Upgrading to Lithium with Solar...

[goohelm65]

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.

Chris
Portland, OR

[memtb]

Thanks Itenerant1, I’ll try and follow up as technology improves.

[Itinerant1]

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]

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]

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]

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]

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]

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]

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]

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]

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!

[2oldman]

I would hope the BMS would take care of low temp charging.

[Itinerant1]

I don't take post as confrontational, it's the internet and sometimes typed words come across flat without emojis, it happens. But that's why we have these forums to help clear up some of the mud that gets stirred up. 😉
Yes, I fulltime in a 5th wheel traveling the western states (30k miles). Have boondocked not paying for camp spots 1,035 days out of the past 3 years with approximately 350+/- cycles on the batteries. Moving with the weather but can be at elevation with colder temps 30f - or places that are 90f +. I don't like either extrem but certainly don't worry about it.

My particular setup is in the front compartment of the 5th wheel. It is unheated and is somewhat open to the outside. What I did was bought a 4x8 sheet of the rigid foam board and cut pieces to fit in the sections of between the frame structure. One piece was cut to fit a 18"×12" opening that can be removed in warmer weather for better air circulation. Doing this has helped in colder weather retaining some heat in the compartment. I do carry a small cube heater that I can plug in that compartment if I was really worried about it.

The reason for the "technical" reply was so folks can understand more of the temp/ battery than the generic respone which is repeated like gospel about charging at sub 32f. Yes ambient might be that but not the lfp cells themselves. Once again I will say that's why being able to see individual cell info is important.

So it's cold where you store it. An lfp battery should stored at 50% +/-, start using the battery it will start warming itself plus having an insulated compartment or some sort of wrap and a warming pad for the batteries... issue solved. Or take them with you.
The heat thing, even with ambient above 95f my 20 cells have never been above 85f. Or below 44f. This is from experience living off of solar/ lfp and I do basically live like being plugged in.

[pianotuna]

There is at least one formulation of LI that can be charged at -25 C. It can be discharged at -40 C. However I've not found them in large capacity (say 100 amp-hours) and up.

Storage temperatures are a gray area, too.

[memtb]

Itenerant1, To remove ourselves from all of the technical jargon, can we simplify this for my limited cranial capacity. I have no doubt, that lithium batteries are far superior to lead/acid or glass mat batteries when stored/used/operated within a given parameter.

You apparently full-time or live off of the grid, so your batteries, can be stored in an environment comfortable for human habitation. If you are in a camper/5th wheel...what special provisions did you make to maintain your batteries in their desired environment. Many of us store our rv’s in zero F to far below zero F during the winter months. Many of us will de-winterize and use our rv’s several times per winter in these winter conditions. Conversely, many of us live in hot climates (90 F temperatures throughout the summer months), and will use the RV intermittently throughout the summer, so these batteries will “live” in a hot environment. Under the previously described scenarios, how does the part-time rv’er maintain their lithium batteries within the proper environment? As an example, it’s a minus 6 F right now, will be colder tomorrow morning and my RV is in an unseated storage!

I’m “not” trying to be confrontational, but want to learn how the average rv’er can convert to and use lithium batteries in temperature extremes. I would like to convert to lithium batteries, but, without major renovations to my camper, what are my options?

Inquiring minds! :h