LiFePO4 with cold temperature protection (lithium)

[markopolo]

It would be good if we could list LiFePO4 battery brands/models that have at least some built-in cold temperature protection. I'll list two that I know of. Please include temperature specifics and balancing voltage if known.

Relion low temperature:
https://relionbattery.com/products/lithium/rb100-lt
No low temperature cutoff disconnect listed that I can see, instead it has an internal heater. Operation permitted down to -4F. Balancing occurs at 14.4V.

Battle Born
https://battlebornbatteries.com/
No internal heater, instead it relies on a low temperature charging disconnect at <25F, low temperature charging resumption 32F. Balancing is triggered at 14V.

[booster]

Originally Posted by markopolo

It would be good if we could list LiFePO4 battery brands/models that have at least some built-in cold temperature protection. I'll list two that I know of. Please include temperature specifics and balancing voltage if known.

Relion low temperature:
https://relionbattery.com/products/lithium/rb100-lt
No low temperature cutoff disconnect listed that I can see, instead it has an internal heater. Operation permitted down to -4F. Balancing occurs at 14.4V.

Battle Born
https://battlebornbatteries.com/
No internal heater, instead it relies on a low temperature charging disconnect at <25F, low temperature charging resumption 32F. Balancing is triggered at 14V.

Interesting on the balancing voltages being different, after the recent discussion of the high balancing voltage on Reneogy at 14.6v. The 14v on the Battleborn would be at the lower state of charge near the knee of the charge curve and would more closely match what is being recommended and used by many manufacturers as a charge cutoff also.


You showed the cell manufacturer spec on balancing in the last discussion, do you know if these are the same cells or manufacturer? Especially the 14v balancing may indicate that the battery does not have to be totally full to be balanced, which with the way the current charge cutoff SOCs are being lowered to less than 100%, that would be a necessary thing so you wouldn't need to do separate balancing operations periodically.


It is going to be very interesting to see how they all do, and rate, the low temp things like heat and cutoff, as those have been the most talked about here and also until recently, most unaddressed things in the market.
Didn't Volta originally not have heaters in their units? I seem to remember that being mentioned way back. They may have had cutoffs all along, though.

[markopolo]

Originally Posted by booster

...................
You showed the cell manufacturer spec on balancing in the last discussion, do you know if these are the same cells or manufacturer? ...............

That was the BMS balancing voltage. It'll vary depending on which BMS is chosen. Battle Born chose to use a BMS that balances the cells at 14V for example.

My understanding is that LiFePO4 cells will eventually get to 95% full if held at 13.6V for long enough. That's different than balancing though. You could end up with 3.5V+3.2V+3.6V+3.3V or worse to make 13.6V. If you had a BMS that balanced at 13.6V then you'd end up with 3.4V+3.4V+3.4V+3.4V = 13.6V. My assumption is that lower balancing voltage = more current wasted or dissipated with basic (low cost) balancer circuits. It's likely mAh though.

Knowing what voltage the BMS balances at is very important IMO.


(some edits from original post)

[booster]

Originally Posted by markopolo

That was the BMS balancing voltage. It'll vary depending on which BMS is chosen. Battle Born chose to use a BMS that balances the cells at 14V for example.

My understanding is that LiFePO4 cells will eventually get to 95% full if held at 13.6V for long enough. That's different than balancing though. You could end up with 3.5V+3.2V+3.6V+3.3V to make 13.6V. If you had a BMS that balanced at 13.6V then you'd end up with 3.4V+3.4V+3.4V+3.4V = 13.6V. My assumption is that lower balancing voltage = more current wasted with basic (low cost) balancer circuits.

I assume that would be the difference between the passive and active balancing? It would be interesting to know if both styles can be done at high or lower voltages. Of course it would also be interesting to know if balancing at 14.6v as often as needed (which we also don't know is how often, I think) would do any real damage, assuming they are correct the charging to full is not a good thing.



