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Battery charger help!

Thread starter #1
Hi all, I'm hoping you can help me out in fixing my dads old battery charger (Century 60amp 6/12v) that is circa 40 years old!

I have ascertained that the rectifier is the problem as I have 31V AC from the two wires going into the rectifier plate from the transformer, but 0.6V DC coming out. I'm aware that having 2x 6 diode plates is old school and is relatively obsolete and expensive to repair (Century have a pack of 4 diodes for $23). What can I use to bring it kicking and screaming into the 21st century and how would I go about wiring it in? (Bearing in mind I've not been involved with electronics since my high school days some 18 years ago, so I'm fairly rusty!)

If it makes any difference, I'm in the UK so the unit has 230v input.

Thanks in advance for any advice!

(Apologies if I've posted in the wrong section!)


Super Moderator
Most Helpful Member
31 volts is rather a lot for a 12v battery charger.
This could be a bi-phase rectifier, rather than the more common bridge rectifier.

Pictures of the insides would help.
A schematic diagram would be even better.

Thread starter #3
Many thanks for getting back to me so quickly! I've attached a pic of the rectifier as it currently sits out of the unit. The 2 wires from the transformer were connected to the studs on top of each set of diodes with the output connected to the bolt on the base plate, which went via a voltmeter on the front of the unit to the battery clamp. I have some pics of it in the unit but are too large to upload so I'll resize them and add them later if needed.




Well-Known Member
Most Helpful Member
Are you sure about the 6 diodes? It looks to me like there are only 2 diodes. I'd guess those big circular plates are selenium rectifiers each sitting on 6 insulators.


Well-Known Member
Most Helpful Member
I'd guess those are standard silicon diodes. If so, be aware that for a given current a silicon diode will drop less voltage than a selenium rectifier plate, so you may need to add some series resistance to compensate.

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