how to build simple charge controller/limiter for 12V batt?
I would like to continue using my 16v/9A power supplies from IBM laptops - surely they provide enough power, but batteries will boil if left overnigh, wasting electricity and aging batts.
To avoid setting timer every time - need to come up with charge control - I'd like to come up with some simple scheme, possibly based on Zener diode to shut off charge once voltage reaches 15v. Just to make sure I am not inventing a bycicle - decided to ask for help first.
I can do some soldering, but looking for a good idea to implement.
Here is what came up to my mind - zener diode in parallel with NC relay and limiting resistor. Once voltage reaches 15v - current should run thru ZD and trrigger relay, thou disconnecting the battery charge, and sending voltage on ZD even higher. LImiting resistor should be just big enough to allow small current thru ZD without overheating it, while it will keep relay open. Light bulb will be a good one to use - it will also indicate Done for particular battery charging
One of converns - ZD are some what flexible on breakthru voltage - for 15v part it can be from 14.3 to 14.8v, while i would like to get better accuracy
ps. this may be a temporary solution until I get settled on batteries/charger AND finish the convertion. So whatever I do - has to be cheap, so I don't have regrets scrapping it later, if, for example, i'll win lottery and will go LiFePo.
Last edited by Stunt Driver; 09-10-2009 at 06:26 PM.