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Old 12-09-2022, 12:23 PM   #1
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lithium batt, winter care ???

Okay, please don't shoot me, but... this is not about a forest river camper..I use to have a Cherakee grey wolf and used this forum for questions and it is a great forum.. My new[ish] trailer is a Lance model 1985 (Hiss, Hiss) ... the Lance forum is kinda sucky (all they seem to care about is where the best camp grounds are and do they have a pool etc) ... Anyway, my question is more generic to all trailers not just Lances.. So, here it is... This trailer has (2) lithium batteries installed (by previous owner) along with a upgraded, lithium I imagine(?) controller...
1.) I am storing the trailer for the winter, plugged into shore power .
2.) the batteries have a disconnect switch
3.) the trailer solar ready but does not have any panels (I don't know if that matters)..

My question is should I turn off the battery disconnect switch, so as not to keep
the batteries at 100% which I have 'heard' is bad for lithium batteries??
I would like to get the full service life from the batteries, or at least not damage them...the voltage reading on the charge screen is 14.61v..
thanks, Frank
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Old 12-09-2022, 01:25 PM   #2
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Take off the negative cable from battery
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Old 12-10-2022, 04:59 PM   #3
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Lithium batteries like to be stored at 50 to 60% capacity. Do you have a shunt meter that gives percent of usage, and have you calibrated it recently? Your shunt meter should have a manual on how to calibrate.
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Old 12-10-2022, 05:14 PM   #4
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Originally Posted by mrfikser View Post
Okay, please don't shoot me, but... this is not about a forest river camper..I use to have a Cherakee grey wolf and used this forum for questions and it is a great forum.. My new[ish] trailer is a Lance model 1985 (Hiss, Hiss) ... the Lance forum is kinda sucky (all they seem to care about is where the best camp grounds are and do they have a pool etc) ... Anyway, my question is more generic to all trailers not just Lances.. So, here it is... This trailer has (2) lithium batteries installed (by previous owner) along with a upgraded, lithium I imagine(?) controller...
1.) I am storing the trailer for the winter, plugged into shore power .
2.) the batteries have a disconnect switch
3.) the trailer solar ready but does not have any panels (I don't know if that matters)..

My question is should I turn off the battery disconnect switch, so as not to keep
the batteries at 100% which I have 'heard' is bad for lithium batteries??
I would like to get the full service life from the batteries, or at least not damage them...the voltage reading on the charge screen is 14.61v..
thanks, Frank
There are many opinions on how to store lithium batteries (lifepo4). Most, but not all, will tell you to store the batteries at 40-60 percent charge. I disconnect them and store them in my connected garage at a temp of 40-50 degrees F over the winter. about every 2 months or so I will check up on them. I do not let them hard freeze. Inside storage also greatly mitigates the chance of theft.
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Old 12-10-2022, 06:38 PM   #5
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Lithium batteries like to be stored at 50 to 60% capacity. Do you have a shunt meter that gives percent of usage, and have you calibrated it recently? Your shunt meter should have a manual on how to calibrate.
For the record, Battleborn recommends that for storage their batteries be charged to 100% and disconnected. If storage lasts for extended periods they recommend charging every 6 months or a minimum of one charge cycle per year.

Starting storage of LiFePo4 batteries at a low SOC can create major problems if storage is prolonged. While LiFePo4 batteries have much lower rates of internal discharge they still have some. A battery left in long term storage at a low SOC can then be in danger of discharging below the LVD (Low Voltage Disconnect) level set in the BMS (which itself is drawing small amounts of power) and if not charged within a very short time (BB says 5 days for theirs) the battery is most likely irreversibly damaged and can't be "awaken".


My solution to the storage issue is to just camp more often. For me my TT is in "storage" no more than 60 days on average n In 3 weeks I'll be on the road for 45 to 60 days, depending on my "fun factor"
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Old 12-11-2022, 08:38 AM   #6
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For the record, Battleborn recommends that for storage their batteries be charged to 100% and disconnected. If storage lasts for extended periods they recommend charging every 6 months or a minimum of one charge cycle per year.

Starting storage of LiFePo4 batteries at a low SOC can create major problems if storage is prolonged. While LiFePo4 batteries have much lower rates of internal discharge they still have some. A battery left in long term storage at a low SOC can then be in danger of discharging below the LVD (Low Voltage Disconnect) level set in the BMS (which itself is drawing small amounts of power) and if not charged within a very short time (BB says 5 days for theirs) the battery is most likely irreversibly damaged and can't be "awaken".


