Protection circuit in a Pila Li-Ion??

Is there anyone who destructed the battery and checked the protection circuitry? I assume the Pila has a round PCB which contains the protection circuit and attached the PCB on top of the plus pole. If somebody has the schematic, it would be great.

I have a schematic but it has a protection PTC between the minus pole of the battery and the minus output and so the ground is not common.

As the price of normal 18650 Li-Ion cell is around U$2-3 in volume from the manufacturer, the price of Pila cell seems away too expensive. I guess somebody can make the protection circuit very small and cheap for all of us.

I think the 18650 is the right size as it is the same size as 2X123 with 3.7V, 2A capacity. No memory effects, 500 charge/recharge cycles. Run 3W LED for 2 hours!

Anyoung Hashimnikka,

I have long thought about selling bare cells. I did unknowingly sell some bare cells out here. I had them made for me but still thought I was getting protected cells.

I think bare cells are ok for those who know what they are doing. But I also think it is dangereous to sell them as light batteries. All it takes is for one person to misuse them and the lawsuit could ruin you forever.

I am more concerned about kaboom than overdischarge.

Most bare li cell manufacturers I contacted provided their datasheet including short circuit test with 0.2 ohm external resistor beside many different types of test.

I even did many of my own unwilling short circuit tests when I accidentaly left my light head short with li connected. After 5-10 seconds, it was pretty warm but not up to the burning temperature.

I agree with you that celling bare cells to non-technical guys or very adventurous guys can be scary.

The PILA (from you) and bare cells from condemned notebook battery go in to my modded police light alternately. But PILA is only one I would give to my wife.

-- dj

I have a few unprotected cells (at least i think they are unprotected) that i bought from Fry's, Although im not 100% sure. You'd think that Fry's wouldnt sell something so potentially hazerdous to the general public. so hopefully they are protected. But just in case they arent, im going to only use them in my Arc4+ so i know when to pull them out and stick them on the charger.

Hallis,

I have been working with the manufacturer of those cells for a year now. I sold a bunch out here. After I sent them some flashlights, they finally started working with me on the new cells.

It turns out that use in cameras and use in flahlights is not the same. The camera give the batteries a rest, flashlights just beat and beat on cells continiously.

oh, be sure that the ARC4 is not a second. I need to gather up all the information from the manufacturer and post them out here sometime.

what exactly is the difference between a first and a second?

Ban-Gap-Seum-Ni-Da!

How was your trip to Penang? I am sure you enjoyed it.

I lokked at the protection circuit in Siemens phone battery and also RCRV3, both have separate charge pin and discharge pin -- single direction and can't be used the way PILA does.

I recently acquired sample of UCC3952 from TI and it does bi-directional protection by isolating negative battery lead from the ground. It requires only a small capacitor (0.1uF) to operate and 16pin 150mm DP soic may fit in 18mm diameter. (not tried yet)

-- dj

[ QUOTE ]
Hallis said:
I have a few unprotected cells (at least i think they are unprotected) that i bought from Fry's, Although im not 100% sure. You'd think that Fry's wouldnt sell something so potentially hazerdous to the general public. so hopefully they are protected.

[/ QUOTE ]

Hallis,

It is like buying a car or anything else, too. If you use abnromally, you tend to damage it or cause damage to other equipment connected.

This is part of the specification of 17650 (3.7V/1300mAh) Li-Ion bare cell from a manufacturer.

<font class="small">Code:</font><hr /><pre> F: Rapid charging--------1300 mA to 4.2V, until the charging current decreased to 18mA, the charging finished.
G: Max. continuous discharging current-----4000 mA.
H: Max. pulse discharging current------------6500 mA for 10 second.
I: Cut-off-voltage--------------------recommend cut-off-voltage is 2.70V per cell.
L: Charging temperature: -30?Ž to +65?Ž.
M: Discharging temperature: -30?Ž to +65?Ž.
N: Max. operation natural altitude: 8000 m. </pre><hr />

Even we use the cell outside of the specification, it may not give you a problem. But if ever anything happens and you were overdischarging or overcharging, I don't think they would compensate you.

Some of the test they conduct include the followings.

<font class="small">Code:</font><hr /><pre> 4. High-temperature test:
5. Low-temperature test:
6. High-humidity test:
7. Vibration test:
8. Over-charged safety:
9. Over-discharging test:
10. Short-circuit safety test:
11. Free-drop test:
12. Impact test: </pre><hr />

During all these test, they watch for no explosion, no fire, no deformation, no leakage and no rust, etc..

