[Cyborg] battery standardization

[Eric Boyd]

Sensebridge,  

I did some research into LiPo batteries.  My conclusion is that we should standardize on the SparkFun batteries.  This conclusion is based on:

Price: SparkFun is quite reasonable, only a couple dollars more than the cheapest batteries I found - 860mAh = $8.95, $8.06 at quantity 10.  The charger is slightly pricey at $20 though.

Safety Circuit: SparkFun batteries all have over-voltage, over-current and minimum voltage protection.  This is unheard of elsewhere, and probably a great idea for prototyping...

Connector: SparkFun batteries come with wires and a nice connector, included for free.

Size: 860mAh = 0.23x1.16x2.0" (5.84x29.5x51mm), although it's slightly larger than others (some camera batteries have ~1.7" largest dimension), it's still quite reasonable.  Also, this pack is "soft", which is probably better for us, since we can bend it a little (e.g. around the ankle).

http://www.sparkfun.com/commerce/product_info.php?products_id=341
 (you can find the charger and other sizes in the list below the featured product)

What does everyone think of this?  I propose we discuss at Sunday meeting and then put in a bulk order if we're agreed.

Also, here's some interesting info on what we can expect for battery lifetime:
http://www.liquidware.com/shop/show/BP/Lithium+BackPack
Claims that even with just Arduino in standby, this is expected lifetime:
600mAh = 9.4 hours
10000mAh = 15 hours
2200mAh = 29 hours

Obviously if we also power sensors and displays, lifetime will be even more limited.

Eric




Other options I found:

MaxAmps   http://maxamps.com/categories.php?cat=8
Huge selection for remote control vehicles, but VERY expensive (1550mAh = $25, cheapest I found, most are $30 or even $50).  Also, most seem to be at higher voltage - 7.4V or even 11.1V.

ShopXtreme
http://shopxtreme.com/advanced_search_result.php?keywords=casio+np-20&gclid=CMbR7M68wZkCFSMSagod7ngYuA
Sells digital camera batteries, including no-name brands
There is a "casio np-20" 800mAh 50.80x32.45x4.60 mm for $5.89 right now, and a charger kit for $16.  There are lots of suppliers for the np-20 format.  
See also CANON NB-6L  1.75 in. x 1.25 in. x 0.50 in 850mAh $7.29
http://shopxtreme.com/canon-nb6l-nb6l-liion-battery-850mah-high-capacity-p-1634.html
The disadvantage of both of these is they ship with just contacts - no wires/connectors.  So it'll be a slight pain to actually hook them up.
If you already have a camera which takes a cell, it might be wise to personally standardize on those cells, if you want to go this route - you already have the charger, and it'll be handy to swap from camera to your armature and vice versa...