Battery pack heat pads installation

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Yvesm

Active member
Joined
Aug 4, 2013
Messages
28
Hello to all,

Last spring, I figured that my new to me 2011 Leaf could need help next winter. I do not have a heated garage or even a garage. The car is always outside at home and work. Only plugged in at home

I saw car engine oil pan heat pads many years ago like:
panInstall_zps7d49b0a0.jpg


So I figured I could mimic the 300 watts Leaf Winter Package by installing 6 x 50 watts heat pads under the battery pack. Took the task this autumn. Unfortunalty it was freezing and the daylight no longer lasting long enough, I did not take pictures.

I bought 6 pads and a thermal cube that turns On at -18C and turns Off at -12C:
The pads: http://www.amazon.com/Kats-24050-Watt-Universal-Heater/dp/B000I8YPQ4
And the TC1 switch : http://www.amazon.com/Farm-Innovators-TC-1-Thermostatically-Controlled/dp/B001ADUKRO
pad_zps9d633510.jpg


I installed them at about those position (of course, not outside) I removed the plastic covers to stick the pads directly to the battery case:
underCar_zpsf337182d.jpg

sousFront_zpsadbc673b.jpg


Here is an other view:
batteryCut_zpscdd9700f.jpg


And this. The thermal switch is between the body and the lower plastic undercover (in front of the battery):
leafCut_zpsa3159bfc.jpg


Maybe the best image is:
batteryPadLocation_zps03e00af7.jpg


The pad are glued with the sticky side, added some silicon around the pad. I a rectangle of pink fiberglass about 2 cm thick (not compressed) and covered with aluminum tape to cover each pad.

I left the 120 volt plug under the hood. So to connect the heat pads, I connect the car like a gas car: open the hood, connect to the house 120volt outlet and close the hood for the night

The result is:
- Even if connected, above -18C, the pads do not turn On
- At -18C they turn On.
Next is an example for a -27C night and -19C day
- The Thermal switch get heat from being near the battery pack
- In the morning, the pack shows 4 temperature bars
- After the work day, it goes down to 2 bars
- As I drive home, it goes up to 3 bars
- I connect the pads at home and the next morning, it get 4 bars again
- If the temps are above -18, all is like any other day. No heat but I charge at 100%

Next spring, I will set the 120 plug in the front electrical trap, not to have to open the Hood everytime.

My experience is that this is better than the Winter Package. My battery being at a higher temp, I can go farther in really cold days like -20C then I can at warmer temp like -15C

P.S.
-12C is 10F
-15C is 5F
-18C is 0F
-20C is -4F
-27C is -17F
 
Having one pad left, I redid a sample install:

Fiberglass insulation, aluminum tape and pad:
DSCF1474_zps3ceebea5.jpg


The material:
DSCF1475_zpsff1fb37f.jpg


Once glues and taped:
DSCF1476_zpsb77b089e.jpg


The 120 volts input:
DSCF1477_zps0c7db1e6.jpg


Today, -21C (or -6F) and the battery is warm at 4 bars, guess-0meter at 98 km (or about 60 miles):
DSCF1479_zps6e41d18a.jpg
 
Thank you very much for posting these details. I may do the same installation in case we have another harsh winter.

Questions:

1/ Was it easy to remove the plastic battery cover?

2/ What is the maximum temperature of the pad or near the pad? I am concerned with a too big temperature gradient or by battery sensors beeing "fooled" by the heat pad.
 
I was thinking about doing something like this as well. My concern would be heating the cells on the inside adjacent to the pad up to much. I was thinking of using the battery warmer ones with a larger surface area http://www.amazon.com/Kats-22200-Watt-Battery-Thermal/dp/B000I8XD9E/ref=pd_sim_auto_7?ie=UTF8&refRID=00ATW8YTB5ZAR3R3NV5V" onclick="window.open(this.href);return false; If I recall correctly those max out at about 75F or 24C I know it would be more difficult to mount them and insulate under them, but I like the idea of lower temps. I am also not sure if they would hold up as well over time.

Thoughts?
 
