Post by thread:[PICLIST] PIC & batteries

Hi, I am going to use a PIC on a battery supplied card. I do not know what are the possible batteries to choose, what are the differences and what is mean life time of the battery (the order of magnitude). I imagine there are so many possible batteries and that the lifetime of the battery heavily depends on the application. In this application the PIC needs to ''know'' the time thus there will be either a RTC chip or the PIC will be used as clock. Do you have an idea of what is the order of duration for some ''standard'' batteries for this problem? Thanks and Best Regards, Andrea. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

When faced with such a question I usually reach for my DigiKey catalog. All their batteries have the mAH and voltage ratings. First you need to give us an idea of what your power requirments are going to be and whether you have any preferences as to battery type and number. Would you like to use 4 AA cells? Two lithium watch batteries? An N or other camera battery? Are you planning on using a regulator? What current will your circuit require? Is there a voltage requirement as well, or can we assume the 3-5.5V range of a PIC? For instance, http://rocky.digikey.com/USCatalog/V3/554.PDF shows some carbon-zinc and alkaline batteries. The alkaline AA is rated as lasting 170 hours on a 100ohm load. This is 15mA for 170H, or 2.55AH (ie, if you could safely draw one amp from it - it would last for 2.55 hours). Its highest rated drain is 130mA, so you shouldn't draw more than that. This is your first check - find your current drain, and then look at batteries that can deliver that rate. Once you've done that you need to determine how long you want the product to last. If it takes 20mA, and you need it to last for 5 days, then you need 20mA for 120Hrs. This is 2.4AH, so 4 AA batteries would be able to meet your needs. -Adam Andrea Aizza wrote: {Quote hidden}> > Hi, > > I am going to use a PIC on a battery supplied card. I do not know what are > the possible batteries to choose, what are the differences and what is mean > life time of the battery (the order of magnitude). I imagine there are so > many possible batteries and that the lifetime of the battery heavily > depends on the application. In this application the PIC needs to ''know'' > the time thus there will be either a RTC chip or the PIC will be used as > clock. Do you have an idea of what is the order of duration for some > ''standard'' batteries for this problem? > > Thanks and Best Regards, > > Andrea. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> Hi, > > In this application the PIC needs to ''know'' > the time thus there will be either a RTC chip or the PIC will be used as > clock. Do you have an idea of what is the order of duration for some > ''standard'' batteries for this problem? > Hi Andrea, the parameters for your battery are fairly easy to calculate once you have an idea of how much current your application might consume. If you PIC has not much more to do than counting time using an interrupt routine then your current needs might well be under 10 microamps, even 2 microamps are possible with a 3V supply. A not too bad 1.5V alkaline battery can have a capacity of up to 1000mA/h. Using 2 of them for example gives you 3V at 1000mA/h. Your lifetime in hours is then CAPACITY divided by CURRENT e.g. 1000mA/h --------------- = 500.000 hours ( or 100.000 hours at 10 microamps ) 2 microamps Fairly easy. Isnt it? Germain Morbe -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Check these sites http://www.duracell.com/OEM/index.html or http://data.energizer.com/ Bill Jacobs Andrea Aizza wrote: {Quote hidden}> > Hi, > > I am going to use a PIC on a battery supplied card. I do not know what are > the possible batteries to choose, what are the differences and what is mean > life time of the battery (the order of magnitude). I imagine there are so > many possible batteries and that the lifetime of the battery heavily > depends on the application. In this application the PIC needs to ''know'' > the time thus there will be either a RTC chip or the PIC will be used as > clock. Do you have an idea of what is the order of duration for some > ''standard'' batteries for this problem? > > Thanks and Best Regards, > > Andrea. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

We have found lithium primary batteries to be very good (as have digital camera makers). They have low self-discharge, which means long shelf life, low internal resistance, which means you can get several amps for a few milliseconds every couple of hours and still last for years. The digital camera guys have built up the volume so that drugstores stock them (at a pretty hefty price), but if you buy boxes of a hundred from a distributor, they are much more reasonably priced. The discharge curve is flat enough that you can run a PIC off one without a regulator and still suck out just about all the juice it has to offer. On many batteries, the last half of those rated mAH comes at such a low voltage that you can't get a processor to run off them. Our most common is DL123 which is 1/3A size, for about $8-9 at the Walgreen's next door or around $3 from a distributor. They go from around 3.2V new to about 2.1V flat dead, and will deliver as much as 10A. 10A sacrifices some mAH to internal resistance, but an amp or two can be had without significantly decreasing the total capacity (though of course you will use it up pretty quickly). We routinely run radios for 5 years, where the PIC sleeps most of the time and wakes up several times a day to turn on the radio and send a 30 mS message. > {Original Message removed}