<VV> Re: Battery Tender Problems (Now transformer and diode)

[RoboMan91324@aol.com]

Hello all,

Your typical transformer will take 120 VAC input and output a different 
voltage level AC.  The operative part is "AC."  An AC current of any voltage will 
not charge your DC battery.  It will tend to heat the battery and ultimately 
discharge it.  In effect, the diode (or rectifier) is a one way current valve 
that will only permit half the AC current to pass through.  This will give you a 
very rough DC current which is not optimal.  The wave form will rise from 
zero to the maximum amplitude then return to zero and stay at zero for 50% of the 
time until the wave form starts to rise again.  This will also create 
heating.  The half sine wave can be buffered with a properly sized capacitor.  The 
best circuit would be a rectifier bridge which uses four properly oriented 
diodes which will eliminate the 50% off time.  You will also need the capacitor to 
smooth out the sine wave somewhat.  Next, the transformer needs to be the 
proper output.  An AC source fully rectified through the bridge and capacitor will 
create a DC voltage level approximately 1.414 (square root of 2) times the AC 
voltage.  In effect; 120 VAC through the circuit will give about 170 VDC.  
You will need about 10 VAC from the transformer's secondary output to get 14 
VDC.  A typical 12 VAC transformer gives you 17 VDC and a 24 VAC transformer 
gives you 34 VDC, etc.  You can easily fry your battery and electrical/electronic 
components in the car.  A little knowledge is a dangerous thing.  If you don't 
know what you are doing, buy a commercial product that is engineered for your 
use.  JMHO.
Doc
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In a message dated 06/03/04 8:11:14 AM Pacific Daylight Time, 
virtualvairs-request@corvair.org writes:

> Message: 2
> Date: Thu, 03 Jun 2004 09:28:54 -0400
> From: Robert Marlow <nortechcorp@optonline.net>
> To: virtualvairs@corvair.org
> Subject: <VV> Re: Battery Tender Problems
> 
> Phil asked:
> 
> Wanted to "poll" the group on experience with the "Battery Tender Plus"
> 
> JR replied:
> 
> Try a doorbell transformer.  I think they put out about 2amps.
> 
> Harry added:
> 
> Don't forget the diode.
> 
> Bob now asks:
> 
> And the diode does... what?