Sorry for late reply.
It is easy to remove the plastic battery covers. Bolts all around.
Heat dissipates on the metal battery casing. Casing not hot when they activate. But they do activate at low temp of 0F. And shuts down at 10F. I never tried at summer temps.
You can try a air dryer of 1500 watts at 0F and you will not see hot air comming out of it. Now these pads add up to 300 wats on a large surface.
I think that a larger battery warmer could isolate the pack in summer and make the temp rize. I chose not to used large one to keep cooling air effect in summer.
The heat from pads in winter temps really dissipates well and slowly to entire pack.
 
Thank you for the reply!


Yvesm said:
Sorry for late reply.
It is easy to remove the plastic battery covers. Bolts all around.
Heat dissipates on the metal battery casing. Casing not hot when they activate. But they do activate at low temp of 0F. And shuts down at 10F. I never tried at summer temps.
You can try a air dryer of 1500 watts at 0F and you will not see hot air comming out of it. Now these pads add up to 300 wats on a large surface.
I think that a larger battery warmer could isolate the pack in summer and make the temp rize. I chose not to used large one to keep cooling air effect in summer.
The heat from pads in winter temps really dissipates well and slowly to entire pack.
 
I really like this!!! very intrigued! do they have these heaters that can run off 240v ? maybe we can tap into power directly from the EVSE so both get power when you plug in the car with the normal 240v evse ??
 
I'm sure that 230/240 VAC heaters are available for international use, but the problem with that would be that as soon as charging stops, the heaters would no longer have power either.
 
Makes a lot of sense. Curious as to how much energy this consumes. Have you tried measuring the electrical consumption over the course of a cold night?
 
I have found 240v units but they are all very high power (lowest is 125watt) no 50watt units and with the success of his units at 50watt times 6 I don't know if I want to risk using THAT much more.

I could use 4 which would be 500watt total but still 200watt more than he used and more concentrated.

I would wire them in BEFORE the EVSE circuitry ie at INPUT power so they would run whether the car is charging or not and would not effect the EVSE operation at all. I am already wired end to end for 30amp so I have plenty of safe power bandwidth to handle 300 or 400 watts of heaters.

at home I can just plug in another device but at work I only have teh one L630 outlet and don't want to pester them for more work. leaving good enough alone in that regard. plus it would just be more elegant. second socket next to the J1772 receptacle and a short little cord to plug into the extra receptacle I would install at the base of the EVSE.

Ohhhhh I screwed up. Grrrr was not thinking clearly. Derp. I forgot that the actual EVSE box is at the other end of the evse cable NOT near the car. DOLT. ok scratch that. no point in merging the units together.
 
If they are a purely resistive type heater, you may find that two 125 watt 240VAC units wired in series might work OK. With half the voltage, they might make half the heat each.
 
which is about perfect. half of 125 watts is 62.5watts. close enough for me.

is this safe? proper way to do it?
 
As long as you are putting things in series, just put two of the 110v/50w units in series. Note that when a 110v charge is going on, the pads will only make 1/4 the heat, or 12.5w each.

Is it right and safe? It'll be as safe as you build it. The concept is sound. Poor execution is the risk.
 
I bought a kw meter and at -22 C, the thermo cube had never stopped the circuit. 300 watts is low heat on such a large battery. So 300 watts for 12 hours at about 8 cents per kwh was about $0.29 for that night.
It cost less than a heated garage for me.

I bought a bluetooth odbii elm327 last week. I tried the leaf spy: cool. I will know the exact battery temp next winter

Nubo said:
Makes a lot of sense. Curious as to how much energy this consumes. Have you tried measuring the electrical consumption over the course of a cold night?
 
Interesting. Anyone else tried this and measured the temp with Leaf spy?

Does anyone have info on how the internal resistance in the battery changes with the temp?

Love from cold Norway with no garage. :)
 
First, thanks Yves (if you get back here). You gave me all I needed to start the project of heating the US 2011 SL Leaf I bought during the very cold winter nights near Montreal (Quebec, Canada).

I installed 2 battery warmers (120V, 80W each) and 4 thermal pads (12V, 90W each) and 5 thermistors protected by aluminum tape and fiberglass insulation. Then I put foil-faced bubble wrap under the plastic protective plates under the car.

Here are 2 images of it.

iodjlf.jpg



2564or6.jpg



I know, some water and humidity can stay between the foil-faced bubble wrap and the metal plate holding the battery cover during the summer. Well, I bought the car, it is now 6 years old and it won't have 10 supplemental years to run. We will see what happen. Anyway. only some salt was present on the grey paint of the plate under the battery cover when I removed the protective plastic plates.
I don't have a lot of autonomy on this old electric car and I don't plan to drive and charge on a quick charge station then drive again, then charge again so I expect that the battery temperature will not rise too much during the hot summer days (30 Celsius degree). It is a choice I have made.

