Sterling charger Schottky diodes

Hoolie

Hoolie

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I have a Sterling Procharge Ultra with one of the outputs with short-circuited Schottky diodes. Does anyone know the purpose of these diodes? Are they the final stage of rectification of the switching mode power conversion or are they just to isolate the three separate outputs? I intend to common up the outputs so don't need any isolation.

In spite of the blown up diodes I seem to get the same voltage on all three outputs, but I haven't connected the device to a battery bank yet so I don't know what current is available on each output.

Thanks
 
Hoolie said:
I have a Sterling Procharge Ultra with one of the outputs with short-circuited Schottky diodes. Does anyone know the purpose of these diodes? Are they the final stage of rectification of the switching mode power conversion or are they just to isolate the three separate outputs? I intend to common up the outputs so don't need any isolation.

In spite of the blown up diodes I seem to get the same voltage on all three outputs, but I haven't connected the device to a battery bank yet so I don't know what current is available on each output.

Thanks
Click to expand...

If its any use, one goes to the house bank, one to the engine battery and the instructions say if the third is not used to parallel it to one other.
 
Sterling advise connecting unused outputs on the Ultra, but it is not a requirement, unlike the previous model, where i had to be connected.

If it works as it should, the maximum current of the charger is available on each output, up to a total of the max current.

For anyone only needing a single output charger, the smaller Victron chargers are a better buy than a Sterling.
 
They are there to create a separator so 1 bank doesn't leak back to the other and so on. Measured before the diode is a slightly higher voltage, to take into consideration the voltage drop across the diode packs.

Can you advise how you have tested the diodes to diagnose a short circuit?



Hoolie said:
I have a Sterling Procharge Ultra with one of the outputs with short-circuited Schottky diodes. Does anyone know the purpose of these diodes? Are they the final stage of rectification of the switching mode power conversion or are they just to isolate the three separate outputs? I intend to common up the outputs so don't need any isolation.

In spite of the blown up diodes I seem to get the same voltage on all three outputs, but I haven't connected the device to a battery bank yet so I don't know what current is available on each output.

Thanks
Click to expand...
 
Diodes cannot short circuit.

They either fail open circuit or closed circuit. In this case, if one fails open circuit there will be no output on the connections. If one fails closed circuit it ceases to be a diode and will allow continuity between that output and the other two. Easy enough to test for both conditions with a multi meter.

If the OP only requires a single output a failed diode wouldn't matter, as such, an open circuit output wouldn't matter as he wouldn't use it and a closed circuit failure also wouldn't matter, as it saves bridging the outputs. The potential problem is why the diode failed. If it failed closed circuit, that's caused by over voltage, so i'd be concerned that the over voltage event might occur again and damage the batteries, or worse. It would be prudent to replace the failed diode/s.
 
matthewriches said:
Can you advise how you have tested the diodes to diagnose a short circuit?
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Maybe some egg sucking here but incase anyone else stumbles across the same issue, here is what I was taught. Any mediocre multi meter will allow you to do a simple diode test.

Anode to Cathode test should be moderately low resistance. In the K ohms scale normally.
Cathode to Anode test should be very high resistance. In the M ohms scale or simply OL.

If above isn't the case...

An OPEN circuit diode will give high resistance both forwards and backwards.
A SHORTED diode will give low resistance forwards and backwards.



Either use another channel on the charger and see what happens or crack a beer, watch TV and deal with it another day ;) Happy to do a postal repair service if you're struggling.
 
Testing diodes in situ isn't terribly reliable. In this case the diodes can be tested very easily without even taking the lid off the charger.

With nothing connected to the outputs, turn the charger on, with the multi meter set to DC volts, measure between neg out and each pos out, any that don't show voltage will indicate an open circuit diode.

Again, nothing connected to the outputs, charger turned off. Test for continuity between the three outputs, any with continuity will indicate a closed circuit diode.
 
PaulRainbow said:
Testing diodes in situ isn't terribly reliable. In this case the diodes can be tested very easily without even taking the lid off the charger.

