Rv conversion to 24 volt Lithium.

[GGameBoy]

I keep changing up what I want to do with these batteries. Well I just bought an rv and I want to install them in it instead of using a mobile solar generator which was my original plan. So now I have to go 24 volt bec I bought a 24 volt bms and a 2000 watt inverter and 8 lifep04 catl cells 310 amps.

I am just not familiar with rv electronics. Do I just disconnect the rv converter and allow the solar too charge the batteries? Or does the rv converter do other things beside charge the 12 volt battery? Bec I can get a 24 to 12 volt regulator but to my limited knowledge that does not work for charging with the rv converter. So do I take it out? Or replace it with another thing?

 

[John Frum]

In the typical setup...
The ac2dc converter charges the batteries and provides power to the dc side of the distribution panel.
If you get an inverter/charger you should disable the converter.
If you have a discrete inverter then you should change the wiring so that the ac2dc converter is only powered via shore power.
This is done to avoid a power loop with your inverter.

 

[John Frum]

Since you have a 24 volt system you have 2 integration options.
1. Disable the converter and power the dc distribution panel via a 24->12 step down converter.
2. Run the converter off the inverter, in this case the only integration between the old and new systems is alternating current.
The second option is easier to setup but much less efficient.

Forgot to mention that the legacy RV dc stuff is 12 volts.

 

[time2roll]

Need a method to charge the 24v battery. Need a method to supply 12v to the RV from the battery.

Need a 24v charger that goes direct from 120vac to the 24v battery to charge when you have utility power or run the generator. You may want a 12-24 DC converter to charge the 24v battery from the 12v chassis system alternator. And by all means connect the solar to the 24v battery with your solar controller.

Need a 24-12 DC converter to supply 12v to the RV systems.

The trick is integrating all this and avoid any power loops where charging and discharging run in a loop.

I would leave the existing converter in place. May want to disconnect power depending on how things are installed. If something fails you would have the converter to supply 12v power if needed.

 

[GGameBoy]

Since you have a 24 volt system you have 2 integration options.
1. Disable the converter and power the dc distribution panel via a 24->12 step down converter.
2. Run the converter off the inverter, in this case the only integration between the old and new systems is alternating current.
The second option is easier to setup but much less efficient.

Forgot to mention that the legacy RV dc stuff is 12 volts.

If I do option 1 do I replace the converter by taking it out completely and in it’s place add the 24 -> 12 step down ? I would disconnect the breaker that powers the converter as well bec the 24 volt batteries would do that. Correct?

 

[chrisski]

On my converter, the breaker is AC and the converter plugs into a 120 VAC outlet, so the breaker would be tripped off. I would not go through the trouble of removing the outlet.

What I’m a bit confused about is the wires from the converter to the battery and how to remove those without leaving a live wire. The wires from the converter are 10 feet from the battery and disappear into the floor. A huge pain to remove the plastic cardboard bottom to access and trace out this wire run, but I may have no other choice.

 

[John Frum]

If I do option 1 do I replace the converter by taking it out completely and in it’s place add the 24 -> 12 step down ?

Its fine to disable it.
The resale value is very low.
As @time2roll said just leave it in place.
The easiest way to disable the converter is to just switch off its breaker.
That should work fine unless you have other people in the RV that might turn it on for some reason.

I would disconnect the breaker that powers the converter as well bec the 24 volt batteries would do that. Correct?

I think the question you are asking is....
Q: how do I power the dc_distribution panel from my new 24 volt system?
A: see drawing below.

dc_domain {
    positive_busbar {
        |->fuse->dc_2_dc_converter->fuse->dc_distribution_panel
    }
    negative_busbar {
        |<-24_2_12_converter<-dc_distribution_panel
    }

}

To make the above drawing less abstract we need a lot of details about your new setup and old.

 

[GGameBoy]

Its fine to disable it.
The resale value is very low.
As @time2roll said just leave it in place.
The easiest way to disable the converter is to just switch off its breaker.
That should work fine unless you have other people in the RV that might turn it on for some reason.

I think the question you are asking is....
Q: how do I power the dc_distribution panel from my new 24 volt system?
A: see drawing below.

dc_domain {
    positive_busbar {
        |->fuse->dc_2_dc_converter->fuse->dc_distribution_panel
    }
    negative_busbar {
        |<-24_2_12_converter<-dc_distribution_panel
    }

}

To make the above drawing less abstract we need a lot of details about your new setup and old.

Ok ok I think I got it. I can just turn off the converter by flipping the breaker for it. Then if I leave the lead acid battery on my rv I can either use a a solar panel to charge it or run a 24 to 12 volt converter to a charger to charge it. Then use this transfer switch. Does this make sense?

MOES Dual Power Controller 50A 5500 Watt Automatic Transfer Switch for Off Grid Solar Wind System ATS​

 

[John Frum]

Ok ok I think I got it. I can just turn off the converter by flipping the breaker for it.

Yep

Then if I leave the lead acid battery on my rv I can either use a a solar panel to charge it or run a 24 to 12 volt converter to a charger to charge it.

That is whole new wrinkle.
We need to flesh that out.

Then use this transfer switch. Does this make sense?

