I've designed and built chargers. Typically you need special circuits to detect full charge. If you want a DIY, try looking through links on this page:
http://www.linear.com/pc/viewCategory.do?navId=H0,C1,C1003,C1037 click on Battery Charger Solutions link for an overview of battery charger circuits. Lithium Ion batteries are another matter, and most Lion batteries have internal circuitry and memory that require custom interfaces. One of the reasons Lion batteries have 3 terminals instead of just 2. NiCad and NiMH have specific charge characteristics that have to be detected. Some of my old NiCad chargers I had to put on a timer or they would smoke the battery by over charging. If you are willing to monitor the battery charging so you don't over charge it, there is no reason you couldn't do what you suggest, just realize if you over charge you may ruin the batteries. Sometimes you can go on that auction sight (*b**) and pick up a used power supply, like a good Lambda supply, that also has a current limit (~$50). With the current limit control you could adjust the current down after a while and let it trickle charge. (eg. look at item 7607470215 ) If you are not in a rush to charge the battery, you can just put a resistor current limit and trickle charge the battery over a 24 hour period. Also, if you measure the voltage of a wall wort, a 9V wort typically puts out 12+ V open circuit. A 12V wall wort would put out over 15V and might be good enough to use (with resistor current limit) The price you pay for the expensive chargers is that they can put out a lot of current and rapidly charge the battery, detect when the batter is close to charge and go into a trickle charge mode, and eventually shutoff. But there is no reason you can't experiment if you want. Just remember if you mess up, you can ruin your battery. Lion batteries are more dangerous if you over charge them. Typical of camera gear like this, they cost 3-4X what other markets charge for the same thing. You might even use a portable drill charger set up for 14.4V NiMH batteries, as these chargers charge based on I-V characteristics to detect full charge. WayneS * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
