LiFePO4 Battery Warmer Install

[Sipma02]

Well, that heat pad is only a 150w, so far, I'm not too concerned (if it were the 500w version maybe I might)... Also the consensus from other forum members was that directly applied to a battery case could be a little hot, but mounted on the bottom-side of an aluminum plate (with aluminum having fast heat transfer properties) will dissipate out that heat across the plate quickly. Also the heat pad is only 5" x 5" square, where the aluminum plate is large enough for the entire bank to rest on.

So I am building 3 of these. The 12v (8x cells) bank has a bottom-plate of approximately 11" x 16" and my 2 other 48v (16x cells each) banks will have bottom-plate of approximately 23" x 16""

All three will use the same size 5" x 5" heat pad. I will likely do some testing and monitoring with it in the beginning... Hopefully I will even get it all together before Spring, otherwise will have to wait til next Winter to see it in action.

I will for sure test the bottom plate temp and see what it has the ability to push up to for temp without any batteries sitting on it first.

I have qty 4, 7 watt heating pads (for a total of 28 watts) on my qty 4 280ah cells, with a 1/16 in steel plate for dissipation. Knowing what I know now, I would have used a thicker aluminum plate. Aluminum dissipates heat better. They have 1/2 to 3/4 of XPS foam insulation on each side, except the top. I'm seeing about a 25-30F raise in temp (compared to ambient) at the top of my cells, which I assume to be the coolest part. The bottom of my cells, where the heating plate is, sees about a 40F rise from ambient. I think you will have more than enough heat—perhaps too much. You could easily modulate the heat with a repeat cycle timer, its basically a little circuit board that you can set to 10 sec on, 10 sec off, 10 sec on, etc. You can set the delay to whatever you want. I found one on Amazon for around $10, but ended up not needing it because my heating pads are small enough that they dont raise the temp too much.

When I had it connected and not touching the batteries, the plate got hot to the touch—it would almost burn me. But once the cells were in direct, firm contact with the heating plate—it now doesnt get over about 70ºF.

 

[Samsonite801]

I have qty 4, 7 watt heating pads (for a total of 28 watts) on my qty 4 280ah cells, with a 1/16 in steel plate for dissipation. Knowing what I know now, I would have used a thicker aluminum plate. Aluminum dissipates heat better. They have 1/2 to 3/4 of XPS foam insulation on each side, except the top. I'm seeing about a 25-30F raise in temp (compared to ambient) at the top of my cells, which I assume to be the coolest part. The bottom of my cells, where the heating plate is, sees about a 40F rise from ambient. I think you will have more than enough heat—perhaps too much. You could easily modulate the heat with a repeat cycle timer, its basically a little circuit board that you can set to 10 sec on, 10 sec off, 10 sec on, etc. You can set the delay to whatever you want. I found one on Amazon for around $10, but ended up not needing it because my heating pads are small enough that they dont raise the temp too much.

When I had it connected and not touching the batteries, the plate got hot to the touch—it would almost burn me. But once the cells were in direct, firm contact with the heating plate—it now doesnt get over about 70ºF.

Good to know, thanks for providing that useful info about the real world performance...

 

[LanduytG]

I have a 150 watt pad that I'm going to use on a bed plate. To controll temp I'm going to use a pid controller. Mount temp sensor to the plate set pid to about 80 degrees and forget about it.
Greg

Amazon.com

 

[HRTKD]

I have a 150 watt pad that I'm going to use on a bed plate. To controll temp I'm going to use a pid controller. Mount temp sensor to the plate set pid to about 80 degrees and forget about it.
Greg

Amazon.com

The thermostat I'm using is DC and costs about 1/4 of the one you linked to. I don't have an inverter active to run an AC device.

 

[LanduytG]

That link was just and example. The have 12v pids also.

Greg

 

[nublu]

Today I got the temperature controllers installed for my warming pads. All that is left is to clean up the wiring and get the controllers secured.

