Lithium Battery Operating Temps

[Boxster1971]

Since we seem to always get stuck on hijacking threads when the subject of lithium battery operating temperatures is introduced into the discussions I thought I’d start a thread where we can all discuss the matter of how temperature impacts lithium batteries. Of course all battery types, Lead-Acid, NiCad, NiMH and Lithium, have some impact from temperature. But the now popular Lithium batteries have some temperature sensitivities not found in other battery types.

I starting researching lithium batteries about a year ago when I was considering them for my battery upgrade. I eventual decided to stay with AGM batteries as it involved less work than switching to lithium batteries and the system changes needed to make them reliable. I live in Maryland, but have used my van in -15degF temps during winter trips to Minnesota.

There seem to be a lot of folks on this forum that don’t want to accept the fact that lithium batteries are impacted by both high (above 90F) and low (below freezing) temps. Davydd has presented the most complete set of facts and experience with lithium batteries at low temps I’ve seen on this forum.

If you have an hour to spare Professor Jeff Dahn of Dalhousie University delivered a lecture entitled "Why do Li-ion batteries die and how to improve the situation". This is a good technical explanation of how and why lithium batteries start to degrade above 40degC. I’ve posted this YouTube link before but here it is again:

https://www.youtube.com/watch?v=pxP0Cu00sZs

There have often been side references to the Electrical Vehicle (EV) applications. I did a quick search on the owner’s manual for the Chevrolet Volt that says you need to drive or stay plugged in if temps are below 32F and above 90F (page 215).

http://www.chevrolet.com/content/dam/Chevrolet/northamerica/usa/nscwebsite/en/Home/Ownership/Manuals_and_Videos/05_pdf/2017-Chevrolet-Volt-Electric-Vehicle-Owners-Manual.pdf

[booster]

I went through the same AGM vs lithium question about the same time as Boxster (and Avanti too I think) and decided that "we don't know what we don't know" about potential issues. As it turns out there are two the would prevent me from going lithium which we didn't know at the time. One is the various temperature issues and the other is the need to have a cutoff charger for all charge sources (relatively handleable).

We live in Minnesota and -4F is extremely common in the winter. The van is inside nearly all the time, but there are times that I need the entire shop area and it has to sit outside. The batteries are underneath, so not particularly easy to remove.

We heard lots of "chicken little" comments about our questions concerning lithium batteries, but as it turns out if you don't have heated storage or a place to plug in and heat the batteries (if they even have heaters) and live in a cold place, you either have to remove the batteries or move south.

I am satisfied with the AGM choice at this time, despite their known warts.

[mojoman]

Better change out your battery in your phone and cordless power tools too.

[booster]

Originally Posted by mojoman

Better change out your battery in your phone and cordless power tools too.

I would if they had to be stored outside!

It does say to not forget your phone or tools in the car console or trunk (which I do often) if it is really cold out

[wincrasher]

Well, the question is, can you keep a bank below 90, and above 32? The answer is a resounding yes depending on how they are packaged and where they are mounted. I have no doubts that ARV is successful with this.

Class B vans may be in a better position to do this than other RV types. Mounting below the van can shield it from the heat of the sun, but also provides ventilation to prevent heat build up that you could get confined to a compartment on a large RV. The downside is in heating - the pack will need it's own heat source for this mounting location. In a large RV, the advantage is in storing in a heated compartment - which, as I stated, becomes a liability when the weather gets hot. I suppose one could provide a temperature controlled environment thru air conditioning or some other cooling system.

I think the primary thing to have is awareness and alarming for temperature monitoring. If you know where they are, then you can take actions to either heat or cool your batteries.

On my new rig, I'm going thru this debate right now. Since I have space and no real weight restrictions, going with a much larger AGM bank could be a set it and forget it system. Granted, you can't really freeze AGMs, but you can certainly cook them in a hot compartment, so that is something I'm looking at. The Lifeline site lists power output on AGM's at a baseline of 77 degrees and then derates them for every 10 degrees above that point (10% each 10?)

[mojoman]

My bank is inside my unit with temp monitor and alarm and thermostaticly controlled cooling fan. Camping in hot weather didn't affect them much but it could be the size of my bank since there is less of a demand on them being 900AH. They pretty much stayed a couple of degrees higher than the temp of the cabin, around 80F.

