36V Replacement Battery for SY25-II Mountain Electric Bike

Choose Your Capacity: 13Ah or 15.6Ah | A+ Grade Cells | 30A Intelligent BMS | XT60 Connector | Charger Included | 30-Day Warranty

Choose Your Battery Capacity

36V 13Ah: Daily commuting & casual riding — 4.3 kg

36V 15.6Ah: Long distance & demanding mountain terrain — 5.5 kg

Select your preferred capacity before adding to basket.

Technical Specifications: 36V 13Ah

Technical Specifications: 36V 15.6Ah

Restore or upgrade your SY25-II Mountain Electric Bike with this high-performance 36V lithium battery from Battery King. Available in two capacity options: choose the 13Ah for reliable like-for-like replacement, or go for the 15.6Ah for significantly extended range and more confident performance on demanding mountain terrain. Built with premium A+ grade EVE cells, an intelligent 30A BMS, and supplied with an XT60 connector as standard no adapter needed for your SY25-II.

13Ah vs 15.6Ah: Which Should You Choose?

Choose 36V 13Ah if you:

• Need a direct like-for-like replacement for your SY25-II Mountain Electric Bike
• Ride mostly on flat or moderate terrain with regular charging access
• Want a lighter battery option for your SY25-II e-bike
• Do shorter daily commutes or casual weekend rides

Choose 36V 15.6Ah if you:

• Want more range per charge on your SY25-II Mountain Electric Bike
• Tackle demanding hills, trails, and longer mountain routes regularly
• Want to reduce how often you charge your SY25-II e-bike battery
• Need stronger, more consistent power output on challenging terrain

Why Replace Your SY25-II Mountain E-Bike Battery?

Replace your SY25-II electric bike battery immediately if you notice:

• Noticeably reduced range on your SY25-II Mountain Electric Bike
• Slower acceleration or reduced assist power on climbs
• Battery draining significantly faster than usual on your SY25-II
• E-bike cutting out unexpectedly during SY25-II mountain rides
• Battery no longer holding a full charge on your SY25-II electric bike

Advanced 30A BMS, Full Battery Protection

Both the 13Ah and 15.6Ah versions include a full intelligent 30A Battery Management System:

• Overcharge protection — automatically stops charging when SY25-II battery is full
• Over-discharge protection — prevents deep discharge damage to your e-bike battery
• Overcurrent protection — prevents damaging current surges to your SY25-II battery cells
• Short circuit protection — keeps your SY25-II electric bike battery and wiring fully safe
• Overheat protection — monitors temperature to prevent heat damage during charging and riding

Key Features

• Available in 13Ah and 15.6Ah — choose the right capacity for your SY25-II e-bike
• Premium A+ grade 2600mAh EVE cells — outstanding lifespan and stable power output
• 30A intelligent BMS — full multi-level protection for your SY25-II electric bike battery
• XT60 connector included as standard — plug and play fit for your SY25-II mountain e-bike
• Wide motor compatibility — supports 200W to 750W motors (13Ah) and up to 1000W (15.6Ah)
• LED battery indicator — monitor real-time charge status during SY25-II e-bike rides
• Anti-theft lock — 2 keys included to secure battery to your SY25-II mountain bike frame
• USB charging port — charge your phone or accessories on the go during SY25-II rides
• On/Off power switch — preserve charge when your SY25-II electric bike is not in use
• Hailong-style durable casing — reinforced aluminium for impact resistance on mountain terrain
• UKCA, CE, UN38.3 and MSDS certified — fully compliant for UK e-bike use
• Charger included — 48V 3A powerful charger supplied with every SY25-II battery order

Package Includes

• 1 x 36V Battery (13Ah or 15.6Ah) for SY25-II Mountain Electric Bike
• 1 x 48V 3A Powerful Charger
• 2 x Security Keys
• 1 x 5-Pin Discharge Cable with Base (XT60 Connector — Default)
• 1 x Mounting Plate 
• 1 x Instruction Manual

Connector Information

Comes with an XT60 connector as standard ready to plug directly into your SY25-II Mountain Electric Bike without any adapter required. If you require an Anderson to XT90 adapter instead, please contact us before ordering and we can advise on the correct option for your setup.

Important Notes

• Always confirm your SY25-II Mountain Electric Bike uses a 36V battery system before purchasing
• Select your preferred capacity — 13Ah or 15.6Ah — before adding to basket
• XT60 connector is supplied as standard.
• Do not expose battery to water, extreme heat, or direct sunlight during storage
• Always charge in a well-ventilated area and never leave unattended while charging
• Contact us for compatibility guidance before purchasing if unsure