2 Packs 20v 4.0Ah Battery Replacement for Worx 20v Battery WA3525 WA3520 WA3575 WA3578

What It Is

This is a pair of aftermarket 20V 4.0Ah lithium-ion batteries designed to replace Worx’s WA3525, WA3520, WA3575, and WA3578 packs. They power any Worx 20V tool or lawn mower that uses the standard slide-on battery platform, including the WG779, WG780, and WG790 series mowers.

Fitment & Compatibility

• Exact OEM replacements for: WA3525, WA3520, WA3575, WA3578.
• Fits all Worx 20V tools with the common slide-on battery mount (check your tool’s battery slot shape).
• Does NOT fit Worx 40V or 56V platforms, or older 18V/24V systems.
• Physical size: 5.2 x 3.1 x 2.6 inches – verify clearance in your mower’s battery compartment.
• Aftermarket – not made by Worx, so no warranty or tech support from Worx.
• Check mower model: Works with most 20V Worx mowers (e.g., WG779, WG780, WG790, WG791) but not with the 40V or 56V lines.
• Charger compatibility: Uses the same Worx 20V charger as the original packs (included with your mower/tool).

Key Things to Know

• Capacity: 4.0Ah per battery – good for ~30–40 minutes of mowing on a small lawn (depends on grass conditions and mower model).
• Installation: Slide on until it clicks – no tools needed.
• Quality note: Aftermarket cells may have slightly lower runtime or degrade faster than genuine Worx packs. Check reviews for long-term reliability.
• Indicator light: Some packs have a push-button charge level indicator; if yours doesn’t, use the mower’s battery gauge (if equipped).
• Storage: Store at room temperature, avoid full discharge for long periods.

Should You Buy It

Buy this if you need a budget-friendly spare set for a 20V Worx mower or trimmer and don’t mind aftermarket reliability trade-offs. It’s a decent value for light-to-moderate use, but for frequent heavy mowing or professional work, stick with genuine Worx batteries for consistent performance and warranty support.