The hold at voltage thing brings up an interesting question in that the quick read of articles on balancing put the reason for being out of balance on the internal impedance of the batteries not being identical, which makes sense. This would likely be worse the higher current is run out of them, both for charging and discharging. They also said that the active balance uses the current from the higher cells to charge the charge the lower cells so it doesn't just get bled off. The need to go to 14.6v and hold until the amps would go very low would seem to indicate that they need to drive the cells that are higher into nearly zero acceptance to force the power to the lower voltage ones, but I don't see how that happens in a series string where all the current is the same in the string. Parallel, absolutely should work that way, but also longer time at same voltage would also, I think.



I need to find out how they do that in more detail, I think.

[Jostalli]

Originally Posted by markopolo

It would be good if we could list LiFePO4 battery brands/models that have at least some built-in cold temperature protection. I'll list two that I know of. Please include temperature specifics and balancing voltage if known.

Relion low temperature:
https://relionbattery.com/products/lithium/rb100-lt
No low temperature cutoff disconnect listed that I can see, instead it has an internal heater. Operation permitted down to -4F. Balancing occurs at 14.4V.

Battle Born
https://battlebornbatteries.com/
No internal heater, instead it relies on a low temperature charging disconnect at <25F, low temperature charging resumption 32F. Balancing is triggered at 14V.

I don’t understand the request. How do you define “cold weather protection”? All “drop-in” lithium batteries that I know of have a cold weather disconnect so they will not accept a charge below freezing.

If you want a list of lithium batteries with actual cold weather protection (ie. built in heating for cold weather charging) then the list is: Relion, Zeravolt and LifeBlue. All three of these perform similarly (most likely copied due to being produced in China).

[markopolo]

Originally Posted by booster

....................

I need to find out how they do that in more detail, I think.

We're counting on that. You have a way making vital info more easily understandable and also have the patience to keep explaining it so that the rest of us catch up

[Davydd]

Balancing does not occur very often in my batteries. They are Elite Power Solutions block type batteries of 200ah, 3.4v assembled in series of 4 to to achieve one nominal 200ah, 12v battery and then in parallel to have a total 800ah bank. That is different than Roadtrek's system of four separate batteries that can be on or off separately which I would imagine would eventually get out of balance or one battery would get used much more than another.

When your batteries are balancing they get very hot. It's an automatic operation in my case and when I first encountered it while balancing I got alarmed from the heat as I did not know what was going on until assured by ARV it was normal. I've only observed balancing once in 5 years and routinely check this Silverleaf monitor and have never observed battery pack "Not Normal".



The cold temperature protection is from 5w electric heating pads sandwiched between two 12v block assemblies for a total of 10w of heating in an external fiberglas box enclosure below the floor where an Onan generator resides on Class Bs. Those 10w total pads can be turned on or off on the touch screen (the green handles indicate on) and are external from the battery thermostatically control to maintain the batteries above 41F. The little flame symbol only shows when the the pads are heating. They come on just to maintain 41F deg. That's how I know that because of the internal heat of the batteries you most likely will remain above freezing when the air temperature gets down to the mid 20's just by observing this. Those 10 watts will keep the batteries above freezing I know at least down to -20F (-29C). I haven't had a chance to observe any lower in my 5 years of ownership.

Winnebago and ARV put their Volta 48V batteries inside the conditioned van space and if you are comfortable underway then the batteries are satisfied. I suspect Pleasure-way and others have the same philosophy. I have no idea what Roadtrek did with their batteries outside the van. I don't know how any handle batteries in cold storage. I haven't contacted ARV in whether they still do heating pads inside, which I think they could easily do if you have a shore power electric source of just a normal outlet of 15a AC as I used to do when I stored outside in the Minnesota winter. I haven't questioned it because I now store in a heated garage.

[Winston]

Originally Posted by booster

. . . it would also be interesting to know if balancing at 14.6v as often as needed (which we also don't know is how often . . . )

Originally Posted by Davydd

When your batteries are balancing they get very hot . . .

Like Davydd we have the Elite system. But unlike Dave, we have no heating pads. To our knowledge, the Elite BMS does not provide any protection against cold weather charging or use. Fortunately this is not an issue for our 'inside-the-coach' lithium pack as we’ve never seen a cell temperature below 45F during normal use. And storage below -4 F is unlikely in view of our indoor storage.

