Ford Transit USA Forum banner

Lithium battery and cold -- end user perspective

3544 Views 56 Replies 20 Participants Last post by  gregoryx
Finally got the van. Planning to have it built out as camper -- I'm not a DIY-type.
Planning on Lithium house. Live where it gets below 0 degrees F often (already 32 in morning), and planning to keep the van on my driveway.
I have read about lithium issues in the cold.
Here's what I am thinking:
Bring lithiums in the house for winter -- just use van as daily driver (have engine block heater).
If I do want to use as camper in winter, put lithium back in (already warm from the house) and go.
While camping, winter or otherwise, the lithiums should stay warm as they are inside the van -- kept reasonably warm for us humans.
Possible hitch: We decide to stay in a motel for a night on route to warmer climes, but motel parking lot goes to 0 degrees F.
Maybe shut down any draw on lithiums overnight, and don't return draw until camper is warmed up in the morning -- I suppose monitoring battery temp.

Let me know if am on a right track as an end user.
Many thanks!
41 - 57 of 57 Posts

Registered
2020 High-Extended AWD EcoBoost Cargo with windows
Joined
4,870 Posts
OP non-engineer, here. Thanks for all the input.
Seems like this can be managed fairly easily -- i didn't know that before.
For winter on the driveway, just shut the lithium electric system down -- can use van as non-camper as desired.
If we want to use it as a camper in winter, we can pre-heat by running the Timberline heater with shore power (didn't realize this was an option) -- this should also work (running the Timberline off the gasoline) for the possible night in a motel. Around here, many motels have plug-ins for engine block heaters -- could even use that to run the heat at night.
Thinking about how a heated battery works -- once it's up to temp, presumably the battery heats itself (so to speak) before the temp gets low enough to reject charging, keeping itself at a functional temperature.
Let me know if I am way off.
Sounds right. Welcome back, OP! 馃ぃ
 

Registered
Joined
2,077 Posts
Grew up east of Cleveland and my Dad did that trick too.

Heaters like these work but realize that in testing, we use them to intentionally ignite cells and batteries.* Do NOT place them directly on the side/bottom/top of the cells!!! You want to distribute the heat evenly as possible in a box.

If you do put one directly on a cell and are using a temp controller, you are still massively shortening the life of the cell because heating the windings or layers will be so uneven. Electricity will always take the path of least resistance, which is where the wear will be, because the warmer area will be the easiest path.

(* While LiFePo4 generally is the safest of the lithiums, once it puts out a bunch of smoke the smell is almost impossible to get out of any cushions, fabrics, or nearby wood.)
You use RV tank heat pads to ignite cells? I find that difficult to believe. They come with an internal solenoid that turns them off around 60F. I tested mine many times and they just barely got hot enough after first receiving power on a very cold day to be vaguely uncomfortable to hold your hand against them, and that lasts only 2-3 minutes before the solenoid kicks in.

I did remove the solenoid in mine, but that's because I have other temp sensors and a timer relay to control them, and I wanted more nuanced output versus the solenoid.

I do agree it's much better to have batteries with a case, both as a general rule and for heating. Mine came with a thick IP68 aluminum case, so the heat transfers well.

But even the expensive lithionics and most other batteries with internal heaters just run a warming pad around the outside of the cell pack. Other companies sell stick-on external ones. In that setup, only the outer edges of the outer-most cells heat first. The center cells, and top and bottom of all cells get no heat, so it's uneven too.

The reason it's not a big issue, either outside heat or below, and the reason no one is seeing any kind of drastic decline in battery life from heating systems, is that the goal is just to heat from 40F to 60F, not raising them to 100F+, or some ridiculous ultra-high 200-300F explosive/burning temp.

In a van with no a/c parked in desert southwest, overnight the entire battery bank cools to about 65F. On an average 100F summer day, internal vehicle temps can reach 120F+, so there's a 55F heating routine going on. I'd be much more worried about that issue than heating from 40F to 60F in the winter.

Cheers.
 

Registered
2016 148MR Cargo
Joined
798 Posts
You use RV tank heat pads to ignite cells? I find that difficult to believe. They come with an internal solenoid that turns them off around 60F. ...
The most common two ways to ignite cells when testing are to either press a sharp penetrator in VERY slowly (called a nail test) or to put a heating pad on or beneath the cell. Something like these:

The heat pads are either unregulated or set to something above 130C/266F because that is enough to melt the plastic separator material. Obviously, we instrument the cell with thermocouples and are monitoring the voltage at a high sample rate to catch the actual breakdown and internal current rush as it fails.

btw - Relying on just one of anything for temp regulation means being susceptible to a single point failure.

