Lesson: Learn the Advantages and Disadvantages of various types of batteries
Goals: Enable students to be better informed about how to purchase and manage rechargeable batteries
Main types of batteries:
Main difference is the way the battery discharges:
Rechargeable NiMH (the most common form of Rechargeable AAs) are rated by how much power they will deliver over a period of time. The HIGHER the mAh, the better...but not all batteries are created equal. Two batteries of the same rating (even of the same brand) may perform completely different:
Here are two ad scans that show the changes to the rechargeable battery industry. The first one shows how chargers have changed.
A word of warning though, even though you CAN charge a battery with a rapid charger...a slow charger is still the best way to charge your batteries:
This 2nd ad shows the impact of the Lithium Ion battery (i.e. cells phone, laptops)...lots of power...in a small package.
Notes about chargers: Not all chargers are created equal. The best charger will charge each battery individually. Unfortunately MOST chargers will charge all of the batteries with the exact same amount of electricity, which is bad and can be dangerous. SMART chargers come with a little chip to detect when the voltage (resistance) builds up in a battery and shuts off and/or switches to trickle mode. Watch out for too cheap of a charger...at the very least...it can damage the battery. Make sure if it has a NiCD/NiMh switch, that it is in the correct setting.
In the picture below, you will see three chargers. The top two are pretty basic, delivering the SAME amount of current (i.e.. charge) to all four batteries. The charger on the bottom is a much better charger because EACH battery gets it own specific, dedicated charge that is JUST right for the internal resistance of the batter, whether it be between brands or with in the same brand.
A little humor…even this young kid understands the importance of keeping the camera running...with an external battery.
This is NOT me...the story behind this picture USED to be here: http://michaelbluejay.com/batteries/.
How to get rechargeable batteries to work for you:
It is true, rechargeable batteries are lots of work. If it were just for the money savings and doing what is right for the environment, most people wouldn't bother. But today's devices REQUIRE the capacity and type of discharge possible with a NiMh or LiON battery...so it is necessary that we learn to deal with rechargeables. My recommendation is to always have three sets of batteries. Run the first set down and have the other set ready to go. If your camera is using AA batteries, the third set should be NON-rechargeable battery, preferably Lithium, so they do not loose their charge and will be ready to go. The next section talks about a brand new battery that is making rechargeable batteries much more mangeable.
The Good News:
In the last 3 years, a brand new rechargeable battery has emerged called Eneloop. It's claim to fame is reduced self discharge. Normal NIMH batteries are pretty much useless after about 2 weeks. This was always a challenge for rechargeable batteries as people shopping for batteries tended to need them to work as soon as they buy them, not a day later after they have charged for 12 hours. Normal rechargeable batteries were always dead on the shelf at the store and immediately needed to be charged before their first use.
The Eneloop batteries are designed to be useful straight off the shelf at the store...and capable of sitting on a shelf for months with 90% of their capacity after 6 months. For more info: http://www.eneloopusa.com/
Eneloops Local Vendors:
"Ready To Use" batteries are now being made by other vendors.
http://michaelbluejay.com/batteries/ - good overall guide to all of the types of batteries
http://www.batterymart.com/ - a good source for rechargeable batteries
http://www.climber.org/gear/batteries.html - a discussion of battery life
http://candlepowerforums.com/vb/showthread.php?t=79302&page=1&pp=30 - NiMH battery Shootout...a comparison of batteries. This a very active forum that regularly tests the latest batteries produced by various companies and how they compare to each other.
http://www.imaging-resource.com/ACCS/BATTS/BATTS.HTM - outdated...but a good explanation of how and why batteries vary.