Batteries (continued)

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Thursday, December 21, 2006

Batteries (continued)

[this is part 2 of 2 part blog]

In most equipment you will want to use rechargeable Nickel-Metal-Hydride batteries. For most applications these will be a better battery than the NiCads. They have no memory effect problem. You can safely substitute NiMh batteries for non-rechargeable alkalines in most equipment like toys. The main limitation these batteries have is their self discharge rate (same as NiCad's). Left alone they lose capacity fast. 20% per month may be typical. They are not good for products like TV remote controls unless you want to constantly recharge them. For digital cameras they are fantastic! You would not want to use them in an outdoor weather station located on your roof. Changing a NiMh (or NiCad) every month or two might prove difficult.

The self-discharge rate of both NiCads and Ni-Mh can be slowed by storage in a refrigerator. If they do discharge because of long term storage you can simply recharge them again to full capacity!

The last battery technology I want to discuss here is Lithium-Ion or Li-Ion. These are used in virtually all laptop computers and many cell phones. These have the advantage of a very high capacity. You don't want to purchase cheap Li-Ion batteries because with their high capacity comes the possibility they can explode or burst into violent flames. These batteries are produced under strict laws and manufacturing codes to have many safety features so by all means, purchase from well known manufacturers and not no-name knock-offs. The other thing I want you to know about Li-Ion batteries is that they also self-discharge at a mild rate of about 10% per year. The self-discharge of a Li-Ion results in a PERMANENT LOSS of battery capacity. If these batteries are for a laptop, but not in use for extended periods, you definitely want to store them in the fridge. It will be helpful to store them at 40% capacity for longer life (the discharge rate is faster at a higher total charge and if the cells falls to 0% low it will cause permanent failure so 40% is a good number).

My final suggestion is to invest in a good quality charger for the Ni-Mh and NiCad batteries. Never try to charge an alkaline or Lithium non-rechargeable battery. Never use any recharger except the recharger that came with your Li-Ion battery when you purchased your equipment (or manufacturer approved replacement). When you buy a NiMh or NiCad charger look for the 'smart' type. Most types you will find in department stores are either trickle chargers or work on a timer. These are the WRONG type. It should specifically say 'smart'. Your batteries will last much longer if you get the smart type. The difference in price may be $10 for a cheapo vs. $20 for a good microprocessor smart charger with a thermal sensor. These smart chargers will also charge your cells in the minimum amount of time and do it safely. It is probably worth doing a little shopping for a good charger. There are many reviews so do a search on Google or Amazon.

There you have it. Everything the average person needs to know about using, purchasing and storing their batteries. Battery technology has come a long way since when I was small, but what you need to know has also gotten to be much more complicated. There is not one battery technology that can be used in any application, but rather a bunch of different battery technologies each with its' own benefit in different applications.

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