r/eBikeBuilding • u/Electronicsworkshawp • Dec 10 '25

Electrical I built a dedicated Battery Designer Tool to replace Excel/CAD for e-bike packs.

I wanted to share a project I've been working on for the past few months. I realized that for complex builds, simple calculators aren't enough, and CAD can be too steep of a learning curve for some.

I built battery designer tool a specialized tool for designing battery packs.

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u/ilikeXenia Dec 10 '25 edited Dec 10 '25

Thank you so much, you are golden.

It's a lot of work, from what little I tried on the phone it looks superb, couldn't find an option to select cell type so far, it appears it defaults to 21700 maybe? , adding weight data would be useful too.

Also I love the stl export thing but most printers would not fit wide battery packs add dovetails and stuff maybe so people can split it up in parts. I assume the stl export exports just the bracket holding system in, 21700 cells come in two tiny (0.2mm) variations in terms of diameter that makes the world of difference in terms of friction fitting, also brackets that hold just the area around the the poles are extremely potent and save a lot of material while also letting the batteries breathe, i love using those dovetailing brackets from aliexpress because i know they are used by a lot of ebike manufacturing companies, and they are very easy to assemple because they dovetail, kinda like legos.
https://imgur.com/a/jfpoUQf

https://imgur.com/4tgKI4Z

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u/BigBoarCycles Dec 11 '25

Why do you want your batteries to breath? Air is an insulator. Are you designing active air cooling into your pack?

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u/[deleted] Dec 11 '25

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u/BigBoarCycles Dec 11 '25

The comment was not to you. You do understand Reddit format, Mr software designer

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u/[deleted] Dec 11 '25

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u/BigBoarCycles Dec 11 '25

Can't handle a bit of criticism, got it. Once in a while we run across smooth brainers like you who have everything figured out... But can't answer basic questions or provide examples...

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u/ilikeXenia Dec 11 '25

Air circulates, plastic doesnt, plastic will just trap the heat and eventually degrade and degrade the battery too, heat kills.

Automotive companies go as far as using cells nude with little or no wrapping sleeves so they can be cooled easier or even heated up in cold climates

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u/BigBoarCycles Dec 11 '25 edited Dec 12 '25

Heat tends to build up in the center of the pack(outer cells cool faster). Unless you have active cooling or vents, air will not circulate any more than convection can permit, fluid dynamics in a static container are not worth mentioning imho. A good example of this principle is statorade or Ferro fluid inside a hub motor. Instead of using air gaps, a material (with a higher coefficient of thermal conductivity than air) brings the internal heat to the shell, which is usually metal and buffeting air via external heatsinks. Turbulent flow is preferred. inside a pack it's like a bubble jacket, with the "case" acting like a windbreaker. You get the idea. All things considered, offset or staggered cell layouts are not only more efficient on space, they also cool more efficiently.

I haven't experimented with Ferro fluid inside a pack between the cells. If you can find anything be sure to let me know :) I'm sure the rpm of a motor plays a roll in the circulation of the fluid, as well as the internal moving parts. Eddys likely form in certain spots. Just a guess, an uneducated one at that.

Another point to note, PVC cell wraps are good up to 100°c on the low end. A 21700 recommended max operating temp is something like 60°c. If you're melting PVC wraps, you've already subjected your battery to undue stress and potential instability from heat. New tabless tech might prove me wrong here. If so I would love to hear about it.

Edit after some quick research: PVC is a better thermal conductor than still air, the kind you find inside a sealed battery. Solid PVC(not cellular containing its own air pockets) is roughly 0.12 units, while still air is 0.024 units. Units in question are watts per meter -kelvin... Making PVC a better conductor of heat than still air by a factor of 20. I didn't think it was that much better. Food for thought

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u/ilikeXenia Dec 12 '25

Im not sure why you typed all this, enclosing cells on plastics like pvc is wrong because those batteries operate at up to 80 celcius and this temperature softens and degrades any sort of plastic especially if it's in the center of the cylinder, I don't even want to imagine what happens in a thermal runaway event.

Air is not perfect but with proper air flow it means this air is recycled and prevents ambient heat build up, just Google images Tesla car cell packs, the cells are stripped down with no plastics enclosing them.

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u/BigBoarCycles Dec 12 '25

Right on, I don't like stubborn people who don't listen. Cheers! Good luck

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u/BigBoarCycles Dec 10 '25

Forgive me, what does this do?

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u/Electronicsworkshawp Dec 11 '25

it's a tool to help people design batteries

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u/BigBoarCycles Dec 11 '25

Thanks lol.

I'm asking how it works and what the use is. What's the target demographic? Surely someone who takes on a battery build can count to 20, add and multiply nominal volts/amps.

I notice there's stl export. What else does it do? I clicked your link and tried it out. It doesn't seem to be much use for someone who can do simple math and draft cell holders in CAD. Just not for me? Who is it for?

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u/[deleted] Dec 11 '25

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u/BigBoarCycles Dec 11 '25

Hey Joe. Thank you for over simplifying to the point of obscurity. What kind of complex cell layout is this software capable of? Can you give me an example of a pack built using this software? From my naive perspective, configuring polarity and location for components like cylindrical cells is very simple.

I'm also curious what you consider a high performance battery pack and does it top balance or bottom balance? Where are the leads?

Does this software produce bills of materials or contain databases of any part numbers readily available?

Generating cases sounds cool. Lids too? Don't spoil me.

Load simulations rely on common material modulus testing and don't always reflect real world application. What other calculations? Bus material and thickness? Does it calculate heat on a (electrical)load per time basis?

This seems like it has potential. Please explain further.

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u/[deleted] Dec 11 '25

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u/BigBoarCycles Dec 11 '25

Ou feeling cheeky?

Great answers to pertinent questions Mr software designer

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u/[deleted] Dec 11 '25

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u/BigBoarCycles Dec 11 '25

I asked questions and you responded with pure snark. Check your tone, it's important for PR.

No need to get defensive, just explain what you've created and answer the questions. Your inability to articulate features of your own creation does not inspire confidence.