How to Recharge Alkaline Batteries
How to recharge a used Alkaline battery
The label says: “do not recharge. May leak or explode.” Yes, they may leak or explode when charged but you may charge them.
Note: This article is based on experience and experiments, and other people’s experience on charging these types of batteries. When trying to charge Alkaline batteries, always assume that they will leak and explode so, take precaution. Move anything valuable or flammable away from the cells.
By explode, we mean pop. Alkaline batteries are not life threatening when they explode. Just don’t touch it while it does and do not ingest the substance that comes out of it.
- Multitester, or volt and ampere meter
- Battery receptacle
- Alligator clips connected to wires
- DC source, like a cell phone charger
- Diodes (any diode) and/or resistors
First, assemble a circuit such where the (+) terminal of the battery is connected to the (+) terminal of the DC source. Arrange the circuit that will run 50-100mA through the battery. A combination of diodes and resistors is suggested. What I use when I charge alkaline batteries are LEDs, six of them arranged in parallel with a 5.7volts source with 600mA max current output. This arrangement runs 50-60mA through the batteries. At 50-100mA, you need to charge the cells the entire day. And what’s good with this configuration is that the voltage drops as the batteries are getting charged. You’ll never fully charge them this way but it decreases the change of a battery leak or explosion.
Use the voltmeter to monitor the voltage of the cells. When they are about to reach 1.8volts, disconnect them and wait for the voltage to drop before reconnecting. Batteries can explode or leak when they reach above 1.8volts. While it’s still below, you are safe. Check the temperature too. If it’s hot or warm, disconnect it and wait for it to cool down. Do this until the batteries gives of 1.65volts or more when disconnected.
You can charge at a very high current but you need to keep on watching the batteries using the above procedure. It speeds up the charging process but increases the risk of leaking and exploding.
Battery brands also have different reactions to recharging. Some can handle an afternoon at 150mA while others will pop. Alkaline Battery Recharging is still an experimental technology. There is always a chance of a leak whatever you do so take precautions when recharging.
Why would you still go for Alkalines and risk a leak when there are NiMH batteries? It’s because alakalines can hold their charge for up to 5 years. NiMH discharges to 0% in two months. Alakline Batteries are more reliable this way even if they only hold about 1500mAh.