Hailong Battery: 36V vs 48V Replacement Guide

The Hailong downtube battery is the most common e-bike battery format in the world — which is good news when it's time to replace one, because options are plentiful. But two questions trip people up: should you get 36V or 48V, and which case and connector does your bike need? This guide answers both so you order the right Hailong battery first time.

What is a Hailong battery?

"Hailong" (sometimes called a "dolphin" or downtube battery) is a standardised battery case that mounts onto a base plate along your bike's downtube. Because it's an industry-standard shape, Hailong batteries fit a huge range of e-bikes — but there are several case variations and connector types, so a replacement still has to match your specific setup.

36V vs 48V: what's the difference?

The voltage affects your bike's power and range:

• 36V — the most common choice for commuting and city e-bikes, typically paired with 250W–500W motors. Efficient and perfectly capable for everyday riding.
• 48V — delivers more power and torque, better for hills, heavier riders and higher-wattage motors. It also tends to feel punchier and can offer more range.

Why can 48V give more range? Because total energy is voltage multiplied by capacity:

Volts (V) × Amp-hours (Ah) = Watt-hours (Wh)
So a 48V 15Ah battery (720Wh) holds more energy than a 36V 15Ah battery (540Wh).

The golden rule: match your bike's voltage

Here's the crucial part: you can't simply choose 48V over 36V. Your battery voltage must match your motor and controller. Fitting a 48V battery to a bike built for 36V (or vice versa) won't work correctly and can cause damage. Always replace like-for-like unless you're upgrading the whole system.

Which voltage does your bike need?

Three easy ways to check:

• Your old battery label — it will state 36V or 48V.
• Your charger output — a 42V charger means a 36V battery; a 54.6V charger means a 48V battery.
• Your motor/controller rating — usually printed on the motor or in the manual.

For more help, see our guide to identifying your e-bike battery.

Don't forget the case type and connector

This is where many replacements go wrong. Hailong comes in several case versions (such as Hailong 1, Hailong 2, Pro and Shark), and the discharge connector varies too:

• Connector pins — commonly 4-pin, 5-pin (round gold pins or flat blade contacts) or 6-pin. These are not interchangeable.
• Base plate / mounting — the plate your battery locks onto can differ between case types.

The simplest approach: photograph your battery's connector and base plate, and count the pins, so you can match the exact type.

Shop Hailong Downtube Batteries →

Choosing your capacity (Ah)

Once the voltage and connector are sorted, capacity determines your range. Higher Ah means more miles — but a higher-capacity battery is also physically longer, so check it fits your frame's battery area. You can usually match your original Ah or step up for extra range, as long as the voltage and connector stay the same.

The charger must match too

Your charger has to match the battery voltage: a 42V charger for 36V, or a 54.6V charger for 48V. If you're staying on the same voltage and connector, your existing charger usually still works. If you need one, browse our chargers collection.

How to order the right Hailong battery (checklist)

• Voltage — 36V or 48V (must match your bike).
• Case type — Hailong 1, 2, Pro, Shark, etc.
• Connector — count the pins and photograph the plug.
• Capacity — the Ah figure, or higher for more range.
• Dimensions — make sure it fits your downtube.

For the full picture, our e-bike battery buying guide walks through every spec. Every battery we supply is UKCA/CE certified, ships free across the UK with same-day dispatch, and comes with a 30-day money-back guarantee.

Not sure which one you need? We'll match it

Send us a photo of your battery label, connector and base plate, and our team will confirm the exact Hailong battery for your bike.

Get Help Choosing →

Frequently asked questions

Can I fit a 48V Hailong battery on a 36V e-bike?

No. The battery voltage must match your motor and controller. Replace 36V with 36V, or 48V with 48V, unless you're upgrading the whole system.

How do I know if my bike is 36V or 48V?

Check your old battery label, your charger output (42V = 36V, 54.6V = 48V), or your motor/controller rating.

Are all Hailong connectors the same?

No. Hailong batteries use 4-pin, 5-pin or 6-pin connectors (and different case types), which aren't interchangeable. Match your exact connector by counting the pins and photographing the plug.

Will a higher-capacity Hailong battery fit my bike?

Usually, as long as the voltage and connector match. Just note that higher-Ah batteries are physically longer, so check it fits your downtube.

Get your e-bike back to full power with the right Hailong battery. Browse our certified Hailong downtube batteries or send us a photo and we'll help you find the perfect match.