I'm fixing two battery chargers, the big ones that can also start a car. There's an amp meter with no apparent connections. Comparing the one I have on the bench right now versus the other one with a similar meter has a clamp that holds wires against it. I've never seen an amp meter like these, but here they are.

The questions are regarding this device:

What is it?
What does it do?
What does it prevent (if anything)?
Is it polarity specific?

The wires to the left come directly from the transformer and are part of the negative jumper lead. The unattached (at this moment) wire terminal (right side) goes to the negative battery alligator. I am assuming current flows from right to left, through the amp meter and back to the transformer. I'd like to move it. I'd also like to understand what it is and how it works.

As for the positive cable, it's attached to a diode heat sink plate, and there are no issues there.

The project started when a neighbor asked if this can be fixed. I have it working but not with the amp meter. So there's no further need for troubleshooting or repair, other than restoring use of the amp meter. THAT is what I'm solving right now. Using the other machine I have determined the correct direction for the cables to go so as to read current to the battery under charge.

So;
What is it?
What does it do?
What does it prevent (if anything)?
Is it polarity specific?

 

https://www.boutiquertbl.com/en/protector-breaker-sch00109

SCHUMACHER part.
https://www.boutiquertbl.com/en/schumacher/charger-1

 

https://www.centurytool.net/3999000107_Circuit_Breaker_32_Volt_DC_90_Amp_p/3999000107.htm

It looked to me like either a fuse or a shunt for measuring current. Appears to be the former

 

Thanks bro's.

Is it polarity sensitive?
Does it need to be mounted to keep it cool?

 

Thanks bro's.

Is it polarity sensitive?

No

Well hang on, it could be in the sense of the mounting screws needing to be at ground. Hopefully you can find a data sheet.

 

Thanks bro.

Is it polarity sensitive?

No idea, I just found it by doing a Google Image search. I'd need to see the datasheet or at least a schematic using the part. Likely no.

Some random schumacher battery charger images.

 

371-01-0700-115
It's a Schumacher thermal circuit breaker 70A 32V. It might be made by Buss.
To prevent gross overload of the battery charger if you are cranking.
I can't see it having any polarity, it might be labelled that way to make mechanics not wonder which way it goes in. Or on the other side maybe an extra switch contact is possible to activate a lamp when it trips. But these are usually in parallel with it.

 

Thanks. Especially for the schematic.

I DO have one wire left to figure out where it goes; the fan speed regulator. If I touch the red wire to the positive of the diode plate the fans respond according to the voltage setting, so I think I know where it goes, but there's no plug for it to be plugged into.

Huah! Seesh! Someone dropped this machine. There's a lot of sheetmetal work to be done.

 

There are no grounding contacts, so painted surface or not - will not make a difference. And having removed it - I can see it's a thermal switch, nothing more.

 

It looks just like the circuit breaker in that great collection of photo catalog items. AND it concurs with the circuit schematic in post #6. And since I see no "fan speed regulator" in that schematic, it may not be your exact model charger.

 

No, I'm sure it's not the exact model. This one has 6V, 12V and 24V. Larger transformer but still rated for 200A max. The Fan Speed Controller (FSC) looks factory original, but some genius has made modifications to the machine. The FSC pugs into something but I couldn't find anything to plug it into. But when I touched it to the DC output it reacted. At 6V it ran fairly quietly. At 12V it ran close to full speed. At 12V 200A it ran at full speed. And full speed at 24V regardless of which setting you chose.

Having both the Schumacher and the NAPA units, the guts looked nearly identical. Having worked on an assembly line myself I saw four different HVAC units produced on the same line, same parts. Only one had a different color. Though each had its own variant of electronic control, there was no other differences between them. Same punch press, same break machine, same welds. The Schu' and the N' have just about all the same elements down to the voltage selector, amp meter and the timer. The major difference is the label. The wheels are the same (not surprising), the frame is basically the same with some slight differences, one has a tilted face.

Talked with the owner last night. He left a distinct distaste in my mouth. If he ever asks for anything else - the answer is going to be "I don't have the time." He will be getting it back today. And he's willing to pay for my time with both machines. The Schu' has a dead transformer. Would cost more just to replace the xfmr than to buy something modern and useful. But that's his decision should he want to get it up and running again.

Thanks all for your help.