Insulated battery box: need advice to finish

[hammick]

My insulated battery box is coming along. I have ordered this seedling heat mat: Heat mat

The dimensions of the heat mat are 10" x 20.75" The dimensions of my cubed 16s pack are 13.5" x 22.5"

The Dupont Styrofoam insulation I used is rated at 15 psi. I have 4" on the bottom (two pieces) and 2" on the sides. I am going to tape the seams with Pella window tape (I have a bunch of it laying around). A 2" piece will rest on top of the side during the cold seasons. So basically my batteries will be inside a heated cooler.

I'm struggling with the installation of the heating pad. I'm thinking of putting a piece of OSB on top of the foam floor and covering it with the foil window tape. Then placing the heating mat on top of the foil taped OSB. Then placing an aluminum plate on top of the mat for heat distribution.

How thick should the aluminum be? Will a square sheet of HVAC duct be OK or is that to thin? I can order a custom cut piece that is 1/4" thick. Should I tape the top of the aluminum with non-conductive tape or are the batteries fine to place on aluminum?

Alternatively I can make an air gap for the heating pad but I'm thinking conductive heat would be better than radiant heat.

Please let me know your guys thoughts. Thanks.

 

[hammick]

I just ordered a full size baking sheet from Amazon. It's 19 gauge and the price is right. My gourmet wife would never cook with a $6 baking sheet but I have no problems with cheap kitchenware as long as it doesn't burn the edges of my batteries ?

Baking sheet

 

[hammick]

So the aluminum baking sheet is 18" x 26" and 19 gauge. I'm thinking of taping the heating pad to the baking side of the sheet and putting it in upside down on four 2x6 studs that will be placed on the foil taped Styrofoam insulation. I will probably wrap the studs with foil tape also. The batteries will be placed on top of the baking sheet.

So the heating pad will apply direct heat to the baking sheet and the foil tape should reflect sinking heat back up to the baking sheet.

Anybody see any problems with this approach? Thanks.

 

[HRTKD]

The heating pads I'm using came from Ultra Heat. When mine are on, there is almost no heat coming from the back side of the pad.

I think the temperature range that your heat mat works with is too high. Mine is currently using a range of 35° F to 45° F. That's the range recommended by Ultra Heat. They are an OEM supplier to a number of drop-in LiFePO4 battery manufacturers.

My battery warmer temperature sensor sits on top of my battery, the pads are attached to the sides of the batteries. You can see my write-up here. If your BMS has an external temperature sensor, I would make use of that and carefully monitor the temperature at the top of the cells. A sensor at the bottom would be help to ensure you're aren't hitting too high of a temperature at the bottom while the top is still cold.

Slightly different topic: Ultra Heat said their RV tank warmers must be attached to the tank. Any air gap would produce incorrect results.

 

[hammick]

I think the temperature range that your heat mat works with is too high.

It has a range of 40 - 108 degrees Fahrenheit. Assuming it is accurate if set at say 40 - 50 degrees won't it be fine? It's from Amazon so I can easily send it back.

My BMS will have a temp sensor. My solar equipment also has a temp sensor. So I can monitor both top and bottom.

I am hoping it will be very seldom that this heating pad even turns on.

 

[HRTKD]

It has a range of 40 - 108 degrees Fahrenheit. Assuming it is accurate if set at say 40 - 50 degrees won't it be fine? It's from Amazon so I can easily send it back.

My BMS will have a temp sensor. My solar equipment also has a temp sensor. So I can monitor both top and bottom.

I am hoping it will be very seldom that this heating pad even turns on.

If you can set the temperature, that's great. I looked at the description, not the picture. A second look shows you can manually set the temp. Sorry for missing that. That pad is rated for 1000 watts!!! That'll cook your battery in no time if you don't have it set right.

My pads are running right now. It's about 20° F outside. I have rigid foam insulation around my batteries, but not as well sealed as yours are.

 

[hammick]

If you can set the temperature, that's great. I looked at the description, not the picture. A second look shows you can manually set the temp. Sorry for missing that. That pad is rated for 1000 watts!!! That'll cook your battery in no time if you don't have it set right.

My pads are running right now. It's about 20° F outside. I have rigid foam insulation around my batteries, but not as well sealed as yours are.

I'm going to put it on a smart plug that I can control remotely so I can power it off if something goes wrong. Thanks for you feedback.

