Why isn't anyone using a smpsu for charging lead acid ? I haven't seen 
any of those. Besides price, any other good reason ? It looks to me like 
a SMPSU is the answer here. With regulated output voltage and input 
power limiting it should be a perfect match to a normal lead acid 
charge, no ? Maybe use one with current foldback regulation to 
accomodate a really flat battery (which requires forming with low 
current). But that should not happen with normal use. So why not ?

Then there is also the problem of charging (or rather not charging) a 
lead acid 12V battery with a 12V wall wart (the wall wart does not have 
enough volts to put current into an almost full battery). A buck 
converter preceded by a current limiter would likely work perfectly 
here. The current limiter would charge from flat, then the buck would 
start when vbatt=vwallwart and provide final charge and trickle. What is 
wrong with this scheme ? One could even use a PIC to control this.

Peter

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