Smallest battery able to power LEDs?

[Sandrock]

I'm looking to install small LEDs in the heads of robots. Their heads are about the size of grapes and usually require a bit of cutting and carving to get them to fit. I can then thread the wires down into the torso but I'm struggling to find batteries of a suitable size. Currently I have coin batteries but they're a bit large and I'm wondering if there's any more compact options.

[Schwarz-Brot]

Coin cells like they're used for hearing aids are the smallest I know about.

 

Edit: Size 10 would be the smallest of these:

 

1,4 Volt / 70 mAh / 0,10 Wh
ø5,8 mm x 3,55 mm
Typical names: ZA10, 10A, 10AP, 10DS, 10HP, 10HPX, 10SA, 10UP, 230AP, A10, AC10, AC10EZ, AC230E, B0104, CP35, DA10, DA10N, DA230, HA10, L10ZA, ME10Z, P10, PR10H, PR230H, PR536, R10ZA, S10A, V10AT, W10ZA, ZL4

 

Information taken and translated from a german website.

 

 

Edited May 3, 2020 by Schwarz-Brot

[bmwh548]

Do you know the cheap Chinese lighters that come with a 5mm LED? You can take one of those apart and grab the battery pack (it's 3xLR41 in there and the good thing is they come with a plastic "box" so it's easier to wire the thing). The LR60 is even smaller but they'll last even less. 

Back when I used to do lights on car models I would use LR44 but space wasn't a huge issue.

[Sandrock]

3 hours ago, bmwh548 said:

Do you know the cheap Chinese lighters that come with a 5mm LED? You can take one of those apart and grab the battery pack (it's 3xLR41 in there and the good thing is they come with a plastic "box" so it's easier to wire the thing). The LR60 is even smaller but they'll last even less. 

Back when I used to do lights on car models I would use LR44 but space wasn't a huge issue.

I ended up doing that last night. I had some super cheap Chinese LED "tea lights" which I took the batteries from. After experimenting I've found 2 Ag4s would light a LED for 12+ hours well and now it's been 18 and it's just starting to become a dull glow. Size wise I doubt I'm going to find much smaller than 2 of those able to reach 3 volts and keep them going for such a long time.

[It's a disease]

Just add a resistor before the led.....

that can increase battery duaration.

 

as I understand things, an led will draw full current without a resistor but can operate with very little current draw.

 

eg a 20mA rated led will still work well enough at 5mA but it will last approx 75% longer.

 

At the very least it will mean you change less batteries! (Or recharge less often)

 

i settled on rechargeable coin cells.