Battery cooling DIY

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arber333
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Battery cooling DIY

Post by arber333 »

I am posting here since battery temperature management should also be a part of the BMS.

Lately I noticed my Jaguar battery is getting warm with normal discharge and immediated charge on my 100km daily route to and from work.
I have measured temperatures about 38°C directly on batteries.
While part of that should probably be also attributed to proximity of inverter which is directly bolted to battery box and could cool the battery down a bit it is also capable to heat it up if i dont use cooling fans in front of the car.

My observation how easy it is to heat the battery up and decision to use CHADEMO fast charging led me to conclusion i will need to use some form of battery cooling/heating. First i noticed this guy online. Its cells are similar if not the same: https://www.diyelectriccar.com/threads/ ... ar.198305/

When i investigated i decided to stay as simple as possible.
Original Jaguar cooling solution is built into the battery box floor. There are section of pressed tubing across the bottom connected by hoses. Battery modules are connected to this through alu structure underneath. This by itself does not lend itself great reaction time, but it provides quite sizable thermal mass which can sink dT comfortably.
Jag cooling1.jpg
Jag cooling1.jpg (8.52 KiB) Viewed 7556 times
My idea is to take similar design to tiger82 with cooling plate between cells but horizontaly. Without racing application dT should not be too much. And cells would be cooled through top/bottom ends. This is also part of Jaguar cooling design...
My cell module configuration is built in two levels. Bottom module is made of 2P8S and connects to upper module of 2P8S. There are 4 modules in front and 2 modules at the back with possibility for expansion. All chill plates will be connected by silicon hoses to a common manifold which will then connect to common cooling system AFTER inverter and before motor and chargers. This way coolant will reach batteries just after being cooled. I may change this to self sustained system separate from motor-inverter cooling.
IMG_20210109_204235.jpg
So i will make 2mm Alu plates to be fit between both modules and between them i will sandwich 8mm twisted copper tube which will move water between plates. To make a uniform sandwich i will fit 8mm blocks alongside tube bends and make countersunk threaded holes and torqued small M4 countersunk screws to hold everything together.
Copper tubing is easy to get and i can bend it at home. Alu plate is also easy to machine and i can get 8mm alu strips cut at local metal workshop.
This will raise my setup by 12mm. I am still comfortable with that under the battery box cover.
Of course i will have a way to start coolant flow in case of hot cells and heating when cold. That would be the task for my BMS.
I will provide more photos.

What would be your thoughts? Do you have a better idea maybe?
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celeron55
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Re: Battery cooling DIY

Post by celeron55 »

A separate system for motor+inverter+charger cooling makes sense because you always want to cool them regardless of outside temperature. Batteries you want to cool, heat or do nothing depending on the battery temperature.

Sandwiching bent copper pipe between aluminium plates sounds like the simplest possible cooling solution for anything so it seems like a good start.

Can there be problems with dissimilar metals? I guess coolant should inhibit corrosion for the insides of the pipes (even if they are in a coolant loop with aluminium parts which all might be grounded) and the outside will stay dry (being in the battery and all) so it won't corrode even while aluminium and copper are literally pressed against each other.

What about adding some kind of heat conducting paste, glue or pads around the pipes to make more contact area for heat to flow through?
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Re: Battery cooling DIY

Post by rstevens81 »

Look at some cheap oil-water heat exchangers (used as water water, from our favourite Chinese marketplace), you could also use your 1st law of thermo dynamics cabin heater to heat the batteries usingbthe heat exchanger.
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Re: Battery cooling DIY

Post by arber333 »

celeron55 wrote: Tue Jul 06, 2021 12:48 pm What about adding some kind of heat conducting paste, glue or pads around the pipes to make more contact area for heat to flow through?
I was just thinking of thermal pads that i have seen beeing used in some chargers, namely Elteks :). They adhere to inductor on one side and heatsink on the other side. They remain fresh to the touch even after couple of years of service. I just have to find where to get them!
But that would increase height of the sandwich... might not be feasible. Have to check.
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Re: Battery cooling DIY

Post by arber333 »

rstevens81 wrote: Tue Jul 06, 2021 3:14 pm Look at some cheap oil-water heat exchangers (used as water water, from our favourite Chinese marketplace), you could also use your 1st law of thermo dynamics cabin heater to heat the batteries usingbthe heat exchanger.
Hah! I figured my system behaved according to II. law of thermodynamics at least in summer. Who knows what will happen in winter.
I would really like to move the entropy to the heat exchanger and contribute to global warming as long as my batteries would be any cooler.

