Lead Acid Charger
In message , John Williamson
writes
Dave Plowman (News) wrote:
In article ,
Rick Hughes wrote:
On 29/12/2012 00:11, Dave Plowman (News) wrote:
In article ,
Rick Hughes wrote:
I have a relatively new Car Battery Charger (twas a gift) claimed to
be electronic 'smart' charger.
Took the cover off and found it to be a straight transformer to full
wave rectifier set of diodes ... and out to croc leads.
Then it will blow up when you try and use it.
Why ?
220V AC step down transformer full wave rectifier giving DC
output to a pair of croc clip ended leads ..
Display gives some LED indication, and there is an in-line fuse
........... why would it blow up ?
Because a lead acid battery has a very low internal resistance. To a
power
supply like that virtually a dead short. A crude charger would have some
form of series resistance to limit the maximum current.
Unless they've cunningly used the transformer's impedance to give a
sagging output with increasing load. Saves the regulator and means the
transformer's cheaper, too.
Snap:-)
--
Tim Lamb
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