MOES Dual Power Controller 50A 5500 Watt Automatic Transfer Switch for Off Grid Solar Wind System ATS​

If you have not bought an inverter yet, I suggest you get an inverter/charger which will be functionally equivalent to an inverter, converter and automatic transfer switch.
Its also way nicer and easier to integrate.

 

[chrisski]

Then if I leave the lead acid battery on my rv I can either use a a solar panel to charge it or run a 24 to 12 volt converter to a charger to charge it.

This is a hole new wrinkle. In my RV, the biggest draw overnight is the 12 volt DC Propane Blower motor. 9 Amps. That adds up.

My RV's battery that came with it was 92 ah, which should only discharge by 50%, so 46 ah. With 15 hours a day when my panels can't provide energy because its dark out, if I were to keep that tiny battery in for an RV conversion, I need to pay close attention to the:

1) DC to DC charger I put in to keep this battery, or
2) Ditch the 12 volt battery and put in a DC to DC converter, which is not as easy as it sounds since my leveling jacks pull 50 amps. That is quite a bit for a converter

There's advantages either way that just need to be planned for.

 

[John Frum]

new wrinkle.

Jinx!!!

 

[GGameBoy]

Yep

That is whole new wrinkle.
We need to flesh that out.

If you have not bought an inverter yet, I suggest you get an inverter/charger which will be functionally equivalent to an inverter, converter and automatic transfer switch.
Its also way nicer and easier to integrate.

Unfortunately I have an inverter that’s 24 volt. Bms 24 volt. That’s why I was thinking about a transfer switch

 

[John Frum]

Unfortunately I have an inverter that’s 24 volt. Bms 24 volt. That’s why I was thinking about a transfer switch

They make 24 volt inverter/chargers so I don't see why 24 volts would be a factor in the decision to get a discrete transfer switch.

 

[12VoltInstalls]

have an inverter that’s 24 volt

What are you big-draw items going to be? As mentioned way back legacy RV is 12V. If you don’t need higher power in my mind it would just be simpler to be 12V and not have to work anything else out.

Granted, having other equipment already that wants to be 24V does bring up apparent financial attractiveness…
24V does have its advantages but if you do not anticipate needing those advantages adding other items to then accommodate 12V seems unnecessary somehow.

 

[Barcafan]

Hello I am new to this thread. I am looking at buying an RV soon and want to run AC off the batteries. I am looking to use Lithium along with solar but was interested in using a DC- DC charger from my Ford 397 amp alternator. If I were to use four large amp 12 volt batteries in parallel and in series would I be able to use one of the 12 volt DC-DC chargers like renogy 60 amp or would I need to use something like the Victron 12/24/15 charger Hoping to build a 24 volt system to keep my cost down and solar capacity high.

 

[John Frum]

Hello I am new to this thread. I am looking at buying an RV soon and want to run AC off the batteries. I am looking to use Lithium along with solar but was interested in using a DC- DC charger from my Ford 397 amp alternator. If I were to use four large amp 12 volt batteries in parallel and in series would I be able to use one of the 12 volt DC-DC chargers like renogy 60 amp or would I need to use something like the Victron 12/24/15 charger Hoping to build a 24 volt system to keep my cost down and solar capacity high.

Charging a 24 volt battery from a 12 volt chassis system requires a 12->24 dc2dc charger.

 

[chrisski]

Hello I am new to this thread. I am looking at buying an RV soon and want to run AC off the batteries. I am looking to use Lithium along with solar but was interested in using a DC- DC charger from my Ford 397 amp alternator. If I were to use four large amp 12 volt batteries in parallel and in series would I be able to use one of the 12 volt DC-DC chargers like renogy 60 amp or would I need to use something like the Victron 12/24/15 charger Hoping to build a 24 volt system to keep my cost down and solar capacity high.

I’m not saying what you’re wanting is I doable, but depending on the size of the RV, could be costly. $15k - $20k. A smaller RV would be better.

Depe ding on the AC, cold deaw from 50 -150 amps from a 12 volt system, which is what most battery DVC to DC chargers are. Unless ou have an alternator dedicated to this, may need to rethink this. My pick up tryuck has a spare space for an alternator I could put one in and do a high idle RPM mod to get the amps, but the entire amps from that alternator would probably power my fifths wheel‘s AC.

Plz do a good kwh energy audit.

 

[Barcafan]

I’m not saying what you’re wanting is I doable, but depending on the size of the RV, could be costly. $15k - $20k. A smaller RV would be better.

Depe ding on the AC, cold deaw from 50 -150 amps from a 12 volt system, which is what most battery DVC to DC chargers are. Unless ou have an alternator dedicated to this, may need to rethink this. My pick up tryuck has a spare space for an alternator I could put one in and do a high idle RPM mod to get the amps, but the entire amps from that alternator would probably power my fifths wheel‘s AC.

Plz do a good kwh energy audit.

Thank you. I will only use the Dc-Dc charger to function as a supplemental charger while I drive. My alternator is huge at 397 amp as I upgraded when I bought truck. I just didn’t know if needed to get a step up charger 12-24 for a 24v system even though the batteries will be 12 volt wired in series. Thank you again

 

[12VoltInstalls]

You can only direct charge those if they are disconnected from each other. Then there’s possible balance issues
A second 24V alternator or a DC2DC charger are the two chassis options- the hardware option is solar panel wattage