Battery warmer to keep battery temperature above 32 degree F

solarvic

Thinking of buying the LIPO 4 batterys and you can,t charge them below 32 degrees. Can anyone suggest a battery heater? I saw a heater that you put on a bee hive to keep the bees thru the winter. It uses 12 vdc at 12 Watts. It also is ok for keeping car batterys warm. Here in northwest. Pa. we had a lot of cold weather this winter.  I could even use ac battery heater as I am grid tied. Was thinking of wraping battery with a heat tape used for a water pipe to keep it from freezing. It has a built in thermostat that turns  on at 38 degrees.

BB.

Try Amazon.ca (Canada)... They have some battery heaters up there:

https://www.amazon.ca/Kats-22100-Watt-Battery-Thermal/dp/B000I8VKZ8
https://www.amazon.ca/ABN-Silicone-Heater-Battery-Engine/dp/B07N41RC1K
https://www.amazon.ca/Zerostart-3400066-Wolverine-BH60CSA-Silicone/dp/B00PMALYPS

They seem to be "generic" (battery, engine oil pan, etc.) and may not have temperature limiting. From the last link:

About this item

• Maintain available cold cranking amps in cold weather by warming the battery
• Slim design to fit in the battery box/tray
• Silicone material is resistant to battery acid
• Notice: This product is NOT recommended for use with lithium ion batteries, nickel cadmium batteries, with battery case material ABS or for use in an insulated battery box
• 5½" (14 cm) x 8½" (21. 6 cm)
• Volts: 120 | Watts: 60 | Amps: 0.5 | Plug Type: 120 Volt, 15 Amp no ground (Type E)
• Heater use not recommended at temperatures above 50°F (10°C)

Then there are space heaters intended for RV water and lithium battery compartments:

https://www.xtremeheaters.com/blogs/news/lithium-battery-heater (120 VAC?)

Battle Born Li Ion heating pad (not cheap):

https://battlebornbatteries.com/product/heat-pad-for-bbgc2/?afmc=rvt_01/ (12 volt, 30 Watt)

-Bill

geosierranevada

How about something like this

iPower Reptile Heat Mat Under Tank Warmer 4W/8W/16W/24W Terrarium Heater Heating Pad with Temperature Adjustable Controller Knob, Digital Thermometer and Hygrometerf or Amphibian, Multi

I am switching over to lifep04 after using lead acid for 21 years. I ordered one of these heat pads and will let you know how it works.

George

Horsefly

For my 8 cell (24V) LiFePO4 battery I built an insulated box (2" XPS on all sides), put an 1/4" aluminum plate under the cells, and put two of these under the plate:  https://www.amazon.com/gp/product/B0794V5J5H  They are 12V 12W, so I put the two in series to be powered by my 24V system.  The aluminum plate spreads the heat out uniformly across the bottom surface of the cells. The key to making something work is that you want to heat the cells low and slow (like smoking meat!).  That way you can get the cells warmed up without cooking the side where the heating pads are.

I controlled the heating pads with one of these cheap thermostats: https://www.amazon.com/gp/product/B076YD8H19  That one is 24V, but they have 12V ones as well.

I've tested the system with the box out in temps below 20°F for 48 hours. I keep the cells between 50°F and 60°F, and it seems to require between 3Ah and 4Ah per 24 hours. Since I'll have my solar charge controller hooked up all winter, my 230Ah battery should stay mostly in float while keeping the cells warm. Even if the panels are covered with snow for a week or two, the battery will still have plenty of juice. Just to make sure I didn't completely discharge the battery, I used a Victron battery protect to disconnect the whole heating system if the battery gets down to 40%-50% or so (25.6V). 

I considered the heaters with built in thermostats, but I don't like the idea. I want to be able to set the temp where the heat turns on and when it turns off.

solarvic

Every persons reply got me on the right track. Geosierri, I think the heater you use is also used for heating soil under a planter to start plants. Where I found it. I saw a review on amazon where a person said it scorched his pillow and melted. I lkied the idea of using one but saw a different brand I liked  All the ones I saw used 120vac.which I will have from grid power.   Horse fly, I looked at your honey bee heater. I kind of think I might go with that but might need a converter to get 12 vdc. I just ordered a new 48 volt inverter today but do not know if there is any 12vdc output or not. Also I have another 24 vdc inverter system. I plan on dedicating to my water pump where the inverter will be in sleep mode till pump needs power. I am going to use my off grid power to run 2 ductless heat pumps and my water pump.  I will be working this spring to get it all running. I started it last summer and got the covid and was on oxygen for 3 months. So I will finish it this year.  PS I was also thinking of using an electric heat tape that is used to keep waterpipes from freezing. I think it comes on at 38 degrees and off about 42 degrees or something like that. I used it on a chicken water tank and it never froze. 

