It is very important to only buy high quality lithium ion batteries. Improperly build battery packs can lead to catastrophic fires resulting in loss of property and life.
Lithium ion batteries can combust when improperly charged or discharged and can't be extinguished by water. as such there are only a few retailers we are willing to endorse. Its highly recommended to go with these resellers or at least do serious research on who you plan to buy packs from. Do not buy battery packs off random ebay/amazon/aliexpress pages, their quality often leaves much to be desired.
Common cell formats
The vast majority of E-bike batteries are based on 18650/21700 Li-ion cell type batteries. This is due to:
- Better customizability due to shape of shells. This results in more variety of configurations without losing volumetric space; bicycles often have complex non-rectangular spaces that batteries are attached to.
- Pouch cell (prismatic) type batteries (small format, we are talking about size of phone batteries here) do not have structural integrity unlike cylindrical cells have. this results in worse reliability for these cells against impacts.
- Pouch cells often have inferior c-rating (continuous current output) rating than cylindrical cells.
- Larger prismatic cells are harder (if not outright impossible) to be used on ebikes, due to their size being a constraint. See point 1.
- Lastly, LFP/Lifepo4 cells have inferior power density compared to li-ion. This becomes a less of an issue for larger electric vehicles (i.e. motorcycles, cars, boats), whereas on a bicycle weight becomes an issue because most bicycles are not designed to have tens of kilograms of extra weight apart from rider's weight. This would mean that you would need to upgrade the frame/tires/motors to ones that can support more weight, and at that point you're essentially turning an electric bicycle to a motorcycle. Additionally, typical LFP/pouch cell battery packs (often prismatic/rectangular) are never meant to be mounted/tied to a bicycle.
Where to buy:
We currently recommend the following dealers.
EM3ev - High quality hand-made batteries shipped from China. Comes equipped with a bluetooth compatible BMS so you can monitor your batteries health and performance with a cellphone app. Highly recommended.
Luna Cycle - high quality batteries shipped from USA
Unit Pack Power used to be on our list, but due to several recently raised safety concerns and a couple of known fires, we no longer recommend this seller
Reputable Cell Providers
Here, we are listing battery cell suppliers known by members to sell legit cells. Cells are purchased only when someone wishes to make a DIY battery pack.