The message to me is -- "All these thing watched during the test can or may happen during the regular usage" rather than "All these things are already tested and no problem".

Some li-ion manufacturers enforce their dealers to buy a hugh 3rd party liability insurance to be allowed to sell li bare cells.

-- dj

Been running Warion's bare R123 in ARC4X for the last two weeks using Li14430's li-ion charger.

Been working out great!!!! I run ARC4X on level 1 and imediately pull cell at first drop in output.
measured depleted cell at 2.54v. charges right back up to 4.15v.

I got a pair of dead pilas and took the protection circuit and mounted them on some Panasonic 2000mAH Li-Ions. The protection ckt is on the bottom of the cell and there is a thing copper strip that runs from the (+) terminal to the sense input of the protection. Haven't drawn a schematic but as I recall, it looks like the circuit is made by Seiko. It looks too much of a PITA to make one or two and I rely on dead Pilas to supply me with the circuits. The cells usually go bad but the circuit can be reused if you know what you're doing. IMO, the protection circuit does nothing against catastrophic cell failure. It does protect against shorts and overdischarge and overcharge. Overdischarge will probably not cause a kaboom, but overcharge (if you do it right) and shorts could. If you take reasonable precautions, an unprotected cell can be just as safe as protected cells. But you need to be very cautious and be aware of the risks involved. For that reason, I would recommend the Pilas to the general public. The main reason I use bare cells is economy and capacity. The Pilas have middle of the road capacities and I find that flashlights tend to task them. An extra couple of hundred mAH can mean 15-20 minutes extra runtime in my lights.

CM

Bare cell is not recommended for sure.

Once the overdischarge happens and the cell voltage declines below 2.7V, you cannot recover the capacity even you charge the battery with low charging current.

Overcharge may induce explosion but as far as you pay special attention it should be okay.

The problem is that once you use boost converters, normally it extracts the juice out of the battery and lowers battery voltage below 2.7V at the end of discharge but you never know as the boost circuit keep pumping up the voltage and maintain the same brighteness.

Thanks DJ and JonSidneyB for the koreans you wrote in your post..

CM, that is what I wanted to know. If you post the picture of the protection circuitry, it would be very nice. If there's anybody who had a dead Pila, I wish I can get it to duplicate the circuit.

Cheers..

Re: Bare cell is not recommended for sure.

xbrite,

I posted several a long time ago with the modified panasonics. I will try to get a shot of just the circuit. I will probably have to email it to you as I don't have a way to post pics.

CM

Re: Bare cell is not recommended for sure.

I've had three Pila 168S which I charged using a Triton charger. I got seven more from JSB because I have on order a couple BE4 powerpacks.

I was just thinking! How about charging two at a time? Either in series or parallel, what's the protection circuit going to do? Is this going to work or not?

Re: Bare cell is not recommended for sure.

Hallis:

The arc4 firsts meet Peter's specs as far as cosmetics, tint, and
current draw. The seconds will produce the same amount (sometimes
more) light as the first since they are "power regulated". However,
they will be less efficient and will pull more power. I've heard
of some that will draw over 1.5A on level 1.

Re: Bare cell is not recommended for sure.

Thanks, CM fopr the picture to come. Please e-mail me at "[email protected]".

I reviewed the reference schematic of TI and Seiko's and both looks similar except TI has internal FET's. I guess I have to put the protection circuit at bottom and copper strip from the Plus pole of the battery to the protection circuit at bottom.

Cheers, Xbrite

Re: Bare cell is not recommended for sure.

CM, you can host your pics very easy at ImageShack . /ubbthreads/images/graemlins/wink.gif

Re: Bare cell is not recommended for sure.

Aw Bart! You keep getting me in trouble by invalidating my excuses /ubbthreads/images/graemlins/grin.gif Pics will be coming up.

Re: Bare cell is not recommended for sure.

Sorry for the poor quality, I don't have good macro capability.


The back side is what you see as the (-) terminal on the cell. There is also an oring that spaces this to the bottom of the cell. The big solder blob on the upper right of the board is where the copper strip from the (+) terminal goes. This is the sense voltage to the circuit.

CM

Re: Bare cell is not recommended for sure.

Dear CM,

Thanks a lot for the picture. This is what I wanted to know.

Cheers, Xbrite