Sterling inverter behaviour

[Theo]

Our 1800W inverter is fading out when the engine is running at cruising speed and fading back in again at tickover. I am not on the boat at the moment but it seems to me that there is a problem with the voltage regulator and it is getting over voltage.

 

This would indicate that the intention to change the Kestrel for something rather more sensible needs to be put into action sooner rather than later. Theodora is cruising down to Nottingham today prior to doing the Midland ring next week. My advice to my son is to turn the domestic batteries off charge for a bit and then keep an eye on the voltmeter on the instrument panel, switching them back on charge with the big round selector switch as necessary. It occurs to me that the starter battery may well be getting cooked with this regime. Perhaps he ought to take this one off charge as well. Taking note that both batteries must not be taken of charge at the same time with the engine running.

 

Any thoughts anyone?

 

Nick

[Sir Nibble]

Assuming your alternator still has it's internal reg fitted, you could fit a switch in the line from alternator to kestre to turn it off. Having said that, it would be a good idea to get some readings to determine if this is running unregulated. Sometimes a short circuit condition arises in the alternator rotor under the centrifugal action of higher speeds to "full field" the unit. Maybe the internal reg is US. Best post some accurate voltages old chap.

[Halo]

Hi, yes, ring Stirling up, they are only too welcome to help, or replace!

[Gibbo]

Our 1800W inverter is fading out when the engine is running at cruising speed and fading back in again at tickover. I am not on the boat at the moment but it seems to me that there is a problem with the voltage regulator and it is getting over voltage.

 

This would indicate that the intention to change the Kestrel for something rather more sensible needs to be put into action sooner rather than later. Theodora is cruising down to Nottingham today prior to doing the Midland ring next week. My advice to my son is to turn the domestic batteries off charge for a bit and then keep an eye on the voltmeter on the instrument panel, switching them back on charge with the big round selector switch as necessary. It occurs to me that the starter battery may well be getting cooked with this regime. Perhaps he ought to take this one off charge as well. Taking note that both batteries must not be taken of charge at the same time with the engine running.

 

Any thoughts anyone?

 

Nick

 

Most external alternator regs get the voltage to somewhere between 14.4 and 14.8 volts then hold it there for a few hours. The Kestrel is an exception. That unit takes the voltage upto 15.5 volts then switches off and the alternator falls back on to its internal reg. It's a just a different way of charging batteries.

 

The high voltage cutout on the Sterling 1800 Watt inverter is at 15.0 volts.

 

Higher charge voltages are becoming more common so most later inverters have a high voltage cutout set at 16.0 volts to accomodate this but unfortuantely not yours.

 

Simple really.

 

Gibbo

[Theo]

Most external alternator regs get the voltage to somewhere between 14.4 and 14.8 volts then hold it there for a few hours. The Kestrel is an exception. That unit takes the voltage upto 15.5 volts then switches off and the alternator falls back on to its internal reg. It's a just a different way of charging batteries.

 

The high voltage cutout on the Sterling 1800 Watt inverter is at 15.0 volts.

 

Higher charge voltages are becoming more common so most later inverters have a high voltage cutout set at 16.0 volts to accomodate this but unfortuantely not yours.

 

Simple really.

 

Gibbo

 

Thanks, Gibbo

 

It looks as if the Kestrel is working rather higher than should, then. The high voltage which was phoned back to me yestereve was 15.86. It was at this voltage that the inverter was seen to cut out. I realise that the overvoltage is not a good thing but is my inverter likely to have suffered or will the protection circuitry prevent any damage. I am not too concerned about the damage to the batteries. They had been run flat before we bought Theodora nearly a year ago and need replacing anyway, as does the 40A alternator.

 

 

 

Nick

[smileypete]

Thanks, Gibbo

 

It looks as if the Kestrel is working rather higher than should, then. The high voltage which was phoned back to me yestereve was 15.86. It was at this voltage that the inverter was seen to cut out. I realise that the overvoltage is not a good thing but is my inverter likely to have suffered or will the protection circuitry prevent any damage. I am not too concerned about the damage to the batteries. They had been run flat before we bought Theodora nearly a year ago and need replacing anyway, as does the 40A alternator.

Nick

Hi,

 

If you've got a Kestrel 90, it looks like the final output voltage can be adjusted, see the installation instructions here:

 

http://www.acornengineer.com/K90_installation.doc

http://www.acornengineer.com/kestrel_alt_controller.php

 

Failing that they may recalibrate to what you want for a reasonable charge

 

cheers,

Pete.

Edited October 7, 2007 by smileypete

[Gibbo]

Thanks, Gibbo

 

It looks as if the Kestrel is working rather higher than should, then. The high voltage which was phoned back to me yestereve was 15.86. It was at this voltage that the inverter was seen to cut out. I realise that the overvoltage is not a good thing but is my inverter likely to have suffered or will the protection circuitry prevent any damage. I am not too concerned about the damage to the batteries. They had been run flat before we bought Theodora nearly a year ago and need replacing anyway, as does the 40A alternator.

Nick

 

It won't have damaged the inverter. The high voltage cut out is simply because it cannot regulate its output voltage with a higher input voltage. The components will stand much more than 15 volts.

 

I think the output voltage of the Kestrel is adjustable. It used to be on the original design.

 

Gibbo