Electronics > Beginners

Capacitive Battery Chargers

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FiveseveN:
If this topic has been covered before I apologise. And if that's the case, could you suggest some search terms? My initial search didn't lead me to an answer, hence the following:

A recent post on HaD led me to this (sketchy) project page: http://screwdecaf.cx/dapimp.html
I've only dabbled in small-signal audio and some basic automation and had never encountered the concept of capacitive charging before, not pertaining to wireless power transfer, anyway. What goes on inside a rechargeable battery is still a mystery to me, so I can't dismiss the idea out of hand. But if it's so simple and cheap to construct a self-regulating charger, why isn't everybody and their dog using one (besides the safety issues)? Would such a design work reliably? Within what limits? And how could it be improved?
Thanks.

PA0PBZ:
There is NO regulation!
The AC is directly connected to the output (via fuse and bridge rectifier)!
This thing will kill your batteries and yourself, not necessarily in that order!
 :--

amyk:
You almost answered your own question. According to the not-a-schematic, it's a standard capacitive dropper supply connected directly to a battery... :o

The capacitors are not even X-rated. :o :o :o

FiveseveN:

--- Quote from: amyk on December 02, 2012, 09:27:53 am ---The capacitors are not even X-rated.

--- End quote ---

Yeah, that was an obvious red flag, though it's an easy fix. Now that I found more info on cap dropper supplies it's all starting to come together. Thanks, guys!

PA4TIM:
Dangerous toy. Only the Rin of the battery limmits the voltage, the not for his use type caps limmit he current. A sort of zapper but using a voltage instead of a current. I use sometimes a charged cap to bring a nicad back to live but most times it is only for a short time. You burn away a short but other cristals that are allmost causing a short stay.

It also has nothing to do with desulfating, he uses spikes but only for a short time. I'm doing a test with a desulfator I made out of curiousity and it is now connected for 3 months to a very sulfated battery. ( from self discharging during a long periode)  I was not able to charge it. I measured the complex impedance then and did a load test. After 2 months it was indeed much better but still way from what it ever was ( i bought an identical new one and measured that too)
So if desulfating with 3A pulses around 100V ( low dutycycle) after 3 months only makes it usable to charge a telephone or burn some led lights then his devise will not save any battery.

It will load them, but in a very crude and dangerous way.

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