Adding Lithium to RV Advice

[Isaac-1]

I agree with most of this mornings messages, but feel that some of the nuances of your installation are not addressed, for example I suspect you would be ok with just your existing charge line from your tow vehicle without the need for a DC-DC charger, though perhaps at less than optimal performance. Let me follow that to say that I am a strong advocate for the use of DC-DC chargers in Vans and motorhomes where the LiFePo4 battery bank is located relatively near the alternator connected with relatively heavy gauge wire. In these situations the charge acceptance rate of the LiFePo4 battery can overload the alternator, this is something that is much less likely to happen with a travel trailer due to the long somewhat smaller chargeline makeing it somewhat self regulating due to voltage drop over distance for any given gauge wire.

As to the mantra of 100AH of LiFePo4 replacing 200AH of lead acid, there is some truth in this for large stationary power banks designed for maximum battery life, this is often not the case in RV applications where batteries typically don't see this day after day, year after year cycling . For typical RV use cases I would tend to say it is more like 160A-180AHH LiFePo4 replacing a 200AH lead acid as RV lead acid batteries are often discharged below the point for optimal service life due to practical real world situations.

p.s. I have used a couple of those $20 DC-DC converters, they do not take the place of a proper DC-DC charger.

 

[Checkthisout]

Some chargers have a desulfate mode which is bad for Lifepo4.

Most still only go to 14.4 20 mins a day

 

[Isaac-1]

True, but some go to 14.8VDC which is more of an issue

 

[Partimewages]

You can choose to ignore the engineering behind things. Then one day down the road wonder why something failed while you were on that great vacation with no power. I'm not saying that will happen but I have learned not to skimp on the engineering and it has of yet failed me.

 

[scrubjaysnest]

Be careful, our 2002 outback has a 7300 that will fry an sla in less then 2 hours. The trailer is used as storage. Have a tow vehicle that came with 7 pin tow connector from the factory, the 30 amp charge line was 22 awg.

 

[arktec1]

Whoa, lots to read through. Thank you.

I have a goal zero and they recommend leaving it hooked up all the time but I am sure different manufacturers have different storage recommendations. I will check with the specs for which ever battery I choose to make sure I store it properly.

I plan on having a 150 Watt solar panel hooked up to the battery when boondocking to ensure its always topped off. It will be mated with a victron solar charger. I have used this set up before on my pop-up tent trailer.

I looked up the DC to Dc chargers and I agree its not worth the time or the money to deal with that mess. I think a solar panel will be enough during travel to keep it topped off.

In regards to the power converter. This was my original question. is it ok? If i am plugged into shore power it will send power to the battery just not enough to charge it completely. I am ok with that because i have the Solar panel. I do not think I need to disconnect it from the system when plugged into shore power. What would be the harm other than not completely charging it?

 

[deeuubee]

Whoa, lots to read through. Thank you.

I have a goal zero and they recommend leaving it hooked up all the time but I am sure different manufacturers have different storage recommendations. I will check with the specs for which ever battery I choose to make sure I store it properly.

I plan on having a 150 Watt solar panel hooked up to the battery when boondocking to ensure its always topped off. It will be mated with a victron solar charger. I have used this set up before on my pop-up tent trailer.

I looked up the DC to Dc chargers and I agree its not worth the time or the money to deal with that mess. I think a solar panel will be enough during travel to keep it topped off.

In regards to the power converter. This was my original question. is it ok? If i am plugged into shore power it will send power to the battery just not enough to charge it completely. I am ok with that because i have the Solar panel. I do not think I need to disconnect it from the system when plugged into shore power. What would be the harm other than not completely charging it?

The converter will not harm your LFE battery. it just won't charge it fully. Unless you're using more power than your converter puts out, you're not really using the battery anyway when on shore power. From experience, the converter sees the LFE at 13+ volts as a charged battery and barely charges it anyway. I've been using my 540 Ah setup this way for 2 years without a problem.

 

[brb58]

I got rid of my trailer's standard converter and bought a Victron 50A IP43 Phoenix charger. What is nice about it is that it has a power supply mode. I can run my trailer indefinitely at 13.2V which is around 60% SOC if I want to when I am on shore power.

 

[0truck0]

Now you're dipping out info slowly....

I have solar on mine and have a DC-DC charger and have never used the DC-DC charger (it is on a breaker switch always turned off) while driving or ever, but it is there. I think it is 20amps, so that is not too much for the alternator, a higher amperage charger will potentially draw too much from alternator and can cause a failure.

Yes, likely your converter/charger on trailer can run with no issues. Lithium batts have higher resting voltage than LA so your charger will be confused, and as everyone says, just put out a trickle charge, but that might be enough to keep you healthy. You still not told us your power needs.

In my experience, when the LA batts get near 50% then the voltage is too low for anything except fans and dim lights. Depends on the battery too and you really dont want to run LA this low repeatedly, but lithium can go to near zero. not zero, near.
This is the 2:1 ratio rule that works good enough given batteries come in 100 amp hour increments.