I decided (for now) to not use the temperature sensor/controller that came with the kit that Ultra Heat created for me. The first controller they provided worked inconsistently. Testing it at home it worked about 50% of the time. I suspect there was an internal wiring issue, but I didn't open it to verify that. The replacement sensor they sent worked every time but the temperature range seemed like it was 30° F to 44° F, not the labelled 35° F to 45° F. I used the temperature sensor from my Fluke 325 meter to check the temperature at the sensor/controller. The Fluke sensor was taped to the Ultra Heat sensor/controller. It isn't clear how accurate it is to tape the two together, but that's all I could figure out.

The new controller I'm using I got off Amazon for $11 based on recommendations from other forum members. It's the LM YN DC 12V Digital Thermostat Module. It has a programmable range, which I prefer to the preset range. Other benefits are that it shows you the observed temperature and the target temperature on the two displays. Each battery now has its own controller. With the Ultra Heat kit, there was only one controller, so it was warming one of the batteries without knowing what that battery's temperature was. Given that the two batteries sat side-by-side and the temp range was conservative there wasn't much risk. With the new setup, there is zero risk.

In the test today, after 40 minutes, the warming pads raised the observed temperature at the top of the battery by 8° F. From ~47 to 53° F. I had to fool the controller by putting the temperature sensor into a gel freezer pack. I could have just raised the target temperature on the controller, but didn't think of that until later.

Each time I checked the current on this circuit, it was no more than 1.68 amps. This was with two warming pads active on a single battery. In my opinion, the results are excellent given the small amount of current that was consumed. The pads must be incredibly efficient.

The temperature reported by the controller was within .75° F of the temperature reported by the BMS's remote temperature sensor. I was pleased to see the two devices report almost the exact temperature. The Victron BMV-712 reported a similar temperature, but it reports only whole numbers. Still, it was close enough to call it accurate. I have both sensors (controller and BMS) taped down together at about the middle of the battery. I used some spare rigid foam to create a hollowed out "cap" over the two sensors so they will be reading the battery temperature without (much) interference from the ambient air. The cap isn't sealed, so this isn't 100% effective.

I checked the backside of the warming pads multiple times during the test. I couldn't feel any heat at all. I used an infrared thermometer and it detected only a 5° F difference between the back of the warming pad and the top of the battery.

The new controller is pretty slick. It's a bit confusing to program at first and comes with no instructions. I found a set of user supplied instructions and cleaned them up. If you want a copy, let me know. I'm going to buy another controller and use it for running a fan to keep the component compartment cool in the summer.

Thx for the info!! how is this controller with input voltage? description says "input: 12v". im looking to do something similar as yourself....but i've read some review of thermostats that look [nearly] the same as the one you linked to that have comments that they burn up with 14v input. since I plan to have a 4s lifepo4 bank...i'll have 14v input at times (most of the time). any better info in the "documentation"?

here's a link to the product i'm referring to: https://www.amazon.com/dp/B07CH7W3XP/ref=wl_mb_wl_huc_mrai_2_dp?th=1

 

[HRTKD]

I would have to check the logs of my solar charge controller to see how high the voltage has been.

The product you linked to displays in celsius and has one readout. The one I'm using displays in fahrenheit and has the current temperature and the target temperature.

 

[nublu]

I would have to check the logs of my solar charge controller to see how high the voltage has been.

The product you linked to displays in celsius and has one readout. The one I'm using displays in fahrenheit and has the current temperature and the target temperature.

Cool, looking forward to seeing what voltage you are running at. And, right, the product you're using is definitely better for those two reasons. But, the board/components look similar to me otherwise. So, if it is the same components (with those two modifications only), and the comments on the product I linked are accurate, there might be issues using at 14v. Maybe it gets fried after prolonged use, or not at all. I dig your setup and the info you posted; very helpful!

 

[Jacob Scoville]

Cool, looking forward to seeing what voltage you are running at. And, right, the product you're using is definitely better for those two reasons. But, the board/components look similar to me otherwise. So, if it is the same components (with those two modifications only), and the comments on the product I linked are accurate, there might be issues using at 14v. Maybe it gets fried after prolonged use, or not at all. I dig your setup and the info you posted; very helpful!

It looks like a few people are using it on 14v systems so it will hopefully work (just bought two of them myself...)

