Liberty's LiPo Hot Box build ( LiPo warmer )

[LibertyMKiii]

One thing racers and speed runners both do is warm their LiPos. Warm LiPos flow current better and the internal resistance drops.
In the past I have put LiPos up on the dash and ran my defroster. With summer coming I just cant run the heater/defroster when it is hot outside on a 1hr drive to my run location.

I decided it was time to make a "hot box". When I run multiple setups during a day I might have as many as 8 LiPos that I want to keep warm so this would dictate what size "box" you need. Insulation is a consideration as well. I have seen people use ammo cans and line them with some insulation, but I wanted something a little larger and this idea took care of a few birds with one stone.

The part I have not figured out is how the temps will run. My thought is maybe an initial high temp like 170f and then after x-number of minutes turn it back down to the desired set temp of 115 - 125 F. (these temp ranges would be safe for all the plastic of the cooler and taco holders)

The setup is the following:

Part Name	Purchase info
41 can cooler	Walmart
40a 12v relay	https://www.amazon.com/dp/B078T8CMF6?psc=1&ref=ppx_yo2ov_dt_b_product_details
Digital temp controller with sensor	https://www.amazon.com/dp/B011VGAPOC?psc=1&ref=ppx_yo2ov_dt_b_product_details
12v heater element with fan	https://www.amazon.com/dp/B0BJ9ZFMSC?psc=1&ref=ppx_yo2ov_dt_b_product_details
taco holders	https://www.amazon.com/dp/B0BQQ6C1QL?psc=1&ref=ppx_yo2ov_dt_b_product_details

Wiring setup for this is a bit interesting....
The temp controller is more or less a switch and not rated for big amperage, for that reason, I also included the 40a relay in the design.
Originally I had picked up a solid-state relay but is just waaaay to large and went back to using a standard automotive relay.

The way this all will work is power is supplied to the temp controller and the relay.
The temp controller obviously will have a thermostat that turns the signal on when the heater needs to run. That signal is sent to the relay that connects the power supply to the heater/fan element.

The only thing I am currently debating on changing would be to move the fan and heater inside the box and close the hole up. For now, I'll try it as is.
Everything is positioned in a way where this will sit on the passenger seat of my car facing me. I'll be able to open the lid and shoot the lipos with an IR gun to double-check that everything is going ok.

The Taco holders were a simple and low-cost solution to make sure the lipos are exposed to heat from all sides. They have holes in them allowing airflow to move around.
Waiting on some very small screws to arrive from Amazon to screw them down.

It is not 100% complete but was excited to share the project that I think is pretty interesting.

 

[Tex Koder]

One thing racers and speed runners both do is warm their LiPos. Warm LiPos flow current better and the internal resistance drops.
In the past I have put LiPos up on the dash and ran my defroster. With summer coming I just cant run the heater/defroster when it is hot outside on a 1hr drive to my run location.

I decided it was time to make a "hot box". When I run multiple setups during a day I might have as many as 8 LiPos that I want to keep warm so this would dictate what size "box" you need. Insulation is a consideration as well. I have seen people use ammo cans and line them with some insulation, but I wanted something a little larger and this idea took care of a few birds with one stone.

The part I have not figured out is how the temps will run. My thought is maybe an initial high temp like 170f and then after x-number of minutes turn it back down to the desired set temp of 115 - 125 F. (these temp ranges would be safe for all the plastic of the cooler and taco holders)

The setup is the following:

Part Name	Purchase info
41 can cooler	Walmart
40a 12v relay	https://www.amazon.com/dp/B078T8CMF6?psc=1&ref=ppx_yo2ov_dt_b_product_details
Digital temp controller with sensor	https://www.amazon.com/dp/B011VGAPOC?psc=1&ref=ppx_yo2ov_dt_b_product_details
12v heater element with fan	https://www.amazon.com/dp/B0BJ9ZFMSC?psc=1&ref=ppx_yo2ov_dt_b_product_details
taco holders	https://www.amazon.com/dp/B0BQQ6C1QL?psc=1&ref=ppx_yo2ov_dt_b_product_details

Wiring setup for this is a bit interesting....
The temp controller is more or less a switch and not rated for big amperage, for that reason, I also included the 40a relay in the design.
Originally I had picked up a solid-state relay but is just waaaay to large and went back to using a standard automotive relay.

The way this all will work is power is supplied to the temp controller and the relay.
The temp controller obviously will have a thermostat that turns the signal on when the heater needs to run. That signal is sent to the relay that connects the power supply to the heater/fan element.