That reminded me i have AC in the car. I may be able to make a simple exchanger fit it to AC outgoing line to better cool down cells while in use. To condition them just start the AC compressor and quickly drain the heat. Like this guy...
https://www.diyelectriccar.com/threads/ ... ost-599786
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Re: Battery cooling DIY

Post by arber333 »

I may have changed my mind. I think i will try buying one 200mm x 250mm x 12mm alu plate, cross drill it with 8mm bore and plug adjacent holes. Then somehow glue in/out alu tubes as fittings and pressure test the thing with my pump.
Should be easy to make and good test setup. Just need to find someone with a large enough drill post. 😇
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Re: Battery cooling DIY

Post by rstevens81 »

Since your cutting aluminium you could use a wood router, there are some videos and discussions scattered around the internet. I was considering this with BMW phev modules, before I brought the Vw phev modules
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Re: Battery cooling DIY

Post by arber333 »

Anyone has any info on thermal conductive tape or silikon? I would need 12x 250mm x 200mm to fit on my cell modules.
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Re: Battery cooling DIY

Post by rstevens81 »

3m thermal tape
TCATT 8805 8810 8815 8820 TDS.pdf
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Re: Battery cooling DIY

Post by arber333 »

rstevens81 wrote: Tue Jul 27, 2021 5:57 pm 3m thermal tape
TCATT 8805 8810 8815 8820 TDS.pdf
Thanks!
I just found some thermal tape on Aliexpress! Heres the link if anyone is interested.
https://www.aliexpress.com/item/3289118 ... 4c4dK3lfjS

I took some 0.5mm 200mm x 400mm and i will make it work when it arrives.
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Re: Battery cooling DIY

Post by XNTRX »

Old thread... I know. Did run across an interesting SAE paper Honda (on the Clarity) put out on the separation of the battery from the rest of the systems. 15% gain in battery longevity just by separating the cooling for the charger (page 329-330). Similar for inverter and motor. So not huge, but worth the effort to sperate if designing a system.
https://www.jstor.org/stable/26789710?r ... read-now=1
SAE International Journal of Alternative Powertrains Vol. 7, No. 3, WCX18 Best Papers Special Issue (2018), pp. 323-334 (12 pages)
For temperature, a simple AliExpress thermostat control project board (normally for A/C or reptile tanks) will work. Use the fan trigger for your pump, and the heat/cool to select direction of a water valve.
Or easier (and what I'm looking at), radiate it into the interior. Either an extra heater core in the vent work, or a sperate fan blower system (look at rear/ 3rd row) heater systems. If automatic A/C (like mine), the car will handle the overall temperature, and will be in the temperature range most batteries (and I) like. Relatively simple PWM fan and pump control based on the temperature delta (battery vs interior).
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Re: Battery cooling DIY

Post by arber333 »

XNTRX wrote: Sun Jul 10, 2022 11:30 pm Old thread... I know. Did run across an interesting SAE paper Honda (on the Clarity) put out on the separation of the battery from the rest of the systems. 15% gain in battery longevity just by separating the cooling for the charger (page 329-330). Similar for inverter and motor. So not huge, but worth the effort to sperate if designing a system.
https://www.jstor.org/stable/26789710?r ... read-now=1
SAE International Journal of Alternative Powertrains Vol. 7, No. 3, WCX18 Best Papers Special Issue (2018), pp. 323-334 (12 pages)
For temperature, a simple AliExpress thermostat control project board (normally for A/C or reptile tanks) will work. Use the fan trigger for your pump, and the heat/cool to select direction of a water valve.
Or easier (and what I'm looking at), radiate it into the interior. Either an extra heater core in the vent work, or a sperate fan blower system (look at rear/ 3rd row) heater systems. If automatic A/C (like mine), the car will handle the overall temperature, and will be in the temperature range most batteries (and I) like. Relatively simple PWM fan and pump control based on the temperature delta (battery vs interior).
No problem! Thanks for the notice.
This is by no means abandoned thread. I have been dormant, but i have made some choices.
1. I decided to implement liquid cooling for my cells. This was a result of a 30kW fast charging session when cells went from 30degC to 47degC!
2. I decided this will be a contained system with own pump and radiator.
3. Additionaly i am playing with the thought of fitting another heat exchanger to AC return pipe to scoop some of the cold from the pipe to cool down the batteries more effectively. It could also have either Chevy volt 700W electric battery heater or diesel webasto heat exchanger on the pipes.

