PCB Batteries

On 02/10/14 09:13, Dushyant Kumar Singh wrote:

Hello all,

I am working on a project where I have to design the PCB. In that I am

using CR2032 battery, but this is quiet large for my project. I am using

CC2541 micro controller and need of 3V batteries......Can I use watch

cell or button cell of same voltage in my project.?? Is there any

library for that.?? since I am new to this eagle....can any one suggest

me any other type of batteries.....or I have to use CR2032..??

 

You can use any cell you can find a holder for, as long as its rating

suits your application. If there isn't an existing Eagle library part

for the one you're using, you can create one. This is a standard part of

the work flow of any PCB design tool, so learn how to do it now.

so it means it depend on the holder.......I will look for it and yeah I will make the library also....

Sorry but I am unfamiliar with Eagle as I use Proteus BUT first of all, the voltage, capacity and battery chemistry are needed to be fixed before you continue.

Remember, the CR2032 is a 3V Lithium based battery but most Watch/Button batteries are only 1.5V (Alkaline or Zinc Carbon) or 1.55V (Silver Oxide).

It is hard to recommend a battery without knowing more.

I designed a product and used a leaded CR1220 which is a 12mm diameter, 2mm thick battery with leads but the leads meant it stuck up too much on the 2nd revision of my design so I then changed to a SMT CR2025 which had a larger diameter at 20mm and was 2mm thick but did not have the leads to lift it from the board.

So is your battery 'quite large' because it takes up too much 'footprint' (the amount of PCB space)?

For both I had to create a library part myself as the library did not support them but I would imagine even for a novice, this would be pretty easy and I am sure there should be examples of creating a simple library part.

I have recently done some calculations on my circuit and find that the smaller battery would only last just under a year but the bigger battery lasts about 3 years in extreme cases. Factoring in normal usage and my calculations lead me to under 2 years for the smaller battery and about 5.5 years for the larger one.

In conclusion, find out what voltage you require and the current drain on the battery. Make sure what you design in has enough capacity to last (there are lots of web sites that have expected life calculators where you enter a couple of parameters and they will tell you how long the battery will last).

Only then are you ready to load Eagle up and design in your chosen battery.

Good Luck.

thanks for your reply....ISL_DAVE

yeah like I want my pcb to be short enough only thing is the CR2032 battery holder its about 20mm large because of this I can't make my PCB short...

I will send u the .jpg image of my pcb board....

And one more thing can you help me in my project as I am making PCB and I am new in this field, I will be very thank full to you if you help me...

Hi,

You need to consider whether the battery is to be replaceable. I am guessing it does.

If not, you could consider something like the CR-2016/F2N (P222-ND from DigiKey). I use this and it is only 20mm diameter and 1.6mm thick. I place it on the opposite side of the board to my components. It has solder tags sticking out each side which add just over 5mm to the dimension.  You would just have to insulate the battery from any tracks/via's if placing on the back of a board.

You could use a smaller battery but at the expense of battery life (CR1220) but the holder from Farnell (2115306) still requires 19.5mm on the footprint.

Other options are a connector and battery pack underneath.

If you are doing the PCB you attached, you look to be doing well enough.  I am not a PCB expert but have designed quite a few. I use a different package and generally go for 4-layers.

My experience is that the CAD software forums are a great place for help and I am sure the Eagle forums are much better placed to help you out with PCB queries.

Good luck,

Dave

Something else you need to address is instantaneous current draw - lots of

these smaller batteries have relatively high internal impedance (especially

when partially discharged), so it is a good idea to have a good bypass cap

across the battery to deal with the spikes that happen with turning things

on or off or processor startup etc.  Often the caps get left off to save

space which ends up causing real problems as soon as the battery impedance

goes up as it discharges (remember the old 9v transistor radios - you could

often double or triple the battery life on the cheap ones with an

electrolytic cap across the battery terminals to keep the impedance down.

mikey

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

thank you so much for the information.....ISL_DAVE

If I have any doubt I will contact you....;)

thank you CAD SOFT