 

[HRTKD]

I warm my batteries like I smoke my meat. Low and slow.

 

[hammick]

I warm my batteries like I smoke my meat. Low and slow.

That's the only way to go. My top balance impatience reminds me of trying to get past the crutch when smoking a brisket. Don't turn up the heat or the voltage and both will come out fine

 

[hammick]

That pad is rated for 1000 watts!!! That'll cook your battery in no time if you don't have it set right.

Where did you see the 1000 watts rating? If I zoom in on the Amazon Photo it says 20 watts on the pad. In the Q&A a couple people say 18 watts. I should have the pad on Friday and will report back with actual power use.

 

[HRTKD]

See the last line. It's the controller that can push 1,000 watts.

High-Quality Construction​

• The easy-to-grip hexagon controller is made of extra-fortified plastic and high-quality components that won’t malfunction under tough conditions.
• Clear, minimalist display, detailed finishing, smooth edges, and tactile buttons demonstrate the controller’s superior craftsmanship.
• Compatible with standard North American outlets and plugs: the secure-fit 3-prong grounded socket grips plugs tightly.
• Electrical specs: 120 Volts/60 HZ/8.3 max Amps/max Wattage 1,000 W.

 

[hammick]

See the last line. It's the controller that can push 1,000 watts.

Nice catch. I was worried that pad could pull 1000 watts. I'll plug it in with and without the controller and get the actual power use.

 

[HRTKD]

Kind of strange - at least to me - to put such a low power pad on a high power controller. My pads are 12v and are each rated at 1 amp.

 

[hammick]

I think this pad is going to work great for me. I put it in my insulated battery box with an aluminum baking sheet on top of it. It was 51 degees in the box when I plugged it in. 80 minutes later and it's at 73 degrees in the box. I have it plugged in directly without the controller for the test.

Best part is it only takes .4 amps according to my Trimetric meter. Hopefully not a lot more when I test it with the thermostat controller.

 

[Bill Taylor]

Nice looking box. Just a reminder, the temperature sensor on your BMS will let it know what the temperature of the batteries is, good idea. Just be sure not to have your solar charge controller or inverter/charger temp sensors connected. That will send the voltages all wacky, and that's no good!

 

[Woody]

I like your construction. Well done! I’ve done something similar for a bunch of L16 batteries but with ventilation. Another approach for others might be to use a cooler. I use this approach for a generator start up battery and micro solar systems. Leave the top open for the summers and closed for the winters. Here’s some pictures of this set up.

 

[hammick]

Nice looking box. Just a reminder, the temperature sensor on your BMS will let it know what the temperature of the batteries is, good idea. Just be sure not to have your solar charge controller or inverter/charger temp sensors connected. That will send the voltages all wacky, and that's no good!

Thanks. With the Schneider equipment you can leave the temp sensor connected and set the adjustment to zero. That way I can use temp sensor as another source of temp data and it won't adjust charge voltages. So I have six total temps sensors. Two on the Schneider equipment, three on the Orion BMS and one on my seed heating pad. I have two more Schneider sensors I can add but that would just be silly.

 

[Honuz]

It has a range of 40 - 108 degrees Fahrenheit. Assuming it is accurate if set at say 40 - 50 degrees won't it be fine? It's from Amazon so I can easily send it back.

My BMS will have a temp sensor. My solar equipment also has a temp sensor. So I can monitor both top and bottom.

I am hoping it will be very seldom that this heating pad even turns on.

Totally different...I got aquariums and..man...do not bet on those temperature regulators, one day or an other they fail and... Stay on...or stay off...the first one is not fun.
Put a low power one (20w seems ok) that even in case of failure will not break anything.

 

[IvIarlboro]

I haven’t built mine yet but I am thinking about using this thermostat to control a heating pad in the winter and possibly a cpu fan in the summer.

DC Thermostat

 

[HRTKD]

This is the thermostat the many of us are using.

Amazon.com: LM YN DC 12V Digital Thermostat Module -58℉ to 257℉ Fahrenheit Temp Display Temperature Controller Board With 20A Relay Waterproof Sensor Probe Dual LED Display Red Blue: Home Improvement

Amazon.com: LM YN DC 12V Digital Thermostat Module -58℉ to 257℉ Fahrenheit Temp Display Temperature Controller Board With 20A Relay Waterproof Sensor Probe Dual LED Display Red Blue: Home Improvement

www.amazon.com