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12V Power to RV

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Booboo

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I have a travel trailer with 1kw solar, 2x 202ah 24V LifePo4 batteries and a Growatt all in one inverter. The original 12V SLA battery that came with the trailer is running the 12V power in the trailer. This 12V battery is being charged by the trailers original converter powered by the 120V from the Growatt.

The 12V SLA battery needs to be replaced. Do I replace it with a new 12V SLA battery, a 12V LifePO4 battery or get rid of the 12V battery and get a 24V to 12V converter to run the 12V power?
 
24-12 converter is simple until you need more power. May need significant power for hydraulic leveling or slides. 12v tank heaters (rare) need 6 to 15 amps each. Need 4 amps per wheel to activate the emergency breakaway braking system. Small 50 Ah 12v LFP and small DC converter might be an option too.

I would not want to power the oem converter into a lead-acid battery as it would seem to consume a lot of power in comparison.
 
I use a 24 volt to 12 volt 70 amp Victron Orion converter, and this has no problems with running the hydraulic leveling system on my 12 k, two axle fifth wheel.

time2roll said:
Need 4 amps per wheel to activate the emergency breakaway braking system.
Click to expand...
I searched high and wide for that amps needed and could not find it. There are only three of us i know of that have ditched their 12 volt battery. Not a lot about running a breakaway on a dc converter—uncharted waters.
 
time2roll said:
Actually closer to 3 amps for diagnostics. I don't want someone to be at just 12a converter to drive two axles.
https://www.etrailer.com/faq-testing-trailer-brake-magnets-for-proper-function.aspx


General lighting can be a significant draw if still running 12v incandescent lamps.
Click to expand...
I’ve replaced all my trailer bulbs with LEDs except the brake lights etc…. Some of the small incandescents i replaced inside were pulling 2 amps. Guess I’ll put the full led replacement on my to do list.
 
I would keep the 12v battery it's cheap to replace. And adds some redundancy to your system. if 24v fails you still have 12v to run off of.
 
I chose to retain the 12v lead acid battery as a separate system. The trailer breakaway brake system, tongue jack and generator all use that battery. I can take my 12v LiFePO4 batteries offline and still start my generator to get 120v AC power. The lead acid battery is much smaller than what used to be there. It was one I had sitting around that was still in good shape.

I have a 150 watt solar panel that keeps the lead acid battery charged. When the generator is running, an AC-DC converter is active to keep the lead acid battery charged, but otherwise the converter is not active. I'll be switching that converter out soon and using the 4 amp charge from the Victron Multiplus. I'll get on that real soon now.
rolleyes.gif
 
Here is a little more detail on the problem I am having. I just installed a new power leveling system. It has a tongue jack and 4 frame jacks. I don't know exactly how much power they draw but they are each fused at 30 amps. The tongue jack runs by itself, and the frame jacks run two at a time. When the jacks run the battery voltage drops low and the controller starts getting buggy. I am assuming this is due to the low voltage. This is why I am thinking of replacing this battery. The trailer is a 2021 built so it and the battery are fairly new. The battery is an Interstate SRM-24, 75AH.

What about getting a Victron 24v/12v 70a converter and installing a switch so I can switch between the SLA battery and the converter to power the 12v system.
 
I would ditch the SLA for the 70a victron and stop powering the converter with the solar powered inverter. Maybe check the real amp draw from the SLA during leveling with a clamp-on DC ammeter to verify.
 
I put an MPP 3048LV in my trailer and went 120vac -> 12vdc 80a power supply. You can buy combined AC breaker/12vdc fuse power distribution centers. This 12vdc subsystem powers the water pump, LEDs, and Husky tongue jack with no problem.

I also put in a bypass (of the MPP/battery) for direct grid -> power distribution panel so the trailer can run from straight grid - especially useful for long term storage but yet the trailer has power.

The power loss in the 120vac -> 12vdc conversion is negligible and since all power comes thru the 120v dist panel, it's easy to have 1 power monitor :)
 
Last edited:
chrisski said:
I use a 24 volt to 12 volt 70 amp Victron Orion converter, and this has no problems with running the hydraulic leveling system on my 12 k, two axle fifth wheel.
Click to expand...
Did you run 2 wires from the ground terminal on the Victron, one to chassis ground and the other to the 24V battery negative?
 
