Battery 36V 20Ah — High Capacity Downtube eBike Battery

756Wh — Significantly More Range Than the 15Ah

The step from 15Ah to 20Ah capacity represents a meaningful real-world range increase for any 36V conversion system. Where the 15Ah pack delivers 468Wh of energy, this battery stores 756Wh — a 61% increase in energy capacity with no change to the motor, controller or voltage platform. For a 250W–350W motor system consuming an average of 15–20Wh per kilometre under mixed conditions, that translates to an estimated range of 37–50km per charge, compared to 23–31km from the 15Ah equivalent.

This extra capacity comes in a pack that is physically only slightly larger than the 15Ah format — 368 × 112mm versus 368 × 92mm — sharing the same length and fitting within the same downtube mounting bracket footprint on most frames. The additional 20mm in width accommodates the larger cell count, and the weight increases from approximately 4.4kg to 4.8kg — a modest difference that is imperceptible in ride feel at this battery location.

4800 Grade A Cells — Premium Cell Chemistry

This battery is built on 4800-grade lithium-ion cells — a premium cell specification that delivers higher energy density per cell compared to standard 18650 formats, enabling the pack to achieve 756Wh within the compact downtube form factor. Grade A cell selection means every cell in the pack is manufactured to tight internal resistance tolerances, ensuring the BMS can balance the pack effectively across every charge cycle and that all cells age at a consistent rate.

The cycle life specification confirms this quality — ≥80% capacity retention after 800 full charge cycles. That is 800 full cycles at 756Wh per cycle before the pack drops to 80% of its original capacity. Under typical riding patterns, most riders will experience significantly longer practical service life.

Voltage Window — From 42V Full Charge to 30V Cut-Off

The 36V nominal voltage represents the average operating voltage across the discharge curve between full charge and cut-off. At full charge, the pack sits at 42.0V — the point at which the BMS terminates charging to protect cell chemistry from overcharge stress. At the bottom of the discharge curve, the BMS enforces a 30.0V cut-off to prevent cell damage from deep discharge. The entire 756Wh of stored energy is delivered within this operating window, with the motor receiving a gradually declining voltage as the pack discharges — a normal characteristic of lithium-ion chemistry that the motor controller manages without issue.

Discharge Current — 40A Continuous, 100A Peak

The discharge specification of this battery is built for motor applications, not general-purpose use. A 40A continuous discharge current sustains full output from any 36V 250W–350W motor system indefinitely without BMS protection tripping or thermal stress on the cells. The 100A peak discharge current handles the high-current demand spikes during hard acceleration from a standstill — the brief, high-amplitude current pulse that a quality BMS and Grade A cells manage cleanly without voltage sag or protective shutdown.

Downtube Format — Practical, Frame-Integrated Design

This battery positions along the down tube of the bicycle frame using a standard mounting bracket and locking mechanism — the most widely compatible battery mounting format across bicycle platforms, fitting road bikes, mountain bikes, hybrid frames, commuter bikes and most custom build platforms without frame modification. The placement keeps the 4.8kg battery weight low in the frame and centred between the wheels, preserving the natural weight distribution and handling characteristics of the bicycle.

This pack shares its 368mm length with the 15Ah format, making it a direct dimensional upgrade on any frame where the 15Ah already fits. The additional 20mm width should be verified against frame clearance before ordering.

BMS — Integrated Cell Protection and Management

The integrated Battery Management System monitors and protects every cell in the pack across every charge and discharge cycle:

This active management is what makes the 800-cycle life specification achievable in real-world use — and it operates transparently, requiring no user interaction or maintenance.

Charging — Standard 3A, Fast 5A

This battery charges at a standard rate of 3A, delivering a full charge from empty in approximately 7 hours — ideal for overnight charging with gentle current that maximises long-term cell health. For faster turnaround, the pack supports up to 5A maximum continuous charge current, reducing full charge time to approximately 4–4.5 hours. The BMS terminates charging automatically at the 42.0V cut-off regardless of charger output.

Compatible Motor Systems

This battery is the high-capacity energy source for 36V motor systems in the 250W–350W range. The primary application is the BAFANG 250W mid drive BBS01B — a 36V system that operates well within the 40A continuous discharge ceiling of this pack and benefits directly from the increased range the 756Wh capacity provides. It is equally suitable for 36V hub motor conversion systems drawing within the continuous discharge specification.

For the full range of 36V, 48V and 52V compatible conversion kits across all formats and power levels, visit the Conversion Kit category page.

Warranty and Returns

Every Battery 36V 20Ah purchased from All4eBikes is covered by a 12-month warranty against manufacturing defects, alongside a 30-day return window for complete purchase confidence.