DIY battery pack cooling

Batteries, Chargers, and Battery Management Systems.
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Headrc   1 W

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DIY battery pack cooling

Post by Headrc » Feb 09 2018 2:16pm

Hi, another newbie on this forum. I have a question regarding the cost of cooling of DIY battery pack builds. I believe everyone here has a good handle on what the cost of building your own packs. But what about cooling? What are the different approaches and costs attached to them? Or is it not a concern meaning no cooling really required? Thanks for a great source of information here. RH

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Re: DIY battery pack cooling

Post by amberwolf » Feb 09 2018 2:54pm

If your pack is getting warm enough to require cooling, it's built wrong.

Either it's too small for the demands placed on it, or the cells are either garbage or not meant for what you're doing with it.

If it's not getting too warm, and you're just trying to extend it's life by keeping it at "room temperature" constantly, (something like the way Tesla packs are done), that's a separate thing.

That said, there's a number of threads around teh forum that discuss cooling the cells in packs. Mostly in the 18650 pack build / design threads.

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Re: DIY battery pack cooling

Post by Headrc » Feb 09 2018 2:59pm

Ok thanks, I tried just a search on "Cooling battery packs" and did not seem to find anything which is why I started the thread. Will look for more answers here as well as search again. Thanks for the response. RH

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Re: DIY battery pack cooling

Post by amberwolf » Feb 09 2018 3:08pm

which of the above reasons do you have for needing to cool the pack?

keep in mind that any cooling system will make the pack less efficient--eitehr it takes more space than it would with out it, or more weight, or more power if it's an active system.

ifspace is the reason,then the extra cells you would add to lessen the heat problem might take less space than the cooling system.


when it comes to searches, you have to think about what words people might have used together in the actual post, because the forum doesn't have the ability to find threads based on what they might be about, only on the actual words in them.

using * as a wildcard for things helps, too.

cool* finds cooling, cooled, cooler, coolest, etc.

batter* finds battery batteries etc

the less words you enter the more it will find.

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Re: DIY battery pack cooling

Post by Headrc » Feb 09 2018 3:17pm

Ok thanks ...will take that advice on the search. Right now I don't have any issues as I have not built a pack yet ...just researching the whole concept of building one for the application that this site is all about. But also for builds for other applications that I am contemplating building packs for. RH

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Re: DIY battery pack cooling

Post by amberwolf » Feb 09 2018 3:24pm

Then I'd recommend looking into how to build a pack that doesn't need cooling, because that's a better, more efficient pack.

It will depend on each specific application exactly what you'll need in the pack, for cells, etc.

Since you won't say specifically what your applications are going to be and what they'll need the pack to do, we can't help you other than very generally.

If for some reason you have to use cells that can't handle the loads you'll put on them, and can't parallel enough of them to reduce the load to supportable levels, then you'll have heat generated in there.

If teh pack is not big enough to run for very long at a time, cooling is not necessary.

If the pack is big enough to run long enough to heat up inside and stay that way, *then* you need to cool it.

But it's still better to build a pack that doesn't heat up in the first place. ;)

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Re: DIY battery pack cooling

Post by Headrc » Feb 09 2018 7:54pm

Oh ... I am not avoiding stating some of the applications. One is for an electric bike. But others are:

1. A Battery pack for an electric mower and electric weedeater that used lead acid batteries previously.
2. A battery pack for an electric power wheel chair that I am repurposing as a RC controlled tool carrier for things like the electric mower and electric weed eater mentioned first.
3. Various other power tools previously using Nicd batteries.
4. A powerwall.

And then who knows what else ....electric car? In general I have an interest in seeing where I can take this as a result of all the great info here as well as other forums and tutorials on Youtube etc.

One step at a time though. And yes I understand the concept of overbuilding a battery pack for the application, which puts less demand on the batteries, generates less heat etc.. But I wanted to study the idea of cooling and see if folks felt it was of concern here. I am finding out of course that not if you build the pack correctly for the application.

