Battery charging question...

D

Dave

Guest
Just a quick question, but aren't we supposed to charge a rechargable
battery gy sending current through it in reverse to the normal polarity of
the battery? Just wondering why it doesn't seem to be working...


Thanks
 
Dave wrote:

Just a quick question, but aren't we supposed to charge a rechargable
battery gy sending current through it in reverse to the normal polarity of
the battery?
Click to expand...

** Not actually the case.

Batteries have the same polarity, discharging or charging - the difference is with the direction of current flow, out of or into the battery.

To make current flow into a battery requires connection a supply with a voltage slightly higher than the battery, so it increases the voltage on the terminals.


> Just wondering why it doesn't seem to be working...

** Reverse polarity charging will steadily reduce the terminal voltage and can ruin the battery.


..... Phil
 
Dave pretended :
Just a quick question, but aren't we supposed to charge a rechargable
battery gy sending current through it in reverse to the normal polarity of
the battery? Just wondering why it doesn't seem to be working...
Click to expand...

> Thanks

Just a little more information would be handy in forming a response :-?

--
John G Sydney.
 
On Wed, 01 Jul 2015 19:57:34 -0500, Dave wrote:

Just a quick question, but aren't we supposed to charge a rechargable
battery gy sending current through it in reverse to the normal polarity
of the battery? Just wondering why it doesn't seem to be working...
Click to expand...

"Polarity" is a confusing term, here, because normally one thinks of
polarity as the voltages on the terminals. You DO NOT charge a battery
by hooking it up with voltages reversed.

You recharge a cell by sending current through it in the reverse
direction of the flow while discharging. This is done by raising the
voltage at the terminals -- i.e. to something like 2.3V/cell for a lead-
acid battery (don't quote me on the actual number -- I'd have to look it
up to be sure).

--
www.wescottdesign.com
 
"Dave" <db5151@hotmail.com> wrote in message
news:V5-dnbiLyvI8OwnInZ2dnUU7-emdnZ2d@posted.internetamerica...
Hmm. So I need to reconnect my 1.2 volt NiMH battery with the power
supply so that the current flows through the battery in the same
direction as the battery's normal currrent flow? God, it's been so long
I've forgotten nearly everything I ever knew. Thank you. Take it
easy...
Click to expand...

The charger needs to be connected so that if you hook a meter across it,
find the positive terminal and connect that one to the positive of the
battery.

While you can not do it, Think of the charger as another battery of a
higher voltage. The two positive terminals (battery and charging battery)
will be connected together.
 
On Wed, 01 Jul 2015 21:49:05 -0500, Dave wrote:

Phil Allison <pallison49@gmail.com> wrote in
news:9457ffc4-17cd-4dde-b235-6dce6cb5d0fd@googlegroups.com:

Dave wrote:

Just a quick question, but aren't we supposed to charge a rechargable
battery gy sending current through it in reverse to the normal
polarity of the battery?


** Not actually the case.

Batteries have the same polarity, discharging or charging - the
difference is with the direction of current flow, out of or into the
battery.

To make current flow into a battery requires connection a supply with a
voltage slightly higher than the battery, so it increases the voltage
on the terminals.


Just wondering why it doesn't seem to be working...

** Reverse polarity charging will steadily reduce the terminal voltage
and can ruin the battery.


.... Phil




Hmm. So I need to reconnect my 1.2 volt NiMH battery with the power
supply so that the current flows through the battery in the same
direction as the battery's normal currrent flow? God, it's been so long
I've forgotten nearly everything I ever knew. Thank you. Take it
easy...
Click to expand...

As noted in my earlier reply, you seem to be using polarity differently
than the rest of us, or at least are making different assumptions.

Yes, the polarity of the _current flow_ is different, but the polarity of
the _voltage_ (which is, I think, what most people assume you mean), is
the same.

Just raise the terminal voltage as necessary to get the right cell
current and/or voltage.

--
www.wescottdesign.com
 
Phil Allison <pallison49@gmail.com> wrote in
news:9457ffc4-17cd-4dde-b235-6dce6cb5d0fd@googlegroups.com:

Dave wrote:

Just a quick question, but aren't we supposed to charge a rechargable
battery gy sending current through it in reverse to the normal
polarity of the battery?


** Not actually the case.

Batteries have the same polarity, discharging or charging - the
difference is with the direction of current flow, out of or into the
battery.

To make current flow into a battery requires connection a supply with
a voltage slightly higher than the battery, so it increases the
voltage on the terminals.


Just wondering why it doesn't seem to be working...

** Reverse polarity charging will steadily reduce the terminal voltage
and can ruin the battery.


.... Phil
Click to expand...

Hmm. So I need to reconnect my 1.2 volt NiMH battery with the power
supply so that the current flows through the battery in the same
direction as the battery's normal currrent flow? God, it's been so long
I've forgotten nearly everything I ever knew. Thank you. Take it
easy...
 
Yes, the polarity of the _current flow_ is different, but the polarity
of the _voltage_ (which is, I think, what most people assume you
mean), is the same.

Just raise the terminal voltage as necessary to get the right cell
current and/or voltage.
Click to expand...

God. Thank you for your patience and understanding. I feel like an
idiot. Now have the battery charging properly and apparently did not
damage it too much. It still functions in some fashion at least.

<shaking head> Thanks again. Cannot tell you how much your help is
appreciated. Will probobably be back later with more ignorance to
dispell. Take it easy...


Dave
 
On Fri, 03 Jul 2015 10:04:50 -0500, Dave wrote:


Yes, the polarity of the _current flow_ is different, but the polarity
of the _voltage_ (which is, I think, what most people assume you mean),
is the same.

Just raise the terminal voltage as necessary to get the right cell
current and/or voltage.


God. Thank you for your patience and understanding. I feel like an
idiot. Now have the battery charging properly and apparently did not
damage it too much. It still functions in some fashion at least.

shaking head> Thanks again. Cannot tell you how much your help is
appreciated. Will probobably be back later with more ignorance to
dispell. Take it easy...
Click to expand...

If we're off of theory and into practice, and if you're building your own
charger, it's probably a very good idea to hunt around a bit on the web
and find a charger circuit for your battery chemistry. Each cell
chemistry has it's own needs for care and feeding, with varying levels of
what's critical and what's not. For the most part, if the charger is not
right for the battery then the best you can expect is a less than optimum
charge. In the case of LiPo batteries you may cause the battery to burst
into flame.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
On 2015-07-02, Dave <db5151@hotmail.com> wrote:
Just a quick question, but aren't we supposed to charge a rechargable
battery gy sending current through it in reverse to the normal polarity of
the battery? Just wondering why it doesn't seem to be working...
Click to expand...

sort-of, reverse the normal (discharging) current direction.
the voltage polarity staays the same.

--
umop apisdn
 
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