12v to (6v times 2)

[legendaryfrog]

hi everybody, yesterday i bought 2 working camcorder batteries at my local goodwil for 3 dollars. they are both 6 volts each, Ni-Cd,and one is 3800 mAH and the other is 4000 mAH. they have 2 oval charger plate thingies on them for charging with a charger which i dont have. i have many 12 volt transformers lying around so i wondered if there is there any way to charge them by attaching some sort of electrical cables from the transformer to the battery?

[Richard Ellis]

OK...lets' walk thru this...do you have the "mount" that the batteries would sit on to charge?..Or do you have solely just the batteries.
If you don't have any of the charger pieces, assembling one from scratch with some 12v transformers lying around is kinda involved & probably not worth the effort....UNLESS you really want to do this project....I could walk you through it if you want.
Perhaps it would be best for you to peruse thru E-BAY to find a matching charger.
_____________________________________Rick........

[legendaryfrog]

no i dont have the mount, just the battery. i checked ebay and like 8 other sites

[Richard Ellis]

Yuk.... nothing found huh?
WELL.... this is how you could do it. First of all find the biggest transformer in your collection & find the one with only two "output" wires....You need to rectify(Change AC to DC...appx.) that 12v...you will need whats called a bridge rectifier. From there you will need to smooth the pulsing DC to a level DC....a rather large Capaciter, and then you will need to drop the voltage down to your six volts to match the battery...this can easily be done with whats called a three pin voltage regulater.
This regulater can be a fixed voltage or a variable voltage version.
You will need a plastic case of some sort to house this stuff complete with a hoard of connectors, switches, fuses, indicators, etc.etc.....being that you could easily make it switchable from 6volts all up thru 12vdc...you can make it to power all sorts of stuff..including charging up 12V batteries( If the transformer is big enough)....I'll see if I can dig up a LONG parts list for ya....OK?
PS.....how would you make the connection to your little rechargables?The terminals are usually smooth & don't take well to anything "attaching" to them.
Another wildcard is that batteries require a voltage over and above the absolute rating of the battery to "charge" them.
As in 6.2 volts for a "Slow" charge or 8.5 volts for a "Fast" charge of a rated Pure 6.0 volt battery......THATS the rub as we don't know how much "overvoltage" is needed for a proper recharge.....it changes from battery to battery......& they can be easily overcharged to the point of wrecking the battery. Further these chargers will taper off the voltage over time..."topping off" the charge. In effect stop charging once there' fully charged.
____________________________________Rick........
_________________________________Rick............

[gmphadte]

The standard charge for a NiCd battery is C/10 for 14 to 15 hours.
This means a 3800 mAH battery will need 380mA current to be passed through the battery for 14/15 hours.

U will need to assemble a constant current source of 380/400mA.
Read the datasheet of LM317T at www.national.com and assemble.

Put up your ideas here and will help.

As for connecting to the battery, u will need two springs and some self made battery support to make the contact.

Bare wire ends and rubber band also can do it if u are in for a quick solution.

Gajanan Phadte

edit:The transformer will supply AC voltage and the IC will need rectified and filtered DC voltage.

[legendaryfrog]

meh. yesterday i put one electrical wire ( - ) inside the plug at the end of the transformer cord, and the other to the outside ( + ) and the other other end of the wire to a wire filter thingy and the output to the battery. after 8 hours i hooked it up to my portable speaker system and it worked fine.

[gmphadte]

I strongly recommend u to understand what u are doing. These things can lead to personal injury.

Remember u SHOULD NOT CHARGE the battery directly from a wall wart unless it is charger.

Gajanan Phadte

[AndrewT]

Hi all,
judging by the comments in post6, can I suggest we leave him well alone. Any advice we might offer could easily be misinterpreted and lead to a serious accident.

I certainly don't want the blame nor the finger pointing at an FAI.

[legendaryfrog]

my methods are a little strange, but they get the job done. and isnt that all that matters