The CHARGATRON Vintage Battery Charger -- What batts charge with AC voltage??

[EssLight]

My father was cleaning out his tool cabinet the other day. It's not a typical tool cabinet, it it actually a kitchen cabinet, underneath the oven. He has lived in the same house since 1965, so alot of stuff had accumulated in the cabinet. He came across a cardboard box, opened it up, and found it contained a battery charger. Not just any battery charger, but an

Automatic
CHARGATRON
Home Battery Charger by Dynamic Instrument Corp.
(see pictures below)

My father offered the charger to me, of course I took it.
I found it intriguing. I glanced at the instructions on the back of it, it looks like a dumb 2 cell in series charger with that can charge two or four batteries at once, or a single 9V battery. I decided to see if it worked. I plugged it in, measured the voltage across the terminals ... and measured -.004 V DC??:thinking: Something was there, but huh?:huh: Then I looked at the power cube. Hmm, looks like it was made in December 1967. 120 V 60 Hz 5 W going in, and 3&8 VAC 100 mA going out. AC voltage??:thinking: I switched my multimeter to measure AC volts, and found 3.80 V AC on each pair of terminals, and 9.40 V AC on the 9 V terminals. So, it still produces voltage, and I imagine it would put out around 100 mA on each channel, but what batteries would charge on an AC voltage? If someone could let me know the answer to that, I would appreciate it.

That silver button on the front of it, it looks like a control, or heat sink maybe? Nope, just a decoration, a piece of metal pressed into the plastic.

A least the charger does have cooling vents on the front, with similar vents to let air in on the bottom. Those vents provide cooling for the... nothing. That front end of the charger, with the silver button on it, is just empty space. No circuitry, not even wiring. Well, there is an old dust bunny in it.

All the voltage conversion is done in the power cube. It feeds three wires back to the housing, I'm figuring a 3 V line, a 9 V line, and a ground. The housing just has the terminals and holds the batteries... and tries to look fancy.

The charger does seem to still work, but I can't figure out what to possibly use it for. Let me know if you have any ideas.

EssLight

 

[Black Rose]

Interesting find.

That power cube is 2 months younger than I am

 

[EssLight]

That power cube is 2 months younger than I am

Hmm, I hadn't thought about it, the same it true for me.

 

[lctorana]

I bet there's a diode in series with each line.

Nothing else - no capacitor or anything, just a single diode.
(actually 3 - one for each line, plus one for the 9V channel)

The theory was, in those days, that NiCads respond well to a pulsing current, so half-wave rectification, which allowed the cells to "rest" for 50% of the time, was commonly used.

This means that this charger can only be used for charging NiCad batteries. Never, ever be tempted to try a NiMH cell in it.

Btw, I would imagine the two main channels would have their diodes wired in opposite directions. This would allow the two bays to charge on alternate half-cycles, halving the transformer requirement.

It sounds like all three diodes have gone short-circuit. But if you're at all handy with a soldering iron, that should be no issue, as 1N4001 diodes can be bought for 10 cents each full retail!

 

[EssLight]

I do not think there are any diodes, burned out or otherwise, in the charger, but I would have to open it up to be sure. And I don't even own a soldering iron, so I couldn't fix it if that were the case anyway.

Edit: Ictorana was right, there are diodes, see post #12.

What I have discovered, if you look at the third photo on the right hand side, the positive terminal for the top pair of batteries is connected by a metal bar to the negative terminal for the bottom pair of batteries. I think those are connected to the ground wire running back to the power cube.

Edit: I have determined that is not the ground line, but the incoming 3 V line.

The other two wires are connected to metal bars that run to the forward part of the charger. But I am still trying to figure out how they are connected to which terminals at the front.

Edit: I have figured it out, when I can take more pictures I will post about it.

I bet there's a diode in series with each line.

Nothing else - no capacitor or anything, just a single diode.
(actually 3 - one for each line, plus one for the 9V channel)

The theory was, in those days, that NiCads respond well to a pulsing current, so half-wave rectification, which allowed the cells to "rest" for 50% of the time, was commonly used.

This means that this charger can only be used for charging NiCad batteries. Never, ever be tempted to try a NiMH cell in it.

Btw, I would imagine the two main channels would have their diodes wired in opposite directions. This would allow the two bays to charge on alternate half-cycles, halving the transformer requirement.

