10S4P battery case — 40 cells, 36 V
A 10S4P pack is 40 cells: 10 groups in series, 4 in parallel in each group. This page lists the 18650 housings that actually take it, in the order of how much room they leave for the BMS and the wiring.
Short answer: 76 of our 110 housings take a 10S4P on 18650. 73 of those leave at least six cells of room — which is the practical minimum once a 10S BMS and the wiring are in.
The pack, in numbers
| Cells | 40 |
| Nominal voltage | 10 × 3.6 V = 36 V |
| Charge voltage | 10 × 4.2 V = 42.0 V |
| Capacity (typical) | 4 × 3.5 Ah = 14.0 Ah |
| Energy (typical) | 504 Wh |
Capacity assumes 3.5 Ah per 18650 cell. Your cells will differ — the cell count and the voltage are exact, the capacity is a working figure.
Housings that take it
| Model | 18650 ceiling | Room left |
|---|---|---|
| ALX003 · Integrated | 40 | 0 |
| ALX011 · Integrated | 40 | 0 |
| ALX014 · Integrated | 40 | 0 |
| ALX006 · Integrated | 52 | 12 |
| ALX015 · Integrated | 52 | 12 |
| ALX019A · Hailong | 52 | 12 |
| ALX019B · Hailong | 52 | 12 |
| ALX029 · Integrated | 52 | 12 |
| ALX054 · Water Bottle | 52 | 12 |
| ALX068 · Hailong | 52 | 12 |
| ALX078 · Rear Rack | 52 | 12 |
| ALX079 · Integrated | 52 | 12 |
| ALX084 · Integrated | 52 | 12 |
| ALX089 · Downtube | 52 | 12 |
Showing the 14 with the most room. The other 62 are in the case selector.
Why room left matters more than the ceiling. A housing listed at 40 cells holds your pack exactly and nothing else — no BMS, no nickel, no cable exit. In practice a 10S pack needs roughly six cells of space beyond the cells themselves, because a 10S BMS is longer than the 10S board these moulds were designed around. That is the single most common reason a build that “fits” does not close. There is a longer explanation in why your 13S5P pack will not fit.
Work out your own configuration
The pack calculator does this for any series and parallel count, and the case selector takes a plain cell count if you already know it.
What 504 Wh actually gets you
The figure above is energy, not distance. A 10S4P pack on 18650 works out to about 504 Wh, which is roughly 42–63 km on low assist and 16–23 km at full assist for a 75 kg rider on mixed terrain. How far a pack will take you explains what moves that figure, and how the same configuration on the other cell format compares.
Common questions
How many cells is a 10S4P pack?
What voltage is 10S?
Which battery case takes a 10S4P pack on 18650?
Can I use a 10S4P pack in a case listed at fewer cells?
Send us the pack and we will confirm the fit
Cell format, series and parallel count is usually enough to answer the same day. If the answer is that none of our moulds fit, we will say so.