Seat post batteries hide your e-bike's power source inside the seat post tube — the stealthiest battery option available, giving converted bikes an almost undetectable electric assist setup.
What is a seat post battery?
A seat post battery replaces the standard seat post with a battery-integrated unit. The battery cells are housed inside the post tube, with electrical connectors running internally to the motor. From the outside, the bike looks like a conventional bicycle with the battery completely concealed.
What capacity do seat post batteries offer?
Seat post batteries are limited in capacity by the physical dimensions of a standard seat post tube — typically 36V 5–8Ah, providing 30–50 km range. They are best suited to supplementary range extension or short-commute applications rather than primary long-range batteries.
Are seat post batteries compatible with all e-bike frames?
Seat post batteries require a minimum seat tube inner diameter and sufficient seat tube length to accommodate the battery. Standard round seat tubes (27.2–31.6mm) on aluminium bikes are usually compatible. Aero, oversized, or internally routed carbon seat tubes may not be compatible.
Can I use a seat post battery alongside a frame battery?
Yes — a seat post battery can serve as a secondary range extender alongside a primary frame or rack battery. This dual-battery approach adds range without the visual impact of a larger primary battery.
How do I charge a seat post battery?
Most seat post batteries charge via a connector near the bottom bracket or under the saddle. Some models require removal from the frame for charging; others charge in-situ. Check the specific model's charging instructions for your setup.