 

[arktec1]

@BRB

I got rid of my trailer's standard converter and bought a Victron 50A IP43 Phoenix charger. What is nice about it is that it has a power supply mode. I can run my trailer indefinitely at 13.2V which is around 60% SOC if I want to when I am on shore power.

This would be ideal

Now you're dipping out info slowly....

I have solar on mine and have a DC-DC charger and have never used the DC-DC charger (it is on a breaker switch always turned off) while driving or ever, but it is there. I think it is 20amps, so that is not too much for the alternator, a higher amperage charger will potentially draw too much from alternator and can cause a failure.

Yes, likely your converter/charger on trailer can run with no issues. Lithium batts have higher resting voltage than LA so your charger will be confused, and as everyone says, just put out a trickle charge, but that might be enough to keep you healthy. You still not told us your power needs.

In my experience, when the LA batts get near 50% then the voltage is too low for anything except fans and dim lights. Depends on the battery too and you really dont want to run LA this low repeatedly, but lithium can go to near zero. not zero, near.
This is the 2:1 ratio rule that works good enough given batteries come in 100 amp hour increments.

"Power needs" is always a tricky question to answer. I just bought this travel trailer and I haven't used it yet because i am sorting out a bunch of odd and ends. My recent experience is from using a pop up tent trailer. I never used the tiny refrigerator so no practical experience there. I would have to go with the assumption that its going to be cold and no power hook ups. So i need enough power for the heater fan, tongue jack and a refrigerator at the very least. I don't know the power consumption on those items are right now because i haven't tested them. Lights and phones are not a problem because I can use other things for that.

 

[richard cabesa]

"Power needs" i

refrigerator ,

Your longest, most often running, load

tongue jack

Your biggest load though briefly running.

Get a handle on those

 

[Aussieguy]

tongue jacks , stabilizers, slides and other stuff for setup... leave the trailer connected to truck (motor running) while setting up
lessen the load on the battery

200-300 ah of battery will last the average user for an extended weekend
12v compressor fridge is high usage so keep the fridge door shut!

solar 2x 200w panels will keep up with a fridge , water pump and lighting etc
+ send some charge back into the battery as long as you get a sunny camping spot
solar on roof works while you are driving.

take along a small generator until you know how long you can last while at camp

 

[arktec1]

I just looked up the Refrigerator and it only runs on gas and 110v. Dometic RM2451. So i can only use gas or shore power.

 

[sunshine_eggo]

I just looked up the Refrigerator and it only runs on gas and 110v. Dometic RM2451. So i can only use gas or shore power.

Absorption fridges are BRUTAL to AC power consumption. That little bugger is likely to use about 2-2.5kWh/day. - about twice that of a typical full size residential fridge.

Run on propane.

 

[richard cabesa]

Absorption fridges are BRUTAL to AC power consumption. That little bugger is likely to use about 2-2.5kWh/day. - about twice that of a typical full size residential fridge.

Run on propane.

And even on propane they still use some 12v to keep their brain alive

 

[richard cabesa]

One more thing about running on propane. My RV had a solenoid that consumed 24watts continuous to hold the valve open. Between that and the brain, it used more power than my compressor fridge does

 

[sunshine_eggo]

And even on propane they still use some 12v to keep their brain alive

True, but this is typically very very small.

One more thing about running on propane. My RV had a solenoid that consumed 24watts continuous to hold the valve open. Between that and the brain, it used more power than my compressor fridge does

That sounds like a defective solenoid. I don't remember the fridge brand, but my 7.6 cu-ft unit was 2W measured.

 

[0truck0]

gas fridge is ideal for you with this little battery (100 amp hr I thinks?). Just keep fridge level at all times unless driving.
Gas fridge will not use any DC power of any significance. Do not try to run if off an inverter off the battery, AC is only for when plugged in. It is fine for a few hours while driving being off.

You blower on your propane furnace will be a killer unless you can recharge every day. The blower pulls a lot of amps. Consider having a little buddy heater as a supplement as it does not need any power (but will make room humid).
I kept my propane furnace, but added a diesel heater because of power needs. I can run diesel heater longer than the furnace.

IDK about the tongue jack, use sparingly. Say it pulls 30 amps and you run it 30 seconds, that is 120th of an hour amp draw, so is not that significant after doing the math.

Lights, if LED, should be minimal draw.
Water pump will be minimal esp as your water tank is limited so pump cannot be a big deal as you run out of water before it draws anything too significant.
Phones wont be significant.

What gets me is things that run all the time, like a fan (in summer), it pulls little amps, but multiplied out by 12 hours becomes a lot.
The Fantastic fan pulls 3+ amps, but I put on a controller so can slow it down to 0.5 amps and it still does plenty - same with the range vent fan, I put on a controller. Otherwise it would be 3 amps times 12 hours = 36 amp hours used. At half an amp it is 6 amps used.

I think since you did not mention any big power needs you will be fine. For me it is the furnace fan that is hungry, followed by the compressor fridge, then the air or diesel heater fans. The rest is not big enough to draw down the batteries over a week or more even with the other loads.
The Fantastic fan would use more than the fridge if I hadnt put the controller on it.

Be stingy with electricity.