What battery does your motor system actually need?
Bafang, TSDZ2, hub motors — people search these expecting that the motor dictates which housing to buy. It does not. The motor sets two things, voltage and continuous current, and those set the pack. This is what each system draws and what carries it.
Short answer: no motor requires a specific battery housing. A motor sets the voltage and the continuous current; the housing only has to hold enough cells to deliver that current without sagging. So pick the motor's voltage, work out the parallel count from its current draw, and then find a case that physically fits your frame.
Why people think the motor decides the case
Because the marketing around mid-drives and hub motors talks about compatibility, and it is easy to read that as “this motor needs this battery”. What is actually being said is that the motor needs a pack of a certain voltage that can sustain a certain current. Any housing that holds such a pack will do.
Two numbers matter, and neither is the cell count:
- Voltage — set by the controller the motor ships with. 36 V, 48 V, 52 V, 60 V, 72 V. This fixes the series count: 10S, 13S, 14S, 16S, 20S.
- Continuous current — how many amps the motor pulls under sustained load. This fixes the minimum parallel count, because each cell contributes a share of the total and a pack with too few in parallel will sag, heat up and lose capacity partway through a ride.
What each system draws
| System | Voltage | Continuous draw | What that means | Typical pack |
|---|---|---|---|---|
| Bafang BBS01 / BBS02 mid-drive | 36 V or 48 V | 18–25 A continuous | A 10S4P or 13S4P pack carries this comfortably. The BBS02 pulls more current than the BBS01, so the parallel count matters more than the cell count. | 13S4P (52 cells) |
| Bafang BBSHD mid-drive | 48 V or 52 V | 30 A continuous | The highest-draw system in common use. 13S5P or 14S6P is the usual starting point — a 4P pack will run, but it is working hard and will sag under load. | 14S6P (84 cells) |
| TSDZ2 mid-drive | 36 V or 48 V | 15–18 A continuous | The most efficient of the mid-drives, so a smaller pack goes further. 10S4P or 13S4P covers most builds. | 13S4P (52 cells) |
| Bafang G020 / hub motors hub | 36 V or 48 V | 15–22 A continuous | Hub motors tolerate a single larger pack better than mid-drives, and a rack or down-tube case holds it without the frame constraints a mid-drive imposes. | 13S5P (65 cells) |
| Direct-drive hub (Crystalyte and similar) hub | 48 V to 72 V | 25–40 A continuous | Direct-drive motors are heavy and current-hungry. Go up a housing size rather than a parallel count — the pack wants volume, not more columns. | 20S5P (100 cells) |
Current figures are typical rather than exact — the same motor can be run at different controller settings. Treat them as the range to design for, and check your own controller's rating.
Read the parallel count, not the cell count
The common mistake is to look at total cells. A 13S8P and a 16S6P are both 96 cells, but the first gives 8 cells sharing the current and the second gives 6. On a 30 A motor that difference is the difference between a pack that holds its voltage up a hill and one that does not.
Series is fixed by the voltage you want and you have no choice about it. Parallel is the free variable, and it is the one that should be set by the motor's current draw. Once it is set, the cell count follows and only then does the housing matter.
Then pick the housing that holds it
| Format | 18650 ceiling | 21700 ceiling |
|---|---|---|
| Hailong | 117 | 80 |
| Downtube | 200 | 160 |
The pack calculator takes the voltage and the parallel count and lists every housing that will take the result, with the room each one leaves for the BMS. If you already know the pack layout and need a length, the size finder works from that instead.
The one thing that will catch you out
Whatever motor you run, the BMS is the part that spoils the fit. A 13S board is longer than the 10S one these moulds were designed around, and a 20S board is longer again. A pack that fits on cell count alone can still fail to close. Allow roughly six cells of room beyond the pack. There is more on this in why your 13S5P pack will not fit.
Common questions
Does a Bafang motor need a specific battery case?
What battery does a Bafang BBSHD need?
What is the difference between 4P and 5P on the same motor?
Can I use a 52 V pack on a 48 V motor?
Tell us the motor and the range you need
We will work out the pack — voltage, parallel count, cell count — and then the housing, and say if nothing in the range fits.