Selenium rectifiers are now dinosaurs. Finding replacements will be difficult & expensive. Better alternative is to replace them with suitable silicone solid-state rectifiers with necessary circuit modifications.

Check out this site. They make and have repair parts for most "box on wheels". The diodes are most likely silicone unless your box is 50 years or older.

It would have been nice to have a name, model number or some other info age etc...

if you do not have any of this just match pictures, charges rates and any other descriptions to your charger.

Hi MetalSmiths,

Great link,

I bought the charger 11 years ago.

The item has been discontinued.

Will check for a replacement.G.A. thanks

Hi Lo Volt,

You are perfectly right about that.

The reason they stick to these metal plates (selenium and copper) rectifiers is because they can make that charger without sophisticated regulation circuits.

The I/U - voltage drop versus current is very suitable for "rough" battery charging.

When the current drops down, voltage over the cell increases and the battery has more chance to survive the "charge".

This battery charger- see the timer- and charge settings - is not made for contineous

use. They need guidance and some help, because they lack every kind of "intelligence". They might not destroy the battery the first time, but yes-- after a while they are killers. GA

I was warned off selenium rectifiers as an apprentice 40 years back. The fumes when they fail I was told are toxic. True or not I've never really checked on, but I've given them as a wide berth as I could.

Given the age of some of the plants I worked on wasn't always possible. If one burnt out it would be quite a while before I'd go near it, the brown smoke didn't make you feel at ease.

I have met some of these rectifiers. I had 2 rectifier stacks once with a parallel configuration of 5 diodes each, good for 200 Amps.

These tiny selenium diodes fall out of the frame, once you take it apart.

Check with ohm meter and throw the bad ones out.

Out of 10, I had 8 good ones left. Arranged these in the frame and have now a 160 Amps battery charger. Do not keep the bad ones in place, but replace if necessary with some isolating material.