So I need 14 batteries. That will make 1000W and 48V and 3000mAh. Seems like I will dry them very easily

Those batteries are LG HG2 li-ions. Very expensive

1000W is a lot for any battery. Are you making an electric motorcycle? Anyway, harnessing that much power from batteries in a safe and efficient manner takes some careful engineering.

I think those exact batteries are very good for this (Yes, electric bicycle), if something drains 3 amps for an hour, one battery can last for around 6 hours. If it is 14 of them, I can afford 42 amps for 6 hours at 3.7V

You should probably increase the number of cells. Also, use a BMS (battery management system) designed for electric bikes. You will not be able to make a good BMS from scratch in your garage unless you're a power electronics pro, so just find a good one to buy. Then read the documentation, and connect the cells as suggested by the BMS manufacturer.

@Dampmaskin That would explain why battery packs are so expensive. 14 of those batteries already cost 105$

They're top quality though. If you want to save money you can check out other 20A cells from Sony, LG, Sanyo or Samsung. A greater number of lower capacity cells may give you better bang for buck. But watch out for fakes.

Also remember you need to charge the cells, and balance charging is mandatory. Either get a BMS that supports charging, or get a separate balance charger that supports the necessary number of cells in series.

It is very hard to determine which battery is fake through ebay though

Usually I watch for price and mAh

never trust batteries that claim to have more than 3500-4000 mAh

I would not buy Lithium batteries from Ebay. Way too risky. Better to find a trustworthy battery web shop in your vincinity. Or an e-cigarette, flashlight or hobby shop.

I am quite satisfied with the LGs I have, they've been unused for months

I find many e-cigarette shops sell 18650s for a reasonable price. And some of them have a reputation to protect, so they will often work hard to avoid selling fakes.

and they still have 3.7volts/20 amps

That's a good option to save money yes. They often sell the blue ones

For 14 lg batteries I think I can move the bicycle for an hour

or so

which is not bad for 100$

And the motor also have speed controller and throttle

Well, start with the BMS and design the battery pack around that. You'll probably need to make several groups of parallel cells, and connect at least 4 or 5 groups in series.

So there could be more economic riding

Depending on the BMS.

I hope it is not very expensive

One of the most important job for the BMS is to protect the cells against overvoltage, undervoltage, overcurrent, and to keep them balanced. It's a good investment if you want your cells to last.

for the undervoltage

a diode at the negative side for the reverse polarity protection

Overvoltage using fuses? Overcurrent you mean?

But how will you keep the cells balanced?

Instead of buying all those bcbs, if the BMS isn't very expensive, it is better to just buy one good BMS

to make a stable psu

You can probably find them pretty cheap on ebay, and hope that the quality is ok.

But if you buy them from ebay, maybe get double the rating you need. Because the sellers tend to exaggerate the ratings.

and a capacitor

and diode and perhaps resistor

would take much time to implement all that

if I had to

I will also put my Arduino to some use

Maybe use the friction of the motors to generate 5V and supply that electronics for the bicycle

and use the Arduino to control it

Yes each battery should probably have a termistor

the speed controller the 94$ motor has actually provides charging board as far as I understood

Time to read the documentation? Maybe it has a full fledged BMS. If that is the case, I guess it's just a matter of connecting the cells as specified in the documentation.

Yes, thank you