I made chilling blocks from 200mm x 250mm x 12mm Alu. I machinned 10mm wide and 8mm deep groove into them in the U shape . Then i bent 10mm copper pipe to that shape and beat it into the groove...DOH! Yes i had to also tack the Alu block near the groove so the pipe wouldnt slide out of the slot. This made simple contact metal on metal. Time will tell if this will be OK corrosion-wise.
Chilling blocks will then be stacked between the cells with silicon tube running between them. I will use thermal tape i got from Aliexpress on both sides to improve contact and keep the load even.
I decided to first try with serial connection of blocks. Paralelling would require complex manifold with lots of tubing and i was not sure i would be capable to deair everything... I will simply connect two top most locations in the battery boxes to deair and keep radiator and coolant pump low under the car. I think this will be enough. I found a good triple copper radiator which should dispose of the heat.
I think i will keep radiator with the 12V pump under the rear seats to keep it separate from the rest of the system. I am also leaning to use a simple 12V 3-way valve to have an option to heat the battery without wasting the heat through radiator.
I found this Honda CBR pump... https://www.aliexpress.com/item/1005001 ... 2e0evBXj2T

System needs to be robust and GOOD ENOUGH! I will need to think over complexity of webasto heat exchanger or AC exchanger as they cause a lot of complexity and they work only when car is active where battery system needs to operate all the time selfsustained regardless of other systems.
For the first application i will probably just tie the pump to the system pump, which runs whenever car is operating or is charging.
Later i will dedicate a VCU and thermostat https://www.aliexpress.com/item/1005001 ... 0910%21seato control both pumps separately.
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dadiowe
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Re: Battery cooling DIY

Post by dadiowe »

I have been thinking about a similar system for a while now.

I see this as not just a cooling problem but also a heating problem because cold batteries don't like being charged.

So with that in mind I have built my battery packs using domestic radiators with the rear fins removed sandwiched between the layers of batteries. I am using VW Id3 batteries, 2 next to each other then a radiator, 600 long 500 wide, 2 more batteries, then another radiator, then 2 more batteries. The 4 connection heads on the radiators have been cut off and at one end they are tapped and plugged the other end have right angled 8mm threaded and pushfit fittings. This gives me a front battery box 600mm long 500mm wide and about 410mm tall with extra space as needed above for my HV control. In the rear of the car I have 3 batteries on their sides sitting on top of a 600mm x 400mm modified radiator. Not fully tested as far as cooling is concerned but at least not leaking.

Regarding heating and cooling, some BMW's have an inline 12v water heater that I believe is PWM controlled readily available from all good breakers on ebay for £15. BMW also have solenoid controlled 3 port valves to either have coolant flowing to both, 1 or no outlets. with this in mind I have drawn up the included "theoretical" flow and wiring diagrams. Please bare in mind these are a work in progress but the theory, I think is sound.

The idea is to heat or cool the batteries when needed. Cool the other components when the car is running and use the water heater to keep my toes warm as necessary.

All theory at this stage, just trying to get a driveable car at the moment.
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Re: Battery cooling DIY

Post by m.art.y »

dadiowe wrote: Tue Nov 22, 2022 7:38 pm So with that in mind I have built my battery packs using domestic radiators with the rear fins removed sandwiched between the layers of batteries.
I would love to see some photos of that if possible? Thinking how to do this myself 🙂
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Re: Battery cooling DIY

Post by MattsAwesomeStuff »

dadiowe wrote: Tue Nov 22, 2022 7:38 pmI have been thinking about a similar system for a while now
You'll get 100x as much participation if you just post images in your post, rather than link to PDFs. Everyone hates PDFs.

Image

Image
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Re: Battery cooling DIY

Post by dadiowe »

m.art.y wrote: Tue Nov 22, 2022 7:44 pm I would love to see some photos of that if possible? Thinking how to do this myself 🙂
Not very good pictures I am afraid, everything is buried in the boxes. The elbows I used are 90 degree for 12mm plastic pipe (not 8) with a 1/4 bsp thread, available on ebay. The plugs are flush fitted. Top picture is a render of the front battery box.

With the metal radiators and the back fins removed they are only about 15mm thick.
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Re: Battery cooling DIY

Post by claverjoe »

Forgive me for thinking in dumb guy terms, but why not just use some aluminum fins (or foam) box slapped onto the underside of your battery box and fill the voids with some nice phase change materials (paraffin wax melts at 37 centigrade IIRC) and have that as a burst supplement to air cooling?

Seems reasonable given that one rarely DCFC for more than an hour or floors it for longer than a few minutes.
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