 

[guyroch]

double it & add 30.

It doesn't take long to get used to deg C when Water freezes at 0 & boils at 100

This will give an approx F and will be fine in most cases.

For an exact conversion, multiply by 1.8 and add 32.

Example 23C => 23 x 1.8 = 41.4 + 32 = 73.4F

 

[RyanNicholas]

Looks awesome! Thanks for the pictures and providing all the information about your install...


I am planning a similar type setup, using these parts:

View attachment 27057 View attachment 27058

Mine isn't so custom (as I just purchased off-the-shelf parts along the lines of some others had done on this forum), but hoping it will get the job done, I guess we'll find out...

Maybe you can update the thread on how well it works for you as time goes on...

How's this working out for you? I'm about to do my first lithium setup, and it's below freezing where I am... I don't have $300 to spend on hearing pads, but I've seen pads like this one on Amazon, etc. What size is this pad? And your battery?

 

[HRTKD]

Working good. It was about 22° F outside when I went down to the storage lot today to refill the rodent lunch box. I snapped this picture of the two thermostats. The red readout is the currently observed temperature as seen at the top of the battery. The blue readout is the max temp. The range is 35° F to 45° F.



If I were to outfit another set of batteries, I would buy just the heating pads from UltraHeat. However, I don't see that type of pad on their website. I sent an email asking if there was a public webpage I could point people to.

 

[diyernh]

Today I got the temperature controllers installed for my warming pads. All that is left is to clean up the wiring and get the controllers secured.

I decided (for now) to not use the temperature sensor/controller that came with the kit that Ultra Heat created for me. The first controller they provided worked inconsistently. Testing it at home it worked about 50% of the time. I suspect there was an internal wiring issue, but I didn't open it to verify that. The replacement sensor they sent worked every time but the temperature range seemed like it was 30° F to 44° F, not the labelled 35° F to 45° F. I used the temperature sensor from my Fluke 325 meter to check the temperature at the sensor/controller. The Fluke sensor was taped to the Ultra Heat sensor/controller. It isn't clear how accurate it is to tape the two together, but that's all I could figure out.

The new controller I'm using I got off Amazon for $11 based on recommendations from other forum members. It's the LM YN DC 12V Digital Thermostat Module. It has a programmable range, which I prefer to the preset range. Other benefits are that it shows you the observed temperature and the target temperature on the two displays. Each battery now has its own controller. With the Ultra Heat kit, there was only one controller, so it was warming one of the batteries without knowing what that battery's temperature was. Given that the two batteries sat side-by-side and the temp range was conservative there wasn't much risk. With the new setup, there is zero risk.

In the test today, after 40 minutes, the warming pads raised the observed temperature at the top of the battery by 8° F. From ~47 to 53° F. I had to fool the controller by putting the temperature sensor into a gel freezer pack. I could have just raised the target temperature on the controller, but didn't think of that until later.

Each time I checked the current on this circuit, it was no more than 1.68 amps. This was with two warming pads active on a single battery. In my opinion, the results are excellent given the small amount of current that was consumed. The pads must be incredibly efficient.

The temperature reported by the controller was within .75° F of the temperature reported by the BMS's remote temperature sensor. I was pleased to see the two devices report almost the exact temperature. The Victron BMV-712 reported a similar temperature, but it reports only whole numbers. Still, it was close enough to call it accurate. I have both sensors (controller and BMS) taped down together at about the middle of the battery. I used some spare rigid foam to create a hollowed out "cap" over the two sensors so they will be reading the battery temperature without (much) interference from the ambient air. The cap isn't sealed, so this isn't 100% effective.

I checked the backside of the warming pads multiple times during the test. I couldn't feel any heat at all. I used an infrared thermometer and it detected only a 5° F difference between the back of the warming pad and the top of the battery.

The new controller is pretty slick. It's a bit confusing to program at first and comes with no instructions. I found a set of user supplied instructions and cleaned them up. If you want a copy, let me know. I'm going to buy another controller and use it for running a fan to keep the component compartment cool in the summer.

Jim,
Thanks for the writeup and photos. I have some questions on the application.

