Relay burnt out & leisure batteries dying...

[RobinJ]

Investigating today, I checked the levels again and they were ok. Someone has borrowed my multi-meter and not returned it (isn't that always the way?), but I do have one of those cheap car battery testers, and that indicated 13.5V. However the battery charger still hums away continuously at full pelt and won't complete the cycle and go back onto float. I also found that my 33RA relay is badly melted. Mysteriously, in trying to figure out how it was wired, I've also found that the Kestrel alternator manager / battery boiler I have in the engine bay appears to be disconnected, although I'm damn sure the LEDs used to light up. I've called on professional engineers at least twice to carry out work in the engine bay, but would someone really tinker like that and not tell me?

Worse, I cannot see how the present installation works. I can only presume that it is wired direct from the alternator to the relay to the batteries, but it is hard to see. The old wiring to/from the Kestrel is still in place but disconnected (grrrr...) just to add to the confusion. It takes me back to my Alfa owning days.

The wiring should be connected through an energising relay from the alternator warning light which would have run both the Kestrel and the Split charge relay.

I have seen on one occasion where a wire coming off the alternator has resulted in relays being fried (presumably becuase the alternator has gone over voltage?).

In any event, if the Kestrel has been disconnected, it is possible it has also disconnected the split charge relay?

I don't know enough about split charge relays and alternator controllers to work out what is going on. How do these things work?

And would the relay burning out cause the batteries to die or is it more likely that dying batteries caused the relay to burn out? Should I just replace the relay and the batteries and hope for the best, or is it time to strip everything out and start again? What should I be testing when I get my meter back, and how?

If the split charge relay is burnt out, then it would not have been charging the domestic bank anyway!

The batteries are at least 2 years old and may have been life expired anyway. The relay is a Lucas unit which may have failed anyway. But it's funny how everything has happened at once.

I think you may have to replace your entire domestic bank, but you need to separate all the batteries and see if they charge up individually to make sure.

You need to find out who has your voltmeter!

Satisfy yourself that the alternator is charging the starter (~14V).

Check the wiring and replace the Split charge relay (bear in mind it needs to be able to handle not just what your alternator can produce (70A?) but also what your biggest battery bank can chuck through it (one bank flat - the other fully charged?).

The small terminals that operate the coil should be connected between the warning light on the alternator and ground, these connections should be in place (but as above may have been modified).

[blodger]

RobinJ makes some salient points amongst is the reference to the charge warning light which is fed from an ignition live and D+ at the alternator.

 

It will be worth checking that you still have continuity in these wires and the charge warning lamp lights&extinguishes as it should.

 

I have come across a couple of boats where the engine and alt are run a fair amount for nothing because they were not and it took some time for self-excitation to occur (especially with infrequent running).

Edited September 6, 2010 by blodger

[Gibbo]

The new relay I've fitted is 120A.

 

That's what it says on the tin. They're Eastern amps, not good old British (ie real) amps.

 

http://www.smartgauge.co.uk/more_relay.html

[sociable_hermit]

RobinJ makes some salient points amongst is the reference to the charge warning light which is fed from an ignition live and D+ at the alternator.

 

It will be worth checking that you still have continuity in these wires and the charge warning lamp lights&extinguishes as it should.

 

I have come across a couple of boats where the engine and alt are run a fair amount for nothing because they were not and it took some time for self-excitation to occur (especially with infrequent running).

 

The charge warning lamp behaves as normal, thankfully. I will check the smaller wires to the relay now I know where they should go!

 

Thanks for the info about relays, Gibbo. To be fair the good ole' Lucas looked pretty flimsy for a 60A relay as well. I'm hoping the 120A Durite one will be ok for a max calculated load of around 70A, but yeah I have been warned! It was a question of what I could find at the time.

 

Funnily enough the Kestrel is connected to one of those tiny little 70A Durite 'pots' but I think / hope this has been by-passed. It is showing no signs of distress. The Kestrel has certainly been disconnected at the alternator. However it may be that the little relay is still being used as an ad hoc junction box for some of the other circuits, and I need to check this when I get my meter back.

 

The most amazing thing is that it's all worked fine for two and a half years. Someone obviously had some idea what they were doing - I just wish I knew what it was...

Edited September 6, 2010 by sociable_hermit

[smileypete]

Thanks for the info about relays, Gibbo. To be fair the good ole' Lucas looked pretty flimsy for a 60A relay as well. I'm hoping the 120A Durite one will be ok for a max calculated load of around 70A, but yeah I have been warned! It was a question of what I could find at the time.

Try and make sure the thick connecting wires aren't pulling on the terminals, or this may well happen (clicky)

 

If both terminals are bolted to a thin sheet of 'tufnol' or even a split bus bar that should keep it all inline.

 

cheers,

Pete.