Lithium Iron Phosphate (LiFePO4) DIY battery heater - anyone make one?

[Yoda]

Well it snowing a bit and shoveling was done yesterday so I got to looking long range at new batterys - of course LiFePO4 I looked in the modification thread and search here, but not much popped up.

Now they come in all brands/sizes with Bluetooth and built in heaters. However the (Bluetooth and especially heaters) seem to be trouble spots, sometimes totally draining the batterys - even among the good brands. So I got thinking build my own that I can control. Am I nuts

During the winter my trailer sits in the cold and I know I cant charge LiFePo4 batterys below 32F .This got me to thinking I could build my own heaters that I could manually activate so I can charge while traveling. I can kill my solar and adjust the battery temp switch in the Multiplus to prevent accidental charging. I have it currently set to flooded - if I remember right, or maybe all it does is read the temp and not control the charge - need to read up on that.

For those batterys that have the built in heaters I don't see a way to manually de-activate that feature, but maybe I did not dig deep enough into the brand information. My plan is to pull the batterys during winter storage and put in the house, or garage (unheated), but I am wondering if the heater will auto come on even when the batterys are not hooked up?

So has anyone built thier own heaters and how did you wire them up and components used. I see battery dedicated heaters and some have used RV water tank heater that turn on at about 40 and off at about 60 which I think is too high, but what do I know. There are a few YouTube vids, but non really helpful so far.

Thanks for any thoughts
Keith

On edit I just ran across this https://dcguy.co.uk/diy-battery-heating

[TucsonJim]

Good morning Keith. I'm not sure what brand of battery you have. But here are the temperature specifications on Battle Born batteries:

Temperature charging parameters (Temperature range where you can charge the batteries)

Low temperature: 24°F
High temperature: No limit

Temperature discharge parameters (Temperature range where you can use the batteries)

Low temperature: -4°F
High temperature: 135°F

I have my batteries on the A-frame of my trailer. I never plan on getting into those low temperatures, but if I do, I can put a Mr. Buddy heater near the batteries to keep them warm enough. But that's probably not an option for your fiver. But now you have me thinking on the opposite end of the spectrum. My batteries are in black battery boxes. I could easily see those exceeding the 135°F upper temp when in direct sunlight in Arizona. I may need to figure out a way to shade those boxes. Dangit.

Jim

[Guest]

Keith,

I remove my battery and store in a semi heated space. Many LiFeP04 battery makers will state to not store in freezing temperatures and to store at 50% SOC. These makers are honest about the limitations of these batteries. The heating pads would be less complicated and easily serviceable. Is your interest primarily for protection while towing in freezing conditions?

Jim

[Yoda]

TucsonJim Guest

Jim and Jim Thanks for the input.

I have not chosen the batterys yet - Still in the planning/research stage. But I will probably be traveling in freezing weather at some point. Right now I am just not thrilled with the automation on the current battery heaters, so was looking for something I can turn on when traveling and if camping in sub freezing temps (below what would allow charging). My resent trip to Mississippi over Christmas would have been one (in low teens) case if I took the trailer with us.

The price of the heater adds about $125 to $175 to the battery depending on the brand. But all work automatically if a charge is present. So if I am installing 3 or 4 batterys that price adds up quickly. And then there is the question do I need the Bluetooth with my Multiplus/BMV 712 set up?

I am looking at a manual option so in the case of a winter or cold weather trip, I reinstall the batterys, and can turn the heaters on manually - like when traveling with my DC-DC charger operation. I will just need to remember to turn it off when not charging, but that can be done with a simple relay if my mind is working correctly. I can also add a relay and switch inside the trailer too to let me know its on.

Maybe in a few years technology will catch up and the built in heater prices drop

Now I did find this video https://www.youtube.com/watch?v=rqdY...3XP78E&index=2 However I really don't think the pads he used are the best option.

Thoughts?

Should I go back to my corner now??????

Keith

[acoleman43]

Yoda I'm a big fan of making your own batteries. But I don't think it's for everybody.

I built my own batteries (well, mostly). In my opinion, here are the pro's and cons for building your own battery:

Cons:
-You need to know what you're doing.
-You need to make the battery correctly. This takes time.
-Warranty does not cover your mistakes (cells may have a warranty, BMS may have a warranty....but not a warranty that covers the all entities of the battery).
-You (probably) will have to create your own battery box

Pros:
-You can customize it.....a lot. Size, capacity, BMS, heater/no heaters....
-Allows more flexibility/function.
-It's kinda cool in a nerdy way.
-Can be much cheaper

So, in my opinion, if you know how to correctly make a SAFE battery, and you want very specific features you can't find with a pre-packaged battery (Battle Born, SOK, etc), making your own battery is a very good option.

I bought a group of cells already put together (terminals were welded already welded together). I then bought a BMS for each battery. I created a battery box for the batteries.

