dkedr 31 Posted March 5, 2012 Share Posted March 5, 2012 So I've been reading some TI propaganda, and they mention that the MSP430 can, using LPM run for 20+ years on a single battery. I'd like to know what kind of battery would last 20 years. I understand that the self discharge rates would kill the batteries well before the 20 year mark. Quote Link to post Share on other sites
cde 334 Posted March 5, 2012 Share Posted March 5, 2012 http://www.ti.com/mcu/docs/mcuorphan.ts ... lp#battery bluehash 1 Quote Link to post Share on other sites
TomKraut 17 Posted March 5, 2012 Share Posted March 5, 2012 Using an ideal 3V CR2032 Coin Cell Battery rated at 200mAh, the MSP430 offers the longest possible battery life. Seems by "ideal" they mean "theoretical, with no self discharge" Cheers TomKraut Quote Link to post Share on other sites
cde 334 Posted March 5, 2012 Share Posted March 5, 2012 http://www.eetimes.com/design/embedded/ ... ed-designs Ideal, not just theoretical. EngIP 1 Quote Link to post Share on other sites
oPossum 1,083 Posted March 5, 2012 Share Posted March 5, 2012 Lithium-thionyl chloride last for 20+ years. Not just theory - I have batteries that are 15 to 25 years old and still working. They where common for memory backup on industrial computers (PLC). They are also used in AMR (automatic meter reading) for gas and water. 20+ year lifetime is common in those applications. bluehash and dkedr 2 Quote Link to post Share on other sites
rockets4kids 204 Posted March 5, 2012 Share Posted March 5, 2012 What TI is saying here is that the MSP430 can be configured to draw less power than the self-discharge rate of the most advanced battery technologies. It is not even terribly difficult to design an MSP430 circuit that pulls less power than the self-discharge current of a CR2032 lithium coin cell, thus giving it a 10 year run-time. Not bad at all for a cheap battery. Quote Link to post Share on other sites
zeke 693 Posted March 5, 2012 Share Posted March 5, 2012 Yeah, okay, but what is it doing for those 20 years? I content that it's doing nothing... useful. oPossum and ike 2 Quote Link to post Share on other sites
oPossum 1,083 Posted March 5, 2012 Share Posted March 5, 2012 Yeah, okay, but what is it doing for those 20 years? I content that it's doing nothing... useful. I agree. It seems like even something simple like a watch would only allow a battery life of 3 to 5 years using a lithium coin cell of the CRxxxx series. There has to be power not only for the MSP430, but also for peripheral devices. The self-discharge rate is in addition to whatever power is required to do work. Drawing current equal to the self discharge rate will, in general, reduce the battery life to half. For applications that do "real work" the lithium thionyl chloride battery has enough energy to run the MCU and peripherals for 20+ years. Quote Link to post Share on other sites
dkedr 31 Posted March 6, 2012 Author Share Posted March 6, 2012 Wow I got a lot more information than I expected, thanks. I'll definitely have a look into Lithium-thionyl chloride batteries. Quote Link to post Share on other sites
cde 334 Posted March 6, 2012 Share Posted March 6, 2012 Well, a watch has to power the lcd (wait till we get eink watches) and has to read the crystal at 60khz or how ever many times per second it clicks. And Isn't the point about drawing the same as the self-discharge rate of batteries that it renders the self discharge of the battery moot? That by drawing that energy out, it's not wasted? Quote Link to post Share on other sites
rockets4kids 204 Posted March 6, 2012 Share Posted March 6, 2012 Yeah, okay, but what is it doing for those 20 years? I content that it's doing nothing... useful. The canonical long-term low-power application is metering and data-logging. If you take a look at TI's early marketing and application notes, you will see that this was one of the primary intended uses of the MSP430. It is worth noting that these devices often have no user-I/O other than the serial port for configuration and data collection. All they need to do is maintain accurite time, sample and store data. This may not be useful to *you*, but it is huge in the industrial word. Quote Link to post Share on other sites
oPossum 1,083 Posted March 6, 2012 Share Posted March 6, 2012 And Isn't the point about drawing the same as the self-discharge rate of batteries that it renders the self discharge of the battery moot? That by drawing that energy out, it's not wasted? An additional load will increase the current draw beyond the self discharge rate - it doesn't magically make the self discharge go away. The self discharge is due to internal mechanisms of the battery that can not be externally changed. The duty cycle of the load can also have a significant influence on the effective battery capacity. The specified capacity is measured under specific conditions that will not be the same as many use cases. Quote Link to post Share on other sites
GeoNomad 8 Posted March 11, 2012 Share Posted March 11, 2012 You could always use a LitroEnergy nuclear powered cell http://factlets.info/Glow.html 12-20 years and enough current to do things. But not available (yet), I think. Quote Link to post Share on other sites
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