Let’s talk about the most common batteries we use every day. These are of course AA/AAA/C/D/9v and custom lithium batteries. We use them daily in electronics such as digital cameras, video cameras, toys & games, and remote controls. Buying regular alkaline batteries (non-rechargeable) can get expensive quick. Also, I’m willi
ng to bet that 98% of people don’t properly discard batteries. So all these batteries are contaminating our landfills and toxic acids are seeping into the ground. So what is the solution to this problem? Rechargeable Batteries! You can get hundreds of cycles out of modern rechargeable batteries today.
Let’s take a look at the different battery chemistries available.
Alkaline – Alkaline batteries get their name from the alkaline electrolyte potassium hydroxide. The capacity of an alkaline battery is greatly dependent on what type of a device it is used in. One AA sized alkaline battery may contain 3000mah (milliamphours) of energy at low drain, but at high drain (digital cameras, toys, rc cars) that same battery only provides 700mah of capacity. Another important thing with alkaline batteries is that their voltage drops steadily as they are used up. A brand new alkaline battery’s voltage is 1.5v. During use this drops to 1.1-1.3v per cell. Each battery in this case is one cell. Alkaline batteries as you and I know them are non-rechargeable. Ideal use for alkaline batteries are remote controls for your TV, and other super low drain devices.
Ni-Cd – Nickel-Cadmium batteries are the first type of rechargeable batteries i will introduce you to today. Ni-Cd batteries are used individually in AA/AAA sized batteries or assembled into battery packs using two or more cells. Ni-Cd cells have a nominal voltage (operating voltage) of 1.2v per cell. If you remember alkaline batteries had a 1.5v voltage. This 1.5v is its initial voltage, which drops as the battery becomes more used. Ni-Cd batteries only drop a tiny amount in voltage as they are used. Ni-Cd batteries have a relatively low self-discharge rate of 10%/month. Ni-Cd batteries can suffer from somethign called “memory effect”. This basically means that if you don’t use the energy in the battery fully and then recharge them, it will get used to this limited range. To avoid this just fully charge them and then don’t recharge them until whatever device your using it in starts complaining about low battery.
NiMH – Nickel-metal hydride batteries are newer, similar and less toxic rechargeable battery than Ni-Cd batteries. NiMH batteries can contain three times the capacity of Ni-Cd batteries, and are great in high drain devices such as digital cameras and toys & games. They also have a slightly higher self-discharge rate than Ni-Cd at 30%/month. NiMH cells have a nominal voltage of 1.2v. There are some new low self-discharge NiMH batteries available, we’ll cover those at a later time.
Lithium Battery – There are many lithium button style batteries, but today I want to showcase the AA versions. Energizer Lithium AA’s are one of the most popular, for this category. They are normally a disposable battery, but are popular because they last 4-8 times longer in high drain devices than alkaline batteries. They also have super low discharge properties, and weigh less than their alkaline counterparts. These Lithium batteries also have 1.5V per cell.
Li-Ion – Lithium-ion batteries are common in consumer electronics that required more performance than just regular AA’s. They can be found in custom shapes and sizes that are best suitable for the device in mind. Li-Ion batteries also don’t have the memory effect that Ni-Cd batteries have. Li-Ion batteries have a nominal voltage of 3.7v. They also offer a very low self-discharge rate of 5-10%/month. If overheated or overcharged Li-Ion cells can heat up and even have cells rupture, and in some cases catch fire. Li-Ion batteries last longer if they are frequently charged vs run all the way down to empty. They should not be stored in full discharge state. If the voltage drops below 2.4 to 2.9v per cell it won’t accept a charge anymore.
Li-Po – Lithium Polymer batteries, are another type of lithium battery but doesn’t normally come in a hard plastic case as lithium ion batteries. They are very popular in the RC (Remote Control) industries. Instead of being placed in metal or plastic hard shells, they normally are manufactured in pouches. Pouches allow the batteries to expand slightly when they are under large load. Li-Po batteries can be found with ratings of 20-60C. This means they can be discharged at 20-60 times their capacity per hour. Fully charged Li-Po’s are 4.23v per cell. Their nominal voltage is 3.7v per cell. Packs range from 1-8cells. Normally they are wired in series, to increase voltage for whatever application they are manufactured for.