Rectifier wanted for battery charger.

[Russell Griffiths]

Greetings.
Can anyone tell me where to obtain a large finned bridge rectifier
for a battery charger.

I have an ARLEC "FORMULA" charger V/75077/PS270.
6V/12V LO/HI 18A - 1 HOUR 12A - CONT.

The bridge is made from 4 square plates (around 10cm square)
separated by spacers.

I know I could replace it with a small 35A bridge mounted on a large
heatsink, but this would take more time.

Thanks,
Russell Griffiths.

 

[Phil Allison]

"Russell Griffiths"

Can anyone tell me where to obtain a large finned bridge rectifier
for a battery charger.

I have an ARLEC "FORMULA" charger V/75077/PS270.
6V/12V LO/HI 18A - 1 HOUR 12A - CONT.

The bridge is made from 4 square plates (around 10cm square)
separated by spacers.

I know I could replace it with a small 35A bridge mounted on a large
heatsink, but this would take more time.

** You could spend an *eternity* searching for a high current selenium
bridge to do the job - they have been obsolete since the 1960s. The 35
amp silicon bridge on a (medium sized) heatsink is the way to go.




............. Phil

 

[KLR]

On 8 Jul 2004 03:58:46 -0700, rg26ce1991@hotmail.com (Russell
Griffiths) wrote:

Greetings.
Can anyone tell me where to obtain a large finned bridge rectifier
for a battery charger.

I have an ARLEC "FORMULA" charger V/75077/PS270.
6V/12V LO/HI 18A - 1 HOUR 12A - CONT.

The bridge is made from 4 square plates (around 10cm square)
separated by spacers.

I know I could replace it with a small 35A bridge mounted on a large
heatsink, but this would take more time.

Thanks,
Russell Griffiths.

how old is this thing - sounds like one of those ancient selenium
rectifiers that disappeared in the 1960's.
(unless its 4 stud diodes or something)

I bet it REALLY STANK when it failed too

You can buy a modern 35a rectifier from any of the major stockists.
Screwing it straight onto the metal chassis (with some heatsink
compound) should be sufficient to keep it cool too as at 10a it will
dissipate about 12w..

if its a centre tapped transformer with the centre as the negative
lead - you will only need 2 diodes. In this case dont connect the
negative terminal of the bridge to anything.


You may have a problem with the output voltage being a little higher
as a result though as these old seleniums were less efficient as I
recall ?


if in doubt measure it, but in this case i dont think it will matter a
lot.

 

[Russell Griffiths]

KLR <> wrote in message news:<hqdqe09cba33mrrjmule7uv872868iqhad@4ax.com>...

On 8 Jul 2004 03:58:46 -0700, rg26ce1991@hotmail.com (Russell
Griffiths) wrote:

Greetings.
Can anyone tell me where to obtain a large finned bridge rectifier
for a battery charger.

I have an ARLEC "FORMULA" charger V/75077/PS270.
6V/12V LO/HI 18A - 1 HOUR 12A - CONT.

The bridge is made from 4 square plates (around 10cm square)
separated by spacers.

I know I could replace it with a small 35A bridge mounted on a large
heatsink, but this would take more time.

Thanks,
Russell Griffiths.

how old is this thing - sounds like one of those ancient selenium
rectifiers that disappeared in the 1960's.
(unless its 4 stud diodes or something)

I bet it REALLY STANK when it failed too

You can buy a modern 35a rectifier from any of the major stockists.
Screwing it straight onto the metal chassis (with some heatsink
compound) should be sufficient to keep it cool too as at 10a it will
dissipate about 12w..

if its a centre tapped transformer with the centre as the negative
lead - you will only need 2 diodes. In this case dont connect the
negative terminal of the bridge to anything.


You may have a problem with the output voltage being a little higher
as a result though as these old seleniums were less efficient as I
recall ?


if in doubt measure it, but in this case i dont think it will matter a
lot.

Greetings.
Thanks for the replies.
One diode in the bridge is open.
The two terminals of the bridge that would normally be connected together
for the negative output of the bridge are conected to a switch.

This provides the LO/HI charge setting, giving half wave or full wave rectification.

The 6v setting uses the centre tap, and the 12v setting uses the full
output from the bridge.

If I use a regular 35A bridge, I will actually need to use 2 of them
to have the LO/HI function. I have 2 35A bridge rectifiers from WES in stock.

Using 2 rectifiers will also help to keep the diodes cooler.

Until now, I have only replaced the bridge in chargers up to 8A, and have
mounted it on the chassis as you suggest. I was just a bit unsure if it
would stay cool enough for an 18A charger.

I cannot say how old it is, it belongs to a customer.

Thanks,
Russell Griffiths.