My solution to the storage issue is to just camp more often. For me my TT is in "storage" no more than 60 days on average n In 3 weeks I'll be on the road for 45 to 60 days, depending on my "fun factor"
The outlier I was referring to in my prior post is BattleBorn. Every other source that I have seen recommends the 40-60 (plus or minus) percent SOC for prolonged storage.

So why does a company like BB say differently? My guess is that it has to do with marketing. RVers probably don't RV, on average, more than 10 years (just my guess) before they move on to something else. BB's limited warranty is for 10 years. However, it is well accepted that lifepo4 has a natural life of 20 years or so if treated correctly which includes storage parameters such as the 40-60 recommendation.

As for convenience, most RVers don't want to spend the time needed to properly care for lifepo4. Like most North Americans, they want to buy it and forget it like they would with a SLA battery. BBs marketers understand this and market their batteries to the recreational market of use it and forget it.

One other possible factor for BBs recommendation is that they use 30 or so 18650 cylindical cells as opposed to 4 prismatic cells like most other RV battery manufacturers use. Both are lifepo4, but built quite differently. This may also account for BBs claim that their batteries can be charged a couple of degrees below 32 degrees F without damaging the battery.
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Old 12-11-2022, 08:56 AM   #7
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I'm curious (and like to learn).....why do lifepro batteries get stored at only 40-60% charge? I've never used one but that goes against logic to me. Guess I'm an old timer (although not that old) and I always try to store batteries at 100%.

Like I said....curious and want to learn....
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Old 12-11-2022, 11:07 AM   #8
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Originally Posted by PhilFromMaine View Post
The outlier I was referring to in my prior post is BattleBorn. Every other source that I have seen recommends the 40-60 (plus or minus) percent SOC for prolonged storage.



So why does a company like BB say differently? My guess is that it has to do with marketing. RVers probably don't RV, on average, more than 10 years (just my guess) before they move on to something else. BB's limited warranty is for 10 years. However, it is well accepted that lifepo4 has a natural life of 20 years or so if treated correctly which includes storage parameters such as the 40-60 recommendation.



As for convenience, most RVers don't want to spend the time needed to properly care for lifepo4. Like most North Americans, they want to buy it and forget it like they would with a SLA battery. BBs marketers understand this and market their batteries to the recreational market of use it and forget it.



One other possible factor for BBs recommendation is that they use 30 or so 18650 cylindical cells as opposed to 4 prismatic cells like most other RV battery manufacturers use. Both are lifepo4, but built quite differently. This may also account for BBs claim that their batteries can be charged a couple of degrees below 32 degrees F without damaging the battery.
Rest assured that Battleborn ( and their parent Co Dragonfly Energy) have invested heavily in research and testing and their recommendations are not "marketing based".

Consider how many battery "marketers" are merely relabeling batteries assembled offshore and have no R&D of their own and then look at Battleborn.

There is a good reason they cost more.

As for the 40-60% storage, I think that has its roots in the requirement "Lithium" batteries be shipped with no greater SOC and that's just to limit the amount of energy that is released in an accident, etc..

All in all, I have yet to see any documentation on how much a LiFePo4 battery is degraded if left for any length of time at greater than 50% SOC.

FWIW. Canbat recommends that their batteries be stored "with more than 50% SOC" in order to prevent possible damage due to over (self) discharge.

Lastly, LiFePo4 battery life is primarily measured in cycles, not years.





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Old 12-11-2022, 11:31 AM   #9
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Originally Posted by PhilFromMaine View Post
One other possible factor for BBs recommendation is that they use 30 or so 18650 cylindical cells as opposed to 4 prismatic cells like most other RV battery manufacturers use. Both are lifepo4, but built quite differently. This may also account for BBs claim that their batteries can be charged a couple of degrees below 32 degrees F without damaging the battery.
Yes, BB uses 30 cells in parallel for each main "cell' but NOT 18550 cells.

More like a type 21700 is ~ 4 ah vs the 1.5 ah of the 18650 cells.

As for prismatic cells, they're the most common cells used because they're cheap and plentiful in both new and used on the Chinese market. Easy to assemble too.
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Old 12-11-2022, 12:38 PM   #10
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As for the 40-60% storage, I think that has its roots in the requirement "Lithium" batteries be shipped with no greater SOC and that's just to limit the amount of energy that is released in an accident, etc..

All in all, I have yet to see any documentation on how much a LiFePo4 battery is degraded if left for any length of time at greater than 50% SOC.
Not necessarily so. There are chemical interactions at play. You seem to have a technical mind so you may enjoy reading this:
https://uwspace.uwaterloo.ca/bitstre...pdf?sequence=3
I got lost pretty quickly - but there is good info in the abstract.


