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Old 09-23-2016, 09:22 PM   #1
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Default Lithium Battery Operating Temps

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 Iíd 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 donít 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 Iíve 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. Iíve posted this YouTube link before but here it is again:




There have often been side references to the Electrical Vehicle (EV) applications. I did a quick search on the ownerís 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
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Old 09-23-2016, 09:36 PM   #2
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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.
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Old 09-23-2016, 09:52 PM   #3
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Better change out your battery in your phone and cordless power tools too.
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Old 09-23-2016, 10:08 PM   #4
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Quote:
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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
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Old 09-23-2016, 10:13 PM   #5
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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?)
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Old 09-23-2016, 10:42 PM   #6
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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.
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Old 09-23-2016, 10:48 PM   #7
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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.
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Old 09-23-2016, 11:04 PM   #8
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I guess I'm spoiled, on the coldest winter day here, you can still wear a t-shirt.
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Old 09-23-2016, 11:47 PM   #9
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Default Lithium Battery Operating Temps

Quote:
Originally Posted by wincrasher View Post
........

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%.



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Old 09-24-2016, 12:05 AM   #10
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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.
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