Golf Cart Charger

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GA Gyro

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I am not sure if this is the correct forum... however my question is electrical...

At the airport where the gyro's are... we have an old golf cart we use to ride around the airfield... it is quite popular, given our hanger is one of the farther from the office and runway.

A week or so ago, the charger quit working... so I brought it home over the weekend.
After taking it apart, I find a BIG transformer, a fuse of sorts, an ammeter, a relay, and a half wave rectifier.

It appears the rectifier opens when a load is put on it... so I am thinking to find a new way to turn AC to DC.

The golf cart has 6 x 8V batteries, for a total of 48 volts. I might mention that one of them measures 4+ volts, two measure 6.25 and 6.33 volts, the other 3 measure 8+ volts... for a total of 41-42 volts. All the 6 batteries have been filled with fresh distilled water.

There is a relay in the charger that is supposed to verify connection to batteries, before starting the charger (controls the 120V AC circuit to the transformer)... I am wondering if the relay is failing... I do not have a variable DC power supply to test it.

Do any of you have experience with these chargers... any and all thoughts, suggestions, comments, pokes, etc... are greatly appreciated.

And one more question: Where would I find a half wave rectifier (two inputs, one output), that can handle 20+ amps @ 48V... preferably 30A would probably be better. THX in advance for any sources!
 
A few things you need to look at. First a Half-wave rectifier is commonly known as a diode and would have 1 input and 1 output . A full wave rectifier is a bridge of 4 diodes with two inputs and two outputs. While there may be something I am not aware of any common AC/DC conversion things that would have 2 inputs and 1 output. Could one of the outputs be disguised as a case/chassis ground? What specifically do you mean by "The rectifier opens when a load is put on it"? What voltage do you get from the rectifier when there is NO load ? Golf carts are extreemly common, I would expect that every part possible is available online both new and used.
 
Boswell said:
A few things you need to look at. First a Half-wave rectifier is commonly known as a diode and would have 1 input and 1 output . A full wave rectifier is a bridge of 4 diodes with two inputs and two outputs. While there may be something I am not aware of any common AC/DC conversion things that would have 2 inputs and 1 output. Could one of the outputs be disguised as a case/chassis ground? What specifically do you mean by "The rectifier opens when a load is put on it"? What voltage do you get from the rectifier when there is NO load ? Golf carts are extreemly common, I would expect that every part possible is available online both new and used.
Click to expand...

To answer your question... which I kinda anticipated... after I posted...
The transformer has two secondaries, in parallel... so the two inputs and one output is two windings. Note the secondary is NOT a center-tap transformer, it actually has two sets of secondary windings, as well as one primary windings.
(As you can tell, I have an electrical background als0... :) ).

The diode bank is a buss bar with a couple of lumps of something, about 3/8 in dia and about the same length, held in place with copper spring bars. The buss is the common, the two CU/spring bars are the terminals.... the lumps must be the diodes.

I was hoping someone that was familiar with golf cart chargers, and knew of a source for modern diodes, would come along with a link... :)

THX for your input, all input is welcome!
 
A diode array with two inputs and one output is called a half bridge. They are commonly used with center tapped transformers to provide full wave rectification. A dual output transformer with the windings in series and in phase functions as a center tapped winding.

Modern diode of ample current and voltage ratings abound. From your description, it looks like you are charging a 48 volt battery bank. You don't say what the charge current is but I would guess somewhere in the neighborhood of 15 to 20 amps. The reverse voltage rating on the diode should probably be 200 volts. If you can't find a half bridge, you can use one half of a full bridge or you can use two individual diodes. You will want to provide adequate heat sinking.

If you check DigiKey, Mouser, or Newark, you should be able to find diodes to meet your requirements. all of them have on-line selection apps to narrow your search. About half bridges; they come in two flavors, common anode and common cathode. you need to pick the correct one. Many of the half bridges have no markings to distinguish one from the other, other than their part number.
 
RJSakowski said:
A diode array with two inputs and one output is called a half bridge. They are commonly used with center tapped transformers to provide full wave rectification. A dual output transformer with the windings in series and in phase functions as a center tapped winding.

Modern diode of ample current and voltage ratings abound. From your description, it looks like you are charging a 48 volt battery bank. You don't say what the charge current is but I would guess somewhere in the neighborhood of 15 to 20 amps. The reverse voltage rating on the diode should probably be 200 volts. If you can't find a half bridge, you can use one half of a full bridge or you can use two individual diodes. You will want to provide adequate heat sinking.

If you check DigiKey, Mouser, or Newark, you should be able to find diodes to meet your requirements. all of them have on-line selection apps to narrow your search. About half bridges; they come in two flavors, common anode and common cathode. you need to pick the correct one. Many of the half bridges have no markings to distinguish one from the other, other than their part number.
Click to expand...

Thank you!

Yes, the charger does charge the entire 48 volt battery array at once...
The input of the charger is 120V and 10A...
The output is 48V and 18A.

Thx for the reverse voltage rating (200V)... that is one thing I did not consider.
I was hoping to find the type of diode that looks like a top-hat, with a locknut... and mount two of them on a finned heat-sink.
Good suggestion to call Digi-key... will do so in the morning.

How would I know whether to use common anode or common cathode?

THX

John/GA
 
THX...

I was thinking about this... I need to go out to the hanger and look at the wiring of the batteries and the charger outlet/plug (between the charger and cart)... to determine the direction of current needed to charge them. This should answer the anode/cathode question...
Sometimes I think I have 'part-seimers'... I have to think about something for a few minutes... and the answer becomes obvious... :rolleyes:
 
GA Gyro said:
Thank you!

Yes, the charger does charge the entire 48 volt battery array at once...
The input of the charger is 120V and 10A...
The output is 48V and 18A.

Thx for the reverse voltage rating (200V)... that is one thing I did not consider.
I was hoping to find the type of diode that looks like a top-hat, with a locknut... and mount two of them on a finned heat-sink.
Good suggestion to call Digi-key... will do so in the morning.

How would I know whether to use common anode or common cathode?

THX

John/GA
Click to expand...
If the common terminal of the half bridge goes to the positive side of the battery array , it is common anode. This is most likely what you would have as the ct of the transformer windings usually is grounded.
In the 30 amp region, it is not likely that you will find the top hat type rectifier. They cost much more to make in that configuration. I have seen some in the 100- 600amp region. They come with braided wire pigtails. If you really want that type of package, you can specify stud mount as one of the search parameters in the selection app.
 
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