Classic Battery Charger

[geodon]

Are there any sparkies out there?

I bought this beast at a swap-meet about 20 years ago & would like to have a crack at getting the booger going.

I like the idea of a 20amp battery charger that does 6 AND 12V!

Not a lot of parts:

1x transformer
1x ammeter
1x rotary switch
4x diodes.

I was expecting a rectifier? Or is that what the 4 diodes do? The rotary S/W is for 6V hi & lo & 12V hi & lo.

Any hints or links on how to start?

JAYSUS! I LUUURRRVE that fuse!

I have a multi-meter.

[Basil135]

Ok, now that is old...

The wiring seems to look ok in the pics.

Have you tried the old, "turn it on & see what happens" method?

It might be worth a go. If you want to be really safe, drop the fuse down a couple of notches.

If you get the right sort of output with no load attached, after checking with your multi-meter, it could be time to try loading it up with a battery.

If you have an old battery laying around, check the voltage with it connected & see what you get. Keep an eye on it over the next few hours & see what happens.

Good luck;)

[bee utey]

4 diodes make a bridge rectifier. That's it for electronic sophistication back then! Have the cord checked, plug it in and stand back.

[Blknight.aus]

heres how it works....

type 1.

the mains comes in and it hits the transformer
the power comes out of the transformer from multiple taps and into the switch
the power goes from the switch and into the 4 diodes
from there it goes into amp meter then to the battery, there should be 2 fuses, a 5a fuse on the mains input and a 20A fuse on the battery leads

type 2 is essentially the same except the switch goes between the mains and the transformer and then he power runs from the transformer to the diodes into the amp meter and then into the battery, fusing remains the same.

I've got the same model.... on low it pumps about 5 amps medium pushes
about 15 and on high 30+ Have a read of the plate, 20A continuous 25A 1HR

[p38arover]

The circuit probably switches transformer outputs to get the voltage change.

Do not change ranges whilst the charger is connected to a battery which is still connected to the car.

To do so can induce very high voltages which can damage electronic equipment - think of breaking the points on an ignition coil.

Many years ago, when I was a trainee electronics tech, I remember another trainee doing just that. The meter across the circuit pinged so hard it bent the needle into an S-shape.

[Blknight.aus]

yep, but in the cars that was designed to charge the points were about the most sophisticated part of the electrical system

with a 15A fuse in the mains socket and a nail in the dc fuse mine will start a small ride on lawnmower..... lets see one of these newfangled multistage switchmode lectronicy chargers do that... Thinking about it that may have been what killed the Amps meter...

[geodon]

OK!

So the various hi/lo 6V/12V are segregated at the transformer in AC form & sent to the rotary switch for selection by the operator (1st photo).

After selection via the switch, the AC current is fed to the diode bridge rectifier:

Diode bridge - Wikipedia, the free encyclopedia

ie the blue wire being pointed at in the second photo.

The common AC feed from the transformer to the diode bridge is in the third photo: the blue wire being pointed to. NB they are both blue as there is no polarity distinction with AC?

The +ve DC feed to the battery is the red wire being pointed to in the 4th photo.

Finally, the -ve DC feed to the battery leads via the bogan fuse and the ammeter is the blue wire being pointed to in the 5th photo.


Beeutey, do I get a Koala Stamp & Gold Star for that & will I avoid getting hair like the late Colonel Gaddafi?

[superquag]

It would be a good idea to get a soft paintbrush and compressed air....blow and gently brush out the 50 years of dust & debris before you get serious with it. :p

- A bit of moisture in the air, and the biteys can take some interesting short-cuts!

[geodon]

I def have 240V power going in.

However. there is no rhyme or reason to the DC outputs so I have to follow it thru from 1st principles.

They don't make switches like this any more. I can dismantle it & clean up the contacts!

Blknight.aus: how many stops can you get on your rotary switch? With 12V and 6V hi,med,lo plus an "off" there should be seven but I can only get 6!?
Is "off" an inbetween the stops position? 1st photo.

Also, how can there be 6 outputs on the SW when there are only 4 inputs from the transformer? Unless 2 get combined for the high powered one?? 2nd photo.

Can anyone tell me how I can measure AC volts? The multi-meter only does DC.

What is the device between the common feed from the transformer & the diode bridge? It's labelled "AUTO BREAK". Last 3 photos

[bee utey]

Also, how can there be 6 outputs on the SW when there are only 4 inputs from the transformer? Unless 2 get combined for the high powered one?? 2nd photo.

The transformer will have two 6 volt windings. In series they will provide 12V



Can anyone tell me how I can measure AC volts? The multi-meter only does DC.

Any $10 Dick Smith cheapie multimeter will have an AC volts range. Or purchase/make a cheap bridge rectifier and connect it to the probes of your DC only meter.



What is the device between the common feed from the transformer & the diode bridge? It's labelled "AUTO BREAK". Last 3 photos

Thermal circuit breaker?

[superquag]

Upgrade to the $20 cheapie from Dicks or Jaycar.... You want better (read "SAFE") leads & probes if there's any mains power nearby....

- We'd like you alive and well and on this forum for a while longer!

Definitely looks like a thermal circuit breaker. That's an Over-Current Protection Thingy that takes time to get hot & bothered...sulks a bit, then Opens. When it cools down it re-sets itself.

- As opposed to a wire fuse that instantly blows at a pre-determined current ("Amps") and needs to be replaced with a new one.

Google Types of fuses for some easy reading.

[geodon]

I'll give it a bit more time & $ and, as I have bigger fish to fry, if not successful I'll put back on the ornament shelf with the old Castrol signs, oil tins etc

[slug_burner]

meters witrh a linear motor don't know if it is rectified AC or DC they are measuring it is just a matter of a calibration factor.

Before going into the 1/square root (2) calibration factor I agree with the others and go out and get a cheap meter.