...
The reason it's not a big issue, either outside heat or below, and the reason no one is seeing any kind of drastic decline in battery life from heating systems, is that the goal is just to heat from 40F to 60F, not raising them to 100F+, or some ridiculous ultra-high 200-300F explosive/burning temp.
...
I'm not seeing the questions about going 40F to 60F, I keep seeing people asking about going from sub-freezing to the 30s or more and we chart this as the cell capacities increase significantly with temperature.

But taken another way, it means that
The resistance drops significantly when coming above freezing, and
The cells with lower resistance will have more activity
The activity means faster wear in those cells.

So having even part of a cell stay below freezing in a pack means that cell will
(A) be at risk of dendrite formation if charging happens and
(B) the rest of the pack will have higher conductivity, so will wear faster.

Since many of our vans have solar, we get a charge cycle by charging during the day to make up for the loss overnight, so roughly 365 cycles/year. Obviously, few of us will do a full charge/discharge cycle, so the actual number to depletion will vary widely but in if the battery has a design life of 2,000 cycles, we could be replacing battery packs at 5.4 years LESS the damage done by differential charging of the cells.



It's important to remember that when one cell wears ever so slightly faster, the wear rate of that cell will accelerate as it's resistance falls over time.
 

Registered
Joined
2,077 Posts
The most common two ways to ignite cells when testing are to either press a sharp penetrator in VERY slowly (called a nail test) or to put a heating pad on or beneath the cell. Something like these:

The heat pads are either unregulated or set to something above 130C/266F because that is enough to melt the plastic separator material. Obviously, we instrument the cell with thermocouples and are monitoring the voltage at a high sample rate to catch the actual breakdown and internal current rush as it fails.

btw - Relying on just one of anything for temp regulation means being susceptible to a single point failure.



I'm not seeing the questions about going 40F to 60F, I keep seeing people asking about going from sub-freezing to the 30s or more and we chart this as the cell capacities increase significantly with temperature.

But taken another way, it means that
The resistance drops significantly when coming above freezing, and
The cells with lower resistance will have more activity
The activity means faster wear in those cells.

So having even part of a cell stay below freezing in a pack means that cell will
(A) be at risk of dendrite formation if charging happens and
(B) the rest of the pack will have higher conductivity, so will wear faster.

Since many of our vans have solar, we get a charge cycle by charging during the day to make up for the loss overnight, so roughly 365 cycles/year. Obviously, few of us will do a full charge/discharge cycle, so the actual number to depletion will vary widely but in if the battery has a design life of 2,000 cycles, we could be replacing battery packs at 5.4 years LESS the damage done by differential charging of the cells.



It's important to remember that when one cell wears ever so slightly faster, the wear rate of that cell will accelerate as it's resistance falls over time.
Okay but you originally insinuated the regulated pads I suggested are risking fire, but now you link unregulated pads that heat to 266F.

If you sell or work for a place that sells batteries and RV gear, I can understand why you would want to cast doubt on DIY solutions, but your systems have risks too. Major battery companies have BMS failures, heating and cooling failures, etc. Even pricey Teslas with all their advanced systems have failure risks.

With that in mind, I agree redundancy beyond a solenoid is wise, which is why mentioned a cost effective solution that pairs nicely with regulated pads -- a timer relay. They can limit the time of a heating cycle, when it occurs (early morning), and they let you program multiple cycles for even greater control.

And of course you also have the final failsafe of the BMS cutting off at ~130F and eliminating power to the heating pads.

All of that is discussed in the links I posted, along with the four additional temp sensors I added in case the mppt sensor fails. It all cost $250-$300 and it saved me $12,500. Worth it.

The reason you want to begin heating sub 40 is that by the time cells reach 32F it's too late to sustain a normal C rate for charging, and even discharging C rates are sufficiently reduced to introduce risk of cell damage if you draw enough amps, which is common when temps are very low. Cold morning, use the water heater, flick on the air heater, microwave, coffee pot, induction cook top, etc.

By beginning a gentle time and temp-limited warming cycle when 39F is reached, even if ambient temps are falling fast, the cells will never reach the threshold for damage at normal C rates. It's the same principle when preventing iced up lines and tanks -- you don't wait until they're frozen.

To save energy you can let the battery cool to freezing overnight using the timer relay, or of course when not in use for long periods by just switching the system off.

Virtually all heating systems use hysteresis to prevent excessive cycling, and going from 39 to 60F works well for lithium. I can post charts and tables backing that up, including the recommended C rates at various temperatures provided by my battery vendor, studies that show even below 76F you start seeing a little temp-related degradation at higher C rates, etc, but it's not necessary for an average user to dwell on that. This thread was obviously not titled "debate the physics of cell degradation at various C rates and temperatures."

I guess my point is there are many safe and reliable solutions to heating lithium, even if we debate the subtleties. Anyone claiming otherwise is usually selling something.

