How exactly are electric vehicles able to use Li-ion as their main power source, the 21700 e.g. has a maximum discharge rate of 35A while tesla motors draw up to 800A (very short research, might be wrong)

If you need 7.6v to power something and you only have 3.8v cells, you connect two in series and you get 7.6 volts. If you need 11.4v you connect 3 in series to get that voltage.

If your device requires 20 amps current flow and your cells can put out only 10 amps max, then you connect two in parallel to get the 20 amps. If you need 30 amps, you connect 3 in parallel.

If your device draws 20 amps and has to run for one hour you need more than 20 ampere hours capacity in your battery pack because 20 amps times one hour equals 20 ampere hours. If it has to run for two hours then you need 20 times 2 equals 40 ampere hours. If it only has to run for 1/2 hour then you only need 20 time 1/2 equals 10 ampere hours.
The ampere hour ratings quoted above are as if the current draw of the device was the same current draw as used when the cells are tested for capacity. This is seldom the case. The more usual case is that the testing of the cells was done at a much lower current and since the apparent ampere hour capacity of a cell decreases with current draw you need a bigger battery than calculated above. The correct calculation for a new battery would be to find it's "P" factor but often you may not want to do that either. In that case you just guess and used cells that are rated a lot higher than you calculate. For example, if you calculate 20 ampere hours then maybe a 30 ampere hours battery would be better. You can get some idea how to increase this number by looking at specs for other batteries with a similar chemistry.

Also, as time goes on the cells loose capacity so at some point if it runs for 1 hour when the cells are new it will run for only 1/2 hour at some point in the future as the cells age and are charged and discharged.

This is a little interesting for me too because i was just looking at high power Li cells yesterday and was amazed at the size you can get these days. You can get 200 ampere hours cells now but they are quite expensive sometimes over $1000 dollars USD.
There are some smaller ones like 12 ampere hour that are less i think like around 60 dollars USD.
You can check them out on Amazon for example.

[EDIT: I said "cells" when really i meant "battery packs" when discussing the large ones on Amazon.]
They are 12v for example at various ampere hour ratings and the package case style looks like a lead acid battery.

 

If you need 7.6v to power something and you only have 3.8v cells, you connect two in series and you get 7.6 volts. If you need 11.4v you connect 3 in series to get that voltage.

If your device requires 20 amps current flow and your cells can put out only 10 amps max, then you connect two in parallel to get the 20 amps. If you need 30 amps, you connect 3 in parallel.

If your device draws 20 amps and has to run for one hour you need more than 20 ampere hours capacity in your battery pack because 20 amps times one hour equals 20 ampere hours. If it has to run for two hours then you need 20 times 2 equals 40 ampere hours. If it only has to run for 1/2 hour then you only need 20 time 1/2 equals 10 ampere hours.
The ampere hour ratings quoted above are as if the current draw of the device was the same current draw as used when the cells are tested for capacity. This is seldom the case. The more usual case is that the testing of the cells was done at a much lower current and since the apparent ampere hour capacity of a cell decreases with current draw you need a bigger battery than calculated above. The correct calculation for a new battery would be to find it's "P" factor but often you may not want to do that either. In that case you just guess and used cells that are rated a lot higher than you calculate. For example, if you calculate 20 ampere hours then maybe a 30 ampere hours battery would be better. You can get some idea how to increase this number by looking at specs for other batteries with a similar chemistry.

Also, as time goes on the cells loose capacity so at some point if it runs for 1 hour when the cells are new it will run for only 1/2 hour at some point in the future as the cells age and are charged and discharged.

This is a little interesting for me too because i was just looking at high power Li cells yesterday and was amazed at the size you can get these days. You can get 200 ampere hours cells now but they are quite expensive sometimes over $1000 dollars USD.
There are some smaller ones like 12 ampere hour that are less i think like around 60 dollars USD.
You can check them out on Amazon for example.

Yea I definitely think Li ion will replace LiPo for RC vehicles in the near future, you can easily get double the flight time for drones and aircrafts.

 

Yea I definitely think Li ion will replace LiPo for RC vehicles in the near future, you can easily get double the flight time for drones and aircrafts.

Well the ones i was talking about are Li-something i am not sure which but they are actually battery packs not individual cells. I made a new note of that in my previous post.

Maybe one day these will replace almost every type of other chemistry at least until the nano tech batteries come out which will have higher energy density.

 

There are many videos where a battery bought on ebay is a fake one.

 

There are many videos where a battery bought on ebay is a fake one.

I once found a supplier who advertises the conversion tubes, and the heat-shrink plastic covers with various names on them

 

The most popular fake 18650 battery name is Ultrafire.
3300mAh is the real maximum but many 18650 batteries are marked 9900mAh.

 

The most popular fake 18650 battery name is Ultrafire.
3300mAh is the real maximum but many 18650 batteries are marked 9900mAh.

Hi ag,

I guess you can call them 'fakes' but i call them 'misbranded' because they do work, just not at the advertised rating or specification. They could be 2000mAh cells for example.
It is funny though as you mention that they have the stupidity to brand them that high. I've seen other products too that are branded way too high. You can tell for sure by looking up the mass energy density of the most recently developed cells and compare that with the item being shopped at the time. If the rating far exceeds the maximum energy density at that weight, then it must be over rated. it might still work, but not at the package specification as you noted. Again i am surprised they try this but maybe they are desperate and figure they will fish in some suckers that see "9000" vs "2000" and think in their mind that "hey that 9000 must be a lot better i better get that one to be sure" ha ha.

I was looking at the big LiFePo cells recently because my Fios wall box started beeping again. It does that when the battery goes south and wont hold a charge any longer. It's kind of dumb because it is made for emergency use of 911 when the power goes out but if you have a wireless phone the wireless phone goes out anyway because it relies on a box plugged into the power line, and besides these days most people have cells phones to call 911 and you dont even have to have a carrier to use 911 with a cell phone. I guess when the box was developed for Verizon it was a long time ago so they had their old assumptions back then.
The large 12v LiFePo cells really go up there in rating, i have seen 200 ampere hours units although the cheapest i have seen for those is about $850 dollars USD.