Thanks folks

RH

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Re: DIY battery pack cooling

Post by Buk___ » Feb 09 2018 8:12pm

Headrc wrote:
Feb 09 2018 2:16pm
Hi, another newbie on this forum. I have a question regarding the cost of cooling of DIY battery pack builds. I believe everyone here has a good handle on what the cost of building your own packs. But what about cooling? What are the different approaches and costs attached to them? Or is it not a concern meaning no cooling really required? Thanks for a great source of information here. RH
I've considered -- but nothing more than that -- using flat copper heat pipes as the negative bus for the p-groups in my next battery.

The challenges -- beyond the cost - aren't insurmountable, but would require testing which could be expensive and time consuming.

1) the condenser end of the heat pipes would need a thermally conductive but electrically insulating connection to a heatsink.

3M 8810 tape seems like a good candidate for this purpose.

2) the evaporator body would need thermally and electrically conductive connection to the cell anodes.

A simple physical pressure connection might be enough if a method of applying consistent positive pressure is found. Eg spring, elastic band or foam.
Or an electrically and thermally conductive adhesive tape (3M 9703 seems to have pretty good conductivity) might work.
Last edited by Buk___ on Feb 10 2018 7:54am, edited 1 time in total.

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jonescg   1 GW

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Re: DIY battery pack cooling

Post by jonescg » Feb 09 2018 8:26pm

Some discussion here:
https://endless-sphere.com/forums/viewt ... 14&t=55074

Cooling is good if you can afford the space/weight/cost. Otherwise, build it to be big enough and of the right C-rating that it doesn't get too hot.

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Re: DIY battery pack cooling

Post by Headrc » Feb 09 2018 9:48pm

Interesting ideas.... anybody ever experiment with phase change materials here for your application?

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Re: DIY battery pack cooling

Post by amberwolf » Feb 09 2018 9:58pm

it's been discussed; don't recall how many experiments were done on diy packs

all instances of the phrase
https://endless-sphere.com/forums/searc ... mit=Search

just with cells
https://endless-sphere.com/forums/searc ... mit=Search

one manufacturer has used it for years
https://endless-sphere.com/forums/searc ... mit=Search

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spinningmagnets   100 GW

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Re: DIY battery pack cooling

Post by spinningmagnets » Feb 09 2018 10:46pm

The larger the pack, the less of a difference there is in the battery-cell-per-volume between the common "rank and file arrangement, and a honeycomb layout.

I prefer honeycomb because the is less air restriction and more air-flow allowed if they are packed-in to the same cell density as a common square pack. I agree a pack should not get hot, but...if a 48V server computer fan draws very little amps, and keeps the pack cooler that it would be otherwise?...eh..why not?

There's probably a dozen sophisticated ways to cool the center of a pack (the warmest part). But I believe a honeycomb layout with a shroud and an air fan (or two?) would work great. I haven't tried it yet, so...who knows?

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Re: DIY battery pack cooling

Post by Headrc » Feb 09 2018 11:20pm

Loving this communication here ...thanks for all those links ...

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Re: DIY battery pack cooling

Post by youyoung21147 » Feb 15 2018 5:55am

What I did on my 10S and 14S ebike packs is varnish the entire pack internals and close the ends with wire mesh. This allows air circulation in the pack and repells big debris. Rain/water can get in and out. Tested for 1 year without trouble and no corrosion !

Airflow is critical to quickly balance cell temperatures in cold/hot climate. Otherwise, the temperature gradient will generate a capacity/internal resistance gradient between the center and the outside of the pack.

A 5°C temperature difference can mean 3% less/more capacity for the same cell.

Headrc   1 W

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Re: DIY battery pack cooling

Post by Headrc » Feb 15 2018 7:54am

What did you use to varnish with? Do you have any pictures you could share? Thanks for the response. RH

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