Lithium for dummies: need advice in simple terms

[profdant139]

I have been torturing myself, trying to develop some sort of a decision tree to see if I should convert to lithium batteries. I have searched the archive for a "lithium for dummies" thread and have come up empty. (If I'm wrong, I am sure someone will let me know! 😉 )

So that is what I am humbly asking for -- is there a really easy to understand site or article that explains or compares lithium batteries to lead/acid batteries for RV use and then guides the shopper through the steps needed to come to a conclusion?

Or maybe this thread can serve as a resource for those of us (like me) who do not have technical backgrounds?

In any event, here are my particular questions:

Aside from the obvious cost difference (which may or may not be a deal killer), my three biggest concerns are weight, capacity, and cold weather charging.

Weight: I am in my eighth decade (!) and am having trouble lifting a group 31 lead acid battery without hurting my back. It looks like lithium is a clear winner on that issue.

Capacity: I'm satisfied with the capacity of a group 31 -- it's nominally at 110 amp/hours, which means I can get about 55 amp/hours from the battery without risk of damage to the battery. Am I correct in concluding that if I were to get a lithium battery with 100 amp/hour capacity, I could use almost all of that capacity?

Cold weather: What does one do about charging a lithium battery when camping in sub-freezing weather? We really like snow camping -- is that a deal killer? We are almost never subjected to temps below ten degrees. And the daytime usually warms up to around 30 or so.

Thanks in advance for your help and advice -- and on behalf of all of us dummies, thanks for keeping it as simple as you can!

[StirCrazy]

Itinerant1 wrote:
One more thought that seems to be parroted is the temperature. When talking about 0c/ 32f its the cells (batteries) temperature not the ambient temperature that's the end all be all of charging and as mentioned hopefully the cells have the cut off to charging from the bms.

Cutting off early morning charging from solar when it's below ambient freezing temps is crazy especially during this time of the year as the day light get shorter and the arc of the sun is lower. Precious charge is wasted if your controller can turn off charging and battery cell temps are above 32f.

I've been in 17f ambient temps, cells showing 38-40f (I can see all 20 cell temps and my bms/ ems can) solar charging at 20-30a and carrying my misc loads. This can extend the need for hooking up the generator for hold over charging, right now with the shorter daylight and my daily "wants", we're 21 days in partial solar charge living of 35% - 92% SOC. As long as my SOC is 60-65% by sundown that leaves enough to run the furnace use the microwave for dinner and breakfast, make a couple pots of coffee, toaster, humidifier usally going 24/7 and charging the phones, tablets and laptops all before the sun comes up. This is going into the 7th winter season fulltime living like this. 😉

this is what I have found this fall also. becasue I was running the furnace the draw on my battery was able to keep the cells much warmer than the space it was in. so in the morning the battery itself was still well above freezing. that and charging will also warm the battery up its self, the question is would it be enough. I think his idea with a yetti cooler and a small silicone heat pad will do the trick. that yetti will keep a block of ice for 11 day in plus 30C weather. haha

[mordecai81]

I don't use a monitor, per se.
We've had this rig long enough that I've gotten pretty good at estimating the amp/hrs we've used and I keep track of the total amps charged through the solar charger and the cheap monitor I've wired between the stand alone charger and the battery. Kind of a cheesy set-up but it works for me.
If there's any doubt I just charge the batt to full in the evening and know I've got enough juice to last for 24 hrs. It's a 125 a/hr batt and the most I've ever used is about 75 a/hrs a day when camping in below freezing weather. I may get ambitious and wire up a Victron but it's not a high priority.
With a capable charger and a small battery bank it's feasible to get to full every day and then not have to worry about exactly what your
state of charge is.

[pianotuna]

profdant139,

I suspect (but do not know) that a good battery management system will inform you of consumption and remaining capacity.

If not, then Victron makes more than one excellent meter or "amp hour counter".

[3_tons]

theoldwizard1 wrote:

profdant139 wrote:
No, seriously, which device will give you an accurate picture of the remaining battery capacity? Using a cheap multimeter, ...