I bought the cells from Signature Solar out of Texas. At the time they were selling just the battery cells alone (just 24v batteries which is eight 3.2V, 100AH cells in series). I bought 4 of these cell groups to create 4 batteries. I then bought Overkill BMS' for the cells.

This gave me 3 things that were important to me: 1-Cost. I saved about $5000 over Battle Born equivalent. 2- I was able to fit the batteries in a space that was not possible with "pre-bought" batteries. and 3- The flexibility/control over each battery.

With the Overkill BMS, you have over/under voltage protection (for both battery and cells, for both charge and discharge), high/low temperature protection (for both charge and discharge, 2 temperature sensors per BMS), charge and discharge over current protection, and also protects itself from short circuit, over/under voltage and over current. It also has cell balancing. You can customize any of these parameters to work with the specific cells you are using (highly recommended you use cell manufacturer recommended parameters). On top of that each BMS has bluetooth which links with an app on my phone. Through this app I can turn on/off charging and/or discharging , turn off battery, configure BMS parameters, See data for each cell.

The cold weather we experienced this past month led me to look into battery heating pads. This will likely happen after summer this year. I plan to connect the heating pads to a temperature relay switch on the Cerbo GX. I'll configure the relay to turn on heating pads when battery temp hits 35 degrees, then turn off when battery temp reach 40 or 45 degrees. That way it is automatic and not heating the batteries when not needed. You can easily do this with a manual switch as well.

Below are some pics of my batteries.

Below are 3 of the "batteries" as I bought them. 8 cells welded in series, strapped together. Basically they came half built





Batteries with BMS' attached at end of each battery. My main restriction in the space where the batteries were to go was the height of the batteries. Installing the BMS at the end of each cell group kept the batteries under 8" in height.




This is the desired location of the batteries. Because I made my own batteries, I was able to have the "false floor" level with the opening.




Batteries installed





Dry fit of "False" floor over installed batteries. Worked nicely

[acoleman43]

Yoda OK, continuation of the previous post


As for the BMS, below are some images of what the app looks like.

Last month I had to travel out of state when a nasty cold front hit our area. I knew the batteries would drop below freezing and didn't want to remove them before I left. I know the temp protection would kick in and not allow any charge/discharge would be allowed....but.....once charge/discharge protection is enabled, the batteries have to warm to around 50degrees before it removes those protections (I can change that in the BMS settings, but I want to follow manufacture recommended settings).

I didn't like that because that means they wouldn't be allowed to charge/discharge for a couple weeks until temperatures were well above 50. I decided to turn the batteries off before I left through the BMS. I was still able to see the battery temp sensor temperatures so I knew when it was "safe" to turn them back on. Once the batteries were above 40 degrees I turned them all back on using the app (didn't have to manually remove or switch anything).

This is the "home" screen for each battery. I was real creative and named my batteries Battery 1, Battery 2, Battery 3, Battery 4. Note you can see overall voltage, each cell voltage, Temp for each sensor, and some session values. It will also list any "alarms". An alarm will populate if one of the parameters is exceeded (like cell overvoltage, over temp, etc). This way you can see what protections were used.




The next 3 pictures are the different parameters you can set for each battery. Note there are parameters for individual cells and parameters for the battery. You can create and save BMS configurations to apply to other BMS'








Finally, this is the finished look of the battery area. I didn't want to leave without showing the finished version

Actually, I'm already changing some things with this. Saving for a later post when it's finished.




For me this was the right decision. It has worked flawlessly since installation. I've driven about 600 miles with the new setup with no issues. We were able to boondock for 9 days straight without any shore power or generator used. We used the microwave, electric kettle, and everything we normally use while connected to shore power....We even ran the AC for about 5 hours one day.

So, if you're comfortable with it, I would highly recommend making your own batteries.

[Guest]

Exceptionally nice! Prismatic cells?

Jim

[Country Campers]

I think one of the "issues" with the batteries and temperatures is the placement of the temp probe inside the battery. Here is a youtube video of a Lion Energy battery being used and charged to 0 F Lithium RV Battery DEEP FREEZE Test (Lion Energy Safari UT1300) - YouTube. It seems to take quite a bit of time for the battery temp probe to see 32 F and shut down. On our last trip last year I seen 28 degrees in the front compartment and the battery case was at the same temp and the batteries were working just fine. I do not think I will put much thought into battery heating pads but may add a furnace vent to the front compartment.

Brian

[Guest]

Yoda Keith,

There are battery heating pads out there where it would be important to be able to regulate how much heat is being generated. The Victron BMV-712 or other victron products will provide an temperature measurement and may be able to control a heater via a 12V relay. There are many options from heating pads, to ceramic heaters, to heat lamps, all in 12V. We used ceramic heaters in the auto industry for soaking cars in cold boxes and they worked very well. But they could be a source of ignition so this would be my least favorable option.