I plan to use a small micro-controller to enable or disable the 2 battery warmers through the use of solid state relays. All the thermistors will be used to stop heating if it is not required anymore.
I also plan to help maintain a bit the battery warm when the car cannot be plugged (like at work) and the car is exposed to temperature like -25 Celsius degree for about 10 to 12 hours by using a big deep discharge 12V battery that could drive the 12V thermal pads. I know it won't be for hours but I don't plan to drive each thermal pad to 90W. I will use pulse width modulation (PWM) to drive them to an equivalent of a quarter or less than 90W and one at a time. Anyway, this has to be tested and scaled.

Now, here is some info about the tests I have done with Leaf Spy Pro. I did only 1 test during a cold evening last winter (for now the 2 battery warmers are permanently powered when the 120V plug I put in the recharge lid is connected.

At 9:16PM, the exterior temperature reported by the car (in the dash) was -12C.
Battery temperature was 1 bar.
Leaf Spy Pro reported the warmest of the 4 temperature sensors in the battery was at -5C.
I plugged the 2 battery warmers (160W of heating, minimal heat going outside due to the foil faced bubble-wrap).
I took also the resistances of the 5 thermistors using a multimeter and I froze my fingers while doing that with a flashlight and writing it down while the wind was blowing.

At 10:20PM, the exterior temperature reported by the car (in the dash) was -13C.
Battery temperature was 1 bar.
Leaf Spy Pro reported the warmest of the 4 temperature sensors in the battery was at -1.3C.
Took the resistance of the 5 thermistor again.

At 11:25PM, the exterior temperature reported by the car (in the dash) was -15C.
Battery temperature was still 1 bar.
Leaf Spy Pro reported the warmest of the 4 temperature sensors in the battery was at 0.6C.
Took the resistance of the 5 thermistor again.

It was late enough and I had data for my next experiments. Battery warmers have been able to get the interior of the battery from -5C to 0.6c in 2 hours. I would expect using less energy to only maintain a temperature than to try to increase it. Not bad for a first test.

Love to Norway people from a Canadian that visited Norway 2 years ago (beginning of june 2015) during the spring. Enjoyed a lot your beautiful and peaceful country.
Hope this help others too like Yves helped me with his original work. Thanks Yves.
 
Hi hwfailure,

i just saw your post, and found my password to reply

I am glad to see what you did. I had not thought about the foil. nice. it must be better than my install in the winter temps
does it increase the battery temperature in the summer ? on the years that there could be a summer (none this year)

for my part, all is well. still running , good mileage, love the car!

Yves
 
Hi YvesM,

Sorry for this late reply. No the foil under the battery don't seems to increase the battery temperature during the summer. I don't make a lot of long runs with my car so I think I saw only once the battery with 6 bars of temperature in the hottest days of july (about 30 degrees C).

I finally finished the code (assembly language) for the micro-controller for the electronic thermostat controlling the 2 battery heaters. I have set the turn on temperature to about -2.5 degrees C and the turn off temperature to about +0.5 degrees C. It is keeping the battery to about 2 bars of temperature with outside temperature of about -10 degrees C.

Here are the pictures of the micro-controller board with all the wires and the location in the trunk of the car.

1zd9phy.jpg


15fhnp0.jpg



With the cold days that we had in December and the ones that are coming in January and February, the battery stays warm without losing too much energy outside with the battery heaters. Hope not much rust is due to the insulation with the foil.

There is a led indicating if the battery heater is currently turned on and the number of approximative minutes it was turned on during this last turned on sequence. I saw as little as 16 minutes turned on and as much as 33 minutes. With colder temperatures, it will decrease the time between the turn on and turn off sequences and it will increase the time the battery heaters are turned on during the turned on sequence.

Thank you again YvesM for giving me the idea to start this project.

For magnemann:

The 4 temperature sensors in my Leaf 2011 as reported by Leaf Spy Pro are indicating temperatures about -3 to -4 degrees C (-1 degrees C for the sensor located upper, under the rear seats). It is consistent with the programmed turn on and turn off temperatures of my electronic thermostat.
 
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