Idea: Can Lithium-ion batteries from Cameras/Cellphones be used?

For typical projects like Arduino-based ones, I often want to make them portable, meaning batteries become necessary. I might be missing something and going out on a limb here since I haven't seen this idea thrown around much but...:

Based on what I've seen, camera/cellphone LITHIUM-ION batteries are: rechargeable (100s of times), not too expensive (10 to 20 USD), light (10 to 25 grams), have very good capacities (500 to 1500 mah), and can be charged with the standard camera/cellphone-brand wall charger, so they seem perfect for portable projects.

Can I request some comments on this: Could one simply use typical camera/cellphone Li-ion batteries for portable Arduino applications, or are there issues I'm not seeing? --Can I safely just take my camera/cellphone Lithium-ion battery and attach wires (some safe method, not solder) to the battery electrodes, and connect the wires to +/- on my project and use it as directly as that? --Do these camera/cellphone Li-ion batteries have protection circuitry INBUILT within the battery itself... or do cameras/cellphones add this externally? (in which case I'd have to go through doing the same on my external circuit)

What is the voltage output on those?

I power a 8 MHz Promini arduino from a 1000mAH 3.7V LiPo battery, bypass the promini regulator, with a 5V recharge circuit similar to the 1851 LiPo charger that sparkfun sells. I use the MAX1811 built into my circuit.

So yes, a method can be worked out to use those.

@CrossRoads: Thank you.. I was initially interested in using LiPo batteries and having a charging circuit on board as you did, but then because of possible safety issues involved (not much experience), I decided to instead try a standard brand camera/cellphone Li-Ion battery that I can periodically charge simply using the manufacturer's wall charger.

An example might be this 3.6V, 895 mah, Li-Ion Panasonic battery from my digital camera which comes with a wall-charger: http://www.amazon.com/Panasonic-DMW-BCG10-Secured-Battery-Packaging/dp/B0029ZA78O

I guess my question is: Would it be functional & safe to directly take one of these standard camera/cellphone Li-ion batteries and connect my 3.3V Atmega-chip/Arduino circuit to the Li-ion battery's + and - terminals, OR do I need additional protection circuitry?

Seems reasonable. My only concern is that I was going to mention that most cell phone batteries output 3-4V, while the USB input on the Arduino is 5V, no? But if it works on less, that should be fine. Keep in mind that the battery's output will fluctuate over it's lifecycle. Though you may start at 3.6, it will likely drop to around 3 while at the end of its charge.

I guess my question is:
Would it be functional & safe to directly take one of these standard camera/cellphone Li-ion batteries and connect my 3.3V Atmega-chip/Arduino circuit to the Li-ion battery’s + and - terminals, OR do I need additional protection circuitry?

It would work like that. Just don’t have any other voltage path wired to the arduino, like a usb cable were it would be possible to have two different voltage sources both wired to your arduino at the same time. Note that running your board at that voltage and at 16Mhz is below AVR specifications for that speed, but most have no problems doing that. If your board is running at 8Mhz then it would be running within specifications.

One caution with Li-po batteries is that they can be damaged if discharged too to low a voltage (=< 3v). So you will have to watch it carefully.

I use a two cell (1000mah I think) Li-po battery from a cheap R/C helicoper to power my arduino boards at times. I attach it to the external power connector as it’s voltage is about perfect for that.

Lefty

Um, yeah, what they said!
8 MHz Promini will work just fine.
MAX1811 is easy to wire up, keeps Li Ion battery from over charging, will recharge from USB or standalone 5v source.
MAX1811 comes in 8 pin SO package, I have mine mounted on a DIP adapter and wirewrapped up on a perf board.

Definitely pay attention to what CrossRoads is saying, OP - you shouldn't just hook up the wall charger to the battery directly, it needs to be a regulated charging circuit, that monitors the battery and other parameters to safely charge the battery. If you don't use such a device like the MAX1811 - you risk fire and explosion when charging the battery (check out some of the youtube videos on what can happen - LiPo's can be dangerous if not handled properly).

Question: OK, so to provide this protection circuitry (by the way, I just tested the battery with two wires from my circuit to the batt contacts directly for a few seconds and things worked just fine!) then... Is there some chip/suggestion to use in the circuit to provide UNDER-voltage protection so that when the battery discharges to below a safe voltage (i.e. 3 V for Li-ion batteries), it cuts off the battery supply?

The MAX1811 chip is for, as you guys mentioned, providing charging in addition to protection but I won't need charging, so is there any chip/recommendation for only under-voltage protection? (my wall battery charger will take care of the over-voltage protection, I believe... it's a Li-ion wall-charger made for that particular brand of battery and sold by the same camera manufacturer, Panasonic)

@crossroads and @retrolefty: I am indeed using an Atmega 328 chip running at 3.3 V and 8 Mhz, just like the Arduino Pro Mini 3.3V. My plan is to follow the Li-ion battery with a TPS63001 chip, which is a buck-boost converter that can output 3.3V with input 1.8-5.5V and >90% efficiency for currents up to 1.2 amps.

So something like this, but capable of running from a lower voltage http://datasheets.maxim-ic.com/en/ds/MAX6399.pdf

You can browse the datasheets here to see if there is a usable part. Unfortunately none of the columns show the operating voltage, and some are just moniter circuits only.

http://para.maxim-ic.com/en/results.mvp?fam=super1

Thank you CrossRoads; yeah, there wasn't a column for the voltage ranges but I was actually able to filter out based on other criteria until I had a few to choose from.

btw, just researched a bit further and TI also has a variety of protection/supervision chips, although curiously all of them are only for TWO or more cells connected in a battery pack: http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=413&uiTemplateId=NODE_STRY_PGE_T

However, I am still debating whether this situation will even need a protection/supervision chip (talking about circuit use, not the charging part)... given that it seems all (or most) Lithium-ion batteries (the ones used in cameras/cellphones) already come with under and over voltage protection built into the BATTERY itself.

I am interested in extra safety though so I will be placing an order for one or two of the Maxim supervisory chips, but just wondering whether it might be excessive, given that the Panasonic Lithium ion battery I'm using will probably shut off by itself when it goes under the safe range...