trucks and More! Typically 12v, and 100-1000w, but the limits are endless!

diysolarforum.com

 

[nosys70]

there is almost nothing to do.
install the 24V system as new, panels, SCC, inverter.
then add a 24 to 12V converter to supply the 12V to the old circuit.
and add new wires for the 120V Ac and for eventually the 24V AC.
IMHO, i would skip the 24V cabling if you already have the 12V one.
either keep it at 12V with 12V devices or convert it to 24V, and install small 12/24V converter at all the ends where you still need 12V.
The 12V wiring should fit the load since 12V ask for twice more Amps than 24v for same power.

 

[kernel]

Plan on making sure that all the switches and loads, fuses, etc are for the new voltage. Alot of the stuff will be 24V compatible, but some may not.

24 to 12 switching power supply will take care of the rest.

Good side effect is doubling voltage improves power capacity on the line. Even if the load will be of improved efficiency, lighting, pumps, ventilation, refrigeration, air conditioning, basically all of the rv systems could offer opportunity for improvement, but rv wiring seems to be commonly undersized for efficiency or having something with more gusto than what was there and still at least meeting ampacity if not high efficiency and proper operation, longer life, etc.

 

[Steve_S]

I would suggest a KISS approach to this, it is far too easy to get deeply into it otherwise.
The existing 12V systems are in place and working, doing what they are supposed to. Unless your gutting everything out and doing a full on rebuild then it is quite impractical to redo everything, not to mention costly too ! You can most certainly use 24V battery bank for your stored energy and use a good respectable Inverter/Charger like a Samlex with Dual AC Input for "shore" and for Genset, so you can keep charged & running in all situations if the sunshine isn't enough to charge you up.

By using a Proper Step Down converter from 24V to 12V to power your 12V side is not a big issue, run it from your battery bank bus on it's own fused line (simplest) and feed your 12V panel and your done. Of course that depends on how your system is wired but likely something like that.
A GOTCHA LURKING THERE ! Most 24V-12V "Buck" converters will NOT tolerate more than 26V input, over that and they fail ! and HORRIBLY ! ie, they fail and PASS the full 24V+ out, watch your 12V stuff get cooked ! I KNOW, BTDT - Lessons Learned ! The BUCK types cannot handle much over voltage. Remember that when an SCC or Charger (even from inverter) are charging the batteries they can and do reach 29VDC or higher depending on batt type and configuration. At 29V the Buck will melt down, plain & simple. You will want a 30V to 12V with regulation, or a "Smart Converter" of some form which can take in up to 30V but put out a regulated 12V and one which will deliver 15% more amps than your 12VDC system could demand from it (room for safe margin on loading). These of course are more expensive than those that many people tout at $10.

Some Examples of Higher DC input with regulated 12VDC output. * Note the amps out support.

24V DC/DC Converter catalog, to convert voltage up or down, retail, wholesale, off-the-shelf and custom, DC/DC 5 watts to 1500 watts, output voltage between 1.5V and 48V, switchmode and linear

24V to 12V converter,12V to 24V,24V DC/DC converters, DC DC power supplies with output voltage 1.5V, 3.3V, 5V, 6V, 9V, 12V,13.8V, 19V, 24V, 48V, and ATX PC computer power

www.powerstream.com

Here is another variant that handles a broad input range. Again these are not the cheap $10 Chinese buck converters.

Encapsulated DC to DC Converters

Industrial Encapsulated DC to DC converters at AutomationDirect. Your source for DC-DC converters at discount prices.

www.automationdirect.com

Hope this helps you,
Good Luck
Steve

 

[kernel]

Samlex sdc are good ones.

 

[Ceefiveceefive]

I would suggest a KISS approach to this, it is far too easy to get deeply into it otherwise.

Agreed. I like simple if I can do it.

The existing 12V systems are in place and working, doing what they are supposed to. Unless your gutting everything out and doing a full on rebuild then it is quite impractical to redo everything, not to mention costly too !

I am tearing all the electrical out and doing a full gutting as we speak. I'm ok with the cost. I am wondering if there is an ideal way to arrange everything since it will be a clean slate.

My rig is 38' long. I am changing some systems, adding some, and removing others to suit my preferences.
All appliances will be electrical save the incinerating toilet which will be the ONLY propane user.