Booboo said:
What about getting a Victron 24v/12v 70a converter and installing a switch so I can switch between the SLA battery and the converter to power the 12v system.
Click to expand...
I am not sure that will fix your problem.

I have the 70 amp model you talked about
Booboo said:
Did you run 2 wires from the ground terminal on the Victron, one to chassis ground and the other to the 24V battery negative?
Click to expand...
I crimped 2 wires into 1 lug. One wire went to 12 volt ground. The other to 24 volt ground. IMO, 70 amps or 25 amps is too much for chassis ground.
 
I have a 38’ travel trailer that I have setup with a 3500 watt all in one inverter charger (same principle as a growatt) I have chosen to leave the existing 12v system intact.
Reasons why?
1. High infrequent Power requirements I have slides powered by an unusually large electric powered hydraulic pump.
2. It’s cheaper. The existing charger converter is upgraded and works well. I already have a fully functional fla battery on the tongue of the trailer. No rewiring or new equipment needed.
3. It creates redundancy. All of the “necessities” of life are available as long as I have 12v and lp available. I keep an inexpensive 48v to 12 converter on hand (my system is 48v) To loose 12 volt I have to have the simultaneous failure of my fla battery/converter charger and AIO. If that happens and the event has not killed the 4 batteries that make up my battery bank I can still convert 48v to 12 or separate the batteries and get 12v that way.
4. Potential damage from a converter failure. Converters have been known to short internally and send full voltage to the 12v output. Bad for 24 but catastrophic at 48.

What I don’t like about it

1. Poor efficiency. My inverter is %90 efficient the converter I expect is a bit less efficient than that. From the get go I am loosing at least %20 of the power sent to the battery. The real problem though is the faradaic efficiency of an fla battery %75 to %80 over all but much less during absorption charge unfortunately I find that my house battery is almost always in float or absorption charge. In addition to these factors is Pukart effect. All in all the power set to the fla battery will likely not produce better than a %60 return and much worse in cold weather.
2.weight. Lead is heavy converters are light.
3. More maintenance. Fla batteries need to have connections and electrolyte checked regularly.

My plan for improvement.

I plan to replace my fla battery with a lifepo4 battery that is identical to the ones I used for my inverter. In so doing I will simultaneously cut my weight in half, double my usable amp hours, virtually eliminate Pukart effect and Faradaic efficiency loss and gain an additional battery should one in my existing bank have a problem. Since I have a leftover 240 watt solar panel I will use a small SCC to charge this battery separately from the inverter. On good days considering the relatively low power consumption from my 12v system I should be able to eliminate charging by inverter altogether.
 
Booboo said:
Isn't the chassis the 12V ground?
Click to expand...
This is where I say I’m no electrician.

i use a chassis ground for small things, not for large items. I hook into chassis ground for one or two amps, like a light bulb. That’s just the way I learned.

There’s some up to amperage limit that it does get hooked to the chassis, but when the 12 volts is flowing at 70 amps, I want it going through an insulated wire. I don’t have access to NEC code to see a limit if they put it in there. An older ABYCC code is available for free download, perhaps its in there.

I’ve also gone through and verified my negative busbar is attached to chassis ground, and it iS.
 
Booboo said:
I have a travel trailer with 1kw solar, 2x 202ah 24V LifePo4 batteries and a Growatt all in one inverter. The original 12V SLA battery that came with the trailer is running the 12V power in the trailer. This 12V battery is being charged by the trailers original converter powered by the 120V from the Growatt.

The 12V SLA battery needs to be replaced. Do I replace it with a new 12V SLA battery, a 12V LifePO4 battery or get rid of the 12V battery and get a 24V to 12V converter to run the 12V power?
Click to expand...
Does that travel trailer have an emergency braking/breakaway system that the 12v battery powers?
 
Niskibum said:
Just an FYI, from what I have read, trailers usually have a separate 12 volt battery that feeds from the vehicle for the brake system. They usually don't feed from the RV batteries.

https://www.etrailer.com/question-153968.html
Click to expand...
That’s true for most trailers. I don’t have unlimited experience with rv trailers. But I have yet to see one with a separate brake away battery. Not that it’s a problem to set one up that way.
 
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