Lithium for dummies: need advice in simple terms

theoldwizard1 wrote:

pianotuna wrote:

Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium occurs on the anode during a sub-freezing charge that leads to a permanent degradation in performance and safety.

You are more aware of battery chemistry than I, so hopefully you can answer this question. I am aware if the cod charging issue, but can you store or discharge LiFePO4 batteries below freezing ? How far below ?

storage differs on the brand and type of cell used. the new 280K's I just ordered from eve can be stored for 1 month at -40 and long term to -20C. they can actualy be discharged down to -30C and charged at full rate at -5C. I am still going to set my charg limit on my BMS at 0C though.

profdant139 wrote:


Second, it sounds like I will have to replace my old WFCO converter/charger, right? That's probably a good idea, anyway, given that WFCO units don't have a great reputation.

That sounds like a fun project! Maybe put the batteries inside a YETI cooler??

I won't take delivery of a new trailer that had a WFCO in it, part of the sale is for them to take it out and put a good charger in. plus if you are going to switch why not have the proper charge available. you just have to replace the charger section.

a yeti for a battery box, if you have the money to throw away on a battery box and don't change the charger... man oh man ;)

profdant139 wrote:

Third, it is true that most of my charging is from my solar panel (120 watts). Most of our snow camping tends to be in Utah and the Sierra, so we usually get lots of sun. But assuming that I go with lithium batteries, I will want to make sure that the software in the battery prevents charging when it is below 32 degrees.

My Victron MPPT solar controller will stop charging if the battery is below a configured voltage. A $30 battery temperature sensor is required to do this.

My switch to a single 100 Ah LifePO4 has worked out great. With my 225w of solar, I have NEVER charged it up with anything but solar in 2 extended summers of ramblin'. Also, my old body can lift it. :)

pianotuna wrote:
profundant,

20% to 85% for Li, so the 100 amp-hour has 75 amp-hours that are usable.

charge them to 100% once every 30 days to reset the battery management system.

Use a dc to DC charger for alternator protection, if planning to charge from the engine.

I can't use LI where I live. Too cold for them. For those that can avoid cold LiFeP04 are the cat's meow.

I would go for SiO2 myself.

Where do yo get the 20% to 85% figures, the EVE prismatic cell cycle rating is full charge to cut off at 2.5 volts @ 1.0C for 3500 cycles.

S Davis,

I got the figures from the wobbly wide web. If I were going Li I'd go 40% to 85%. I never will due to cold.

Your document is too blurry for me to read.

pianotuna wrote:
S Davis,

I got the figures from the wobbly wide web. If I were going Li I'd go 40% to 85%. I never will due to cold.

Your document is too blurry for me to read.

Ok well I have read just about every spec sheet for the currently available LifeP04 cells and have never seen that in any of them, all their definitions of a battery cycle are from full charge to 2.5 volt cutoff at the stated amount of cycles.

Do you have any spec sheets that say that? If not you are giving out false info. You can use 100% of the stated capacity and still get the rated cycles according to the manufacturers of the cells.

I will try and get a better screen shot, this might be a little better.

Like everything else, changing from old faithful, & cheap, wet cells to something else simply depends.

LifePO4s look great. They are lightweight. They outperform everything else. They have a service life of 15 years plus. They are still quite expensive.

I have a 2007 5er which at the moment is about halfway through the life cycle of it's second AGM battery bank. The first was good for nine seasons. By the time this AGM needs replacing the trailer will be almost 20 years old & have well in excess of 100,000 miles & 2500 nights use on it.

It will be ready for retirement to some seasonal CG, if not the salvage yard.

Can't justify the expense of LifePO4 on that.

S Davis wrote:

pianotuna wrote:
S Davis,

I got the figures from the wobbly wide web. If I were going Li I'd go 40% to 85%. I never will due to cold.

Your document is too blurry for me to read.

Ok well I have read just about every spec sheet for the currently available LifeP04 cells and have never seen that in any of them, all their definitions of a battery cycle are from full charge to 2.5 volt cutoff at the stated amount of cycles.

Do you have any spec sheets that say that? If not you are giving out false info. You can use 100% of the stated capacity and still get the rated cycles according to the manufacturers of the cells.

Mal-information reboot - Groundhog Day :W

3 tons, enjoying my 126a *LFP Keurig brew while at zero% SOC - lol

*(actual bench test capacity = 7% greater than advertised capacity…)

*************

My oops, For clarity, 200advertised a/hr LFP bench tested at 215 actual a/hr

S Davis.

