Step down transformer as a battery charger ?

[Mint]

I salvaged a 9.6 V NiCd battery. 800 mAh

Could I use a 9.0 volt transformer to charge the battery?

I have one that outputs 100 m.a. and another at 200 m.a.

Thanks,
Andy

 

[krw@att.bizzzzzzzzzzzz]

On Wed, 29 Dec 2010 20:37:29 -0800 (PST), Mint <chocolatemint77581@yahoo.com>
wrote:

I salvaged a 9.6 V NiCd battery. 800 mAh

Could I use a 9.0 volt transformer to charge the battery?

No, NiCd batteries want to be charged with a current source and the voltage
must be monitored for full charge, and then the current discontinued (it's a
little more complicated than this). A simple voltage source will not do it
and certainly not one less than the battery voltage. Get a proper charger or
something bad is going to happen.

I have one that outputs 100 m.a. and another at 200 m.a.

Those are the maximum ratings.

 

[Phil Allison]

"Mint"

I salvaged a 9.6 V NiCd battery. 800 mAh

Could I use a 9.0 volt transformer to charge the battery?

** Only if it is an AC type.

Sounds like it is not.


..... Phil

 

[ehsjr]

Mint wrote:

I salvaged a 9.6 V NiCd battery. 800 mAh

Could I use a 9.0 volt transformer to charge the battery?

I have one that outputs 100 m.a. and another at 200 m.a.

Thanks,
Andy

Yes, assuming it is a _transformer_ and not a DC supply. Here's a
simple "14 hour" type charger that will automaticaly reduce the
charge rate from C/10 while the pack is below 11.2V to about C/80
when it reaches 11.2V. That will keep the pack topped off, but
won't overcharge it. The circuit uses an LM317 adjustable voltage
regulator to set the current, and a TL431 as a "programmable zener"
to reduce the charge rate when the pack is fully charged.

-----
9VAC --->|---+---in|LM317|out---+
| ----- |
| adj [15R]
+ | | |
[100uF] +---+-----+-------+
| | | | |
| | [470R] | |
| | | [220R] |
| | [LED] | |
| | | | |
| + N +-----+ |
| i __|__/ |
| C / / \ \
| d /431\---->/ 10K pot
| | --- \
| | | |
9VAC----------+--------+---------+-------+

The 15 ohm resistor sets the current through the LM317 to 80 mA,
which is the correct 14 hour charge rate for an 800 mAH NiCd pack.
Set the 10K pot so that the TL431 draws current and the LED lights
when the voltage measured across the NiCd reaches 11.2 volts. That
will "steer" the charging current to about 50 mA through the 220 ohm
resistor, and about 20 mA through the LED and 470 ohm resistor,
leaving about 10 mA throught the pack, which is too small to harm
it. The 100 uF cap shown can really be most any value between
say 10 and 220 uF, but make it at least 16 volts.

Ed

 

[Mint]

On Dec 29, 11:44 pm, "k...@att.bizzzzzzzzzzzz"
<k...@att.bizzzzzzzzzzzz> wrote:

On Wed, 29 Dec 2010 20:37:29 -0800 (PST), Mint <chocolatemint77...@yahoo.com
wrote:

I salvaged a 9.6 V NiCd battery. 800 mAh

Could I use a 9.0 volt transformer to charge the battery?

No, NiCd batteries want to be charged with a current source and the voltage
must be monitored for full charge, and then the current discontinued (it's a
little more complicated than this).  A simple voltage source will not do it
and certainly not one less than the battery voltage.  Get a proper charger or
something bad is going to happen.

I have one that outputs 100 m.a. and another at 200 m.a.

Those are the maximum ratings.

1st item

Power injector for use with 10 dB in line amplifier

Actual output without a load is around 13.5 volts.

--------------------------------------------------------------------

2nd item

Class 2 transformer RoHS Adaptor

Input 120 V 60 Hz 65 mA

Output of 14.0 v at no load


Andy

 

[m II]

On 10-12-29 10:45 PM, Phil Allison wrote:

"Mint"

I salvaged a 9.6 V NiCd battery. 800 mAh

Could I use a 9.0 volt transformer to charge the battery?


** Only if it is an AC type.

Sounds like it is not.

None of the DC transformers I've tried have ever, ever worked. Not even
with new batteries. I think it's because they are communist Chinese
manufactured.


mike