How Long to Charge a Cordless Reciprocating Saw (20V, 4Ah)?
Charging a Cordless Reciprocating Saw (20V, 4Ah) from empty to full takes about 2 h 49 min with its standard 40W charger. The battery holds roughly 80 Wh, and this page estimates the time for every common charger wattage, using the Lithium-ion (Li-ion / Li-Po) chemistry it actually uses.
Charge time calculator for Cordless Reciprocating Saw (20V, 4Ah)
Estimated charge time
2 h 49 min
Includes the slower li-ion taper phase above 80%.
Charge time by charger wattage
| Charger | Power | Full charge (0-100%) |
|---|---|---|
| Standard charger | 25W | 4 h 31 min |
| Fast charger | 40W | 2 h 49 min |
| Ultra-fast charger | 65W | 1 h 44 min |
Battery capacity: 80 Wh · Chemistry: li-ion
The high-capacity lithium-ion battery in this reciprocating saw is engineered to handle extended cutting sessions without frequent interruptions. When tackling demanding pruning or demolition projects, the battery's robust energy density means you can work through multiple sections of thick branches or structural materials before needing a swap. To maintain peak performance over the life of the saw, develop a charging routine that avoids letting the battery completely deplete before recharging—lithium-ion chemistry responds best to regular top-ups rather than waiting for the power to fade entirely. This approach keeps the internal cell structure stable and extends your battery's working lifespan considerably.
Storage conditions play a crucial role in protecting your investment during off-seasons or extended breaks between projects. Keep your charged batteries in a cool, dry environment away from direct sunlight and moisture, as lithium-ion cells are sensitive to temperature extremes that can degrade their ability to hold a full charge. If you plan to store the saw for several weeks or months, charging the battery to a moderate level—rather than leaving it fully depleted or completely full—creates the ideal dormant state. Additionally, never store the tool with the battery engaged in damp basements or near corrosive materials; the electrical contacts must remain clean and dry to ensure safe, efficient charging every time you're ready to work again.
With the fastest charger listed here (Ultra-fast charger, 65W) it takes about 1 h 44 min. With the slowest (Standard charger, 25W) it takes about 4 h 31 min. This high-capacity battery supports extended cutting tasks for pruning branches and demolition work.
Frequently asked questions
- How long does it take to charge a Cordless Reciprocating Saw (20V, 4Ah)?
- From 0% to 100% with the standard 40W charger, it takes about 2 h 49 min. Using a faster charger shortens that; using a weaker one extends it, see the table above for exact numbers.
- Why does my cordless reciprocating saw feel less powerful after a few months of regular use?
- Lithium-ion batteries naturally experience gradual capacity decline over time with repeated charge cycles, especially if charged immediately after heavy work or stored in warm conditions. This is normal aging; however, you can slow the process by allowing the battery to cool slightly before charging and by keeping unused batteries stored in a moderate temperature environment rather than in a hot garage or workshop.
- Can I use multiple batteries and rotate them to extend my working day?
- Absolutely—having a second battery on rotation is an excellent strategy for long demolition or pruning jobs. While one battery is charging, you can continue working with the other, keeping your project momentum going. Just ensure both batteries are stored properly between uses and that your charger is designed to handle sequential charging without overheating, as back-to-back charging cycles generate heat that affects lithium-ion longevity.
- How is this charge time calculated?
- We divide the energy needed (80 Wh times the percentage you're charging) by the charger's effective power, which is the charger's wattage times the battery chemistry's real-world charging efficiency (85% for Lithium-ion (Li-ion / Li-Po)). The same formula powers both this page and our API.
ChargeTimeCalculatorestimates are based on typical charger efficiency and battery chemistry, not a live connection to your device. Always follow your manufacturer's charging guidance.