cell phone batteries
LoopyByteloose
Posts: 12,537
I just came across my old Nokia cell phone that I have retired for a Samsung.
It has a Lithium cell inside and makes a great recharger. So I put together a board to power an SX-28 with the unregulated output because it is roughly 3.9 volts peak.
My problem is that I really don't understand the Three connector pins on the battery. One nears the corner is + and then I get two that appear to be negative. But between the Plus and the middle pin I get 3.74volts fully charged and between the Plus and the inner most pin I get 3.98volts fully charged.
If I use an LED to indicate output. I get a very bright LED between to Plus and the 3.98v Negative Pin. But I cannot get the LED to light in any combination of the middle pin.
Am I missing something? Is this two cells and one is going bad? Or is the middle pin a 'sense' lead of some sort to prevent excessive discharge of the battery?
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
It has a Lithium cell inside and makes a great recharger. So I put together a board to power an SX-28 with the unregulated output because it is roughly 3.9 volts peak.
My problem is that I really don't understand the Three connector pins on the battery. One nears the corner is + and then I get two that appear to be negative. But between the Plus and the middle pin I get 3.74volts fully charged and between the Plus and the inner most pin I get 3.98volts fully charged.
If I use an LED to indicate output. I get a very bright LED between to Plus and the 3.98v Negative Pin. But I cannot get the LED to light in any combination of the middle pin.
Am I missing something? Is this two cells and one is going bad? Or is the middle pin a 'sense' lead of some sort to prevent excessive discharge of the battery?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Comments
since you don't need them any more for their first purpose, I'd say, "take 'em to the bandsaw!" and carefully cut them open to see. You can always patch them back together again.
I'd bet it's a sense line.
We have a couple of old Nokia's here too actually...
Sharping my blades,
Howard
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Buzz Whirr Click Repeat
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
- H
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Buzz Whirr Click Repeat
sounds like you're speaking from experience... ever had to extinguish a DELL laptop?
- H
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Buzz Whirr Click Repeat
www.youtube.com/watch?v=mlZggVrF9VI
OBC
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Anyway, a LiPo and LiIon can be damaged by both over charging and draining excessively. The telltale sign is that the battery starts to swell. I considered buying some for a project, but I didn't want to incinerate my BOEs. Plus, they were twice as expensive as a NiMh battery of the same Ah. Anyway, the guys at a model hobby shop (racing cars, helicopters, and planes) seem to know quite a bit about different battery types and what voltages and currents to use.
I have had an R/C Lithium cell swell up like a pregnant guppy. I got rid of it immediately as I had visions of the charger going up in a fireball. Since it was a $30USD battery, I was quite annoyed. But, better safe than sorry.
Apparently, the purpose of the middle contact is indeed for a thermistor or other solid-state thermal sensor. One can use the battery without it being connected.
In this context, I think I can safely ignore it. The thermistor will be engaged when charging in the old cell phone. And the SX-18 board that it will be used on is not going to make excessively quick drainage of the battery. I am setting up a timer for battery recharge station.
I am going to use the internal comparator on the SX to limit the discharge to about 3.0 volts. Lithium cells and just about any rechargible battery doesn't like to go below 50% of its rated output. Such deep discharges usually cause damage.
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan