Choosing a battery for a wearable servo...

Other Hardware Motors, Mechanics, Power and CNC
1

Hi all,

I need to choose a battery to power a small servo that will be worn in an assisted-thumb that I am designing for osteo-arthritis sufferers (like my wife) - ideally it would be a LiPo battery for weight consideration. I am using a Seeeduino Film (http://www.seeedstudio.com/depot/seeeduino-film-p-689.html?cPath=132_133) - an Arduino compatible micro on a thin film. I will be running the Seeeduino from a 110mAh battery but it will be controlling a servo, so I want to power the servo independently and just connect the ground.

The Seeeduino charging and power frame is rated at a max of 280mAh, hence seperate batteries.

The batteries I was considering in series give me 7.4v @ 2000mAh (http://www.coolcomponents.co.uk/catalog/product_info.php?cPath=87&products_id=157)? If so, is it possible to charge them in-circuit or is it best to disconnect them and charge them seperately?

The servo I am considering is Servo Shop. This gives me the right amount of torque, programmability and size.

Regards,
Morrolan

2

Hi, great project..

I would suggest using separate cells that can be separately charged. Lithium batteries with multiple cells need a charger that will equalize the charge between the cells.

type 18650 cells would be good. 2200mah or so, relatively low cost on Ebay. Two give you the 7.4V your advanced type servo needs..
Or USA here: http://www.all-battery.com/li-ioncylindricalrechargeablebatteries.aspx

in the long run you probably would want a 2-cell pack and matched charger, if you make some quantity of these.

Being able to change the motor batteries without them affecting the arduino reliability sounds like a good idea.