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Hi ive been looking everywhere and figured this would be the best place to go to.
Ive been debating between using Panasonic like in tesla's or using car batteries but the thing i forgot about after wanting to do it for so long is; how do i cool it?
When I see a conversion with car batteries it looks like theyre just in there with no extras.
If I use car batteries do they need a cooling system? Or are they made to handle this kind of stress?
If anyone does use Panasonic, how do you cool them?
Thanks in advance!
 

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Ive been debating between using Panasonic like in tesla's or using car batteries
I presume by "car batteries" you mean lead acid batteries that look like they're the same size as a car starter battery?

If so, you should be aware that, while that would work, you would very quickly ruin the starter batteries (like, in a week or two of daily discharge). What look like, but aren't starter batteries in the builds you see, are actually deep discharge batteries. They usually make them in the same form factors as starter batteries, but they're built differently internally. Starter batteries have delicate honeycombs so that they have as much surface area as possible, but if you keep discharging them that delicate honeycomb breaks off and falls apart. Deep discharge batteries have heavier duty plates that don't have as much peak power, but aren't as fragile, and they usually have more empty space below the plates at the bottom of the cell for the parts of the plates that eventually corrode and break off, making them last (at reduced capacity) a bit longer.

I've never seen a build using starter batteries, they've all been deep cycle.

Regardless, do not use lead acid batteries of either type. No one's done that in years. There is no category that they do better than lithiums, and are even more expensive than used Lithiums too. You can't save money and they have lower performance.

Tesla batteries are not that popular for DIY EVs, they are expensive and large.

Inside Tesla batteries are 18650 form factor cells (Model S and X) or 21700 cells (Model 3 and Y). 18650 (18mm x 65.0mm) are what you also find in laptops and most tools.

You don't want to build a pack out of 18650s. They are not cost effective.

An option you don't seem to be aware of are the larger form factor OEM EV cells like those from Nissan Leafs, Chevy Volts, etc.

Leaf cells are the size of hardcover books. Volt cells a bit larger and coffin-shaped. There are many others.

but the thing i forgot about after wanting to do it for so long is; how do i cool it?
Nissan Leaf cells are air cooled. But they suffer for it with reduced life (cells become junk sooner).

Most others are water cooled. Including Tesla packs. The cells are arranged in a honeycomb grid, with a little bit of space between cells. There's a metal tube (like an almost-crushed paper-thin garden hose) that snakes between them where coolant runs.

When I see a conversion with car batteries it looks like theyre just in there with no extras.
Usually that was the case, though the area would be air vented as they do get warm.

Most Lead-acid battery types have a handy feature of being filled with water, so they can take a tremendous amount of energy without heating up as much (5-10x as slowly compared to metal).

Also, lead-acid batteries just kind of suck, you can't get energy out of, and certainly not into them very fast. So they can't cause a lot of heat.
 

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Ha yeah lead acid doesnt seem that great. Ive always wondered if people go through the expense why use those?

Shouldve been more clear, was thinking about lithium ion, probably optima for the weight but not sure how many miles per battery id get, from what i gather 1 lithium ion car battery is gets you roughly 10 miles?

And you are right sir have never even considered the leaf or volts but i shall look into those now. Just assumed theyd be expensive or worn out by the time someone would put them up for sale (unless they sell new ones somewhere?). Only looked into the tesla batteries because I knew I could buy them off the shelf like car batteries. Funny actually thought they'd be cheaper and able to stuff 'em where i could cram 'em more than the car batteries so thanks for correcting me on that.
 

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Shouldve been more clear, was thinking about lithium ion, probably optima for the weight
I don't think I've seen anyone do that. So, must be because they're not cost effective.

Just assumed theyd be expensive or worn out by the time someone would put them up for sale
Generally, avoid first gen Leaf cells, they had worse cooling and their cells tend to be junk. At least, insist on tested capacity and then verify that when you purchase.

Otherwise, they seem pretty bulletproof. It's rare to find an OEM cell that's gone bad. I don't think I've even heard of a single Volt cell that went bad. I'm sure there are, but, they must be extremely rare.

[]quote'Funny actually thought they'd be cheaper and able to stuff 'em where i could cram 'em more than the car batteries [/QUOTE]

There is that advantage, IF you were building the pack from 18650s yourself. That's why Tesla went with them I suspect.

But Tesla modules are among the worst because they're the largest. You could try tearing them apart to get at the cells and then rebuild your own pack your way, but there's like 3 layers of housing glued on where the glue is stronger than the case so it rips apart... a nightmare. I've never seen anyone actually go through with it.

And, you don't want to build a pack from new 18650s, not cost effective.

A third option are large form factor Lithium-Iron-Phosphate. These are large format cells with lower voltage that were popular 7 years ago, but generally smaller size than OEM batteries which is important if you need enough cells to reach a certain voltage, not just the right amount of battery in general. But I don't know if I've ever heard of a vehicle that *didn't* have issues with at least 1 cell on their car after a couple years. Generally no one does this anymore. OEM EV is the way to go.
 

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Most others are water cooled. Including Tesla packs. The cells are arranged in a honeycomb grid, with a little bit of space between cells. There's a metal tube (like an almost-crushed paper-thin garden hose) that snakes between them where coolant runs.
Most EV battery modules are liquid-cooled, which is the important point. Only Tesla uses this particular cooling arrangement, but the details of the various designs don't matter so much as the fact that circulating coolant is necessary for proper performance of these modules.
 
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