Stop right there ! Spend the money and get a QUALITY battery monitor. Victron makes some nice ones. Get their base model. It does what you want.

X2, you might consider either their Smart-Shunt or the BMV-12, both are LFP capable, and have built-in bluetooth along with good phone graphics.

3 tons

[theoldwizard1]

profdant139 wrote:
No, seriously, which device will give you an accurate picture of the remaining battery capacity? Using a cheap multimeter, ...

Stop right there ! Spend the money and get a QUALITY battery monitor. Victron makes some nice ones. Get their base model. It does what you want.

[theoldwizard1]

profdant139 wrote:

This may be a deal killer because we are almost always away from the trailer during daylight hours, hiking or snow-shoeing or skiing. So we would not be in a position to monitor the battery and the solar charger in real time, to make sure that we are not damaging the system and that there is enough juice to run the fridge, etc.

Do you take a generator when boondocks ?

Install the batteries inside. When you get back from your outside adventure, start the generator and a couple of electric heaters. If you have a good battery management system it will not allow the batteries to accept a charge until they are at a safe temperature.

Watch the Will Prowse YouTube channel. He reviews solar panels, inverters, chargers and batteries. He always comments if the battery management system has cold weather protection.

[S_Davis]

profdant139 wrote:
Mordecai, what do you use to monitor whether you are short amps? (Different from a short circus, I think.). 😉

No, seriously, which device will give you an accurate picture of the remaining battery capacity? Using a cheap multimeter, I often check the voltage on my lead acid batteries, on the theory that any reading below 12.1 means that I've got a state of charge less than 50%.

But with lithium batteries, the voltage does not drop, I think. The battery goes from "full" to "dead," if I remember correctly.

Full charge is about 13.4 volts, at 12 volts you are at about 10% charge with LifeP04. Voltage does drop with state of charge just not as much as lead acid.

[profdant139]

Mordecai, what do you use to monitor whether you are short amps? (Different from a short circus, I think.). 😉

No, seriously, which device will give you an accurate picture of the remaining battery capacity? Using a cheap multimeter, I often check the voltage on my lead acid batteries, on the theory that any reading below 12.1 means that I've got a state of charge less than 50%.

But with lithium batteries, the voltage does not drop, I think. The battery goes from "full" to "dead," if I remember correctly.

[mordecai81]

I like making things more complicated than they need to be as much as the next guy, but it's actually pretty simple, even with the battery living on the tongue. I set up the heater per the manufacturer's instructions. It keeps the batt above 37 degrees-ish. The solar does it's thing. If I'm short amps in the evening I fire up the genny, charge at 45 amps for between 20-60 minutes and call it a day. Easy peasy. It most likely woulb be more complex at -30c but whose crazy enough to camp at that temp:)

[3_tons]

profdant139 wrote:
Some of the preceding discussion is over my head, so let me bring things back to a more basic level. It looks like I will need an insulated battery box and a heater to keep the lithium battery above freezing. But the heater draws current, of course.

So I would have to budget a reserve of power in order to make sure that the battery is warm enough to accept a charge.

This may be a deal killer because we are almost always away from the trailer during daylight hours, hiking or snow-shoeing or skiing. So we would not be in a position to monitor the battery and the solar charger in real time, to make sure that we are not damaging the system and that there is enough juice to run the fridge, etc.

Hmmm. We may not be ideal candidates for lithium, until they work out the temperature issues. That is really too bad. But I am not ready to give up on snow camping.