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Originally Posted by jd4010 View Post
I'm curious (and like to learn).....why do lifepro batteries get stored at only 40-60% charge? I've never used one but that goes against logic to me. Guess I'm an old timer (although not that old) and I always try to store batteries at 100%.

Like I said....curious and want to learn....

Read the first 3-4 posts in this thread (started by an electrical engineer):
https://diysolarforum.com/threads/ho...y-part-2.3703/

Also, if you can get past the science, the other article posted for Mike. At least the abstract.
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Old 12-11-2022, 01:41 PM   #11
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Not necessarily so. There are chemical interactions at play. You seem to have a technical mind so you may enjoy reading this:
https://uwspace.uwaterloo.ca/bitstre...pdf?sequence=3
I got lost pretty quickly - but there is good info in the abstract.





Read the first 3-4 posts in this thread (started by an electrical engineer):
https://diysolarforum.com/threads/ho...y-part-2.3703/

Also, if you can get past the science, the other article posted for Mike. At least the abstract.
Good reading. It also supports my belief that SOC is not the main item of importance when storing LFP batteries From the uwaterloo.ca paper

Quote:
Cells stored at 60oC regardless of their SOC, reached their EOL very prematurely, only being
able to sustain aging in the storage conditions for a maximum of 4 months. Cells tested at 50oC
displayed a much slower rate of decline in capacity, and those stored at 35oC showed only a
marginal decrease, even despite being stored at high SOC. After 28 months of storage a cell
stored at 35oC and 100% SOC was only removed in order to perform post-mortem analysis for
comparison with other cells

35 Celsius is 95 Fahrenheit. Note that the cells that were greatly degraded wre stored as high as 150 Fahrenheit.

It's no surprise here that heat plays a huge factor in degradation of battery cells regardless of chemistry. Hottest temp I've ever seen on my batteries was on a 100 degree day and battery temp was shown as 85 F. (29C)



Another thing to note in the paper is that the capacity tests were at a 1C rate. Unless one is running the A/C or Microwave extensively, the average RV owner with a pair of 100ah batteries will see an average discharge rate more like .025C (5 amp) to .075C (15 amp). Lower C-rates will yield more usable capacity.
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Old 12-11-2022, 02:55 PM   #12
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There is little doubt that temperature control is the main concern in the life cycle of LFP. However, SOC charge seems to be the second. From the uwaterloo.ca paper (page 26):


"The main factors affecting capacity fade and impedance increase in cells under OCP conditions is the temperature at which they are stored at, the SOC at which the cells are stored, and the length of storage.
. . .
Testing of various cells at different SOCs but under the same temperature storage conditions has led to the determination that SOC plays a major role in cell degradation. From Ohue et al. results of cells stored at equal temperatures but for different SOCs were found to not age in the same manner [61]. The cells stored at elevated SOCs experienced increased battery degradation compared to those stored at lower SOCs [61]. SOC represents the proportion of ions present on either electrode, thus, for high SOC there is a significant number of lithium-ions available at the graphite electrode to partake in potential side reactions with the electrolyte."


P.S. - For some reason the link to the uwaterllo.ca paper I gave seems to no longer work. It can still be reached thru the diysolarforum link. Check post #4 or #5
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Old 12-11-2022, 03:30 PM   #13
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There is little doubt that temperature control is the main concern in the life cycle of LFP. However, SOC charge seems to be the second. From the uwaterloo.ca paper (page 26):


"The main factors affecting capacity fade and impedance increase in cells under OCP conditions is the temperature at which they are stored at, the SOC at which the cells are stored, and the length of storage.
. . .
Testing of various cells at different SOCs but under the same temperature storage conditions has led to the determination that SOC plays a major role in cell degradation. From Ohue et al. results of cells stored at equal temperatures but for different SOCs were found to not age in the same manner [61]. The cells stored at elevated SOCs experienced increased battery degradation compared to those stored at lower SOCs [61]. SOC represents the proportion of ions present on either electrode, thus, for high SOC there is a significant number of lithium-ions available at the graphite electrode to partake in potential side reactions with the electrolyte."


P.S. - For some reason the link to the uwaterllo.ca paper I gave seems to no longer work. It can still be reached thru the diysolarforum link. Check post #4 or #5
All points are valid but I am of the belief that those obsess over storing at a reduced SOC will still be faced with their batteries aging out around the same number of years as those who "just use them".

If the average RV owner with LiFePo4 batteries uses them 180 days per year (6 months) and completes a full cycle (100% discharge/charge) every 2 days that's 90 cycles per year. If the low end estimate of cycles for their batteries is ~2,000 it's going to take them 22 years to reach that number. By that time it won't be just the batteries that age out for most of us
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