Jim

[acoleman43]

Exceptionally nice! Prismatic cells?

Jim

Yes, UL listed prismatic 3.2v A+ cells.

[Yoda]

acoleman43 All I can say is WOW!!!!!!

I had not thought of building my own - probably not in my wheelhouse. I would end up with a real mess and let the magic smoke out of the wires.

My intent is to get SOK or Battle Born, Lion or other good brand based on current reviews (Will Prowse), and build a heated box for them. What I am trying to figure out is the components and box and how to set the heater up for manual control. I had not thought of using the Cerbo GX so I will need to look into that. Thanks for the tip.

Great set up BTW.

Keith

[acoleman43]

I think one of the "issues" with the batteries and temperatures is the placement of the temp probe inside the battery. Here is a youtube video of a Lion Energy battery being used and charged to 0 F Lithium RV Battery DEEP FREEZE Test (Lion Energy Safari UT1300) - YouTube. It seems to take quite a bit of time for the battery temp probe to see 32 F and shut down. On our last trip last year I seen 28 degrees in the front compartment and the battery case was at the same temp and the batteries were working just fine. I do not think I will put much thought into battery heating pads but may add a furnace vent to the front compartment.

Brian

I agree. From what I've read the best place for the temp sensor is between cells in the middle of the pack. This means the outside temp of the cells will be cooler than what the temp sensor is reading. The battery box will probably be even cooler.

Also when cells are discharging, heat is generating within the battery. Once you stop a cell from discharging, the temp of the cell will decrease. In other words the outside temp can be lower than 32 degrees, but the cell temp will be in a safe range to charge/discharge because it is generating heat.

I don't think you really need heating pads for batteries unless you will see temps below freezing in the battery compartment and you will need to have use of those batteries for an extended period of time (you don't want the under temp protection to kick in locking the batteries for a while). If your batteries are in storage, I would just turn them off anyway.

[Guest]

Monitoring these batteries can be a challenge since the cells in most batteries are suspended from the case. The Victron temp probe connects to the positive battery post so an accurate temperature measurement would need time. Same for most all batteries that incorporate a single probe to one cell. Best to not rely on the BMS for temperature cutoff but to avoid the temperature limit all together.

For the travel interest that Keith is after, the pads operated for the duration of the trip could work along with other devices. When stopped, a heated cabin may work. Our Imagines passthrough gains plenty of conduction heat from the cabin.

Jim

[acoleman43]

acoleman43 All I can say is WOW!!!!!!

I had not thought of building my own - probably not in my wheelhouse. I would end up with a real mess and let the magic smoke out of the wires.

My intent is to get SOK or Battle Born, Lion or other good brand based on current reviews (Will Prowse), and build a heated box for them. What I am trying to figure out is the components and box and how to set the heater up for manual control. I had not thought of using the Cerbo GX so I will need to look into that. Thanks for the tip.

Great set up BTW.

Keith

Making your own battery is not as difficult as you would think. If you know how to wire a distribution panel, inverters, solar, etc....it's not a far leap

Setup to use the Cerbo programmable relay with temp sensors is super easy. I believe the Cerbo comes with a temp sensor (Victron part number ASS000001000 - make sure you get the right one). If not, you can order them online. There is a place in the back of the Cerbo for temp sensors (I think you can have up to 6 temp sensors). I would place the other end of the temp sensor within your battery compartment. If you have a GX touch, you configure the relay through the GX Touch screen. It takes about 1 minute to configure - very easy.

Note: The Cerbo only allows 2 programmable relays. If you are using the Cerbo to start/stop a generator when your energy levels reach a specific voltage, that will use both programmable relays leaving you without a relay for you temp sensor.

I have both my Cerbo programmable relays set to temp for a system of fans I have to cool the solar charge controllers, DC/DC converters and help flow air around the multiplus. If (when?) I get the heated battery pads I'll combine both fan circuits into one to use just one of the programmable relays, then use the other for the battery heating pads.

[acoleman43]

Monitoring these batteries can be a challenge since the cells in most batteries are suspended from the case. The Victron temp probe connects to the positive battery post so an accurate temperature measurement would need time. Same for most all batteries that incorporate a single probe to one cell. Best to not rely on the BMS for temperature cutoff but to avoid the temperature limit all together.

For the travel interest that Keith is after, the pads operated for the duration of the trip could work along with other devices. When stopped, a heated cabin may work. Our Imagines passthrough gains plenty of conduction heat from the cabin.

Jim

To support this: I have a temp sensor on the positive battery post of my battery closest to the exterior (this battery will see the most extreme temps) which is connected to my multiplus. That temp sensor is currently reading 55 degrees. However the 2 temp sensors from the battery BMS (one on each side of the middle cell) read 52.3 and 52.9 degrees. Outside air temp is currently about 58 degrees.