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[More Coffee]

Here's a circuit I built for my friends young lad to look after his bike battery, and to top up his dad's car when he's away. It also charges his NiCad battery packs,
I was really impressed with it, constant current,constant voltage ,I was able to turn this thing down to 10ma at 13.8 volt.. and crank it up to 25volt at 5amp. or 13.8 at 5amp  and then 7volt at 5amp..
If you have an old automotive type charger (iron core transformer) this circuit could be built so a guy could hook the battery charger to this circuit and charge your batteries..
It reverts to constant voltage when the battery is full,and constant current when the battery needs a recharging or top up.
I added two extra pass transistor's(4 in total) and inserted TIP3055's in place of the 2N3055 ,increased the heat sink..
Most parts were scavenged ,, the heat sink came from the local scrap yard at scrap price.. some old computer power supplies.a case from a local thrift shop (it started out life as a cassette deck.)
Hopefully some of you guys will find it handy as an add on, to turn your old buzz box into a mulit use charger..
 

[malcolmfrary]

Looks like a handy circuit - I would just question the use of the 7808 as its a rare bird over here.  Perhaps a 7805 would power that bit of circuit just as well with only minor recalibrating.  Or, if 8 volts was really required there, inserting a 2v7 zener in the ground line of the 7805 would raise its output voltage. 
Also, just using 1/4 of the 339 seems a bit wasteful when a single 741 would do the job.  Unless there was a surplus of 339's in the spares box or a hidden use for the other 3 elements in there.

[More Coffee]

I see your points as valid..
However the two IC's are less than $4 for 5pc's each.
Its a global world,with point click technology.. I cant even get a voltage regulator where I live unless I travel 5hrs away.. nothing is really rare anywhere these day's if a person has an internet connect

[malcolmfrary]

I suppose that the other three elements of the 339 could provide control for three more outlets (charge 4 different batteries at one time)
I am fortunate in my location, my local supplier is a 5 minute drive away, traffic and road works willing, but they do tend to stick with a limited range of "proven sellers", and my preference is to use what I know I can get hold of, just in case. 

[More Coffee]

Im on the same wave length as you.My family and friends usally give me a call before setting things out in the E-Trash.
I find the best parts in old computer tower power supplies,computer monitors,television cable boxe's and the like.
your aboslutly right, with a large enough transformer or power supply ,some volt and amp meters a guy could whip up a multicharger pretty easy.

[irishcarguy]

Now if you did not live in an Igloo & did not have to hitch the dogs to the sled everytime you needed parts, life would be much easier I would think, Mick B.

[More Coffee]

I don't mush/"mush"
 
Dogs would probably be cheaper in the end...
 
Igloo's are not all that bad...The dust from the tarsands tends to wreck'em

[irishcarguy]

It is not the only thing the tar sands wreck, Mick B.

[More Coffee]

No doubt,
Syncrude has enough sulfur byproduct to supply every man,woman and child on earth a case of matches