Replacement 4.0Ah 40V Battery for Kobalt 40V Battery MAX 2540C-06, Compatible with KB640-03 KB540C-06 KB440-03 KB245-06 KB240-06 KB540-06 KB2540C-06 Cordless Tools

What It Is

This is a replacement 4.0Ah 40V lithium-ion battery for Kobalt 40V MAX cordless lawn mowers, string trimmers, blowers, and other outdoor tools. It powers machines that use the Kobalt 40V platform, giving you runtime for medium-sized yards (up to ~1/3 acre depending on tool and load).

Fitment & Compatibility

Check your tool model number – this battery is compatible with Kobalt 40V MAX tools listed in the title: KB640-03, KB540C-06, KB440-03, KB245-06, KB240-06, KB540-06, KB2540C-06, and others using the same slide-on 40V interface. It will NOT fit older Kobalt 24V or 80V tools – verify the voltage and connector shape (rectangular slide mount with two rails). Measure the battery compartment on your mower or tool: this battery is roughly 6.5" x 4.5" x 3.5" – confirm clearance if your tool has a tight battery bay. This is an aftermarket replacement (not OEM Kobalt), so it may have slightly different plastic molding or label, but the connector and voltage are matched.

Key Things to Know

• Quality varies – at 4.2 stars from 36 reviews, expect decent performance but possibly shorter lifespan than OEM. Some users report cell degradation after 1-2 seasons of heavy use.
• Installation is simple – slide the battery onto the tool’s mount until it clicks. No tools needed. If it doesn’t lock in place, check for debris or a damaged latch.
• Charger compatibility – works with any Kobalt 40V charger (model KRC-40 or similar). Do not use with 24V or 80V chargers.
• Common gotcha – aftermarket batteries may not show full charge level on OEM tool indicators. Monitor runtime manually the first few uses.

Should You Buy It

Buy this if you need a budget-friendly spare or replacement for your Kobalt 40V tool and don’t mind slightly lower build quality than OEM. It’s a good option for occasional use or as a backup battery, but for daily heavy mowing on a large lawn, consider spending more for an OEM Kobalt battery for longer life and consistent performance.