Making Battery Packs

Hey guys,
i’ve been browsing this forum because i’m finding electric motors and batteries extremely fascinating and i always love a good project.

So i’ve just been researching battery methods because it seems this can make or break an EV.

I have noticed that if you want to buy pre-made battery packs such as lithium ion, lipoly, or nimh, they are extremely expensive. Yet the components of said packs are supremely cheaper. I am comfortable with my electronics skills, soldering, voltage, amperage, etc. I feel confident that i could put together a battery pack for fairly cheap.

Are there certain batteries that are not suitable for EV’s? I don’t know much about discharge rates and such, what is an acceptable discharge rate?

I plan on just buying Li-ion, li-poly, or nimh cells and fabricating battery packs. Can anyone give me some insight i may be missing? THanks!

You didn’t say what pack voltage you are aiming for, but, for example, a 72 volt system is going to cost at least $2000 (most likely more) by the time you fabricate the battery pack boxes and put together your batteries - and that does not include the cost of a DC to DC converter, a controller, a charger, a main on-off switch, or heavy duty wiring.

where would you buy the components? i was concidering the same option of just building my own battery pack but it appears that when buying cells you wouldnt be saving any money. ive been looking into li-ion and have found 3.2v 200ah packs for $500 and 3.7v 2000mah (2ah) for $10, thats only $2.50 per ah for the pack and $5.00 per ah to build your own pack (given its 3.2v instead of 3.7v but its more cost effective) i hope this does not come across as pompas or argumentative, i just would like to know where you are finding your components. i think that building your own cells would also be able to fit your custom application far better.

well, 100Ah 3.2V cells are around 200 bucks a pop. No BMS. To get 72V, you need ~22… so thats nearly $4400 for a 100Ah pack. No BMS or charger.

you say 10 bucks a piece for 3.2V 2Ah cell… so thats 50 of those to do 100Ah 3.2V cell… so thats nearly $500, and 22 of those parallel packs… is $11,000. No charger or BMS. 22s50p

you WILL spend over $2000 for a 72V pack, he was just using that as an example. Some places (there’s one in oregon, but i forget the name) quoted be $3600 for only 50Ah and 72V with charger.

And you’ll likely find that Li-Ion chemistries like Li-Cobalt and LiPoly are unstable and very finicky. They tend to like to burn if they’re overcharged. If you can FIND NiMH, and afford it, then go ahead… but its considered unobtanium around the EV world.

Do some research on Thundersky, LionEV, Valence…etc.