"High Temperature" and LIFEPO4 Batteries In Vehicles

[Catastrofe]

I'm a little confused. . .most LIFEPO4 companies advise not using/storing their batteries where temperatures will exceed 120F as it will degrade the battery's life expectancy. However, in the summer (and probably other times of year), the temperature inside a car (the interior, not the engine bay) will exceed this value. I'd wager the same applies to trailers, RVs, etc.

So should I be concerned about trying to build a system that would sit in the back of my black SUV 24/7/365?

 

[Catastrofe]

Anyone?

 

[John Frum]

Anyone?

From your post it seems the doco says this is an issue.
What do you reckon the temperature will be in the back of your SUV?

 

[Catastrofe]

From your post it seems the doco says this is an issue.
What do you reckon the temperature will be in the back of your SUV?

The interior of an automobile will typically reach 120 degrees or more on a warm/hot day. . .30-40 degrees above the outside temperature. So other than winter time, it seems that keep LIFEPO4 cells in a vehicle (or trailer battery compartment) would exceed most manufacturer's recommendations. As an example, Battleborn specifically said that they wouldn't recommend using their batteries where the temperature is consistently above 120 degrees.

I haven't seen this addressed anywhere, and I'm trying to figure out if it's something that will come back to "bite" me (and possibly many others) down the road, or if I'm overthinking it.

 

[John Frum]

I haven't seen this addressed anywhere, and I'm trying to figure out if it's something that will come back to "bite" me (and possibly many others) down the road, or if I'm overthinking it.

Have a look at this BB CEO interview

 

[grizzzman]

I'm a little confused. . .most LIFEPO4 companies advise not using/storing their batteries where temperatures will exceed 120F as it will degrade the battery's life expectancy. However, in the summer (and probably other times of year), the temperature inside a car (the interior, not the engine bay) will exceed this value. I'd wager the same applies to trailers, RVs, etc.

So should I be concerned about trying to build a system that would sit in the back of my black SUV 24/7/365?

Although lifepo4 will tolerate heat there is a cost. Heat is the biggest killer of lifepo4 cells/batterys. (Overcharge is the next killer) lifepo4 likes the temps we like. Ask your self would you enjoy the temp of the rig in the sun with the Windows rolled up in the summer? The cost? Less cycles.

 

[Catastrofe]

Have a look at this BB CEO interview

Thanks. . .I already saw this. Denis makes my point. . .if temps consistently exceed 100 degrees (I have an email from Jodi at Battleborn that says 120 degrees), battery life will be negatively impacted. Yet, everyone is treating LIFEPO4 as the holy grail for RVs, campers, and trailers when in reality, the use case may not be that great.

 

[John Frum]

Thanks. . .I already saw this. Denis makes my point. . .if temps consistently exceed 100 degrees (I have an email from Jodi at Battleborn that says 120 degrees), battery life will be negatively impacted. Yet, everyone is treating LIFEPO4 as the holy grail for RVs, campers, and trailers when in reality, the use case may not be that great.

IIRC the BMS's on BB and other batteries log the number of charge/discharge cycles.
I wonder if they also log some temperature data.

 

[Solarfun4jim]

Would siting the battery pack inside an old chest freezer with fans attached(ducted from outside the RV) be any use? Input and output fans could be activated at 25degC from the temp probe? Constant flow of cooler air over the top of all terminals....so long as you minimised the volume above the batts, you could get a good flow through???

 

[nebster]

Yet, everyone is treating LIFEPO4 as the holy grail for RVs, campers, and trailers when in reality, the use case may not be that great.

There are tons of places on many RVs, campers, and trailers where the temperature stays pretty moderate. Choose thoughtfully.

 

[Baughb]

I'm a little confused. . .most LIFEPO4 companies advise not using/storing their batteries where temperatures will exceed 120F as it will degrade the battery's life expectancy. However, in the summer (and probably other times of year), the temperature inside a car (the interior, not the engine bay) will exceed this value. I'd wager the same applies to trailers, RVs, etc.

So should I be concerned about trying to build a system that would sit in the back of my black SUV 24/7/365?

Since my lithium/solar/DC setup is portable and currently only 40AH, it is not big so it goes into the vehicles, sedan/SUV, and I make sure it gets tucked in somewhere out of direct sunlight, typically on the floor behind the driver seat.

I then shield the vehicle(s) from the sun as best as I can although I also have a reflective cover for each vehicle that goes on the outside of the vehicle... portable shade (https://www.itscoolinhere.com/), and I leave the widows down a bit under the shades for venting.

Even with this, my white SUV in the Eastern Sierra, on a summer day will still creep into the 90's. I dread the horrific results of an electrical fire while I'm out fishing.

 

[jj11]

I'm Thinking about this as well, 2 years later can you provide an update of your experience?

 

[toms]

My experience has been that charging to high voltages (over 3.5V) or charging when over 35°C is what accelerates degradation.

Just being hot, as long as the cells aren’t being charged, doesn’t seem to be an issue.