Does the heater turn on when it's cold, using the battery power, or any charging available? I would like to only have the heaters on when there is charging available. I have my camper unattended and could have days when it's cold storage with no charging. I only need the heaters to be run by the charging power, not the batteries. I don't need to discharge the batteries to heat if the is no charging source.

Does your Amazon heater control work below freezing? Most PID or other heat controllers are made of commercial rated electronics, not automotive or military grade. Everyone I've tried stops working when the ambient temp at the controller is 32F. They just blink EEEE until it warms up. They do well with sensor temperatures cold, but not with the control board being cold.

Carl

 

[Just John]

Cool, looking forward to seeing what voltage you are running at. And, right, the product you're using is definitely better for those two reasons. But, the board/components look similar to me otherwise. So, if it is the same components (with those two modifications only), and the comments on the product I linked are accurate, there might be issues using at 14v. Maybe it gets fried after prolonged use, or not at all. I dig your setup and the info you posted; very helpful!

For the price (under $15) and since most people already have a power supply for top balance, just power it up for a week at 15 volts and see if it smokes.

 

[HRTKD]

Cool, looking forward to seeing what voltage you are running at. And, right, the product you're using is definitely better for those two reasons. But, the board/components look similar to me otherwise. So, if it is the same components (with those two modifications only), and the comments on the product I linked are accurate, there might be issues using at 14v. Maybe it gets fried after prolonged use, or not at all. I dig your setup and the info you posted; very helpful!

The specs for the board says the input power is 12v +/- .5v. That's certainly not in the upper range at which a LiFePO4 battery can be charged. My boards are wired off the common bus bars in my system. They're seeing pretty much whatever the solar charge controller or converter is pumping out, so a voltage as much as 14.4v is likely. So far, it's working.

However, it is a concern. Maybe run thinner wire so you get some voltage drop? Normally, I wouldn't recommend such a thing.

Does the heater turn on when it's cold, using the battery power, or any charging available? I would like to only have the heaters on when there is charging available. I have my camper unattended and could have days when it's cold storage with no charging. I only need the heaters to be run by the charging power, not the batteries. I don't need to discharge the batteries to heat if the is no charging source.

Does your Amazon heater control work below freezing? Most PID or other heat controllers are made of commercial rated electronics, not automotive or military grade. Everyone I've tried stops working when the ambient temp at the controller is 32F. They just blink EEEE until it warms up. They do well with sensor temperatures cold, but not with the control board being cold.

I thought I answered this already, but I don't see my post.

My thermostat is active 24 hours a day. It, and the warming pads, will use solar when it's available, otherwise, it's battery power. So far, I haven't seen my state of charge drop below 97% on my 560Ah of battery capacity. A system that only warms the batteries when power from solar is available could be done, but it increases the complexity of the system.

There are parasitic draws on an RV's electrical system. Some of these are hard to control. The gas detector is hard wired into the 12v system from what I hear. You can turn off the trailer's 12v disconnect but the gas detector will still be on.

Yes, the thermostat works below freezing. My thermostat board is going to be the same temperature as the unheated trailer. I've been working on the trailer when it's below freezing, so I know the thermostat is still going in those conditions.

 

[Just John]

Thx for the info!! how is this controller with input voltage? description says "input: 12v". im looking to do something similar as yourself....but i've read some review of thermostats that look [nearly] the same as the one you linked to that have comments that they burn up with 14v input. since I plan to have a 4s lifepo4 bank...i'll have 14v input at times (most of the time). any better info in the "documentation"?

here's a link to the product i'm referring to: https://www.amazon.com/dp/B07CH7W3XP/ref=wl_mb_wl_huc_mrai_2_dp?th=1

If you are concerned about the higher voltage burning it out, here is two regulated 12 volt power boards (1.2 amps each) for $7 (even free next day for me). They will draw next to nothing if your thermostat does, but rock solid 12 volts DC.

 

[Just John]

Today I got the temperature controllers installed for my warming pads. All that is left is to clean up the wiring and get the controllers secured.

