Hi!
Could anyone recommend the best LiPo battery
( or lightweight alternative ) for Arduino Pro 5v/16MHz ?
There are a plenty of LiPo's on Sparkfun but all of them
are 3.7v 
On the other hand 7.4v batteries from
other suppliers have incompatible connectors - Arduino Pro
requires 2-pin JST connector.
I would be grateful for any help 
!
LiPo is a great battery, to get around the 3.7V limitation you need a "step up" board (or you can run a 3v Arduino). Sparkfun makes a couple of different DC-to-DC step up boards, depending on your current needs:
This is actually how most people who want to run an Arduino off a battery are doing it. For example the battery "shields" sold by liquidware and nuelectronics use 3.7 LiPos with similar DC to DC step up circuits.
Liquidware's sheild is here: http://www.liquidware.com/shop/show/BP/Lithium+Backpack
Nuelectronics sheild is here: http://www.nuelectronics.com/estore/index.php?main_page=product_info&cPath=1&products_id=17&zenid=1742cfc53bbb37773251e29fa4110884
LiPo battery cells all have a nominal 3.7 vdc rated terminal voltage. Battery packs are made by wiring single cells into pack to increase terminal voltage and/or increase current capacity.
The battery suppliers usually use a nomenclature to show this arrangement, xSyP, where x = number of cells wired in series strings, and P = number of series strings wired in parallel, so 3S1P would mean 3 single cells wired in series to gain a nominal battery voltage of 11.1vdc. That way just about any combination of cells can be made to generate the voltage and current requirement of a given application.
Charging these multi-cell LiPo batteries does require a more sophisticated charger, many that tap into each cell so that a 'balanced' charge or discharge can be done, as having unbalanced cell can result in overcharging or over discharging a given cell within a multi-cell battery. This can be dangerous with LiPo batteries so it's very important that the charger used is correct for the battery voltage and current rating being used.
I use a small 2 cell LiPo battery that came from a cheap R/C helicopter set. It's around 800mah and about the same size as a standard ARduino shield size board. It plugs into the Arduino's external power jack and has worked very well. This came with it's own charger that can handle charging two series connected Lipo battery packs properly.
LiPo is a great battery technology, with the best density/size/weight ratio out there, however one does have to learn and understand their capabilities and cautions.
Lefty
Hi!
Thanks a lot for such immediate and comprehensive response !
I'm also considering an option to solder DC barrel jack and power
Arduino Pro 5v from 4 AA battery holder. It would provide 4.8 v
but from what I understand Arduino Pro have internal voltage regulator so I'll get 5v on the output pin's... Is that correct ?
Thanks :)!
Posted by: retrolefty Posted on: Yesterday at 17:13:34
LiPo battery cells all have a nominal 3.7 vdc rated terminal voltage. Battery packs are made by wiring single cells into pack to increase terminal voltage and/or increase current capacity.The battery suppliers usually use a nomenclature to show this arrangement, xSyP, where x = number of cells wired in series strings, and P = number of series strings wired in parallel, so 3S1P would mean 3 single cells wired in series to gain a nominal battery voltage of 11.1vdc. That way just about any combination of cells can be made to generate the voltage and current requirement of a given application.
I see that there are LiPo batteries for sale on Ebay that come in various sizes, voltages, and prices. Some for $5.00 and some for over 50bucks.
Why the great disparity in prices?
Many of them are at 11.1 volts, some are 7.4v, with variations in mAH. I suppose that the greater the Amp-hour rating the higher the price.
Perhaps a cell phone battery of 3.7v, rechargeable, along with a dc to dc converter, such as AZRobbo suggested would work well with an arduino project.
What do you(anybody) think?
Posted by: AZRobbo Posted on: Yesterday at 16:47:44
LiPo is a great battery, to get around the 3.7V limitation you need a "step up" board (or you can run a 3v Arduino). Sparkfun makes a couple of different DC-to-DC step up boards, depending on your current needs:
5V DC to DC Step Up - VPack PCB - PRT-08290 - SparkFun Electronics
NCP1400-5V Step-Up Breakout - PRT-08999 - SparkFun Electronics