Old napa 85-120 charger help

[scooterbonbon]

I have an old charger some one pulled apart and left it a mess. Napa 85-120. There is a series of plates with spacers disks “ about 8 or 9” . Is there any info on order in that they need to be put in? There is square playes , round disks, metal washers, insulator washers, think metal tabs to connect to 3 different insulated circuit.

 

[BillK]

That is a rectifier. Yes it needs to be assembled in order but I don't have a clue what the order is on your particular unit. Unless you can find someone with the same exact unit its going to be hard. Is a new rectifier available ?

 

[scooterbonbon]

Im going to guess the disk goes on bottom of plate. Then a metal washers to conduct to the metal strip. Insulator after that. The metal strios have holes for bolts so its a matter of try and error. I can try napa maybe for new one. My cousin brought it into a guy once but thats as far as it went. No idea who took it apart and left all mixed up

 

[BillK]

Do a search on "plate rectifier" and you should find some pictures but the order of assembly is pretty specific to each unit. Are there any numbers on any of the plates ?

 

[BurtEggley]

that is a selenium plate rectifier and it would be unreliable at this age. They go bad over time. The unit needs to be rewired with modern diodes.

Unless one has a need for fast charging, the newer trickle maintenance chargers are really better for battery life.

 

[scooterbonbon]

Im going back tomorrow for a week. All i can recall was dust on one side of plates . That side up. I can figure out the order by how the holes line up. One set is bent upwardsone set down and other is flat. I think im gonna start with insulator on bottom , then plastic spacer, metal tabs, metal washer, then plate. Keep building it up and see.

that is a selenium plate rectifier and it would be unreliable at this age. They go bad over time. The unit needs to be rewired with modern diodes.

Unless one has a need for fast charging, the newer trickle maintenance chargers are really better for battery life.

its going in the service truck for boost jump

 

[BurtEggley]

Im going back tomorrow for a week. All i can recall was dust on one side of plates . That side up. I can figure out the order by how the holes line up. One set is bent upwardsone set down and other is flat. I think im gonna start with insulator on bottom , then plastic spacer, metal tabs, metal washer, then plate. Keep building it up and see.

its going in the service truck for boost jump

not with a 60 - 75 year old selenium rectifier. 99% chance it will leak AC thru to the battery. You can replace it with a modern diode bridge if you know how to solder it in and how to size the diodes. Most likely there is rotted cloth wiring in it too.

 

[scooterbonbon]

Im going to guess thats why somebody took it apart and left it.
Going to have to do some reading . I remember in school the zener diode trio - electric check valves in alternators.
This seems like a good group here . I hope i can return the favor helping out.

 

[scooterbonbon]

not with a 60 - 75 year old selenium rectifier. 99% chance it will leak AC thru to the battery. You can replace it with a modern diode bridge if you know how to solder it in and how to size the diodes. Most likely there is rotted cloth wiring in it too.

Somebody told me while ago the reason alternators are not used in starting units was the rectifier would have to be the size of empire state building for it to work

 

[BurtEggley]

There are articles out there. Basically you will need to figure out what the AC or DC wattage is depending on the circuit, depending how the selenium rectifier was used. If it has a stepdown transformer then you will need maybe an 80 - 100 amp silicone diode bridge. If it has a transformer then the 4 silicone diodes made up into a bridge convert the appx 14V AC to 14V DC after the transformer is done with the AC. If it instead has no transformer and used the selenium rectifiers along with a big resistor or heat coil to drop the voltage, then you will need to add a large wattage resistor to drop the voltage because selenium rectifiers had a higher resistance in them than silicone diodes do. You can use a large varistor to dial in the best resistance then choose a fixed high wattage resistor in that amount. If it has capacitors in it, they will need to be changed out also because they seldom live that long either. I am probably not making sense but it all depends how the circuit was wired. My best GUESS is that the unit dropped 120V AC to about 20V AC thru the transformer, then the selenium rectifier changed the AC to DC and dropped the voltage too. Since silicone diodes don't have as much resistance, you have to add a large wattage resistor in to make up for the selenium rectifiers not being there anymore. The size of the diodes all depend on their placement in the circuit.