Help idinifying circuit from Battery Charger

[R_J]

Re: Help idinifying circuit from Battery Charger

Your picture does'nt give enough information because the wires are disconnected. I would guess that the secondary of the transformer has a center tap, this could be connected to the either the negative or positive lead going to the battery, the two other leads from the transformer each connect to two of the diodes and all the diodes have there (either anode or cathode) connected to the other lead going to the battery. The voltage selection is usually done with the primary winding.

[redwire]

Re: Help idinifying circuit from Battery Charger

Yeah, the picture doesn't make sense- all the heatsink's back side has insulators and we're missing the transformer connections.

These car battery chargers usually use just two rectifier diodes and a transformer with center-tap. Not four diodes as a full-wave bridge, which costs more money.
They might have put two pairs of smaller diodes in parallel to get more amperage.

I drew a rough schematic of two possible rectifier configurations which might make it easier to understand, or OP can give more pictures.

[R_J]

Re: Help idinifying circuit from Battery Charger

It will be like the lower diagram, Mine is not as fancy but it shows how it is likely connected, This one uses 4 diodes because of the 100 amp boost/start function, On many I have seen they connect the diode heatsink to the negative line, I think in case something shorts the heatsink to the case, it is at negative potential and not +14v

[davg]

Re: Help idinifying circuit from Battery Charger

It will be like the lower diagram, Mine is not as fancy but it shows how it is likely connected, This one uses 4 diodes because of the 100 amp boost/start function, On many I have seen they connect the diode heatsink to the negative line, I think in case something shorts the heatsink to the case, it is at negative potential and not +14v

Tks RJ you are close the heatsink is connected to the negative line through a 12V/50 Amp breaker?? to the battery negative lead. A center tap from the transformer to the Amp meter to the positive lead to the battery. Not sure how the leads from the diodes were connected because these were missing. I can only assume they were similar to what is shown in the picture post #1 Your drawing is correct but with the Amp meter on the positive line

[R_J]

Re: Help idinifying circuit from Battery Charger

The amp meter can be in either line, This is likely how the diodes were connected. Best I can do with paint.

[davg]

Re: Help idinifying circuit from Battery Charger

The amp meter can be in either line, This is likely how the diodes were connected. Best I can do with paint.

Thanks R_J that's a lot better than I can do in paint. I was thinking the flow was in the other direction?

[redwire]

Re: Help idinifying circuit from Battery Charger

I guess the rectifier diode's stud needs to be the anode?
But the popular diode VC-70HF80 configuration is cathode to stud, or special version diode VC-70HF(R)80 which has the anode to stud.
Or it might be possible to rewire the charger so the heatsink is (+) out to use the parts you have.

I can draw a schematic quick because of the libraries, same as what R_J drew.

[stj]

Re: Help idinifying circuit from Battery Charger

does this thing have a visible make / model?

[eccerr0r]

Re: Help idinifying circuit from Battery Charger

nice...parallel diodes...hope they're matched...

[davg]

Re: Help idinifying circuit from Battery Charger

does this thing have a visible make / model?

tks stj Here is what is visible 15/2/100amp-6/12v with these #'s 11-1556-6 and 141-153 and carry the Canadian Tire Corporation brand Motomaster.

[davg]

Re: Help idinifying circuit from Battery Charger

Yeah, the picture doesn't make sense- all the heatsink's back side has insulators and we're missing the transformer connections.

These car battery chargers usually use just two rectifier diodes and a transformer with center-tap. Not four diodes as a full-wave bridge, which costs more money.
They might have put two pairs of smaller diodes in parallel to get more amperage.

I drew a rough schematic of two possible rectifier configurations which might make it easier to understand, or OP can give more pictures.

I screwed the two 72HF80M diodes to the heat sink using the bottom drawing configuration but with just the two diodes and the thing works fine but I have reverse polarity on the output. any suggestions

[eccerr0r]

Re: Help idinifying circuit from Battery Charger

As many people have pointed out earlier, that is the trouble with the stud diodes. The case is cathode or anode depending on model and you can't change it without buying a different model. You'll have to either isolate the diode from the case or ... creatively use the situation as it stands - if possible (like isolating the whole heatsink if it makes sense or possible; perhaps just swapping the charge wires is the easiest solution.).

[davg]

Re: Help idinifying circuit from Battery Charger

As many people have pointed out earlier, that is the trouble with the stud diodes. The case is cathode or anode depending on model and you can't change it without buying a different model. You'll have to either isolate the diode from the case or ... creatively use the situation as it stands - if possible (like isolating the whole heatsink if it makes sense or possible; perhaps just swapping the charge wires is the easiest solution.).

Tks got ya appreciate it

[redwire]

Re: Help idinifying circuit from Battery Charger

I would reverse the wiring (two wires) at the rectifier's output, going to ammeter (+) and the battery (-) out. Would need a picture of the insides to see which ones.

[davg]

Re: Help idinifying circuit from Battery Charger

I would reverse the wiring (two wires) at the rectifier's output, going to ammeter (+) and the battery (-) out. Would need a picture of the insides to see which ones.

Tks redwire I just changed the colors on the output leads used black tape to cover the red lead and red tape to cover the black lead. Good to go. Doubt if I will ever use it for charging batteries?? More of a learning tool. Thanks to everyone who contributed. Great community great source of knowledge. I have been here for a long time but my greatest regret is that I don't always remember the things I know?? Seniors moments I think.