Air-cooled for 18650 Li-ion battery pack

[nhattan12]

Hi all,

Here is a battery pack of eBike, have properties is 72V 68Ah.

Here is a picture outside of pack:

As i know, this pack have only 1 vent behind the pack to cooling battery system. At current version, 1 vent is enough to cooling, but in the future version, I think it's not !

So, now I want to create a passive air-cooled (don't use energy). But, the most problem are dust, moisture, water tiny insect can be infiltrate inside. It can be destroy from inside; corrosion, ...

So, my question is: how can i do to cooling the battery pack while still anti dust, moisture, ...

I mean, because battery pack is fixed into a block, how I adjust the case outside?

Thank you so much !
Please help me.

 

[99t4]

What internal temperatures are you seeing under heavy use?

Possibly some intake ram-air piping with filter at intake entrance, intake entrance at safer location (under seat, away from water?).

Think of where offroad ICE motorcycles put their air filters.

 

[Chalo]

What makes you think everybody else is doing it wrong?

It's an honest question, because I don't assume everybody else is doing it right. The technology is relatively young.

 

[GalFisk]

Conducting heat out safely is probably easier than getting air in safely. If you want a meaningful amount of air to enter through a filter, you need a pretty beefy fan. Think vacuum cleaner territory. And you still need to keep moisture from condensing inside.

Oil immersion cooling would probably be better. The oil could simply conduct the heat to the battery chassis (fitted with a finned heat sink if necessary), or be pumped through a radiator.

Heat pipes might also work, though they're relatively costly.

 

[eMark]

Conducting heat out safely is probably easier than getting air in safely. If you want a meaningful amount of air to enter through a filter, you need a pretty beefy fan. Think vacuum cleaner territory. And you still need to keep moisture from condensing inside.

Oil immersion cooling would probably be better. The oil could simply conduct the heat to the battery chassis (fitted with a finned heat sink if necessary), or be pumped through a radiator.

Heat pipes might also work, though they're relatively costly.

It doesn't get that hot in Sweden. I'd be more concerned about keeping the battery warm for winter use than keeping it cool in summer ... (assuming you really live in Sweden) :wink:

https://technode.global/2021/04/13/with-2-6m-pre-series-a-vietnams-dat-bike-aims-to-drive-the-future-of-southeast-asias-e-bike-market-qa-with-founder-ceo-son-nguyen/ ... "Our bikes can reach 100 Kph with a 5,000-Watt motor. And of course, it is designed to carry two adults."

If there is a Sweden distributor(connection), one would think there'd be an American distributor(connection) ??

 

[amberwolf]

since the op asking the question is in vietnam according to their profile, it's not really relevant whether sweden is cool or hot....

Conducting heat out safely is probably easier than getting air in safely. If you want a meaningful amount of air to enter through a filter, you need a pretty beefy fan. Think vacuum cleaner territory. And you still need to keep moisture from condensing inside.

Oil immersion cooling would probably be better. The oil could simply conduct the heat to the battery chassis (fitted with a finned heat sink if necessary), or be pumped through a radiator.

Heat pipes might also work, though they're relatively costly.

It doesn't get that hot in Sweden. I'd be more concerned about keeping the battery warm for winter use than keeping it cool in summer ... (assuming you really live in Sweden) :wink:

https://technode.global/2021/04/13/with-2-6m-pre-series-a-vietnams-dat-bike-aims-to-drive-the-future-of-southeast-asias-e-bike-market-qa-with-founder-ceo-son-nguyen/ ... "Our bikes can reach 100 Kph with a 5,000-Watt motor. And of course, it is designed to carry two adults."

If there is a Sweden distributor(connection), one would think there'd be an American distributor(connection) ??

 

[Chalo]

Still there is the issue: if your cells are getting hot enough to need cooling, you're abusing them. Use more cells, or cells with a higher current rating.

 

[nhattan12]

Still there is the issue: if your cells are getting hot enough to need cooling, you're abusing them. Use more cells, or cells with a higher current rating.

Thank you for your reply.
you mean the best solution is control the power of battery system, right? instead of cooling it first ?

 

[nhattan12]

What internal temperatures are you seeing under heavy use?

Possibly some intake ram-air piping with filter at intake entrance, intake entrance at safer location (under seat, away from water?).

Think of where offroad ICE motorcycles put their air filters.

