Looking at the datasheet, the voltage does drop considerably with current drain, which is typical for long-life Lithium non-rechargeable batteries. They do not show a discharge curve for anything above 20mA, but the 20mA one looks like the voltage is about 3.2 instead of 3.6, so extrapolating to 55mA we would get 2.5V as the voltage at 55mA. I have previously used the LTC3400, which is a tiny 6 pin boost switcher IC, to boost one NiMH cell up to 3.3V for an XBee module. The entire footprint of the switcher circuit is about 1/2 inch by 3/4 inch. It works very well. It DOES dominate the circuit current drain when the XBee and PIC are asleep, but it gets down to around 2 or 3mA from the input side. It actually goes into a low power mode where it turns itself off and waits until the output capacitor discharges 1% of the nominal voltage. It then turns back on and recharges the cap. Sean On Sun, Feb 8, 2009 at 12:55 AM, William Chops Westfield wrote: > > On Feb 7, 2009, at 7:33 PM, Funny NYPD wrote: > >> I'm currently using a Tadiran TL-5955 Lithium battery >> > >: >> 1.5Ah, max. pulse 150mA, 2/3AA size. >> >> I thought that this type of battery has a voltage that's rather >> independent of charge state until it is almost dead. But what I find >> is >> that the voltage under 55mA load dips below 2.8V much earlier in the >> lifetime than I expected, considering the battery capacity and the >> current consumption. > > That does seem pretty counter-intuitive; it's a 3.6V battery after > all... Have you confirmed the current draw/etc? It'd be more > understandable if you're exceeding that 155mA spec. (and have you > talked to tadiran?) > > Alternatives might include the CR2 "photo" batteries, but since those > are 3V, you'd almost certainly need a boost converter to keep voltages > above 2.8V. Or perhaps the Li-ion rechargeable CR2s, which are up > near 4V (but are likely to have much less capacity, given that they're > rechargeable.) And I think the CR2s are a bit fatter than an AA. (I > don't know that there are are "popular" 3.6V consumer batteries.) > > BillW > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist