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[DPRG] Lithium Ion Batteries from BGMicro

Subject: [DPRG] Lithium Ion Batteries from BGMicro
From: Dale Wheat dale at dalewheat.com
Date: Tue Mar 30 08:31:30 CDT 2010

[Posted this the wrong way - never made it to the list, apparently]


Good news & bad news:

The "PCB" (protection circuit board) in these cells is a very good one.  It's 
not a replacement for a proper charging circuit, but for what you're wanting to 
do, it will work, within reason.

BG has a detailed document characterizing the performance of the PCB and the 
cell itself.  Finding that document may prove, shall we say, challenging.  Billy 
is on the "injured reserve" list these days and is only in the office a few 
hours a day, if at all.  I think he's the only one that knows where the document 
is.  I've seen it, but that was many months ago.

One of the very nice surprises was that the PCB contained a PTC over-current 
device, instead of a fuse.  In my experiments with these cells (doing pretty 
much what you've been doing) I saw that the PCB limited the input voltage to 
just under 4.2V going into the cell, as well as cut out as the cell voltage 
dropped below, umm, I forget, but somewhere near 2.2V or so, to keep from 
permanently damaging the cell from exhaustion.  It also has some sort of 
temperature monitoring but I haven't tested that in the extreme.

These cells make a great combination with their 4.2V solar cells.  :D  90mA in 
full sunlight.  One of the highlights of the mysterious document was test 
results from hammering a nail through the cell.  The desired, and expected, 
result was "no effect".

In re the "blowing up problem":  It's a solid polymer battery, so the spew 
factor is minimal.  I recall Mike [of His Hobby Shop] doggedly *trying* to get a 
cell to misbehave:  overcharging, hammering and filing away at it to no avail. 
Your mileage may vary.  Beware the cylindrical cells, as they have a fluid 
electrolyte that *does* overheat & spew when abused.

Please keep us updated as to your findings.  These cells are a great bargain.


Dale Wheat

(972) 486-1317

On 3/28/2010 9:33 AM, Ed Paradis wrote:
> Hi everyone,
> I remember a few people getting these small lithium-ion batteries from
> BGMicro when were still meeting at the warehouse:
> http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=12861
> The description mentions that it has some protection circuitry.  Is
> this 'true' protection circuitry?   Can I, for example, charge these
> with a series resistor to limit current off a 5V line indefinitely?  I
> would just try it and write off any destroyed cells as experimentation
> but for Li-Ion batteries' tendency to start fireworks.
> I know that it general you can't do this, but the description suggests
> it has some smarts built in, which usually means that you can.
> Ed
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