Common E-bike Battery Capacities
Branded systems (Bosch, Shimano, Yamaha, Giant) use 36V. Aftermarket systems (Bafang) commonly use 48V or 52V. Higher voltage does not mean more energy. Compare Wh to compare actual capacity.
| Brand | Model | Voltage | Ah | Wh |
|---|
| Bosch | PowerPack 300 | 36V | 8.3 Ah | 300 Wh |
| Bosch | PowerPack 400 | 36V | 11.1 Ah | 400 Wh |
| Bosch | PowerTube 500 | 36V | 13.9 Ah | 500 Wh |
| Bosch | PowerTube 625 | 36V | 17.4 Ah | 625 Wh |
| Bosch | PowerTube 750 | 36V | 20.8 Ah | 750 Wh |
| Shimano | BT-E6010 | 36V | 11.6 Ah | 418 Wh |
| Shimano | BT-E8035 | 36V | 14.0 Ah | 504 Wh |
| Shimano | BT-E8036 | 36V | 17.5 Ah | 630 Wh |
| Yamaha | 500Wh | 36V | 13.9 Ah | 500 Wh |
| Yamaha | 600Wh | 36V | 16.7 Ah | 600 Wh |
| Giant | EnergyPak 500 | 36V | 13.8 Ah | 500 Wh |
| Giant | EnergyPak 750 | 36V | 20.0 Ah | 750 Wh |
| Bafang | Standard 48V | 48V | 13.0 Ah | 624 Wh |
| Bafang | Large 48V | 48V | 17.5 Ah | 840 Wh |
| Bafang | Performance 52V | 52V | 20.0 Ah | 1040 Wh |
What Is Wh and Why It Matters
Watt-hours (Wh) measure total energy a battery stores. It is the product of voltage (V) and amp-hours (Ah): Wh = V x Ah. Two batteries can look very different on paper but store the same energy. A 36V 17.4Ah battery (Bosch PowerTube 625) holds 625 Wh. A 48V 13Ah battery (Bafang) holds 624 Wh. Nearly identical capacity despite different voltage and Ah numbers. When comparing e-bike batteries or shopping for a replacement, always compare Wh. Ah alone is meaningless without knowing the voltage.
36V vs 48V vs 52V Systems
Branded e-bike systems (Bosch, Shimano, Yamaha, Brose, Giant) all use 36V. Aftermarket and DIY systems (Bafang, Luna Cycle) commonly use 48V or 52V. Higher voltage means the motor draws less current for the same power output, which can be more efficient and generate less heat. However, higher voltage does not automatically mean more range. Range depends on total Wh, not voltage alone. A 36V 750Wh Bosch battery provides more range than a 48V 624Wh Bafang battery despite lower voltage.
Why Chemistry Changes the Ah to Wh Sum
Amp-hours alone never told you how much energy a pack holds, and cell chemistry is the reason it is worth repeating. Watt-hours are amp-hours times volts, and the two chemistries now appearing on e-bikes have different nominal cell voltages: LFP cells are 3.2 V, NMC cells 3.6 V. Packs are built by wiring cells in series to reach the system voltage, so a 36 V NMC pack is ten cells while an LFP pack of similar voltage is twelve. The practical consequence is the one this page has argued from the start: compare watt-hours, never amp-hours, and never assume two packs with the same Ah figure hold the same energy. Which chemistry you have, and what it means for how long the pack lasts, is covered on the battery life page.
Range Extenders and Dual Battery Systems
Two batteries add up in watt-hours: a 500 Wh main pack with a 250 Wh extender gives you 750 Wh to spend, and that is the number to feed into any range estimate. There is no bonus and no penalty in the arithmetic itself, which is why watt-hours remain the only figure worth comparing across systems.
What it means for range. Extra capacity buys range in proportion to what you already had, not in absolute terms, so the same extender is worth much more on a light pack than a large one. Our e-bike range calculator makes the point with its own example: a 160 Wh extender on a 400 Wh lightweight bike is a 40 percent capacity increase and buys roughly 40 percent more range, while the same extender on a 750 Wh full power bike adds only about 20 percent. The extender itself weighs on the order of a kilogram or so, which barely moves the result next to the energy it adds.
