Unusual drawback of owning a variable input battery charger.

[pagoda]

Our boat has (had) a Sterling international Battery Charger. It's designed to cope with anything between about 80V and 300V input voltage.

It achieves that by having a voltage sensor at the front end. When the mains supply is as low as 80-110V - the device configures itself as a voltage doubler, to generate close to normal UK/EU mains power. That is then put through a switched mode power supply - with high voltage smoothing capacitors to get rid of ripple.
Fine and dandy for differing mains supplies? Yes and no....

Our yard power supply suffered a burned out mains contactor, with nasty intermittent loss of power to the consumers in the yard.
The boat power supply tried to compensate for the variation, but ultimately failed.
It had presumably had the mains drop really low - due to the faulty contactor, then come back up to 240V in milliseconds- and drop again. The net result is a blown battery charger. No major damage, no fuses blown, but 3 capacitors and a regulator bit the dust.
The device self protected by vapourizing two tiny bits of PCB track by flashing over. Which I can fix mind you.

Don't go opening switched mode power supplies yourselves, they can be really dangerous- due to big high voltage capacitors- and half the PCB running at mains volts or above..!

If an otherwise good charger quits? ask your neighbours first, and whoever is in charge of the yard..

I'm in communication with my yard...

Maybe a simpler charger would be a good idea!!

Graeme

 

[William_H]

Our boat has (had) a Sterling international Battery Charger. It's designed to cope with anything between about 80V and 300V input voltage.

It achieves that by having a voltage sensor at the front end. When the mains supply is as low as 80-110V - the device configures itself as a voltage doubler, to generate close to normal UK/EU mains power.

I wonder if your assessment of the circuit is correct. certainly most smaller switch mode power supplies use a feed back system to ensure that the output voltage is correct. regardless of input voltage (within certain parameters) it varies the mark space ratio of the pulses to the transformer to give correct output voltage.
I have never seen any voltage sensing circuit as you describe nor a voltage doubler rectifier in the mains rectification. But then I may be wrong.
it might suit you to blame the yard power supply problems on your charger failure but I am not sure it is so. Of course if it did configure itself as a voltage doubler as used on 110 v supply then the voltage retured to 250v then a high voltage DC could be there causing problems. Switch mode power supplies are probably the least reliable of all current domestic electric devices. (with the exception of battery contacts in poertable devices) olewill
good luck olewill

 

[coopec]

Don't go opening switched mode power supplies yourselves, they can be really dangerous- due to big high voltage capacitors- and half the PCB running at mains volts or above..!

If an otherwise good charger quits? ask your neighbours first, and whoever is in charge of the yard..

I'm in communication with my yard...

Maybe a simpler charger would be a good idea!!

Graeme

Now, have I got this right? If your charger quits don't try and fix it yourself ( it would be too dangerous) but ask your neighbour or the Yard Manager to have a go at it? :disgust:

 

[pagoda]

Now, have I got this right? If your charger quits don't try and fix it yourself ( it would be too dangerous) but ask your neighbour or the Yard Manager to have a go at it? :disgust:

Not at all, Simply check with nearby boats if anybody else is having problems with mains/ chargers, before approaching the yard manager with more questions...

 

[GEB]

If your yard supply is derived from a three phase distribution system the initial fault may be to blame. If the neutral conductor is disconnected, even momentarily, the system voltages will become unstable and could rise to 400 volts or more at your boat connection.

I would blame Gustav Kirchhoff - his theories are at play here.

GEB

 

[pagoda]

The device at the Front end is an STR83145 high voltage automatic switch, using a triode thyristor. The adjustment to mains voltage is done at the front end, so could be caught out by rapid changes in voltage level. The capacitors were rated to 400V, but they might have seen more, briefly.
It either voltage doubles or full wave rectifies depending on the level is sees coming in. Not any more!
I may well be able to fix this by replacing a few large capacitors, the STR82145 and bridging the two short vapourised PCB tracks with wire. Cheaper than replacing it anyway.
It's a smart design, but almost too clever for it's own good...

 

[coopec]

Not at all, Simply check with nearby boats if anybody else is having problems with mains/ chargers, before approaching the yard manager with more questions...

I am so relieved!!!:apologetic:

 

[john_morris_uk]

I wonder if your assessment of the circuit is correct. certainly most smaller switch mode power supplies use a feed back system to ensure that the output voltage is correct. regardless of input voltage (within certain parameters) it varies the mark space ratio of the pulses to the transformer to give correct output voltage.
I have never seen any voltage sensing circuit as you describe nor a voltage doubler rectifier in the mains rectification. But then I may be wrong.
it might suit you to blame the yard power supply problems on your charger failure but I am not sure it is so. Of course if it did configure itself as a voltage doubler as used on 110 v supply then the voltage retured to 250v then a high voltage DC could be there causing problems. Switch mode power supplies are probably the least reliable of all current domestic electric devices. (with the exception of battery contacts in poertable devices) olewill
good luck olewill

I agree with you Will. The advantages of the switched mode design as far as manufacture is concerned is that it eliminates the need for a very hefty transformer with a large amount of copper in it which makes the battery charger expensive and heavy. I haven't seen a voltage doubler built into the circuit of any switched mode power supply and I wonder if the OP has analysed the circuit correctly. We both may be wrong but….

I can't imagine that the yard is going to take too much ownership or responsibility for the regulation of the mains supply either unless they were doing something that was so out of order that they disrupted it and should have known better.

 

[nigelmercier]

I haven't seen a voltage doubler built into the circuit of any switched mode power supply and I wonder if the OP has analysed the circuit correctly...

I agree, the nature of a SMPS is that they can easily cope with a wide range of input voltages.

 

[pagoda]

I agree, the nature of a SMPS is that they can easily cope with a wide range of input voltages.

The voltage doubler arrangement is to allow automatic compensation for different mains voltages, while presenting the actual switched mode power supply with as little variation as possible. IE It should always see +- 220-240V, regardless of the outside world voltage..
Sterling make clever chargers....

This is the device on the front end..
http://www.electronica-pt.com/datasheets/ps/STR83145.pdf

The yard contactor box almost burned out and an electrician shut the whole yard down until the switchgear was replaced...
Awaiting a response from the yard..

 

[nigelmercier]

The voltage doubler arrangement is to allow automatic compensation for different mains voltages, while presenting the actual switched mode power supply with as little variation as possible...

Fair enough.

 

[William_H]

The voltage doubler arrangement is to allow automatic compensation for different mains voltages, while presenting the actual switched mode power supply with as little variation as possible. IE It should always see +- 220-240V, regardless of the outside world voltage..
Sterling make clever chargers....

This is the device on the front end..
http://www.electronica-pt.com/datasheets/ps/STR83145.pdf

The yard contactor box almost burned out and an electrician shut the whole yard down until the switchgear was replaced...
Awaiting a response from the yard..

Thank you for the link. It is always good to learn something new olewill

 

[danielefua]

I have never seen any voltage sensing circuit as you describe nor a voltage doubler rectifier in the mains rectification. But then I may be wrong.
olewill

The few switching power supplies I opened - not many I reckon - do have a voltage doubler circuit right at the input end. Just two properly connected diodes, a few resistors and condensers. Moreover I understand it is a common feature; sometimes switched on by a toggle switch sometimes switched on automatically in order to match the power standards of different countries.

Daniel