Original price was: £240.90.£209.90Current price is: £209.90.
Upgrade your electric bike with the 36V 20Ah Lithium-ion Ebike Battery, built for efficiency, reliability, and extended range. With a large 20Ah capacity, this 36V 20ah battery provides long-lasting power
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More range. Same voltage. No compromises. The Battery 36V 20Ah is a high-capacity, Grade A cell downtube lithium battery pack built for 36V motor systems running between 250W and 350W — delivering 756Wh of stored energy in a compact downtube format that keeps weight low in the frame and handling balanced. Built on 4800-grade lithium-ion cells with a rated capacity of 21Ah, this 36V 20ah battery is the step up from the 15Ah format for riders who need more range per charge without changing their motor system or conversion platform. The Battery 36V 20Ah is the right choice for longer commutes, touring builds, and any rider who wants to spend more time riding and less time charging.
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, the Battery 36V 20Ah 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. For daily commuters covering longer distances, cargo riders who want reserve capacity, or touring builds where range between charges matters, the 36V 20ah battery delivers a fundamentally different riding proposition than a smaller pack.
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.
The Battery 36V 20Ah 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.
The 36V battery 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.
The discharge specification of the Battery 36V 20Ah 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. This is the discharge profile of a properly specified 36V ebike battery, designed specifically for the demands of e-bike motor applications rather than repurposed from a general lithium storage application.
The downtube format positions the Battery 36V 20Ah along the down tube of the bicycle frame using a standard mounting bracket and locking mechanism. This is 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. A rear-rack or seat-tube mounted battery at the same weight would shift the centre of mass significantly higher and further rearward — the downtube position avoids both of those handling compromises.
The 36V 20ah battery 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. For a direct capacity comparison, the Battery 36V 15Ah is the lower-capacity alternative for builds where frame clearance or weight is a priority. For the complete range of downtube, triangle, and alternative format battery options across all voltages, visit the Batteries category page.
The integrated Battery Management System in this 36V ebike battery monitors and protects every cell in the pack across every charge and discharge cycle. Overcharge protection prevents any cell from exceeding 42.0V. Over-discharge protection enforces the 30.0V cut-off to preserve cell chemistry. Temperature monitoring limits current under thermal stress conditions. Cell balancing during charging ensures every cell in the series string reaches the same state of charge, preventing capacity divergence and premature ageing of individual cells. 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.
The Battery 36V 20Ah 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, so there is no risk of overcharge regardless of which supported charge rate you use.
The Battery 36V 20Ah 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.
| Spec | Detail |
|---|---|
| Compatible Motor Power | 36V 250W–350W |
| Nominal Voltage | 36V |
| Rated Capacity | 21Ah |
| Energy | 756Wh |
| Cell Type | 4800 Grade A lithium-ion |
| Cycle Life | ≥80% capacity after 800 cycles |
| Weight | ~4.8kg |
| Dimensions | 368 × 112mm |
| Standard Charge Current | 3A |
| Max Charge Current | 5A |
| Max Continuous Discharge | 40A / 40A |
| Peak Discharge Current | 100A / 100A |
| Charge Cut-off Voltage | 42.0V |
| Discharge Cut-off Voltage | 30.0V |
| Format | Downtube |
The Battery 36V 20Ah is the high-capacity 36V ebike battery for builders who need more range from their 36V conversion system. Premium 4800 Grade A cells, 756Wh of stored energy, 40A continuous discharge capability, integrated BMS protection, and 800-cycle longevity in a compact downtube format — the Battery 36V 20Ah is the correct energy source for any serious 36V 250W–350W e-bike build that demands genuine range alongside genuine reliability.
Emma Davies –
Very fast delivery!!!