View attachment 292720

The only thing I am currently debating on changing would be to move the fan and heater inside the box and close the hold up. For now I'll try it as is.
Everything is position in a way where this will sit on the passenger seat of my car facing me. I'll be able to open the lid and shoot the lipos with an IR gun to double check everything is going ok.


View attachment 292721

The Taco holders were a simple and low cost solution to make sure the lipos are exposed to the heat from all sides. The have holes in them allowing airflow to move around.
Waiting on some very small screws to arive from Amazon to screw them down.

View attachment 292722

It is not 100% complete, but was excited to share the project that I think is pretty interesting.

Looks Great!!
Nice prototype mockup!

But, once you've finalized the design and ready for the actual 'box" ,perhaps consider something more sturdy and will withstand most malfunctions (from heating element or lipos..)
Like a handy dandy 40mm ammo can = $20

What are you using for the heating element?

 

[LibertyMKiii]

Looks Great!!
Nice prototype mockup!

But, once you've finalized the design and ready for the actual 'box" ,perhaps consider something more sturdy and will withstand most malfunctions (from heating element or lipos..)
Like a handy dandy 40mm ammo can = $20
View attachment 292723

What are you using for the heating element?

It is in there

When I run multiple setups during a day I might have as many as 8 LiPos that I want to keep warm so this would dictate what size "box" you need. Insulation is a consideration as well. I have seen people use ammo cans and line them with some insulation, but I wanted something a little larger and this idea took care of a few birds with one stone.

 

[jkflow]

Suggestions, some of which you already mentioned.

Move the fan+heater to the inside and close that hole, you want to circulate your warm air, not blow in uncontrolled air from the outside. Also, exchange or add a large PC style fan for more airflow, I'd even double up on those.

Actually, you would have extreme poor performance in your current design, assuming it's somewhat airtight. Your fan will only be noisy, but very little air will go inside your box due to static back pressure.

170F sounds scary, Lipos will degrade rather quickly. I have proven this many times myself. I understand this is for initial warm up only, but it will fail eventually. I'd max it at 140F and increase airflow instead, you will easily gain 30-40% efficiency that way and won't need those high pre-heat temps.

Suggest an over temp alert or cut-off, there are plenty of temp controllers in the Aquarium world, but mostly 115V.
A cheap independent alarm might be the way to go. Opening the box and checking with a gun just seems silly.

At the end of the day, I'd have all the wiring inside and maybe integrate the display as well, else you will just rip it off during transport.

'Cool' idea though, or dare I say it's a 'smokin' idea?

 

[King blitz]

Looks Great!!
Nice prototype mockup!

But, once you've finalized the design and ready for the actual 'box" ,perhaps consider something more sturdy and will withstand most malfunctions (from heating element or lipos..)
Like a handy dandy 40mm ammo can = $20
View attachment 292723

What are you using for the heating element?

I was just about to suggest something like this..seems alot safer with all those lipos at them temps

 

[LibertyMKiii]

Suggestions, some of which you already mentioned.

Move the fan+heater to the inside and close that hole, you want to circulate your warm air, not blow in uncontrolled air from the outside. Also, exchange or add a large PC style fan for more airflow, I'd even double up on those.

Actually, you would have extreme poor performance in your current design, assuming it's somewhat airtight. Your fan will only be noisy, but very little air will go inside your box due to static back pressure.

170F sounds scary, Lipos will degrade rather quickly. I have proven this many times myself. I understand this is for initial warm up only, but it will fail eventually. I'd max it at 140F and increase airflow instead, you will easily gain 30-40% efficiency that way and won't need those high pre-heat temps.

Suggest an over temp alert or cut-off, there are plenty of temp controllers in the Aquarium world, but mostly 115V.
A cheap independent alarm might be the way to go. Opening the box and checking with a gun just seems silly.

At the end of the day, I'd have all the wiring inside and maybe integrate the display as well, else you will just rip it off during transport.

'Cool' idea though, or dare I say it's a 'smokin' idea?

Agreed on all points.
I was trying a SKYRC tire warmer and had to crank it all the way up to 180F to get the lipos up to 120f within a 45 min time window. So that was the idea behind the "warm up" phase. I think you are right with the correct airflow inside that should be a good resolution.

 

[King blitz]

Suggestion what about trying hot hands super warmers? They can get up to 163 degrees Fahrenheit.it would eliminate wires.

 

[LibertyMKiii]

Suggestion what about trying hot hands super warmers? They can get up to 163 degrees Fahrenheit.it would eliminate wires.

I have a big case of them. Tried them many times as many as 6 hand warmers in a bigger lipo safe bag that fits 4+ lipos.

They seem to output enough heat to maintain but not enough to warm up.

At least for me they didn't work.