Here is what I will have that will need power so far:
1. Microwave/convection oven (Daily use)(AC)
2. Compact water heater ×2 (Frequent daily use)(heat elements will be DC)
3. Mini Split Heat Pump (Constant use)(DC or AC, still debating which one I will get)
4. Incinerator Toilet vent fan (Daily use)(DC)
5. Mini Fridge <5 cu' (Constant use)(AC)
6. Security Camera System (Constant use)
7. Five or six small ventilation fans to go in select areas (Constant use)(DC)
8. LED lighting (Moderate daily use)(DC)
9. Fantastic Fans ×2 (Moderate use)
10. Gaming system (Occasional use)(AC)
11. Screen projector (Occasional use)(AC)
12. Crock Pot (Occasional use)(AC)
13. 3-D Printer (Occasional use)(AC)
14. Freeze Dryer (Occasional use)(AC)
15. Power Tools (Occasional use)(AC)
16. Laptop (Frequent Daily use)(AC)
17. Chargers (Frequent Daily use)
18. Internet setup (Constant use)
19. Ice Maker (Occasional Daily use)


I've removed or will be removing:
1. Ceiling Air Conditioner Units ×2
2. Oven
3. Dometic Fridge 10cu'
4. Conventional RV toilet
5. OEM water heater

I'm gutting the entire RV to have a minimalist open floor plan.

Are there good strategies in setting up all new wiring?

You can most certainly use 24V battery bank for your stored energy and use a good respectable Inverter/Charger like a Samlex with Dual AC Input for "shore" and for Genset, so you can keep charged & running in all situations if the sunshine isn't enough to charge you up.

I'm thinking about getting one of the Victron sets. Is Victron recommended for large setups? I would like and estimate I will need at least 1800 watts solar.

 

[kernel]

I would run conduit and sub panels to areas that have lots of stuff. This would allow upfit or changes later instead of being shut out of the wiring access.

There are flexible thinwall conduit materials available.

Saves on spaghetti where there are so many wires coming to one place.....

 

[Steve_S]

Agreed. I like simple if I can do it.

I am tearing all the electrical out and doing a full gutting as we speak. I'm ok with the cost. I am wondering if there is an ideal way to arrange everything since it will be a clean slate.

My rig is 38' long. I am changing some systems, adding some, and removing others to suit my preferences.
All appliances will be electrical save the incinerating toilet which will be the ONLY propane user.

Here is what I will have that will need power so far:
1. Microwave/convection oven (Daily use)(AC)
2. Compact water heater ×2 (Frequent daily use)(heat elements will be DC)
3. Mini Split Heat Pump (Constant use)(DC or AC, still debating which one I will get)
4. Incinerator Toilet vent fan (Daily use)(DC)
5. Mini Fridge <5 cu' (Constant use)(AC)
6. Security Camera System (Constant use)
7. Five or six small ventilation fans to go in select areas (Constant use)(DC)
8. LED lighting (Moderate daily use)(DC)
9. Fantastic Fans ×2 (Moderate use)
10. Gaming system (Occasional use)(AC)
11. Screen projector (Occasional use)(AC)
12. Crock Pot (Occasional use)(AC)
13. 3-D Printer (Occasional use)(AC)
14. Freeze Dryer (Occasional use)(AC)
15. Power Tools (Occasional use)(AC)
16. Laptop (Frequent Daily use)(AC)
17. Chargers (Frequent Daily use)
18. Internet setup (Constant use)
19. Ice Maker (Occasional Daily use)

I've removed or will be removing:
1. Ceiling Air Conditioner Units ×2
2. Oven
3. Dometic Fridge 10cu'
4. Conventional RV toilet
5. OEM water heater

I'm gutting the entire RV to have a minimalist open floor plan.

Are there good strategies in setting up all new wiring?

I'm thinking about getting one of the Victron sets. Is Victron recommended for large setups? I would like and estimate I will need at least 1800 watts solar.

Looks like a fairly though out plan has been worked on so far. I se only one gotcha in the list. The water Heater with elements. Resistance devices = big load & eat batteries hard & fast. I have On-Demand Hot Water and a separate on-demand for my radiant heating, wonderful tech, low operation cost (even with LPG) ad endless hot water. There are some really good smaller ones that are quite affordable.

I'm not an RV'er or Boater, my 12VDC wiring experience is creating wiring harnesses for cars & trucks or restoring wiring harnesses for them, therefore I can't answer particulars. We do have boaters, RV'ers and such here and they are likely better able to answer specifics.

I don't know if you've looked but Check Out BlueSea systems, they have a wiring wizard and more and their bit'n pieces are top notch https://www.bluesea.com/ check out their DC Panels and switches too. They also have specific catalogues which may be a good resource on their own.