Cheers.
 

Registered
2016 148MR Cargo
Joined
798 Posts
Okay but you originally insinuated the regulated pads I suggested are risking fire, but now you link unregulated pads that heat to 266F.
...
What seems to have set this off is that I missed that your original post was about regulated pads.
Good discussion - Moving on.
 

Registered
Joined
2,077 Posts
What seems to have set this off is that I missed that your original post was about regulated pads.
Good discussion - Moving on.
Fair enough. Sorry I got a bit chippy.

Cheers.
 

Registered
2020 High-Extended AWD EcoBoost Cargo with windows
Joined
4,870 Posts
Glad you gave that detailed description, @Checkswrecks, since your original post on that specifically showed the Facon pads... and I was thinking same as @Van Gogh apparently: how TF do you ignite a cell with a pad that doesn't go over 70F???

I was even trying to imagine whether you had to remove the regulators and then stack a bunch of them... or if you actually meant to post photos of the heat-pad units used for 3D printers - those get hot.

Thanks for clearing that up, y'all.
 

Registered
Joined
3 Posts
gregoryx 鈥 did you end up putting heating pads on your two Big Batteries? I鈥檝e read your excellent build thread, and like the powered vent to protect during a high-temp case if your AC fails, but didn鈥檛 see anything about heating pads. Or perhaps your plan is to always keep your van warm with the heater when in ski country.

I鈥檝e got a van on order (which hopefully I鈥檒l get in the next few months/years) and am considering two of the Big Batteries. I spend a lot of time in the Denver/Boulder area, so low-temp protection is top of mind for me.
 

Registered
2022 R2X
Joined
159 Posts
Discussion Starter · #49 ·
Simple (hopefully) question: Is there a cold temperature that the lithium batteries should not see?

Background: I am NOT talking here about temperatures for safe charging or discharging or even about long-term storage -- just sitting on the driveway between uses (using a few times per week). My batteries have a BMS and internal heaters that should protect against charging or discharging at unsafe temps. If they can safely discharge at -4 F, it seems like it would be okay for them to get to that temperature on the driveway (at least for some period of time; hmm, how long?).
 

Registered
2016 148MR Cargo
Joined
798 Posts
Simple (hopefully) question: Is there a cold temperature that the lithium batteries should not see?

Background: I am NOT talking here about temperatures for safe charging or discharging or even about long-term storage -- just sitting on the driveway between uses (using a few times per week). My batteries have a BMS and internal heaters that should protect against charging or discharging at unsafe temps. If they can safely discharge at -4 F, it seems like it would be okay for them to get to that temperature on the driveway (at least for some period of time; hmm, how long?).
Most of their specs cite -20C (-4F) as the cold limit for discharge, which you seem to be aware of. Colder than that, the real constraint is simply to not charge or discharge them.

The electrolyte oil just gets too thick for the lithium ions to move thru it evenly. Small metallic crystals called dendrites will form if there is a charge, even at very low rates, and the dendrites can do all sorts of bad things. Discharging will cause very focused ion transfer creating localized weak spots in the layers, and those weak spots will become where future discharges will focus, either killing the battery fairly quick or in non-LiFePo4 possibly creating a hot spot.
 

Registered
Joined
1,289 Posts
Simple (hopefully) question: Is there a cold temperature that the lithium batteries should not see?

Background: I am NOT talking here about temperatures for safe charging or discharging or even about long-term storage -- just sitting on the driveway between uses (using a few times per week). My batteries have a BMS and internal heaters that should protect against charging or discharging at unsafe temps. If they can safely discharge at -4 F, it seems like it would be okay for them to get to that temperature on the driveway (at least for some period of time; hmm, how long?).
Another member posted this video (time stamped to take you to the part about cold weather):


In it, the professor tells us that LiFePO4 batteries were tested to see if they could survive a lunar night by being frozen with liquid hydrogen (I assume for 14 days) and says, "You can freeze them. No big deal."

If you watch the whole thing you will find that he is talking about cylindrical cells (he says the best available are cells made by A123). I did not catch any reference to the prismatic or pouch formats.

If your battery is constructed with cylindrical cells, chances are freezing will not be an issue. If they are made with prismatic or pouch cells, this data may not apply. Right now my theory is that prismatic cells are not as tolerant of temperature extremes as cylindrical cells, but it is only a theory. I have not seen a paper that addresses these question directly.

Bottom line is probably to adhere to your battery manufacturers specification, or stray at your own risk. I have Battleborn Batteries, made with cylindrical cells. I will try to keep my batteries above the recommended storage temperature of -10F but if they get colder I'm not going to freak out. Based on the above video, I think they will be fine no matter how cold they get. But because they are so expensive, I will try to take good care of them.
 