Thank you for your reply !
I got your answer. But i have a question: do you think air-cooled with the ambient air through inside battery pack is a good solution, or any other solution (like using heat pipe - air inside; air flow outside using case with outter-fin).

I want using air-cooled only. That's my aim.

Thank you.

 

[nhattan12]

What makes you think everybody else is doing it wrong?

It's an honest question, because I don't assume everybody else is doing it right. The technology is relatively young.

Thanks for your reply !

Because here is a electric bike start-up company in Viet Nam. This model just a 2nd model. Now, this bike can go 200km /1 charge.
Long distance, hot weather in Viet Nam. I think it will be over-heat at further version (distance will up to 300km 400km).

 

[nhattan12]

Actually, I'm working for graduation thesis in university. The topic is Air-cooled for battery (BTMS).

I want my thesis realistic, applicable, instead of just on paper.

So, the battery pack in image above is a battery pack of electric-bike company in my country.

I really need your answer!

 

[Overclocker]

this battery really doesn't get hot so this is just the bare minimum of battery cooling. basically i just don't want to trap heat i.e. have a way for heat to get out

 

[nhattan12]

IMG_20210805_130849.jpg

IMG_20210820_225822 (1).jpg

this battery really doesn't get hot so this is just the bare minimum of battery cooling. basically i just don't want to trap heat i.e. have a way for heat to get out

Thank you. The image is amazing !

But, in second image, I can see a conductive trip from outside, so water and dust can be destroy battery, right?
And, what is the power (Wh) of your battery pack?

 

[Chalo]

What makes you think everybody else is doing it wrong?

It's an honest question, because I don't assume everybody else is doing it right. The technology is relatively young.

Thanks for your reply !

Because here is a electric bike start-up company in Viet Nam. This model just a 2nd model. Now, this bike can go 200km /1 charge.
Long distance, hot weather in Viet Nam. I think it will be over-heat at further version (distance will up to 300km 400km).

Extreme range means the battery is discharging at low intensity, which makes cooling less important rather than more.

 

[Overclocker]

it's a small 1.1kwh

you can't wash this bike w/ a pressure washer, but i've ridden it in the rain

 

[Overclocker]

here's another tip for you. if you'll notice i got 2 separate battery packs w/ a bit of air gap in between. so the inner walls of the battery cases can be made from the perforated "speaker grill" material i showed earlier. so you can have a bit of passive cooling going on in there while being fairly splash resistant to water

 

[amberwolf]

Actually, I'm working for graduation thesis in university. The topic is Air-cooled for battery (BTMS).

I want my thesis realistic, applicable, instead of just on paper.

So, the battery pack in image above is a battery pack of electric-bike company in my country.

I really need your answer!

well, the real answer is still that if you need to cool the battery, you are pushing it too hard and need a bigger battery, or a better one.

 

[Overclocker]

well, the real answer is still that if you need to cool the battery, you are pushing it too hard and need a bigger battery, or a better one.

that idea only applies to low-power ebikes. once the application requires high-performance and battery longevity then you need consider battery cooling which could range from extremely elaborate (tesla style ribbon cooling tubes) to something simple like using thermally-conductive potting to the aluminum outer case

 

[amberwolf]

ok

well, the real answer is still that if you need to cool the battery, you are pushing it too hard and need a bigger battery, or a better one.

that idea only applies to low-power ebikes. once the application requires high-performance and battery longevity then you need consider battery cooling which could range from extremely elaborate (tesla style ribbon cooling tubes) to something simple like using thermally-conductive potting to the aluminum outer case

 

[99t4]

What internal temperatures are you seeing under heavy use?

Possibly some intake ram-air piping with filter at intake entrance, intake entrance at safer location (under seat, away from water?).

Think of where offroad ICE motorcycles put their air filters.

Thank you for your reply !
I got your answer. But i have a question: do you think air-cooled with the ambient air through inside battery pack is a good solution, or any other solution (like using heat pipe - air inside; air flow outside using case with outter-fin).

I want using air-cooled only. That's my aim.

Thank you.

Again: Need to know what temperatures are at the battery internal to know how radical a cooling solution to design.

 

[Chalo]

well, the real answer is still that if you need to cool the battery, you are pushing it too hard and need a bigger battery, or a better one.

that idea only applies to low-power ebikes. once the application requires high-performance and battery longevity then you need consider battery cooling which could range from extremely elaborate (tesla style ribbon cooling tubes) to something simple like using thermally-conductive potting to the aluminum outer case

He's claiming 200 to 400 km/charge. That implies a low C rate that shouldn't get hot unless something is very wrong.

