Fellow RVers,My first post here, so please excuse any ignorance on my part. I have a 2012 R-Vision Crossover, 19' travel trailer. I have been using a 160w roof-top solar panel to charge two 12v deep-cycle batteries while out and about--I have a charge controller. I am thinking about replacing the batteries with a lithium-ion phosphate battery; however, I am not sure which one would be the best fit. I have researched quite a bit online, but there seems to be so many opinions and variations of what works best. When I'm dry camping, I don't use much juice. I have to two fantastic fans I occasionally use at the same time. There's the fan for the heater. The water pump, of course. I do plug in a small power inverter to charge my laptop, phone, small stuff. I'm thinking of getting a 100amp hour lithium batter or 170amp hour (big price difference, I know), but I don't know which would work best. I don't use a microwave or ac when dry camping. I'd just like someone to give me a little advice as to which battery would work best, and is my charge controller still needed.Thank you, and again, please excuse my ignorance about this subject. ChrisPortland, OR

Well, this will keep everyone busy today.It all depends on how often you are out in the cold wintery weather. That furnace fan will eat your available power very very quickly. I suspect even with a Lithium, the problem will exist. The rest of your consumption is almost negligible. You have enough solar to re-supply your present batteries as long as the panels aren't covered in snow or shade. It will come down to the money. How much are you going to spend for Lithium and will they allow your furnace fan to run for as long as you want it to. I have 3 Deep Cycle 12v's and 250 solar and I am happier than a pig in dirt with that.More reading for anyone considering...https://www.rvtravel.com/want-lithium-battery-pack/Gary Haupt

In my opinion, given your current solar panel, your estimated usage, and the size of battery you are considering, your planned system seems out of balance. I don't think your stated usage would require as large a battery as 170Ah. If it does, then you also need more solar panel capacity.....at least double what you have. Lastly, don't overlook the possibility your current solar charge controller may need to be replaced with a unit that can safely charge Lithium batteries.Just my opinions.

Ed_Gee wrote:In my opinion, given your current solar panel, your estimated usage, and the size of battery you are considering, your planned system seems out of balance. I don't think your stated usage would require as large a battery as 170Ah. If it does, then you also need more solar panel capacity.....at least double what you have. Lastly, don't overlook the possibility your current solar charge controller may need to be replaced with a unit that can safely charge Lithium batteries.Just my opinions.Was just reading about the need to have the right controller..and ensure it is remains healthy. Interesting.Gary Haupt

Thank you for the quick responses! Much appreciated. I'm leaning more toward a 100amp hour lithium battery at the moment, but I'm in no rush. I want to do it right. Thanks again!

garyhaupt wrote:Was just reading about the need to have the right controller.... the one you can adjust to the correct voltages. This thread may get moved to Tech issues.

Upgrading to Lithium with Solar... | Good Sam Community

memtb
Explorer
Mar 07, 2019
Thanks Itenerant1, I’ll try and follow up as technology improves.
Itinerant1
Explorer
Mar 07, 2019
Here is something for the guys in colder temps that are on the fence for lfp.

Coming Soon
Low Temperature models Available in 100AH, 150AH, 200AH and 300AH Charge and Discharge down to -20°C!

http://www.lifebluebattery.com/rv-boat-lithium-ion-batteries-1/index.html
memtb
Explorer
Mar 06, 2019
2oldman wrote:
memtb wrote:
with very cold batteries while in storage, I could wrap the batteries or heat the inclosure, to slowly warm the batteries.....and all would be well?
In storage.. not sure why you'd need to heat them there.

2oldman, My storage, in winter, can often see temperatures in the minus -20 F range. As we will occasionally de-winterize during the winter months.....my concerns were getting the batteries to a usable temperature prior to “setting sale” with the RV.
Itinerant1
Explorer
Mar 05, 2019
Fyi, most of the dropin also have low voltage cut off, so if you where to use the battery/ batteries to such a point of that low of a SOC they shut themselves down (protecting cells) till the are charged or the voltage gets above a certain level. That is part of the BMS. ;)
allen8106
Explorer
Mar 05, 2019
So I have 520 watts of solar feeding two 6 volt 240 amp hour batteries which gives me 120 amp hours of usable juice. I run my furnace on a low t-stat setting all night and normally my batteries are around 65%-70% when I get up in the morning. Assuming it's 70% then I'm using 72 amp hours for the furnace overnight leaving me with 48 amp hours to spare before I get to the 50% discharged level which is considered dead. So using that as a baseline if you have 100 amps of lithium that you can take down to as low as 20% this would cause you to have about 24 amp hours remaining in the morning until the sun starts hitting your solar panels or the batteries get below recommended discharge level.

My opinion, what you want to do can be done but there's risk. At the cost of lithium batteries you certainly don't want to take them too low.

Plus another consideration is that lithium batteries cannot be charged even once when temps are below 32 degrees F. Many are recommending no lower than 41 degrees when charging. I camp to much in cold climates to even think about lithium batteries.
Shearwater
Explorer
Mar 03, 2019
Our Advanced RV unit came with a 600 Ah pack of Li batteries. They power pretty much everything including cooking - there is no propane, which is a real advantage.

Their setup includes 1) A second alternator on the engine to deliver the correct charging voltage, 2) A temperature sensor for each cell with an electronic readout, 3) An overheat shutoff, and 4) A battery pack heater.

They warn that charging the batteries when the cell temps are less that 32F or storing the batteries at temps below 14F.

There are Li batteries that use a different chemistry that are less temperature sensitive but these may have other drawbacks.

For your needs, I think you would be better served with a pair of true deep cycle AGM 6 or 12 V batteries.
2oldman
Explorer II
Mar 03, 2019
memtb wrote:
with very cold batteries while in storage, I could wrap the batteries or heat the inclosure, to slowly warm the batteries.....and all would be well?
In storage.. not sure why you'd need to heat them there.
memtb
Explorer
Mar 03, 2019
A good valid point, had my head “submerged”. My basement, obviously is heated when camper is in use. So, with very cold batteries while in storage, I could wrap the batteries or heat the inclosure, to slowly warm the batteries.....and all would be well?
Itinerant1
Explorer
Mar 03, 2019
2oldman makes a good point and forgot to add it to my previous post that most these dropin and my prismatic cell package came with safety features for the protection of the batteries.

Memtb if you could heat the compartment by your forced air than I would certainly not think cold camping would be an issue for the batteries.

In my front compartment my heat duct actually ends above my batteries just no opening, which can easily be corrected if I wanted the heat from the furnace in there.
memtb
Explorer
Mar 03, 2019
Itenerant1, For most rv’ers,I can see the benefits of a system similar to what you described. However, we live in what some would consider extreme.....and camp likewise. For my particular situation, my concerns would be keeping the system warm enough, when boondocking in zero or subzero temperatures , with minimal generator use. I realize that they generate heat as a byproduct of consumption/use. With that in mind....do you think that in an enclosed/insulated enclosure of minimal cubic feet, with the batteries being used ( running RV forced air ), do you think that they would produce enough exothermic heat to maintain adequate temperatures inside the enclosure? I realize under these extreme conditions that some generator use is necessary, but would like to minimize.

Thanks for your patience!

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