Registered
2016 148MR Cargo
Joined
798 Posts
Another member posted this video (time stamped to take you to the part about cold weather):


... If they are made with prismatic or pouch cells, this data may not apply. Right now my theory is that prismatic cells are not as tolerant of temperature extremes as cylindrical cells, but it is only a theory. ...
We freeze cycled a number of 8Ah (pretty big) prismatic cells with no problem. It's all about whether there is current or not.
 

Registered
2022 R2X
Joined
159 Posts
Discussion Starter · #53 ·
Thanks for the above info -- very helpful.
Since getting the van home, I have been cautious and running a ceramic heater (mostly at night) on a thermostatically controlled power cord off an AC outlet in the van's "garage" while connected to shore power. Outdoor temps by morning have ranged from -7F to +5F; battery temps 32 to 45 (depending mostly on how I set the thermo-cord). Given the last few posts here, it seems that, if I am not in a hurry to charge the batteries, that I could safely lower the thermo-cord to +10F or even lower -- or even not use it all (given the moon test -- though my cells are prismatic -- LifeBlue LT).

Now I'm thinking that shore power is probably trying to charge the batteries, and so they are likely going through their self-warming sequence -- unnecessarily if I am not looking to keep the batteries immediately chargeable. Maybe that is a non-issue. Or, maybe I should unplug from shore power, but keep the ceramic heater set to +10F just to be cautious -- then I think I would have to close the back door on the heater's power cord -- or maybe there is a way to use shore power w/o it attempting to charge the batteries. There is a master switch that shuts the whole electrical down, but I don't know how that might affect the shore to AC connection. I may have to contact the builder on that one.

Or maybe I shouldn't worry about it at all until I need to charge the batteries, and then heat things up in any number of ways -- keeping an eye on battery temps especislly for discharge purposes.

More than happy to have my ideas corrected (or confirmed) by those with more knowledge/experience.
 

Registered
2022 U8U
Joined
698 Posts
it could easily be 24 hours or even longer.
Really? That seems like a very long time. Why do you believe this? If you are right, I certainly want to know it.

Edit:
Poking around a little, I found this manufacturer's infomercial:
which claims that their internally-heated battery can heat itself from -20掳C to +5掳C. in ~40 minutes. (N.B., I can't vouch for this source, but it is a plausible-looking paper). An external heater would take longer, but not THAT much longer, I would think.
 

Registered
Joined
1,289 Posts
Really? That seems like a very long time. Why do you believe this? If you are right, I certainly want to know it.

Edit:
Poking around a little, I found this manufacturer's infomercial:
which claims that their internally-heated battery can heat itself from -20掳C to +5掳C. in ~40 minutes. (N.B., I can't vouch for this source, but it is a plausible-looking paper). An external heater would take longer, but not THAT much longer, I would think.
Just basing it on experience gleaned from living in Alaska for 46 years. A number of factors will determine how long it takes. Primarily:

1. size of the battery
2. how cold the battery gets
3. what the heat source is

A big, very cold battery that is brought into a garage that is 50 degrees is going to take a long time. A small battery that is not very cold that is warmed by a blazing woodstove is going to heat up very quickly.

A battery with a well executed internal heater should heat up far more quickly and efficiently than one that is just brought in from the cold.

That said, I wasn't really thinking that we only need to bring it up to 0掳C -- so maybe not quite as bad as I indicated.
 

Registered
2020 High-Extended AWD EcoBoost Cargo with windows
Joined
4,870 Posts
gregoryx 鈥 did you end up putting heating pads on your two Big Batteries? I鈥檝e read your excellent build thread, and like the powered vent to protect during a high-temp case if your AC fails, but didn鈥檛 see anything about heating pads. Or perhaps your plan is to always keep your van warm with the heater when in ski country.

I鈥檝e got a van on order (which hopefully I鈥檒l get in the next few months/years) and am considering two of the Big Batteries. I spend a lot of time in the Denver/Boulder area, so low-temp protection is top of mind for me.
Yup. Heat-pads installed. I've gone with them and without in sub-freezing temps to see how it goes. Even 30 below freezing, the batteries never dropped below 40F or so - meaning still quite capable of accepting a charge. That's with the van heated inside to ~60F or more. But usually, we turn on the heat-pad and the batteries seem to stay above 55F or so (according to the sensor attached to the Victron Cerbo). Even with the internal down to ~45F (if parked without the space heater turned on).

One lesson learned recently: in really solid winter storms, we get zero solar charging - not likely with two feet of snow on the roof and a couple inches of rime right on the panels. Add that to running the heating-pads for two water tanks and the batteries plus the heater 24/7 and fridge/freezer, cooking and everything else and we go about 4kWh of usage in 24 hours. It all adds up!
 
41 - 57 of 57 Posts
Top