It sounds like all three diodes have gone short-circuit. But if you're at all handy with a soldering iron, that should be no issue, as 1N4001 diodes can be bought for 10 cents each full retail!

 

[UncleFester]

I had something like this when I was a kid. I THINK it used a night light bulb for current limiting and a rectifier. The (safety) line cord was on the lid and the two prong round male part was on the chager body. When you closed the lid, power was applied to the bulb/diode circuit which was in series with the bateries being charged. Pretty barbaric.

 

[Flash_Gordon]

I do not think that is a charger for rechargeable cells. I think it was intended to "recharge" primary cells. There were a lot of them sold at that time, especially on TV.

Didn't really do much good but at 100 mA max, was not too dangerous either. Notice the label refers to 1.5V batteries and does not contain a warning about inserting non-rechargeable batteries

Then as now primary cell rechargers are a gimmick.

Mark

 

[tslrc]

I also remember a similiar charger when I was a kid, the colors were different and I remember a night light bulb. The 'vent' and lid look familiar. The insides look about the same as I remember it. I don't remember the Chargatron name on the side. I'm thinking mine was all beige, but I may be mixing it up with another charger I had.

 

[MrAl]

Hi,

To find out if any diodes exist in the circuit, connect a 0.1uf
cap across the so-called "ac" output and then measure with
the meter set to DC, not AC. If you then measure a DC
voltage there is at least one diode in series. If there is no
diode you will still measure close to zero.

If it turns out that there is no diode you can add one as
someone mentioned if you intend to use this with NiCd cells,
but you should then also check the charge current so you
know about how long to leave them on charge.

This is really probably something that should go into the
old electronic stuff museum in the attic rather than be put
back into service

 

[SirVette]

I have a Radio Shack charger of similar or same electrical design, much newer 1979. Output 3 & 8 VAC 100MA. More info. is on it. Some:
Charging Time
NiCd AA 7-8 hours
All other
AA, C & D 14-16 hours

9 Volt 5 hours

EssLight
Hope this helps. Something else that may not be clear is probably that if 2 bats. are charged they should be placed as in Fig. 1 (not in the other pair holder). Also the "button" may be a battery tester.

Interestingly it says
"For all carbon-zinc and nickel-cadmium batteries in AA,C,D or 9 volt sizes."

It will charge AAA w/ a metal extender like a small socket added.

It was purchased to charge NiCds.
lctorana is correct that it is a NiCd charger.

Any comments from the experts on "For all carbon-zinc ..."?
I never tried carbon-zinc in it.

 

[snakebite]

yes that is a newer version of one i had as a kid.
note the blockout plug where the bulb once was and the holes for the ac interlock "cheater cord"
the bulb was to set a current limit.the contacts were made to break the circut when a battery was inserted.they would all charge in series.
never had any problem with mine other than a occasional leaker.
i would just put it in the dishwasher to clean it up.
yet another questionable electric gadget from the 60's.like the hotdogger.
i bet ul made them go to the wallwart.
and there are 2 1n4xxx diodes inside.
a 100ma charge rate on modern nimh should be safe even if you miss it a few days.

 

[EssLight]

Thanks everyone for the replies.

It turns out there are a couple diodes in the charger, just located where I couldn't see them without opening the charger up. And I realized that my multimeter does have a diode test function :duh:, of course I had never used it before, but I was able to check that they are there and functional.

What I don't understand, with the charger plugged in, I measure the same 3.80 V AC both through the diodes and directly to the ground plate bypassing the diodes. Would it be different if I measured the voltage across a load, instead of across an open circuit?

I did open up the charger, I will try to take pictures and post more info sometime...

EssLight

Edit: I found the patent for the charger, Patent 3237079. When my brain is working I may try to read and understand it.

 

[Bonky]

dude.. it says 1.5v not 1.2v so it must be for recharging alkys.

This must be the legendary alky recharger that the battery companies removed from the market because they didn't want people to start recharging and stop buying new batteries!!

Throw some old alkys in there, plug it in and see what happens.

 

[KD5XB]

I think Flash is right -- we had one of these too, whan I was a kid -- ours was mostly white with a black cover. It was sold to us to recharge carbon-zinc batteries -- you know, the "9 Lives" kind!