 

[eMark]

Actually, I'm working for graduation thesis in university. The topic is Air-cooled for battery (BTMS).

I want my thesis realistic, applicable, instead of just on paper.

You need to open up the battery enclosure to see if the cells can even be air-cooled efficiently. The battery may be partially shrink-wrapped or overwise protected so even if you had water resistant top vents with rear exhaust fan it still wouldn't have enuf sufficient air-cooling that you've got in mind.

For a "realistic applicable thesis" you first NEED to open up the enclosure, remove the battery pack from enclosure (if possible), take photos of battery showing any protective shielding that may reduce/restrict airflow over cells. And photos showing any necessary modifications. You need to post photos of battery configuration and any shielding that could reduce/restrict airflow over the cells with photos of problem-solving modifications. Perhaps a few water resistant vents on top of each side of enclosure with rear exhaust fan will be sufficient.

You may have to remove any restrictive covering over top of battery to get good air flow over all the cells. Also may need water resistant vents on each side at bottom of enclosure. Need to have free airflow throughout all the cells not just 50% of the cells. That means you may also need water resistant vents at the front of the battery enclosure. Where there's the will, there's always a way, but is it practical to do so.

Until you can provide inside photos of battery enclosure with problem-solving mods for your air-cooling solution your thesis is incomplete. A "realistic applicable" equalized air-cooled solution throughout 100% of the cells may not be practical or possible.

 

[nhattan12]

Actually, I'm working for graduation thesis in university. The topic is Air-cooled for battery (BTMS).

I want my thesis realistic, applicable, instead of just on paper.

You need to open up the battery enclosure to see if the cells can even be air-cooled efficiently. The battery may be partially shrink-wrapped or overwise protected so even if you had water resistant top vents with rear exhaust fan it still wouldn't have enuf sufficient air-cooling that you've got in mind.

For a "realistic applicable thesis" you first NEED to open up the enclosure, remove the battery pack from enclosure (if possible), take photos of battery showing any protective shielding that may reduce/restrict airflow over cells. And photos showing any necessary modifications. You need to post photos of battery configuration and any shielding that could reduce/restrict airflow over the cells with photos of problem-solving modifications. Perhaps a few water resistant vents on top of each side of enclosure with rear exhaust fan will be sufficient.

You may have to remove any restrictive covering over top of battery to get good air flow over all the cells. Also may need water resistant vents on each side at bottom of enclosure. Need to have free airflow throughout all the cells not just 50% of the cells. That means you may also need water resistant vents at the front of the battery enclosure. Where there's the will, there's always a way, but is it practical to do so.

Until you can provide inside photos of battery enclosure with problem-solving mods for your air-cooling solution your thesis is incomplete. A "realistic applicable" equalized air-cooled solution throughout 100% of the cells may not be practical or possible.

Thank you so much !

Actually, now I dont have this bike, and this bike is a quite newly version, so no one teardown it (except bike manufacturer), so now I can't show up it.

You know, if we take the ambient air as much as possible, it is a total pressure of air ( dynamic + static) (the vent is located in front of battery pack) . It will be include water and dust. On the other hand, if we just take static pressure of air, we can reduce a little bit.

Btw, thank you for your solution (vents on top of each side of enclosure with rear exhaust fan). I'll consider it carefully.

 

[nhattan12]

well, the real answer is still that if you need to cool the battery, you are pushing it too hard and need a bigger battery, or a better one.

that idea only applies to low-power ebikes. once the application requires high-performance and battery longevity then you need consider battery cooling which could range from extremely elaborate (tesla style ribbon cooling tubes) to something simple like using thermally-conductive potting to the aluminum outer case

He's claiming 200 to 400 km/charge. That implies a low C rate that shouldn't get hot unless something is very wrong.

what you say I haven't thought about it. Why do you think like it? I think in a new version of this bike, it can go further /charge, charge time is reduce, acceleration is faster, load capacity will bigger. So I still think battery cooling is necessary. It's right?

 

[Chalo]

I think in a new version of this bike, it can go further /charge, charge time is reduce, acceleration is faster, load capacity will bigger. So I still think battery cooling is necessary. It's right?

What's the maximum controller amps versus the battery Ah capacity? Batteries that discharge over a long period of time don't generate much heat, and they have a long time to dissipate it.