Well, situations often differ, so in this regard I can only speak to my own situation…In my case, the OEM exterior battery box extended beneath the dinette seat, so I simply removed the nylon battery box, sealed and insulated the exterior door, and put two 200a/hr LFP’s in-parallel beneath the dinette seats..During unattended winter camping we leave the furnace set on 55d/f anyways (to heat enclosed basement tanks, dump valves and plumbing), so solar charging can be concurrent…

Example: Do to evolving needs over time (lol!) I’ve now expanded to having three separate solar PV systems (a 500w, 260w rooftops, and an occasional ground deployable 360w for longer desert excursions), each system having it’s own independent charge controller…

This may sound a bit haphazard :h yet in actual practice, by operating just one of the three separate systems (or some wattage combination thereof), I can reasonable project and plan for the expected amount of per hour harvest return while absent…

When enjoying extreme off-roading, the added charge flexibility here (regardless of season) has proven to truly be a major bonus, since I can reasonably plan for a desired amount of harvest!

FWIW, one of my controllers (the BlueSky) is programmable for voltage parameters and for timed duration at 100% SOC - so were I to opt for a FULL unattended charge (*however unlikely...) the controller would shutdown shortly thereafter…

* (unlike wet-cells, a routine ‘full charge’ is required only occasionally.)

Hope this helps,

3 tons

[S_Davis]

It really doesn’t take a lot to keep the cells warm, I use a 3”x3” 12 volt 25 watt silicon heat pad on each battery and they have worked perfectly down to 8f in back seat area of my crew cab. I have them set about 50 degrees, with two 280ah batteries I can spare the ah to run them.

[Grit_dog]

^ Yeah, so much for real world advice and NOT diving into the weeds....

I think the simple answer is move the batteries inside the camper somewhere. Storage and discharge below freezing aren't so much the issue as trying to charge a cold battery. Presuming you arent letting the camper cold soak down well below freezing and at the same time expect to be charging the batteries, that's a good compromise since you're not really going down into extreme cold temps.

Remember it's the battery "core" temp that matters. I use a LFP on my snowbike. It is certainly in the "cold" all day. Older original battery needed much more "warm up" before it would discharge at a fast enough rate. Couple bumps of the starter to load the battery momentarily and then off to the races.

If you are to the point where insulated boxes with pad heaters are needed, just scratch LFP as being practical. If you can do the above suggestion to keep them warmer without extra effort, then IMO it will work fine.

[profdant139]

Some of the preceding discussion is over my head, so let me bring things back to a more basic level. It looks like I will need an insulated battery box and a heater to keep the lithium battery above freezing. But the heater draws current, of course.

So I would have to budget a reserve of power in order to make sure that the battery is warm enough to accept a charge.

This may be a deal killer because we are almost always away from the trailer during daylight hours, hiking or snow-shoeing or skiing. So we would not be in a position to monitor the battery and the solar charger in real time, to make sure that we are not damaging the system and that there is enough juice to run the fridge, etc.

Hmmm. We may not be ideal candidates for lithium, until they work out the temperature issues. That is really too bad. But I am not ready to give up on snow camping.

[Itinerant1]

One more thought that seems to be parroted is the temperature. When talking about 0c/ 32f its the cells (batteries) temperature not the ambient temperature that's the end all be all of charging and as mentioned hopefully the cells have the cut off to charging from the bms.

Cutting off early morning charging from solar when it's below ambient freezing temps is crazy especially during this time of the year as the day light get shorter and the arc of the sun is lower. Precious charge is wasted if your controller can turn off charging and battery cell temps are above 32f.

I've been in 17f ambient temps, cells showing 38-40f (I can see all 20 cell temps and my bms/ ems can) solar charging at 20-30a and carrying my misc loads. This can extend the need for hooking up the generator for hold over charging, right now with the shorter daylight and my daily "wants", we're 21 days in partial solar charge living of 35% - 92% SOC. As long as my SOC is 60-65% by sundown that leaves enough to run the furnace use the microwave for dinner and breakfast, make a couple pots of coffee, toaster, humidifier usally going 24/7 and charging the phones, tablets and laptops all before the sun comes up. This is going into the 7th winter season fulltime living like this. 😉

[3_tons]

Dendrites are to LFP’s what Sulphation is to lead-acid - in both cases, the ‘informed user’ will easily avoid either (par for the course…).This is where ‘knowledge’ can overcome the cultivation of fear…

3 tons