The question of balancing is interesting. First, the Elite system has no cells in parallel and therefore each cell is, one might say, "individually" balanced. (This, in contrast to battery packs such as Battleborn which we all recently witnessed being dissected on YouTube - - where there are many smaller cells in parallel forming each of 4 layers.) We offer no opinion whether a group of cells in parallel ‘forces’ balance between the cells forming the group. But having fewer, and non-parallel, cells does provide a unique view of every cell (voltage, temperature, and whether the cell balancing shunt is active).

The author of the oft-quoted Compass Marine dissertation on lithium has said that, after initial balancing, balancing is no longer required. He cites the fact that he has forced a test pack through 800 full discharge cycles and the pack remains in balance. Like Dave, we have found that our Elite cells remain within a few hundredths of a voltage without balancing. Thus the question of cell damage during prolonged or repeated balance cycles should be insignificant assuming, of course, that one is not taking their pack into the lofty “14 volt” region on each charge cycle. Booster, we think the answer to "how often" is "very infrequently".

And, Dave, on the question of cell temperature during charging/balancing, we don't think the cells get very hot. What you are witnessing is a quick rise in temperature when a cell goes into 'balance mode' . . . this is not the actual cell temperature that could not rise that quickly, but the individual cell control pc board on which, and in close proximity to one-another, are both the thermistor which measures the temperature and the several watt heat-generating shunt balancing resistor.

[booster]

Thanks, Winston, good information. Especially on the frequency of balancing needed and the heat reading locations.

[markopolo]

Originally Posted by Jostalli

............. How do you define “cold weather protection”?...................

Good point. Let's say temps from 32F to 14F. No add-ons, just as the battery was sold and usability level being that you can get into a cold soaked van, start the engine & drive without having to give much thought about the LFP bank.

Originally Posted by Jostalli

....................If you want a list of lithium batteries with actual cold weather protection (ie. built in heating for cold weather charging) then the list is: Relion, Zeravolt and LifeBlue. All three of these perform similarly (most likely copied due to being produced in China).

Thanks for that info. Do you know what temperature they disconnect at or is heat the only protection?

Originally Posted by Jostalli

.........All “drop-in” lithium batteries that I know of have a cold weather disconnect so they will not accept a charge below freezing............

Are Renogy LFP's in the group of "drop-ins" that you know about? If so, what temperatures do they disconnect and reconnect at? Would you happen to know at what voltage balancing happens with Renogy LFP's?

Same question about Trojan Trillium's - much appreciated if you can share the temperature info. (I've read the PDF's on their site) I think balancing happens at 14.4V with the Trilliums.

[markopolo]

Winston - would your approach or view of balancing change for a 4S30P battery?

[markopolo]

Originally Posted by Winston

.................
The author of the oft-quoted Compass Marine dissertation on lithium has said that, after initial balancing, balancing is no longer required. He cites the fact that he has forced a test pack through 800 full discharge cycles and the pack remains in balance. ..............

If you have a link please post it, it could be interesting to read. Was it an accelerated test?

[Winston]

Originally Posted by markopolo

Winston - would your approach or view of balancing change for a 4S30P battery?

30P? Thought the Battleborn was 30 total. In any event, clearly packs made of dozens of smaller cells don't lend themselves to individual cell monitoring. Indeed, we were 'kinda overwhelmed' when we discovered we had 20 monitoring boards.

We have no objection to a series connection of parallel clusters. But for our limited number of cells (20) we have become 'enamored' with the ability to monitor every cell so we're not unhappy that Elite went this direction.

That Compass Marine article supports the parallel connection of cells into clusters . . . which is why our initial intention was to go that route. He argues, or at least assumes, that if you connect identical cells together in parallel, the will eventually equalize. Sounds good as long as they're equal which is why we hesitated to endorse that conclusion (of equality between parallel cells) . . . because, at some point, probably, they're no longer going to be identical.

We'll find that article cite and post it later this evening.

[Winston]

Originally Posted by markopolo

If you have a link please post it, it could be interesting to read. Was it an accelerated test?

There's a lot of useful information in this article, although its organization is uncertain. The article is many years old, now (unless he's updated it) but it was clear to us that he has done much testing and has substantial experience.

