Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: pomprocker on January 13, 2009, 01:51:56 PM

Title: Coin Cells
Post by: pomprocker on January 13, 2009, 01:51:56 PM: How come I never see anyone using coin cells in their robot?

Aren't they pretty small and carry a good amount of voltage?

Couldnt I stack two coin cells and I would get the 6volts I need that I get from my 5-cell AA NiMH pack?

http://www.powerstream.com/licoin-charger.htm (http://www.powerstream.com/licoin-charger.htm)
Title: Re: Coin Cells
Post by: Soeren on January 13, 2009, 02:12:58 PM: Hi,

Quote from: pomprocker on January 13, 2009, 01:51:56 PM
How come I never see anyone using coin cells in their robot?
There is at least one on the net - a tiny line follower, but it's rather boring.

Quote from: pomprocker on January 13, 2009, 01:51:56 PM
Aren't they pretty small and carry a good amount of voltage?

Couldnt I stack two coin cells and I would get the 6volts I need that I get from my 5-cell AA NiMH pack?
Voltage is not enough.
With less than 200mAh in LiIon button cells, you need very low current motors for any kind of fun.
Besides, primary LiIon button cells cannot deliver very high currents and the rechargeable types even less

Much better to use Zinc/Air for small 'bots. The 675 cell holds around 650 mAh (1.4V) in the same size of an AG13, so they are very good power/weight and capacity/weight wise. Alas, they are primary cells.
Title: Re: Coin Cells
Post by: Razor Concepts on January 13, 2009, 08:19:27 PM: I got 20 2032 batteries (20mm 3v) for under 4 shipped here, best deal.
http://www.dealextreme.com/details.dx/sku.751
Title: Re: Coin Cells
Post by: Ro-Bot-X on January 13, 2009, 08:46:26 PM: Quote from: Razor Concepts on January 13, 2009, 08:19:27 PM
I got 20 2032 batteries (20mm 3v) for under 4 shipped here, best deal.
http://www.dealextreme.com/details.dx/sku.751

All you need is some small enough geared motors and you can build your own Robotic Ant Farm! Try the motors that get/eject the floppy in a Mac floppy disk drive.
Title: Re: Coin Cells
Post by: SmAsH on January 13, 2009, 09:04:21 PM: well i got 50 2032's shipped here for $9.60 from ebay, so nanananana! but as everone else has been saying they dont provide enough mah for their size (plus theyre usially quite expensive!!) so its usially cheaper to get a couple of AA's or AAA's for the same price!
Title: Re: Coin Cells
Post by: Admin on January 23, 2009, 06:06:11 AM: At one time I was designing this ultra tiny robot for a DARPA project . . . here is some info on small batteries I gathered:
http://www.societyofrobots.com/robotforum/index.php?topic=1127.msg7406#msg7406

The project never left the design phase because it was easy to prove just using math that the whole concept wouldn't work. The major issue is traditional actuators are too weak in the micro size. Couldn't get high voltages with tiny batteries to power anything interesting for long periods of time . . .
Title: Re: Coin Cells
Post by: pomprocker on January 23, 2009, 11:05:52 AM: so using two of those 3v coin cells couldn't replace the NiMH pack on my $50 robot?
Title: Re: Coin Cells
Post by: frodo on January 23, 2009, 12:05:19 PM: by the sounds of it, no. :P
Title: Re: Coin Cells
Post by: Razor Concepts on January 23, 2009, 12:40:59 PM: You can use them but only two will mean that the batteries will die within a minute or so of running.
Title: Re: Coin Cells
Post by: Ro-Bot-X on January 23, 2009, 07:58:56 PM: Quote from: pomprocker on January 23, 2009, 11:05:52 AM
so using two of those 3v coin cells couldn't replace the NiMH pack on my $50 robot?

Use 3 of them to replace the 9V battery that powers the electronics, since the current for electroics is little compared to the current for motors.