Some take away's about LiFePo4 batteries

"There is more to calendar life and how quickly a LiFePO4 battery will age: State-Of-Charge has something to do with it as well. While high temperatures are bad, these batteries really, really do not like to sit at 0% SOC and very high temperatures! Also bad, though not quite as bad as 0% SOC, is for them to sit at 100% SOC and high temperatures. Very low temperatures have less of an effect. As we discussed, you cannot (and the BMS will not let you) charge LFP batteries below freezing. As it turns out, discharging them below freezing, while possible, does have an accelerated effect on aging as well. Nowhere near as bad as letting your battery sit at a high temperature, but if you are going to subject your battery to freezing temperatures it is better to do so while it is neither charging nor discharging, and with some gas in the tank (though not a full tank). In a more general sense, it is better to put away these batteries at around 50% – 60% SOC if they need longer-term storage.

Melted battery

If you really want to know, what happens when a lithium-ion battery gets charged below freezing is that metallic lithium is deposited on the negative (carbon) electrode. Not in a nice way either, it grows in sharp, needle-like structures, that eventually puncture the membrane and short out the battery (leading to a spectacular Rapid Unscheduled Disassembly Event as NASA calls it, involving smoke, extreme heat, and quite possibly flames as well). Lucky for us, this is something the BMS prevents from happening."

So if you have solar--turn it off during storage. I don't like that.

This is the summary from the article:

"To sum up, for long and happy LFP battery life, in order of importance, you should be mindful of the following:

Keep the battery temperature under 45 C (113 f) (under 30C if possible (86 f)) – This is by far the most important!

Keep charge and discharge currents under 0.5C (0.2C preferred)

Keep battery temperature above 0 C (32 f) when discharging if possible – This, and everything below, is nowhere near as important as the first two

Do not cycle below 10% – 15% SOC unless you really need to

Do not float the battery at 100% SOC if possible

Do not charge to 100% SOC if you do not need it"

The above are from https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

another good page on care and feeding:
https://dakotalithium.com/2021/09/22/how-to-charge-dakota-lithium-and-lifepo4-batteries/

pianotuna wrote:
S Davis.

Some take away's about LiFePo4 batteries

"There is more to calendar life and how quickly a LiFePO4 battery will age: State-Of-Charge has something to do with it as well. While high temperatures are bad, these batteries really, really do not like to sit at 0% SOC and very high temperatures! Also bad, though not quite as bad as 0% SOC, is for them to sit at 100% SOC and high temperatures. Very low temperatures have less of an effect. As we discussed, you cannot (and the BMS will not let you) charge LFP batteries below freezing. As it turns out, discharging them below freezing, while possible, does have an accelerated effect on aging as well. Nowhere near as bad as letting your battery sit at a high temperature, but if you are going to subject your battery to freezing temperatures it is better to do so while it is neither charging nor discharging, and with some gas in the tank (though not a full tank). In a more general sense, it is better to put away these batteries at around 50% – 60% SOC if they need longer-term storage.

Melted battery

If you really want to know, what happens when a lithium-ion battery gets charged below freezing is that metallic lithium is deposited on the negative (carbon) electrode. Not in a nice way either, it grows in sharp, needle-like structures, that eventually puncture the membrane and short out the battery (leading to a spectacular Rapid Unscheduled Disassembly Event as NASA calls it, involving smoke, extreme heat, and quite possibly flames as well). Lucky for us, this is something the BMS prevents from happening."

So if you have solar--turn it off during storage. I don't like that.

This is the summary from the article:

"To sum up, for long and happy LFP battery life, in order of importance, you should be mindful of the following:

Keep the battery temperature under 45 C (113 f) (under 30C if possible (86 f)) – This is by far the most important!

Keep charge and discharge currents under 0.5C (0.2C preferred)

Keep battery temperature above 0 C (32 f) when discharging if possible – This, and everything below, is nowhere near as important as the first two

Do not cycle below 10% – 15% SOC unless you really need to

Do not float the battery at 100% SOC if possible

Do not charge to 100% SOC if you do not need it"

The above are from https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

another good page on care and feeding:
https://dakotalithium.com/2021/09/22/how-to-charge-dakota-lithium-and-lifepo4-batteries/

Ok so you are getting it from a company trying to sell batteries instead of the manufacturer of the batteries, their recommendation has more to do with warranty than affecting cycle life.