Handling your 9V rechargeable battery inappropriately may not end well. You may even see the worst-case scenario– as inappropriate charging can kill your battery in as little as a few hours.
Exposing your battery to too high a charge voltage causes its premature aging. Here’s how it happens. Excessive current flows into the battery, the water in the electrolyte decomposes and the battery heats up.
This is the process called thermal runaway and it can destroy your battery.
To stop this from happening, choose a charger with the right voltage.
Ideally, opt for quality chargers with an integrated microprocessor control unit. They are less likely to heat up and burn your hands.
Now, below is a breakdown of how to safely recharge a 9V battery with 8.4 nominal voltage. There are ways to do it even with a 5V charger, however, you’ll be able to charge it only up to 5 volts.
Similarly, you can charge a 9V battery with a 12V charger, and we show it in more detail below with Lithium-ion and NiMH batteries.
The 9V li-ion battery is made of two 3.6V cells lending it a nominal voltage of 8.4. To safely recharge it you need a voltage source of 8.4V. To regulate your 12V source to 8.4V you’ll need a variable voltage regulator (such as the LM317T).
The rest is down to the Battery Management System (BMS) inside the 9V li-ion battery. It will automatically stop the charging once each cell voltage reaches 4.2V and the battery is full.
Next, this is how you charge a 9V NiMH battery with a 12V charger. The battery consists of seven 1.2V cells and has a nominal voltage of 8.4V. To recharge it safely, you need to figure out the capacity of your battery in Ampere/hour C.
“Assuming your battery capacity is 500mA/h, you need a current of 50mA to recharge it. A simple resistor R will be adequate to design a crude current source from your 12V source.
For this to happen you need to interpose 75 ohms and place a 1/4 watt resistor between your 12V source and your 9V battery.” Réal Morrissette, Electronic Engineer Research & Development at Intelligent Technologies
How Long Does It Take to Recharge a 9 Volt Battery?
It depends on the charger, the battery chemistry, and the battery brand. Yet, it will take you an average of 8 hours to charge a dead 9V rechargeable battery to its full capacity.
Is There a Difference In 9V Batteries?
9V rechargeable batteries are available in different chemistries. Yet, Nickel Metal Hydride (NiMH) and lithium rechargeables are most commonly found at the sellers.
Much depends on the battery chemistry. It plays in and determines how fast you’ll be able to charge the battery. It also affects the three major quality attributes of rechargeable batteries:
- Battery run time. This stands for how long a battery lasts in a single use.
- Shelf life. This refers to the lifespan of a battery while still on the “shelf.”.
- Cycle life. Denotes the number of times you can charge and discharge a battery before it goes bad.
The table below will help you compare NiMH and lithium at a glance.
||Battery Shelf Life
||Battery Cycle Life
|Nickel Metal Hydride (NiMH)
||Slow charging: 12–36 hours
Fast Charging: 1 hour
|-4°F to 122°F
||Slow charging: variable
Fast Charging: 1 hour
|40°F to 140°F
Unlike Lithium ions where you can set a maximum charge voltage while charging, NiMHs are charged by forcing current through the battery.
That said, if you settle for a NiMH battery pack, make sure it includes a BMS. This will prevent it from overcharging and damaging the battery’s cycle life.
Which Is the Best 9V Battery?
I-Power 9V 800mAh Li-Polymer Rechargeable Battery
I-Power 9V Li-Polymer Rechargeable Battery is ideal for use in high powered devices and has a wide application in the sound and audio niche.
It’s a high-performance battery with a working voltage of 8.4V~6.5V and 800mAh capacity. This battery pack is designed with safety and longevity in mind. The Build-in Protection IC system safeguards it from over-current and ensures maximum cycle life.
To increase the battery’s lifespan, stick to the manufacturer’s guidelines:
- Charge it with iPowerUS 9V Fast Smart Charger only; other chargers may shorten its life.
- Make sure you fully recharge it before storage.
- Recharge it quarterly to extend its shelf life.
Energizer Industrial 9V Bulk Box of 12
Energizer Industrial 9V Batteries are alkaline batteries you can rely on both in a commercial and an industrial setting. Although single-use, you can trust them to power your high-drain devices.
Energizer Industrial batteries are a synonym for long-lasting performance and they hold power for 10 years in storage.
Knowing they come from makers of No. 1 longest lasting AA battery brings extra peace of mind.
Energizer Industrial 9V alkaline batteries boast some enviable product features. They:
- Display long-lasting power in different devices
- Perform at operating temperatures between -30C and 55C
- Feature Powerseal Technology protection, which prevents leaks for up to two years after fully used
Stryka 4 x 9V Lithium & Charger Combo
Stryka is a popular battery brand that brings advanced technology power solutions. Their batteries undergo a few months of rigorous quality testing to ensure they reach the end-user in top quality.
You can rely on Stryka 550mAh Lithium Rechargeable 9V Batteries for all kinds of applications, from mobile phones and power tolls to cameras and audio equipment.
These professional-grade batteries come at 550mAh capacity and a compatible Stryka 4 bay Lithium charger.
Recharging your 9V batteries safely saves you money in the long run. It brings you peace of mind knowing you’ve made the most of your battery lifespan. It prevents your investments from going down the drain.
9v rechargeable batteries have longer battery service than most disposable batteries. You may as well keep it that way, especially when this simultaneously means lowering your operating costs—and it does.
HBPlus Battery Specialists is Australia's largest volume distributor of Duracell and Duracell Dry Cell bulk batteries. We’re carrying rechargeable batteries from 40+ manufacturers for your convenience, featuring some of the premium brands such as Procell, Energizer and Duracell.
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