charging 3.7v batteries!

[Peter Nabil]

Hi guys,
i've 2 battery 3.7 volt, 600mAh each
i am using them serially in order to get 5 volts for my project,
the problem is i want to charge them serially, so i am using an adapter 7.5 volts, .5 Amper , they charge well, but after 30 minutes from the charging i found them empty!!! ZERO volt !!!
i am goin' crazy, i can't realize this phenomenon!
somebody tell me where the error exist ?!

 

[Someone Electro]

did you conect the positive of your suply to the positive of the batery?If not you tosted your batery

 

[eblc1388]

Check to make sure that your voltmeter is (not) working using another good battery.

 

[Nigel Goodwin]

You don't have enough voltage to charge the batteries! - you need a fair amount more that their terminal voltage to charge them, and use a current limiting resistor (or constant current source) to provide the charging current you require.

 

[Peter Nabil]

did you conect the positive of your suply to the positive of the batery?If not you tosted your batery

yes i connected the positive of the battery with the positive of the charger

Check to make sure that your voltmeter is (not) working using another good battery

yes the voltmeter is workin' properly !

You don't have enough voltage to charge the batteries! - you need a fair amount more that their terminal voltage to charge them, and use a current limiting resistor (or constant current source) to provide the charging current you require

well, i will raise the charger to work on 9 volts , okay ?
and as i did that before, i can tell you it won't work too !
ah by the way, my source is a constant current source

 

[Nigel Goodwin]

You don't have enough voltage to charge the batteries! - you need a fair amount more that their terminal voltage to charge them, and use a current limiting resistor (or constant current source) to provide the charging current you require

well, i will raise the charger to work on 9 volts , okay ?
and as i did that before, i can tell you it won't work too !
ah by the way, my source is a constant current source[/color]

If your voltage source was only 7.5V before, you had nowhere enough voltage for the constant current source to work - depending on it's design 9V might not be enough?.

I'm presuming you have a multimeter?, put it in series with the batteries and monitor the charging current.

 

[evandude]

what kind of batteries are these?

Judging by the 3.7v voltage, it sounds like they could be Polymer Lithium Ion batteries, which are 3.7v output. (the flat ones, like these: **broken link removed** )

if they are, you should stop trying to charge them with such simple methods... they require specialized chargers and you'll probably end up destroying them if you continue.

also, if you measured ZERO volts after charging, it sounds like you may have damaged the batteries already, no matter what type they are...

If they aren't that type, well then disregard this message.

 

[Peter Nabil]

what kind of batteries are these?

Judging by the 3.7v voltage, it sounds like they could be Polymer Lithium Ion batteries, which are 3.7v output. (the flat ones, like these: **broken link removed** )

if they are, you should stop trying to charge them with such simple methods... they require specialized chargers and you'll probably end up destroying them if you continue.

also, if you measured ZERO volts after charging, it sounds like you may have damaged the batteries already, no matter what type they are...

If they aren't that type, well then disregard this message.

Nope
my battery is Nickel Cadmium ,
Panasonic P-P501
KX-A35

 

[Edmond]

If your batter is Ni-Cd and 3,7V that means, that there are three cells inside. The cell voltage is 1,2V so 3x1,2=3,6V. The charged cell voltage is 1,44V so the charged pack voltage is 3x1,44=4,37V. If you connect two packs serial then the charged voltage is 8,64V. The battery bust be charged with constant current generator with over voltage protection (8,64V). Your 7,5V charger is unusable for charging the batteries connected serials. Charge them separately.

 

[Nigel Goodwin]

The battery bust be charged with constant current generator with over voltage protection (8,64V). Your 7,5V charger is unusable for charging the batteries connected serials. Charge them separately.

There's no need for voltage protection, you just require a limited or constant charging current - and you require a reasonably higher voltage to generate it.

 

[Peter Nabil]

Oh God!
finally,
now i am going crazy indeed, you know why ?!
the error was in the internal connection between the batteries,
unexpected error, huh ?
Panasonic made one connection as a thin wire ( fuse ) to protect the battery from being damaged by over current !
i simplu replaced the wire with a new one !
:lol:

anyways, thank guys for helping me !