 

[Ceefiveceefive]

Looks like a fairly though out plan has been worked on so far. I se only one gotcha in the list. The water Heater with elements. Resistance devices = big load & eat batteries hard & fast. I have On-Demand Hot Water and a separate on-demand for my radiant heating, wonderful tech, low operation cost (even with LPG) ad endless hot water. There are some really good smaller ones that are quite affordable.

Thank you for your response.
How many watts does your on demand water heater use?

I considered getting one, but I thought they used alot of power?

 

[Steve_S]

As I said, my heaters are LPG (propane), the hot water, in standby it's next to nothing, just the flow sensor, and when running the fan and a bit, like 1 amp worth.

 

[Ceefiveceefive]

As I said, my heaters are LPG (propane), the hot water, in standby it's next to nothing, just the flow sensor, and when running the fan and a bit, like 1 amp worth.

Ah, I missed your reference to it being propane.

Since I do not want any more devices that operate with propane, I'm sticking to electric only water heaters.

 

[Steve_S]

On demand electric (properly sized) is still cheaper to operate than a "Tank" which uses power every 15 minutes to maintain tank heat 7/24. Many folks really do not realize just how much power is chewed up by tank type heaters, damned things should be illegal.

 

[kernel]

Mini split hot water!

 

[dashdrum]

I'm gutting the entire RV to have a minimalist open floor plan.

Not necessarily related to electrical, but I would like to see the floor plan. I've never seen open in an RV before.

 

[Ceefiveceefive]

Not necessarily related to electrical, but I would like to see the floor plan. I've never seen open in an RV before.

Ill be happy to show and tell when its done. Estimated time of completion is sometime this summer.

 

[Ceefiveceefive]

Mini split hot water!

I've wondered about doing just that. Do you have info on how to make that work? Would you use the mini-split as a heat exchanger??

 

[FTRVR]

I would suggest a KISS approach to this, it is far too easy to get deeply into it otherwise.
The existing 12V systems are in place and working, doing what they are supposed to. Unless your gutting everything out and doing a full on rebuild then it is quite impractical to redo everything, not to mention costly too ! You can most certainly use 24V battery bank for your stored energy and use a good respectable Inverter/Charger like a Samlex with Dual AC Input for "shore" and for Genset, so you can keep charged & running in all situations if the sunshine isn't enough to charge you up.

By using a Proper Step Down converter from 24V to 12V to power your 12V side is not a big issue, run it from your battery bank bus on it's own fused line (simplest) and feed your 12V panel and your done. Of course that depends on how your system is wired but likely something like that.
A GOTCHA LURKING THERE ! Most 24V-12V "Buck" converters will NOT tolerate more than 26V input, over that and they fail ! and HORRIBLY ! ie, they fail and PASS the full 24V+ out, watch your 12V stuff get cooked ! I KNOW, BTDT - Lessons Learned ! The BUCK types cannot handle much over voltage. Remember that when an SCC or Charger (even from inverter) are charging the batteries they can and do reach 29VDC or higher depending on batt type and configuration. At 29V the Buck will melt down, plain & simple. You will want a 30V to 12V with regulation, or a "Smart Converter" of some form which can take in up to 30V but put out a regulated 12V and one which will deliver 15% more amps than your 12VDC system could demand from it (room for safe margin on loading). These of course are more expensive than those that many people tout at $10.

Some Examples of Higher DC input with regulated 12VDC output. * Note the amps out support.

24V DC/DC Converter catalog, to convert voltage up or down, retail, wholesale, off-the-shelf and custom, DC/DC 5 watts to 1500 watts, output voltage between 1.5V and 48V, switchmode and linear

24V to 12V converter,12V to 24V,24V DC/DC converters, DC DC power supplies with output voltage 1.5V, 3.3V, 5V, 6V, 9V, 12V,13.8V, 19V, 24V, 48V, and ATX PC computer power

www.powerstream.com

Here is another variant that handles a broad input range. Again these are not the cheap $10 Chinese buck converters.

Encapsulated DC to DC Converters

Industrial Encapsulated DC to DC converters at AutomationDirect. Your source for DC-DC converters at discount prices.

www.automationdirect.com

Hope this helps you,
Good Luck
Steve

Steve, Is there any reason to oversize a step down converter. My maximum 12v load is 20a. I am looking at the Samlex SDC-23. Do you think this should be sufficient, or would you recommend the SDC-30?