 

[King blitz]

I have a big case of them. Tried them many times as many as 6 hand warmers in a bigger lipo safe bag that fits 4+ lipos.

They seem to output enough heat to maintain but not enough to warm up.

At least for me they didn't work.

Gotcha .just figured I'd mention it because I have some friends that do it and they say it helps .hope your method works bud and good luck ..break some records post some vids .I'd love to see them

 

[LibertyMKiii]

Gotcha .just figured I'd mention it because I have some friends that do it and they say it helps .hope your method works bud and good luck ..break some records post some vids .I'd love to see them

Thanks! I wont be able to get out and run till sometime in May but expecting some records on 2s, 3s, and 4s for the 1/7 scale.

This method above should work for sure, just have to move the heating element inside the box and it will basically work like an airfryer LOL
Pull the LiPos out and I can cook lunch too

 

[Cereal_killer]

That’s what I’ve been doing with my lipos tossing them on the dash for a good 15-20 minutes before running. With the temperature reaching 80s outside and the glass and defrost has to be around 130s. But this idea is pretty cool!

 

[LibertyMKiii]

Small update.
I moved the heater element inside the box and tested it from the ambient 68 F to a thermostat set point of 81 F. It warmed up to the set point within a minute or two. The heater/fan seems to move air around inside very well due to the rounded corners of the cooler.

The taco holders (LiPo holders) were screwed in place and its basically ready to use. It was exciting/rewarding to see it run and work as expected.

 

[SrC]

I see that racers generally shoot for 120F lipo temps before charging for their next event. And they time the charging so when done charging, they are on the track within minutes. Punch is greatly improved this way due to the very low IR's that result. This is generally not the way to preserve lipo longevity however. But better performance does result. Also, Pro Track guys like to Charge at a very high Amp rate. Sometimes as high as 5c rates. 20 amp rates for a 4500mah 4s pack in many cases. And they also get warm for sure this way. Pros don't expect much life from their Lipos. Its all about getting the win at the sacrifice of the lipo. Expensive race packs at that. They don't care. Whatever it takes for the win. A few months of steady racing and they are buying new packs again. Tracks always have steel cans with sand all around the pit areas for lipo fires/ bad lipos.

 

[Diem Turner]

I found that my ETHIX heater bag was a bit asthmatic trying to heat two bigger lipos up to operating temperature. It gets quite toasty in there but it takes a really long time for enough of that energy to penetrate the lipos sufficiently. It was taking anywhere from one and half to two hours to get them warm (not really warm, just warm) and that's just not acceptable so I switched to a 2-stage heating process a while back and it works a treat.

I preheat my oven to 65°C/150°F using both the top and bottom heating elements and the rack in the middle position. I bake them for 30 minutes, flipping them once at the half way marker. After I pop them in the oven, I turn on and pre-heat my ETHIX heater bag. I've augmented it with a section of Styrofoam cut to fit just inside the top in an attempt to boost insulative properties.

After the half hour has elapsed, my lipos are nice and golden brown but still soft and squishy in the middle. Temp gun reads between 120-130°F and you can definitely feel that the battery is warm throughout and not just on the surface. I immediately transfer the batteries to my heater bag and button it up again with the Styrofoam. The ETHIX bag may be a bit underwhelming when it comes to transferring heat into the lipos (the oven does it ten times better), but maintaining the temperatures is no problem.

 

[LibertyMKiii]

I found that my ETHIX heater bag was a bit asthmatic trying to heat two bigger lipos up to operating temperature. It gets quite toasty in there but it takes a really long time for enough of that energy to penetrate the lipos sufficiently. It was taking anywhere from one and half to two hours to get them warm (not really warm, just warm) and that's just not acceptable so I switched to a 2-stage heating process a while back and it works a treat.

I preheat my oven to 65°C/150°F using both the top and bottom heating elements and the rack in the middle position. I bake them for 30 minutes, flipping them once at the half way marker. After I pop them in the oven, I turn on and pre-heat my ETHIX heater bag. I've augmented it with a section of Styrofoam cut to fit just inside the top in an attempt to boost insulative properties.

After the half hour has elapsed, my lipos are nice and golden brown but still soft and squishy in the middle. Temp gun reads between 120-130°F and you can definitely feel that the battery is warm throughout and not just on the surface. I immediately transfer the batteries to my heater bag and button it up again with the Styrofoam. The ETHIX bag may be a bit underwhelming when it comes to transferring heat into the lipos (the oven does it ten times better), but maintaining the temperatures is no problem.

My experience as well. I bought a SkyRC tire warmer setup that has 4 straps that are heating elements.
I tried placing them in a lipo-safe bag with the LiPos on top and I could tell after 20 mins there was very minimal heat transfer going on.