[wincrasher]

LiFePO4 batteries do not generate much in the way of heat thru their discharge. It's more a matter of how the absorb the heat in a hot compartment.

If you didn't ventilate your van, kept it sealed up, it could get to 120 degrees F in there is an hour or so in the summer sun. The question then becomes, how hot could your pack get, and how long would it take to get there? That question is very much a function on how you installed the pack and if you insulated it.

Someone not in the know could install it in a cabinet next to a window that has the sun beating down on it. It could get very hot even if the ambient in the van is relatively comfortable.

[mojoman]

I guess I'm spoiled, on the coldest winter day here, you can still wear a t-shirt.

[Boxster1971]

Originally Posted by wincrasher

........

Granted, you can't really freeze AGMs, but you can certainly cook them in a hot compartment, so that is something I'm looking at. The Lifeline site lists power output on AGM's at a baseline of 77 degrees and then derates them for every 10 degrees above that point (10% each 10?)

AGMs will freeze if discharged and cold soaked. According to the Lifeline Tech Manual the electrolyte will freeze at -13F if battery is at 50%.



- - Mike
2013 Airstream Interstate from 2012 Sprinter 3500 tall & long

[booster]

As Boxster says, the AGMs will freeze if they are discharged far enough. They do seem to have a low enough self discharge rate to make a Minnesota winter if disconnected, so no load, and in outside storage, from what folks I know have told me. Of course, they have to be full going into storage.

[wincrasher]

Yes, you don't want to store an AGM as a partially discharged state anyways.

[booster]

Originally Posted by wincrasher

Yes, you don't want to store an AGM as a partially discharged state anyways.

Absolutely true-

[mojoman]

Whats the debate? A battery heater would benefit any type of battery in such harsh conditions. Whats the big deal leaving your investment plugged in with a battery heater and a block heater on a timer? I doubt if my unit will ever come close seeing those low temps yet I installed automated self-contained safeguards to prevent damage, which were simple and low cost.

[Boxster1971]

No debate. Just discussions to make all more aware of the temp limits associated with lithium batteries. Most won't experience those low, below freezing temps. The bigger issue is that lithium batteries start to degrade at 90degF. The damage from high temps is a subtle loss of capacity.


- - Mike
2013 Airstream Interstate on 2012 Sprinter

[booster]

I remember seeing a lifecyle chart somewhere on the Lifeline site, before they changed everything there, that showed number of cycles vs temperature for their AGMs. IIRC, it showed AGMs losing life at high temps in a very similar way to the lithiums. I may even have posted it on this site somewhere but don't remember for sure. I will have to look and see if I can find it somewhere.

on edit

I did a quick search and didn't find any Lifeline chart, but did come across this one, which shows a huge falloff of life vs temp.



And this one which also shows damage risk:

[mojoman]

Well I learned something new thanks, I didn't realize the AGM battery Capacity is rated at 70f and significantly increase and decrease so much depending on temp. I routed my heater ducting to pass alongside my Aux AGM battery, which I though might degrade the battery faster, now it turns out to be a plus.

[wincrasher]

Yes, I'm dying to hear how all of you are going to install cooling systems for your AGMs.

[mojoman]

Just means folks with batteries mounted outside will be replacing them sooner than those with inside mounted batteries, no matter the type.

[booster]

Originally Posted by mojoman

Just means folks with batteries mounted outside will be replacing them sooner than those with inside mounted batteries, no matter the type.

I would agree that while actually camping that would very likely be true. If a van is stored outside when not in use, then the inside could very well run substantially hotter than the underbody, and for much longer times than when camping, so could be worse inside.

I think there are lot more (even if less than desirable) remedies for temp issues. At the high end you are severely limited by ambient temperatures. As the second chart shows, cooler temps than rated make them last longer, so if you live in cool country or store in a cool area, you might break even on rated cycles, as it does average. If you live in a hot climate, nothing you can really do, I think. If you are driving all the time with them underbody, you will also shorten life, it appears. I am sure this is one of the reasons that RV never last as long as the rated cycles would indicate.

[Viperml]

I think people will be doing more comparisons between different batteries in the near future. Other future batteries such as graphene batteries are starting to come into the market.
There is one company in Spain that is coming out with them now for electric cars.
Scientists Develop a Better Graphene Battery