Re: Home Brew Chargers anyone?

RogerN wrote:
> Years ago I started working on what was supposed to be an alternative to
the 
> Alpha 4.  The basic concept seemed simple enough but I wasn't sure how
to 
> get components to handle reverse polarity and short circuits without
smoke. 
> About the time other multi-chemistry chargers came on the market, I quit

> working on it.  The interest has been there and over the years I've
learned 
> what I needed to know then.  Also, now there is more available in free 
> simulation tools, etc.
> 
> I've been studying different switch mode power supply topologies.  SEPIC

> would allow you to charge batteries over a wide voltage range but I
haven't 
> found very high powered SEPIC controllers.  I have found Linear
Technologies 
> has Boost controllers that can give 50V at 5A (250 Watts) from a 12V 
> (Actually 10V to 28V) source.  Then you can use a buck converter to
lower 
> the voltage to what you are charging.  Add some analog outputs and
op-amps 
> to allow a microcontroller to set the current and analog inputs to read
the 
> voltage and current and that should be a pretty powerful charger.
> 
> I'm interested in getting something going on this and let the schematics
and 
> firmware be open source.  That way the software can be improved,
features 
> added, or new charging algorithms added as new battery technology comes
out. 
> If anyone's interested I can give links to the simulation software and 
> circuits.
> 
> I'm not sure on the microprocessor or microcontroller to go with.  I
want 
> something that anyone interested can program for low cost.  Anyway, I've
got 
> to get the details ironed out and tested in the analog circuitry first.
> 
> RogerN
> 
> 
> 
> 
Join RCgroups and look in the DIY electronics forum. Several designs 
have been posted.

Mist use a commercial buck regulator chip plus additional smarts to 
condition the voltage/current/time regime. And of course a big fat FET 
or two to do the power side.

However, most people simply buy a commercial charger or three..they are 
not that expensive.