Horsefly

solarvic said:

Every persons reply got me on the right track. Geosierri, I think the heater you use is also used for heating soil under a planter to start plants. Where I found it. I saw a review on amazon where a person said it scorched his pillow and melted. I lkied the idea of using one but saw a different brand I liked  All the ones I saw used 120vac.which I will have from grid power.   Horse fly, I looked at your honey bee heater. I kind of think I might go with that but might need a converter to get 12 vdc. I just ordered a new 48 volt inverter today but do not know if there is any 12vdc output or not. Also I have another 24 vdc inverter system. I plan on dedicating to my water pump where the inverter will be in sleep mode till pump needs power. I am going to use my off grid power to run 2 ductless heat pumps and my water pump.  I will be working this spring to get it all running. I started it last summer and got the covid and was on oxygen for 3 months. So I will finish it this year.  PS I was also thinking of using an electric heat tape that is used to keep waterpipes from freezing. I think it comes on at 38 degrees and off about 42 degrees or something like that. I used it on a chicken water tank and it never froze. 

For a 48V battery you have enough cells that you need more than one of the heating pads I pointed to. I think you can just put 4 of the 12V pads in series, so it will look like one 48V heating pad. It will still draw only about 1.0-1.5A when on. The bigger issue is the thermostatic controller for the heat pads. I'm not aware of a 48V version of the cheap little thermostat I linked to, so you would probably need a small 48V-to-24V or 48V-to-12V buck converter to power the thermostat. That draws very little current, so the cheapest buck convert your can find would be powerful enough. Just don't try and run the heat pads off of it. Only run the thermostat.

The heat tape idea would work, except I think they all run off 120VAC, so you'd need the inverter power all the time, and your idea of leaving the inverter in sleep mode would not work.

solarvic

I guess I need to explain my system a little better. I am grid tied and plan to run a 240  vac line from house to my solar shed.  I have an old 24 vdc fork truck battery about 12 years old and just want to dedicate it to my deep well pump with a trace inverter and  and auto transformer  that I have. . IT will be in sleep mode most of the time. I bought a 48 vdc growatt inverter To connect to the 9 solar panels I already have so I can power a bosch 18,000 btu  mini split heat  pump To heat and air condition my house. Going to buy a couple of those rack mount lipo 4 batterys from Signature solar.com. Originally I bought 9 solorworld 290 watt solar panels and was going to have a 24 volt system with a midnight solor charge controler but decided to go with the growatt inverter. What I like about it is it also has a 100 amp charge controler and has a ac battery charger and can get power from the grid to add to the load to run the minisplit. That wayI don,t have to bother with a transfer switch. If I have too many low power days I still have the propane for a backup. When the gaswell that I had quit around thanks giving It cost me about $,4,000 dollars to get a used 500 gal tank and 400 gallons of fuel. I decided to go the mini split route when I was told that it is cheaper to heat than propane. My daughter had her 500 gal tank filled a couple weeks ago and it cost over $1,000.00 to get her tank filled and her tank is the same size as mine. For people that don,t know you only fill a propane tank 80% and have to leave the other 20% for expansion when the sun heats up the tank.   

solartrout

How about just a heating pad?

bbbuddy

It's getting cooler so I thought I'd add my "experience" such as it is to this thread. 

I built a 432ah lifepo4 battery bank 6 years ago in a large coleman cooler.
It has a false bottom of plywood on two 2x4s with a space under the cells of 3.5 inches.   The plywood purposely is not a snug fit.

I ran a lightbulb holder in through the drain hole and a 25 watt light bulb kept the cooler and batts at 50-70 degrees easily in minus 0°f weather.

The downside was... the light bulbs would burn out, thus necessitating dismantling the battery 
to replace.
Solved this with a 25 watt terrarium heater "bulb", which is just old school wire embedded in ceramic. Nothing to burn out. This has worked without a problem through 4 winters.
There a wireless thermometer sensor in with the battery so I can see when to turn on the heater.

This year I'm adding a 560ah battery in another cooler.   Built same way.  But in 6 years the BMSes have "grown up" and have bluetooth, so I can monitor temps from my phone.  I am adding a remote bluetooth switch where the heater bulbs plug in so I can turn the heaters on and off without walking out to my little powerhouse.

What I like about the false bottom and heater underneath is the battery is not resting on a matt that could go wonky, the entire cooler is heated uniformly.  Of course the plastic cooler is protected from the heater actually touching the plastic....