With nothing connected to the outputs, turn the charger on, with the multi meter set to DC volts, measure between neg out and each pos out, any that don't show voltage will indicate an open circuit diode.

Again, nothing connected to the outputs, charger turned off. Test for continuity between the three outputs, any with continuity will indicate a closed circuit diode.
Click to expand...

Hmm Not quite that simple.
Wont you will have to do two checks between each pair with opposite meter connections ( maybe also using the diode test range .... not sure if that is necessary with Schottky diodes or not)

Between two good diodes you'll get no continuity either way. Between a good diode and shorted diode you'll get continuity one way. Between two shorted diodes you'll get continuity both ways.
 
Bit disconcerting this. I've just bought a sterling pro Charge Ultra 60A specifically because you can use the custom setting to set absorption and float voltages the same, (14.7V). Do I have to worry about failing Schottky diodes being a common problem?
 
Richard10002 said:
Bit disconcerting this. I've just bought a sterling pro Charge Ultra 60A specifically because you can use the custom setting to set absorption and float voltages the same, (14.7V). Do I have to worry about failing Schottky diodes being a common problem?
Click to expand...

Don't think it's a common thing Richard, i have one and it's performed faultlessly. This is the fisrt time i've heard of failed diodes in one.
 
VicS said:
Hmm Not quite that simple.
Wont you will have to do two checks between each pair with opposite meter connections ( maybe also using the diode test range .... not sure if that is necessary with Schottky diodes or not)

Between two good diodes you'll get no continuity either way. Between a good diode and shorted diode you'll get continuity one way. Between two shorted diodes you'll get continuity both ways.
Click to expand...

I thought it went without saying, if you found continuity between two outputs you would need to do addition testing to determine if the fault was with one or other of the diodes.

You could take the charger apart and use the diode tester, but that should be unnecessary.

I wouldn't think Shottky diodes would be any different than any other diode in this case ??
 
PaulRainbow said:
I thought it went without saying, if you found continuity between two outputs you would need to do addition testing to determine if the fault was with one or other of the diodes.

You could take the charger apart and use the diode tester, but that should be unnecessary.

I wouldn't think Shottky diodes would be any different than any other diode in this case ??
Click to expand...

You might carry out a simple continuity test with the meter connected so that it does not detect the continuity of a shorted diode . Hence the reason to reverse the meter polarity and repeat the test.

You need to use the diode test range on digital multi-metes rather that the resistance ranges because the forward voltage drop of silicon diodes is high enough t prevent a forward resistance reading. Schottky diodes have a must lower forward voltage drop so may respond if tested on a resistance range but using the diode test range will, I guess, guarantee results whereas a resistance range may not
 
VicS said:
You might carry out a simple continuity test with the meter connected so that it does not detect the continuity of a shorted diode . Hence the reason to reverse the meter polarity and repeat the test.

You need to use the diode test range on digital multi-metes rather that the resistance ranges because the forward voltage drop of silicon diodes is high enough t prevent a forward resistance reading. Schottky diodes have a must lower forward voltage drop so may respond if tested on a resistance range but using the diode test range will, I guess, guarantee results whereas a resistance range may not
Click to expand...

I think that a continuity test using the buzzer should work. But, thinking about it further, the diode test setting could also be used without taking the charger apart and would cut out additional tests as you could test individual outputs using an adjacent output for the anode connection.
 
Thanks all for your comments and suggestions.

The diodes are accessible behind a removable panel and I used a multimeter to test them. Each output has two diode packs - DSSK48-0025B that contain two diodes with a central cathode. The defective ones were v. low resistance anode/cathode. The diodes were apparently destroyed by some careless action by the previous owner. I'm sure they didn't fail spontaneously!

Paul - your comment about full rated current being available on each output is perhaps confirmed by dual 25A diodes for a 50A power supply!

Thanks to all again, I think I will just common up the two apparently OK outputs.
 
Thanks. I was prepared to replace the diodes as they're not that expensive but really a bit of a faff as they are PCB and heat-sink mounted.
 
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