 

[backwoods]

I monitor the temps in my travel trailer where my lifpo4 is stored. The highest temp I have seen with the doors closed was high 90's.
This is sitting in a driveway with no shade at all and temps in the low 90's. (no conditoning going, just a fan moving air)
I do believe it is a valid concern. Unless you monitor temps, you're only guessing. I also was under the impression, if the battery isn't being used in that hot of a environment, it should be safe? (agreeing with Toms above^)

 

[littleharbor2]

Figure I'd add what I have done to my LiFePo4 230ah 2s8p bank to help in the summer. I purchased this 12 vdc refrigeration unit and digital thermostat . It seems to be working fairly well. I do have a dedicated 12 volt solar panel, controller and battery powering the unit. It's pretty humid here in the summer so I had to create a waterproof chute to get the condensation out of the battery box.

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1 x NTC sensor (3m cable). For example, If you choose Heat mode(Set HC to H). Set Temperature Value to 80°F. Set d value to 20°F. The relay will be connected when the temperature drop to 60°F(set temperature value-d value).

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[Al D]

Would siting the battery pack inside an old chest freezer with fans attached(ducted from outside the RV) be any use? Input and output fans could be activated at 25degC from the temp probe? Constant flow of cooler air over the top of all terminals....so long as you minimised the volume above the batts, you could get a good flow through???

This is a couple years late, but in case anyone else is wondering if this will work, it won't. Fans don't cool equipment. They can move heat away, but in this set up, where is the hot air going? It's in a vehicle, which is a contained system. You'll actually be generating more heat by the operation of the fan if you try this.

If you can't actively cool your batteries, the next best thing is to crack a window. The temperature inside the vehicle should be within a few degrees of the ambient air temperature. So, unless you're in 110F+ weather (totally possible), cracking a window is probably the easiest and least expensive option.

 

[backwoods]

fans don't generate that much heat, yes motors create heat... but lets be real it is not enough to raise ambient temps. especially if it's a 12v fan which I would think would be used in a situation such as this.
Otherwise I agree, you need a way to move the hot air out and fresh air in, even if it's just ambient air you're moving, it's still moving the heat buildup away from the component.

 

[cs1234]

I always tell everybody, every watt of electricity you use is a watt of heat.

If the area where the watt of heat is added were 100% airtight, the fan would help for a bit to "distribute" the heat evenly around the hot box instead of letting it sit on one hot component. The battery is probably pretty hot in whatever spot the BMS is sitting inside of it, getting the heat off that spot faster would be helpful, but it's not going to help long term if the heat can't be vented out of the area. If the area has pretty good heat dissipation qualities (heatsinked walls of a nice heat transferring metal) it might help to distribute the heat to the walls and get it out of there.

I agree with the others, if it's not charging or pushing out huge loads while sitting in a hot box, it's probably not a big deal. Charging would certainly be the worst though, as wherever the watts of electricity "end their lifecycle", "get used", "converted to a chemical process", tends to be the place where most of their heat goes.

You can get large pieces of aluminum heatsink and attach those to the sides of the battery to help get the heat off the battery faster. It would work better for a metal cased battery than a plastic one, but even a plastic one it might help, especially if combined with a fan.
large heatsink example

The BMS is probably the real problem with the batteries in hot environments more so than the lifepo4 cells themselves, think about your phone/computers, etc.. they get pretty darn hot, and the BMS is similar but it's locked inside of a box with no airflow and strapped to lifepo4 cells with the dinkiest little metal plates or heatsinks on it.

 

[cs1234]

To continue my pontification :

Efficiency of devices and heat.. every watt used by a device is a watt of heat it must get rid of. Say you have a 95% efficient Victron charger. Charging your battery, not counting cable losses and such, if you push 1000 watts through it, it has used/lost 50 watts as heat, inside of itself across whatever it's surface area is. Now think of your battery, in a box, in your RV. It receives 950 watts, which it stores inside of itself, it is using the 950 watts and that generates 950 watts of heat. That's a good amount of heat.

Get a space heater, put it inside your box, run it inside your rv box until it has consumed 950 watts. It's going to get hot in there, really hot.

The initial starting ambient temperature inside your box (assuming no direct sunshine hitting it) is whatever the outside temperature is, roughly. Measure the temperature of your battery when you are charging 1000 watts into it inside your garage or other large area.. it gets hot. The difference between a starting ambient temperature of 70 degrees or 120 degrees is probably a pretty small consideration compared to the ability to remove the heat being added to it. Without ventilation, it's going to be bad.

Now discharging the battery, you are only generating inside the rv box whatever the efficiency losses of the battery cells / BMS are. Let's say 95% efficiency for easy numbers.. the box is now only filling with an extra 50 watts of heat inside if we are pushing out 1000 watts through to the rest of your system. That's easier for the poor battery to get rid of.

All in all, the starting ambient temp probably means a lot less than whatever amount of wattage you are using inside the box. Clearly a lower ambient starting temp is good, but you will quickly make the starting ambient temp almost meaningless compared to what you are adding to the box if you are charging.