Then I tried wrapping 2 of them tightly around each lipo and still, it struggled to get them up to temps after another 20 mins. Finally, I gave up on that setup. (tried set temps up to max of 180 and still sucked)

When putting them up on my dashboard defroster it took about 40 mins to get them warmed throughout.

This hot box should work well. It is basically like an oven or air fryer with how it moves the air around inside. I just have to figure out how hot to set the thermostat. It may need a 20 min time at 150 and then back down to 120 F. to reach the desired internal lipo temps of 120f. temps after a 40 min time span.

2 mins of operation of this hot box the air inside was warmer than 20+ mins of the other attempts.

I see that racers generally shoot for 120F lipo temps before charging for their next event. And they time the charging so when done charging, they are on the track within minutes. Punch is greatly improved this way due to the very low IR's that result. This is generally not the way to preserve lipo longevity however. But better performance does result. Also, Pro Track guys like to Charge at a very high Amp rate. Sometimes as high as 5c rates. 20 amp rates for a 4500mah 4s pack in many cases. And they also get warm for sure this way. Pros don't expect much life from their Lipos. Its all about getting the win at the sacrifice of the lipo. Expensive race packs at that. They don't care. Whatever it takes for the win. A few months of steady racing and they are buying new packs again. Tracks always have steel cans with sand all around the pit areas for lipo fires/ bad lipos.

Many places wont let them heat the lipos directly so they charge and discharge rapidly as way to do the same thing.
Heat makes a significant difference in speed running which is why we do it.
I cannot say how damaging it is to the lipos since I am still charging them at 1c rates, and getting the heat from an external source, but so far it seems fine.

 

[jkflow]

Yes, all the rapid charging will do is heat the Lipo, it actually prevents the Lipo from reaching full capacity. Then again, they don't use full capacity and that impact is negligible. No idea on cycle life, but they won't make it through more than 1 season with some moderate use, would be my guess.

 

[Diem Turner]

My experience as well. I bought a SkyRC tire warmer setup that has 4 straps that are heating elements.
I tried placing them in a lipo-safe bag with the LiPos on top and I could tell after 20 mins there was very minimal heat transfer going on.

Then I tried wrapping 2 of them tightly around each lipo and still, it struggled to get them up to temps after another 20 mins. Finally, I gave up on that setup. (tried set temps up to max of 180 and still sucked)

When putting them up on my dashboard defroster it took about 40 mins to get them warmed throughout.

This hot box should work well. It is basically like an oven or air fryer with how it moves the air around inside. I just have to figure out how hot to set the thermostat. It may need a 20 min time at 150 and then back down to 120 F. to reach the desired internal lipo temps of 120f. temps after a 40 min time span.

2 mins of operation of this hot box the air inside was warmer than 20+ mins of the other attempts.


Many places wont let them heat the lipos directly so they charge and discharge rapidly as way to do the same thing.
Heat makes a significant difference in speed running which is why we do it.
I cannot say how damaging it is to the lipos since I am still charging them at 1c rates, and getting the heat from an external source, but so far it seems fine.

Sounds promising

 

[SrC]

I found that my ETHIX heater bag was a bit asthmatic trying to heat two bigger lipos up to operating temperature. It gets quite toasty in there but it takes a really long time for enough of that energy to penetrate the lipos sufficiently. It was taking anywhere from one and half to two hours to get them warm (not really warm, just warm) and that's just not acceptable so I switched to a 2-stage heating process a while back and it works a treat.

I preheat my oven to 65°C/150°F using both the top and bottom heating elements and the rack in the middle position. I bake them for 30 minutes, flipping them once at the half way marker. After I pop them in the oven, I turn on and pre-heat my ETHIX heater bag. I've augmented it with a section of Styrofoam cut to fit just inside the top in an attempt to boost insulative properties.

After the half hour has elapsed, my lipos are nice and golden brown but still soft and squishy in the middle. Temp gun reads between 120-130°F and you can definitely feel that the battery is warm throughout and not just on the surface. I immediately transfer the batteries to my heater bag and button it up again with the Styrofoam. The ETHIX bag may be a bit underwhelming when it comes to transferring heat into the lipos (the oven does it ten times better), but maintaining the temperatures is no problem.

Do you prefer to marinade in soy sauce first, then braze it, or wait for the charge cycle?

 

[Diem Turner]

Do you prefer to marinade in soy sauce first, then braze it, or wait for the charge cycle?

I've been on a Soy-Teriyaki marinade mix as of late. It sustains higher discharge rates as the voltage drops, it's pretty remarkable.

 

[SrC]

TYVM. WIll try that next time.