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paulz
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# Posted: 7 Jan 2020 19:19 - Edited by: paulz
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I have a small portable, rechargeable radio I use outside at my cabin. About the size of a deck of cards. Goes dead after a couple of hours. 3.7v battery, like a cell phone. I also have a bigger 3.7 v battery out of a portable TV that died that I could tape to the radio. But the radio battery has 3 brass connectors, the TV battery has red and black wires only.
Can I use it, either by itself of connected with the radio battery?
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paulz
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# Posted: 7 Jan 2020 19:38
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Forgot to mention, the radio recharges off a USB port.
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ICC
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# Posted: 7 Jan 2020 19:43 - Edited by: ICC
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The third contact point is usually for temperature sensing. The charger can slow the charge if the battery gets too hot.
How would you charge the battery from the TV?
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paulz
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# Posted: 7 Jan 2020 22:42
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Hmm, glad you mentioned that. TV had a 9v wall wort. Which got me thinking, how would that do with a 3.7 battery. So I just had another look at it, looks like it says 3.7x2.
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ICC
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# Posted: 7 Jan 2020 23:04 - Edited by: ICC
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Quoting: paulz it says 3.7x2
So that may mean 3.7 volts x 2 = 7.4 volts as in serially connected. It strikes me as an odd labeling.... makes me wonder why they don't state 7.4 volts???? Do you have a multimeter? Measure the voltage.
3.7 x 2 could also mean connected in parallel. ??? Anyhow, measure the battery volts. It may very well be that connecting that to the radio would not be good. 
If the radio has a USB port how about trying a power bank plugged into the radio with a few elastic bands holding them together?
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paulz
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# Posted: 7 Jan 2020 23:45
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7.9 volts. Good thing I didn't start farting around with it. Power bank, good idea. Don't have one of those things yet.
Thanks ICC!
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Brettny
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# Posted: 10 Jan 2020 08:44
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18650 battery are about 3.7 volts. What are the dimentions of that pack and what is the battery make up? No car? Lithium?
Usually if you search for a battery pack voltage the size you want will come up. There's many dif shapes and sizes but usually voltage matches a size baring an oddball one off pack.
Most of the lithium stuff in portable battery packs are going to be 18650 battery. Most of the cordless hand tools, vacuum, laptops and I'm sure there's a lot more.
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ICC
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# Posted: 10 Jan 2020 10:53 - Edited by: ICC
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There are an almost endless variety of sizes of lithium-based cells or batteries that are rated at 3.6 or 3.7 volts. They come in both flat cells like the ones used in most smartphones and cylindrical shapes in a wide array of diameters and lengths. There is no standard size. The 18650 is the most common cylindrical cell. The rated voltage is normally 3.6 or 3.7 volts. The capacity can vary from only a 100 mAh to thousands of mAh and the cells can deliver much higher amperage than the alkaline cells we are very familiar with.
If one is going to mess about with lithium cells one should also be aware that a short circuit can result in a fire involving the cell itself. I do use them in many projects and have never had any dangerous situations arise, but bad things do happen especially if one is not careful and knowledgable about the potential dangers.
It is possible the cell in the radio is wearing out. A replacement could rectify that issue. Or perhaps the cell is simply too small a capacity for the current use.
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paulz
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# Posted: 29 Jan 2020 08:29
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Speaking of not knowlegable, I figured I could cut the battery open and split it into two 3 volters. Didn't work, ended up with a long flat unrolled coil of smelly mess.
Did I get a bunch of toxic PCBs or something all over my myself?
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ICC
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# Posted: 29 Jan 2020 14:28
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Not PCB's but likely at least one of a variety of heavy metals. Lithium-ion cells have a few different heavy metals inside them and any heavy metals can be detrimental. Lithium-based cells should be taken to recycle centers and not disposed of in landfills or incinerators. Problem is, that the recycle places won't want a cut-up cell.
You may have been lucky that it did not short circuit and burn. Fumes from that can be very bad. Some lithium chemistries are worse than others.
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paulz
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# Posted: 30 Jan 2020 11:05
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Actually when I first cut into the thin plastic covering I did get a spark! At that point I figured I ruined it already but still took it apart figuring I would learn something. Guess I learned not to take them apart..
So do people take their old cell phones to recyclers? I bet they go in the trash can, battery and all. Not that it's right but likely what happens.
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