Custom battery for Bosch Gen 4, Shimano EP801, Specialized(Brose) motors feasibility?

scm007

Member
Mar 23, 2022
43
3
Seattle
Before I purchase my ebike I want to make sure that these motor systems will take a custom battery charged to the correct voltage. Essentially I'm going to build N x 100wH batteries (probably 6) so that I can make it TSA legal and fly with it, reassembling the battery when I land.
1.) Do these motors have some special software interface with their proprietary batteries that will prevent it from running even if a properly charged battery is connected?
2.) Do any of these motor systems support connecting batteries through the charging port so that this could be an external battery?

Any other thoughts?
 

ebsocalmtb

Active member
Sep 29, 2021
218
229
Southern-Cal
Before I purchase my ebike I want to make sure that these motor systems will take a custom battery charged to the correct voltage. Essentially I'm going to build N x 100wH batteries (probably 6) so that I can make it TSA legal and fly with it, reassembling the battery when I land.
1.) Do these motors have some special software interface with their proprietary batteries that will prevent it from running even if a properly charged battery is connected?
2.) Do any of these motor systems support connecting batteries through the charging port so that this could be an external battery?

Any other thoughts?
they will essentially not take a custom battery. So to answer your questions:
1) yes, it's in the bms
2) depends on which bike, but again, it's bms dependent.

There are some people that have accomplished this on some motors with mixed results. Some successes but with some caveats such as the bike not knowing exactly what the capacity/status of the battery and thus showing not real %'s remaining. All the way to not working consistently.

One thing is for sure, it will require harvesting the bms out of an existing battery that is compatible (in your case, multiples), and then plowing forward and praying.

As someone whom has fiddled around with building my own batteries for bafang/tsdz2 conversions and would love to do this for my own oem built turn key emtb's... the answer for me is no. I know enough to do it in theory, but the uncertainty of the bms compatibility and the locked nature of the firmware on these motors is enough to stop me from trying.

It's one of those situations where if you have to ask, you likely don't know enough and aren't ready to plow forward down a path with absolutely no historical information or guides to accomplish it. On the flip side, provided you have the right scopes/tools (I'd estimate that I'd need about 500-700 of equipment to do it right) and have an absolute crap load of free time and patience, it could feasibly be done.

If i were truly hell bent on flying with my ebike, I would buy a transition relay and take the battery out and ship it to my hotel. Still not kosher or legal as you can't technically ship a battery with this much capacity via ups... but it would be the most feasible way to accomplish this.
 

Ura

Member
Feb 11, 2022
13
0
Ukrain
and if an additional self-made battery, connect it instead of a charger? and go like that? original batteries are expensive, self-made ones are three times cheaper
 

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