The limits worth knowing before you buy. An extender or second battery has to be the one your motor system supports, because the pack talks to the controller and a generic battery of the right voltage is not a substitute. Systems differ in how they draw from two sources: some discharge them together, some run one down before switching, and where the manufacturer defines an order you cannot override it. You are also carrying the extra weight on every ride, including the ones where you do not need the range. Check the total against your bike's rated payload with the cargo weight calculator if you load the bike heavily.
How Battery Capacity Affects Range
A rough rule of thumb: divide Wh by 10 to 20 to estimate range in km. At 10 Wh per km (high assist, hills, heavy rider), a 500 Wh battery gives approximately 50 km. At 20 Wh per km (eco mode, flat terrain, light rider), the same battery gives approximately 100 km. Real consumption depends on assist level, terrain, wind, rider weight, tyre pressure, and temperature. For a more precise range estimate, use the E-bike Range Calculator.
Finding Your Battery Specs
An older pack will not deliver its nameplate Wh any more. Estimate what is left with the battery health estimator. Your battery's voltage and Ah are printed on a label on the battery itself or in the owner's manual. Look for a sticker with specifications. Bosch labels show both Wh and Ah. Shimano typically shows Wh. Bafang aftermarket batteries usually show voltage and Ah. If you only see Wh (e.g. "500Wh"), divide by the system voltage to get Ah: 500 Wh divided by 36V = 13.9 Ah.
Related E-bike Tools
To estimate how many seasons your battery has left based on age and usage, use the E-bike Battery Life Estimator. If your battery is showing symptoms like reduced range, charging failures, or cutoffs, the E-bike Battery Health Checker narrows the likely cause. For a realistic range estimate based on your battery Wh, rider weight, and terrain, the E-bike Range Calculator uses a physics-based model. For eMTB riders, the eMTB Tyre Pressure Calculator accounts for the extra weight of the motor and battery.
Frequently asked questions
How do I calculate capacity with a range extender or second battery?
Add the watt-hours. A 500 Wh main battery with a 250 Wh extender is 750 Wh of usable energy, and that total is what any range estimate should use. Range grows in proportion to what you already had, so a 160 Wh extender is worth about 40 percent more range on a 400 Wh lightweight bike but only about 20 percent on a 750 Wh full power bike. The extender has to be the one your motor system supports, since the pack communicates with the controller.
How do you calculate Wh from Ah?
Multiply Ah by voltage. Wh = Ah x V. Example: 14 Ah x 36V = 504 Wh. This is the total energy capacity of the battery.
Is a higher Ah battery always better?
Not necessarily. Ah must be compared at the same voltage. A 13Ah battery at 48V (624 Wh) stores more energy than a 14Ah battery at 36V (504 Wh). Always compare Wh for an accurate capacity comparison.
What is a good Wh for an e-bike?
400 to 500 Wh for city commuting (30 to 60 km range). 500 to 750 Wh for longer rides and hilly terrain. 750 Wh and above for touring and eMTB. Most mid-range e-bikes come with 500 to 625 Wh batteries.
How many Ah is a Bosch 625 battery?
17.4 Ah at 36V. Bosch PowerTube 625 = 36V x 17.4 Ah = 625.4 Wh (rounded to 625 Wh).
What voltage is best for an e-bike?
36V for branded systems (Bosch, Shimano, Yamaha). 48V for aftermarket and higher-power setups. 52V for maximum performance (higher top speed and hill climbing torque). Higher voltage is more efficient at high power but requires compatible components.
How do I compare batteries from different brands?
Compare Wh only. Ignore Ah and voltage in isolation. A Bosch PowerTube 625 (36V, 17.4 Ah, 625 Wh) and a Bafang 48V 13 Ah (624 Wh) have nearly identical capacity despite different specs.
Battery specifications are based on manufacturer data as of 2026 and may vary by production batch. Actual usable capacity is typically 90 to 95% of rated capacity due to BMS reserves. Range estimates are approximate.
Last updated: June 2026