www.recumbents.com
10 kW
An easy to build battery pack
There has been an explosion of choices in new high power batteries for the intrepid e-biker, but the best option as of this writing are the 18650 form factor Lithium ion batteries using the NMC formulation. These batteries are called INR or NMC and are of Lithium manganese nickel formulation. This chemistry combines the safety of LiFePo4 batteries and the high energy and density of LiPo. A disadvantage is that they do not have the longevity of some other formulations. After 250 cycles these cells will be down to about 60% capacity. Is this really a problem? Not for me, it will take me several years of fair weather commuting in the Midwest to get to that many cycles and by then a new, better, cheaper batter will be available.
The biggest issue with building e-bike battery packs out of a bunch of small batteries is how to connect them together. They can be soldered together but the heat of soldering may damage the battery. They can be spot-welded but that requires specialized equipment that is not available to the average home builder. In addition, many battery pack builders just heat shrink the batteries together which leaves them vulnerable to damages from dropping or crashes. Initially I thought that building a battery pack in a Hammond aluminum box would be a good idea, but I ran into issues and abandoned the build.
I am now working on a build using plastic battery holders, Click this link to skip to the start of the 18650 battery holder build
or your can read through the sordid tale of the abandoned build that came before it...
Some of the comments below may not make sense because I changed this first post (sorry!).
-Warren
There has been an explosion of choices in new high power batteries for the intrepid e-biker, but the best option as of this writing are the 18650 form factor Lithium ion batteries using the NMC formulation. These batteries are called INR or NMC and are of Lithium manganese nickel formulation. This chemistry combines the safety of LiFePo4 batteries and the high energy and density of LiPo. A disadvantage is that they do not have the longevity of some other formulations. After 250 cycles these cells will be down to about 60% capacity. Is this really a problem? Not for me, it will take me several years of fair weather commuting in the Midwest to get to that many cycles and by then a new, better, cheaper batter will be available.
The biggest issue with building e-bike battery packs out of a bunch of small batteries is how to connect them together. They can be soldered together but the heat of soldering may damage the battery. They can be spot-welded but that requires specialized equipment that is not available to the average home builder. In addition, many battery pack builders just heat shrink the batteries together which leaves them vulnerable to damages from dropping or crashes. Initially I thought that building a battery pack in a Hammond aluminum box would be a good idea, but I ran into issues and abandoned the build.
I am now working on a build using plastic battery holders, Click this link to skip to the start of the 18650 battery holder build
or your can read through the sordid tale of the abandoned build that came before it...
Some of the comments below may not make sense because I changed this first post (sorry!).
-Warren