I decided (for now) to not use the temperature sensor/controller that came with the kit that Ultra Heat created for me. The first controller they provided worked inconsistently. Testing it at home it worked about 50% of the time. I suspect there was an internal wiring issue, but I didn't open it to verify that. The replacement sensor they sent worked every time but the temperature range seemed like it was 30° F to 44° F, not the labelled 35° F to 45° F. I used the temperature sensor from my Fluke 325 meter to check the temperature at the sensor/controller. The Fluke sensor was taped to the Ultra Heat sensor/controller. It isn't clear how accurate it is to tape the two together, but that's all I could figure out.

The new controller I'm using I got off Amazon for $11 based on recommendations from other forum members. It's the LM YN DC 12V Digital Thermostat Module. It has a programmable range, which I prefer to the preset range. Other benefits are that it shows you the observed temperature and the target temperature on the two displays. Each battery now has its own controller. With the Ultra Heat kit, there was only one controller, so it was warming one of the batteries without knowing what that battery's temperature was. Given that the two batteries sat side-by-side and the temp range was conservative there wasn't much risk. With the new setup, there is zero risk.

In the test today, after 40 minutes, the warming pads raised the observed temperature at the top of the battery by 8° F. From ~47 to 53° F. I had to fool the controller by putting the temperature sensor into a gel freezer pack. I could have just raised the target temperature on the controller, but didn't think of that until later.

Each time I checked the current on this circuit, it was no more than 1.68 amps. This was with two warming pads active on a single battery. In my opinion, the results are excellent given the small amount of current that was consumed. The pads must be incredibly efficient.

The temperature reported by the controller was within .75° F of the temperature reported by the BMS's remote temperature sensor. I was pleased to see the two devices report almost the exact temperature. The Victron BMV-712 reported a similar temperature, but it reports only whole numbers. Still, it was close enough to call it accurate. I have both sensors (controller and BMS) taped down together at about the middle of the battery. I used some spare rigid foam to create a hollowed out "cap" over the two sensors so they will be reading the battery temperature without (much) interference from the ambient air. The cap isn't sealed, so this isn't 100% effective.

I checked the backside of the warming pads multiple times during the test. I couldn't feel any heat at all. I used an infrared thermometer and it detected only a 5° F difference between the back of the warming pad and the top of the battery.

The new controller is pretty slick. It's a bit confusing to program at first and comes with no instructions. I found a set of user supplied instructions and cleaned them up. If you want a copy, let me know. I'm going to buy another controller and use it for running a fan to keep the component compartment cool in the summer.

FYI, that does look like an ideal solution. Great flexibility with the settings and actions it can take (the thermostat model). I know these cells have a large thermal mass, so hopefully starting above 40 degrees just keeping their temperature up. It does keep the capacity up too. I live in the desert, it seems to have application for cooling as well.

 

[Just John]

The specs for the board says the input power is 12v +/- .5v. That's certainly not in the upper range at which a LiFePO4 battery can be charged. My boards are wired off the common bus bars in my system. They're seeing pretty much whatever the solar charge controller or converter is pumping out, so a voltage as much as 14.4v is likely. So far, it's working.

However, it is a concern. Maybe run thinner wire so you get some voltage drop? Normally, I wouldn't recommend such a thing.

Here you go, easy solution:

https://smile.amazon.com/KOOBOOK-Terminal-Regulator-Voltage-Regulated/dp/B07S88BWBM/

 

[HRTKD]

If you are concerned about the higher voltage burning it out, here is two regulated 12 volt power boards (1.2 amps each) for $7 (even free next day for me). They will draw next to nothing if your thermostat does, but rock solid 12 volts DC.

According to the graphic below, the input voltage starts at 15v. Elsewhere, it says it starts at 1.5v. So is it both a buck and boost converter?

 

[Just John]

According to the graphic below, the input voltage starts at 15v. Elsewhere, it says it starts at 1.5v. So is it both a buck and boost converter?

It has a voltage regulator, 7812 which has been used for about 40 years that I know of.
I didn't look closely at that one, but also notice it has a bridge rectifier so it can also be A/C. Trust me, it only puts out 12 volts DC, that is what the 7812 was designed for.