While the ideas presented here are good, I'd have absolutely NO=20 confidence in any calculation. The only time I'd feel confident is to: 1. Purchase the exact battery that the customer will use, whatever that=20 is, and install it into the breadboard. PURCHASE is a keyword; anything you have laying=20 about is stale. 2. Subject the product to the temperature range expected. 3. Using a small A/D converter and timer (a PC application is fine),=20 monitor the battery usage. 4. When the batteries are too low to operate the product, that is the=20 end of the battery's life. 5. Do this at least 3 times, with 3 different batteries, to handle=20 normal variation. NOW you have good data; the average of the 3 is the battery lifetime. Everything else is BULL----. --Bob On 3/14/2011 5:48 AM, Sean Breheny wrote: > While there is a lot of good info in this thread, I think that you may > be confusing two different kinds of Lithium Primary cells. > > The ones which are targeted as replacements for Alkaline batteries are > Lithium Iron Disulfide. They have better high-current discharge > abilities and I believe that they are also lighter than Alkaline. New > cells have an open-circuit voltage a little above 1.5V (Wiki says > 1.8V). I do not think that they have better shelf life than Alkaline. > > The ones used for battery back-up for real-time clocks, etc., are > Lithium Manganese Dioxide. They have a voltage of about 3V and have a > shelf life several times longer than Alkaline. > > http://www.nexergy.com/lithium-manganese-dioxide.htm > > > On Mon, Mar 14, 2011 at 7:15 AM, Forrest W Christian = wrote: >> Michael Watterson wrote: >>> The Camera type Primary Lithium batteries (non-rechargable) may not be >>> the same kind as used in Memory/Clock backups, not sure. They almost >>> certainly perform better in constant low current drain than in >>> intermittent high peak current applications though. >>> >> I meant in comparison to Alkaline - and in applications where a larger >> (say AA-sized) battery would be in use. >> >> The 'rated' capacity of a Lithium AA and an Alkaline AA are nearly the >> same - about 3000mAh. However, the Alkaline can only provide that at >> the low end of the current scale - say under 50mA of load. So, if >> you're drawing under 50mA, and within normal temperature ranges, it >> doesn't seem to make any fiscal sense to use Lithium over Alkaline, >> considering Lithiums are easily 2x the price of an Alkaline. For >> better comparison between the two, the datasheet at >> http://data.energizer.com/PDFs/l91.pdf seems to do a really good job. >> >> You can also compare to the datasheet of an 'industrial' Alkaline at >> http://data.energizer.com/PDFs/l91.pdf . Of particular interest are >> the 'busty' voltage curves on this and the datasheet above. >> >> I will say that Lithiums are definitely more usable in a wider range of >> temperatures and applications. Personally, the 'Emergency Primary' >> batteries I keep in the car are almost all Lithium cells. For memory >> backup, I'd use a lithium coin any day over about anything else - except >> perhaps a supercap capacitor (1F or larger) if the amount of time for >> backup was in line with what could be stored in the capacitor. >> >> -forrest >> >> -- >> http://www.piclist.com PIC/SX FAQ& list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .