Storage Guide: 50% State-of-Charge & Cool, Dry Places

When you're not riding your e-bike for an extended period—whether it's for a long vacation, a seasonal break, or a cold winter—improper storage is one of the fastest ways to kill your battery. The key to preserving its capacity and maximizing its lifespan is to understand and adhere to the $50\%$ State-of-Charge Rule and the Cool, Dry Place Rule.

This guide provides the simple steps you need to take to ensure your battery is in its most stable and lowest-stress state while in storage, guaranteeing it's ready to go when spring rolls around.

The $50\%$ State-of-Charge Rule (The Chemical Sweet Spot)

For long-term storage, the battery industry recommends storing lithium-ion packs at a $40\%\text{ to }60\%$ state-of-charge. The middle ground, $50\%$, is the chemical "sweet spot."

Why Not $100\%$? (The High-Stress Zone)

• Accelerated Degradation: Storing a battery at $100\%$ charge for weeks or months places the cells under maximum internal voltage and pressure. This high-stress state accelerates the chemical reactions that cause capacity loss (aging). When you take it out of storage, it will have noticeably less total range than when you put it away.

Why Not $0\%$? (The Danger Zone)

• Risk of Deep Discharge: All batteries self-discharge naturally over time. If a battery is stored at $0\%$ charge, this self-discharge can pull the voltage below a critical threshold. Once a battery goes into "deep discharge," it can become irreversibly damaged, permanently unusable, and in some cases, unsafe to recharge.

The Fix: Aim for $50\%$

1. Check the Gauge: Before storing, check your battery's gauge. If it's near $100\%$, go for a quick ride to bring it down. If it's low, charge it up.

2. Target: Aim for your gauge to read approximately three out of five bars or right around the $50\%$ mark. This range minimizes internal voltage stress while leaving enough reserve to protect against self-discharge.

3. Periodic Check: Check the charge level every one to three months. If the charge has dipped below $40\%$, recharge it back up to $50\%$ and return it to storage.

The Cool, Dry Place Rule

Once the charge level is correct, the environment where you store the battery is equally important for both safety and longevity.

1. Temperature: Cool is Best

• Avoid the Garage: Unless your garage is climate-controlled, it is usually the worst place for long-term storage.Summer heat and winter cold in a garage can severely damage your battery.

• Best Spot: A spare closet, a climate-controlled basement, or a storage room inside your home that maintains a relatively cool, stable temperature is ideal.

2. Humidity: Keep it Dry

• Avoid Moisture: Never store your battery in a highly humid environment, like an outdoor shed, a leaky basement, or directly on a cold concrete floor. Moisture can lead to corrosion on the connectors or, worse, penetrate the casing, potentially short-circuiting the internal electronics.

3. Safety: Clear and Secure

• Off the Bike: Always remove the battery from the e-bike itself.

• Secure Area: Store the battery on a $\mathbf{non}-\mathbf{flammable}\text{ surface}$ (not carpet or wood shelving) and away from flammable materials (paper, solvents). Keep it in a location where it won't be exposed to physical impact or be a tripping hazard.

By following these simple storage rules, you are making a small effort now to ensure your high-value battery is protected against chemical aging and ready for thousands of miles of riding when you return.