cengland0 wrote:Your math may be correct but you didn't account for a couple other factors:
1. Cost of electricity to charge the batteries.
2. Inconvenience factor to have to wait for the charge cycle to complete.
3. Regular batteries have been engineered to have a low-toxicity so they can be thrown away and put into the landfill. Rechargeable Nicads have cadmium, and NiMh are less toxic than Nicads, but it is still recommended that they be recycled instead of thrown away.
4. The shelf-life of a rechargeable is horrible. Put one in a clock that requires a AA battery and it will be dead in 30 days but an Alkaline will last about a year.
5. The voltage is only 1.2V (or 1.25) for rechargeable and 1.5 for regular. This voltage difference can cause some devices to not function -- especially when they require 8 of them to make 12 volts. For example, there are some 5W Walkie-Talkies that require 10 rechargeable or 8 Alkaline and then you insert dummy batteries to take up the rest of the space.
6. When you have several rechargeable batteries and some go bad, it's hard to tell if the battery needs charging or is dead and needs replacing. So after sorting through a bucket of Alkaline batteries, I can test them and if they are low in energy, I throw them away. If I test a rechargeable and it shows bad, do I throw it away or charge it -- I find myself charging up dead batteries only to find it's still not charged and I don't notice until the device doesn't work and I then get frustrated.
I'm sure there's more I could add but I've already typed enough for now.
Electrical Engineering faculty hat on.
Now, let me correct a few things. My doctorate was actually in energy storage, batteries specifically. And I would be specifically talking about the latest generation of NiMh batteries (like the Sanyo Eneloop).
1) The cost for charging a battery in terms of electricity is negligible, even over the lifetime of the batteries. In pennies.
2) Eneloops can be charged at high C (high capacity-current) with little to no degradation. Charging time can be as little as 30 minutes to reach over 80% of its capacity. Full charge can be as little as 2 hours. That's also negligible.
3) Low toxicity, in high quantity, becomes high toxicity. Alkaline batteries' chemistry is not very toxic any more, but it's also VERY stable and the half life is very long. Cumulative toxicity can become significant. When NiCad or NiMh are recycled, the materials are REUSED and do not leak into the environment in any form. And on top of that, there is a lot of waste with single-use batteries (packaging and the packaging of the battery cells itself). Those also go into landfill. Overall, I did some calculations, that Eneloops far surpass ANY single use batteries in environmental impact by over 100x.
4) The shelf-life for Eneloops is not horrible at all. And the time-dependent degradation is very low. After 3 years, 80+% of the capacity is left, AND the overall capacity has hardly diminished. The sitting, usable shelf-life for Eneloops is well over 5 years.
5) As for voltage, for low drain devices, your argument is very true. But most high drain applications would have a lot of ohmic drop for the alkaline batteries due to higher internal resistance. Eneloops' internal resistance is about 1/20th of an alkaline battery during high drain, making them to have identical terminal voltages. The only applications (low drain) that I would still recommend alkaline use would be something like a smoke detector, a clock etc. Those are low drain applications. Any toy with motors, any lighting, any communications related applications, rechargeables win by a very large margins. No contest in terms of cost and longevity.
6) If one invests ONCE is a La Crosse or any other slightly more advanced battery chargers (less than $50), all of them can detect "bad" or "unrecoverable" batteries. It takes less than 5 seconds to run that test.
In short, I highly recommend Eneloops (as of this moment in time). It is the most economical energy storage choice for consumer, it is the most green, it is also the most reliable and performs far better than alkaline in high drains applications. With a thorough calculation on cost and benefits, there is absolutely no contest. And Eneloops have been tested, by multiple independent institutes, that they can be recharged over 1000 times, and still retains 85%+ of its initial manufacturing capacity.
I hope this is helpful to many Wooters.