We don't remember the exact parameters of his test . . . indeed, as we remember, the actual number of cycles may have been updated in a later post of his . . .

http://www.pbase.com/mainecruising/lifepo4_on_boats

[markopolo]

Thanks. His batteries are still in great condition. I think he always does full charge and full discharge so no PSOC cycling. I'll quote just the summary of care he nicely provided:

Before you get too excited these cells have:

--Never been floated, they get charged, then discharged
--Only absorbed to a net 8A - 10A at 13.8V -14.0V
--Not charged above 14.0V unless for testing purposes (I now have a few other banks for that)
--Max charge rate at approx .3C
--Stored at 50% SOC when not being used or cycled
--Stored in 45-60F temps when not being used or cycled
--Only very rarely exceeded 80F
--Highest voltage they have ever seen was 3.8VPC while top balancing initially.

You have to wonder about the effects of any deviations such as charge voltage, floating, PSOC cycling, temperature etc. would have.

[booster]

The more I read about this stuff, the more it seems to be an awful lot of the same arguments for top and bottom balance, just different ends. Or the pushers of each just use each others claims


I wish they would all describe the wiring of their cells, though, as it would sure clarify things a bit, at least for me, as we hear of series and series/parallel strings for the RV stuff, it appears.


One of the big points both sides make is that that on charging all the cells see the exact same charge. The only way that could happen, from an amp hour standpoint, would be in series where all the currents have to be the same. You put in all the same amount of power to each cell each time, and the discharge comes out of all the same, they will be balanced at whatever reference is used top or bottom, plus any point in between it appears as I found lots of examples of balancing at less then 100% full and over 20% full. Not full cycles at all, which is good, I think as you don't want to do either end very much, from what we hear these days.


But what happens when you have a series/parallel setup, as the current could be different to each string? Do you balance just the parallel strings, or do both banks separately? It appears to me you would have to have individual cell voltage readings and a good controller to balance an series string without separating the cells.



The most basic claims actually may make more sense for the masses trying to use their batteries, I think. Get enough capacity to leave 20% at each end of your range unused and set the limits there. If the batteries go out of balance there is very little issue because it doesn't hurt lithium to never get full so having cushion to catch the mismatch to prevent overcharge is all you need to do. Same on the bottom end because all you need to do is make sure you don't go to zero, which the cushion takes care of on the mismatched cells. More money for sure, but less worry and hassle too.

[markopolo]

Originally Posted by booster

.................But what happens when you have a series/parallel setup, as the current could be different to each string? Do you balance just the parallel strings, or do both banks separately? It appears to me you would have to have individual cell voltage readings and a good controller to balance an series string without separating the cells.................. .

120 cells in Battle Born or Renogy 100Ah batteries for example. 4S30P 4 series, 30 parallel.

Some Li-ion light reading: A Study of Cell-to-Cell Interactions and Degradation in Parallel Strings: Implications for the Battery Management System -> http://wrap.warwick.ac.uk/81616/1/WR...cell_cell_.pdf Some of the references cited are LiFePO4

[Boxster1971]

Lithonics offers an internal heater as an optional accessory for their batteries.

https://lithionicsbattery.com/produc...al-heater-kit/

[booster]

Originally Posted by markopolo

120 cells in Battle Born or Renogy 100Ah batteries for example. 4S30P 4 series, 30 parallel.

Some Li-ion light reading: A Study of Cell-to-Cell Interactions and Degradation in Parallel Strings: Implications for the Battery Management System -> http://wrap.warwick.ac.uk/81616/1/WR...cell_cell_.pdf Some of the references cited are LiFePO4

That article/paper is.......scholarly.


It appears, if I waded through correctly, that you can't do a whole lot about mismatch in cells in parallel shortening life, with lots of different things contributing to the degradation. All they seemed to come up with was a "simpler" way to monitor it.



It did mention that parallel did balance it self, but it must be only for voltage.



We need to see something this detailed on the different types of balancing and how well they work for the various wiring setups.

[markopolo]

With the drop-in type batteries with internal heaters, is the heater activated only when seeing a charging voltage? If so, does anyone here know specifically what voltage is needed?