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Old 11th Feb 2020, 10:08 pm   #1
G1RAO keith
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Default Phone batteries

Hi all
Thought I had a great idea to use redundant lithium ion Mobile phone batteries to power my vintage radio valve heaters, via a regulator of course, question is will the battery have to be in a phone to charge it or Can i connect it to a phone wall charger directly or is there something in the phone that is part of the charging process,
I think there is a thermistor in the battery on the third terminal to monitor temperature but that can't control the simple two terminal wall charger,if I do it direct am I likely to loose a few fingers,any ideas .keith.
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Old 11th Feb 2020, 10:55 pm   #2
Maarten
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Default Re: Phone batteries

It needs a stabilised current limited voltage to charge. 4.0 to 4.1V (in no case higher than 4.2V) and limited to about 1/5C just to be safe.
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Old 12th Feb 2020, 8:37 am   #3
Electronpusher0
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Default Re: Phone batteries

Quote:
Originally Posted by G1RAO keith View Post

I think there is a thermistor in the battery on the third terminal to monitor temperature
I think you will find that the third terminal is connected to the junction of the two internal cells. This is used to balance the charge on each cell. Failure to balance the charge will result in undercharging on one cell and overcharging on the other. If repeated over several cycles this can lead to catestrophic failure of the overcharged cell.

Peter
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Old 12th Feb 2020, 12:11 pm   #4
paulsherwin
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Default Re: Phone batteries

Standard mobile phone batteries are just a single lithium cell and can be charged by a charge controller chip using two connections. You can buy charge controller modules from Chinese eBay sellers for pennies which work with a standard 5V USB charger.

e.g. https://www.ebay.co.uk/itm/2PCS-TP40...e/202851920328

I use such a module to charge scavenged 18650 cells which I use to power workaday radios.
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