About this battery system
STIHL AK is a cordless garden-equipment battery family intended for compatible homeowner tools. AK and the professional AP system are distinct despite both being described as 36V systems.
AK and AP packs are not interchangeable merely because both are nominally 36V.
Manufacturer-supported example specifications below; individual tool fitments and Amazon availability still require checking.
Battery chemistry, cells and energy
Lithium-ion; specific cell format is not verified here.
Energy (Wh) = nominal voltage (V) × capacity (Ah). Divide by 1,000 for kWh. These are nominal estimates, not measured usable energy or guaranteed runtime. A 90Wh pack is 0.09kWh; at an illustrative constant 90W load, ideal runtime would be one hour before losses. Real power tools draw variable power.
Verified example pack part numbers and capacities are being researched for this system.
Technical reference: Manufacturer documentation ↗. Manufacturer specifications are not Amazon price or stock verification.
Choosing a replacement battery
Platform family is an initial research grouping, not a verified fitment for every tool or generation. Check exact tool model, battery part number, connector and charger compatibility. Do not assume matching voltage means interchangeable.
Genuine manufacturer packs
Look for the manufacturer's exact part number, supported charger and capacity in Ah.
Search genuine packs on Amazon UK ↗Third-party compatible packs
Check model-specific compatibility, seller identity, independent safety evidence and warranty.
Search compatible packs on Amazon UK ↗Safety and fitment
Avoid modified adapters and unverified packs; confirm BMS, protection, charging requirements and product safety documentation. Never assume that matching voltage, similar colour or an advertised adapter makes two packs interchangeable. Stop using swollen, damaged or overheating packs.