S Davis
Western WA
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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.
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3 tons
NV.
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“So if you have solar--turn it off during storage. I don't like that.”
During storage, this point is almost immaterial IF the battery (via open switch) is in electrical isolation during storage, OR with a solar controller that features programmable float voltage and timed absorption cut-off such as BlueSky or comparable. Some controllers also have programmable temp parameters as well.
As for the notion of a ‘30 day rule’ (e.g. for cell-balancing - this, without regard to number of discharge cycles??), to my knowledge no such rule exist…Rather, a consideration of the interactions between the ‘number of discharge-cycles’ count, and ‘depth of discharge’ excursions is in my view a far more realistic strategy - the interactions between the two can contributor (say overtime…) to dreaded cumulative SOC meter drift, and impact the frequency for meter resynchronizations…
As far as paralleled mis-matched LFP battery capacities goes, YES it’s doable but one might consider the following caveats (there may be others…).
1) Under a heavy discharge scenario, once the capacity of the smaller battery lowers enough, the larger capacity will send a portion of it’s current to charge the smaller battery while continuing to satisfy the heavy appliance load - this heavy loading may cause it’s BMS to cut-out.
2) SOC meter accuracy (assuming a common single-shunt and meter) is more likely to undergo meter drift and go astray….This unrecognized current diversion (i.e. waste heat) may necessitate a ‘more frequent’ full recharging regime (resynchronizations, and cell rebalancing) to maintain meter accuracy…Meter wise, determining SOC’s for a LFP is not as straightforward as it is with wet-cell types.
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Itinerant1
Itinerant
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pianotuna wrote:
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.
Pianotuna you have good advise most of the time but I have to disagree with you on some of your interpreted reading of LiFePO4 (LFP) batteries.
But maybe your reading material is better than my hands on experience living off of them. ![[emoticon]](https://forums.motorhome.com/sharedcontent/cfb/images/wink.gif "wink")
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.
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3 tons
NV.
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Itinerant1 wrote:pianotuna wrote:
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.
Pianotuna you have good advise most of the time but I have to disagree with you on some of your interpreted reading of LiFePO4 (LFP) batteries.
But maybe your reading material is better than my hands on experience living off of them.
I concur, one should be wary of ‘armchair experts’ and LFP ‘fear merchants’ (per numerous past renderings…).
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StirCrazy
Kamloops, BC, Canada
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Joined: 07/16/2003
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S Davis wrote: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.
![[image]](https://i.imgur.com/gOIyL1Wl.jpg)
he thinks all Li chemistry has the same properties and takes numbers from older chemistry types and throws them out there to make Li sound not as good.
2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumberqueen WS100
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StirCrazy
Kamloops, BC, Canada
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Joined: 07/16/2003
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pianotuna wrote:
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/
not a good page at all, In LFP the largest cause of dendrite formation is from charging, or rather overcharging.
"Lithium dendrites are metallic microstructures that form on the negative electrode during the charging process. Lithium dendrites are formed when extra lithium ions accumulate on the anode surface and cannot be absorbed into the anode in time."
sorry I like to quote scientific studies instead of sales lititure....
when you look up somthing don't just pick the first thing you see that looks like you thought it would, look at a bunch and sort out the **** from the truth man.
with LFP (eve cells) you will get aproximatly 3500 cycles in you go from 100% to 0% every cycle, after that you will still have 80% of the capacity of the battery that will function just like a 20% smaller battery. if you stay between say 10% and 90% for your limits that will proabably increast to 5000 and if ou retrict it even more and shallow discharge, up to 8000. but this isn't like your SiO2 or a normal battery where after the cycle life is over they go in the garbace. the cycle life of a LFP is that you will get that many cycles before the battery is reduced to 80% of its original capacity. kinda like the lumin drop off of LED lights.
you have countless people here who use LFP batteries telling you your a little off on your stuff but you refuse to believe the people who actualy use them over what a sales person in a store who is trying to sell you something says.. then you campain against LFP like your getting paid from a sio2 manufacture to convince people there better. there not better in so many ways. the only way they are is for charging when at -30 if you don't fell like making it so the batteries are warm which is easy.
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pianotuna
Regina, SK, Canada
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Joined: 12/18/2004
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Itinerant 1,
Living off grid with Li makes you someone to listen to, and certainly "trumps" any online only articles.
I believe Li are the cat's meow except in cold.
My choice, for now, remains SiO2. But first I have to destroy the telcom jars that are still meeting more than my needs. Since I managed 9 years with Marine jars, and I'm no longer full time, this may take a few years.
Perhaps by then, the cold issue will be resolved in an economic fashion.
BTW my latest cell phone (yes, I know it is not LiFePo4) has a setting to stop charging at 85%. The stated purpose is to extend the cycle life.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.
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Itinerant1
Itinerant
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My concern for the OP would be having lfp batteries on the outside of trailer and doing long extended camping in cold weather were the temps do not get above freezing for extended periods. Even them being in a a cooler like a Yeti or Otter would still need extra insulating even with the heat types of batteries. I have a 65qt Otter box cooler and it does keep ice pretty long but can also freeze water in the bottom of the cooler when no ice is present during the winter months in the back of my inclosed truck. Any of these "well" insulated coolers will need more insulation and the coolers aren't cheap to start with.
If lead batteries have been working for you under these circumstances I would probably stay with them.
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3 tons
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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…
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Itinerant1
Itinerant
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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.
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