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antares
antares

Posted: Tue Sep 11, 2012 3:56pm

Post Subject:

Hi Tony, Because my Lister TS3 has only one alternator (A127 70amp) I have been using a split charge relay. This failed recently in that it put all charge to the Starter battery & non to the domestics. The result was a ruined battery and rather warm alternator! I am seriously considering converting to a manual 1/2/both switch (Blue Sky do one rated to 350amps) Apart from the absolute requirement that the switch should never be switched off when the engine is running; can you advise of any other pitfalls? The alternative seems to be to go to the other extreme and fit Smartbank plus regulator. I would welcome your advice .Regards Vic Moses

Tony-B
Tony-B

Posted: Tue Sep 11, 2012 7:56pm

Post Subject: Split charge relay

First off the person who fitted the relay originally took the easy option rather then the best. They left the alternator wiring as it was connected to the starter battery and used the relay to charge the domestic battery. The effect of this is to ensure the relay always carries the highest charging current instead of the lowest. It also trends to introduce voltdrop on the more vulnerable of the two circuits - the domestic bank. In my view the main alternator output should have been connected to the domestic bank and the relay used to charge the engine battery which, until faulty, is always pretty much fully charged. I hate 1-2-both switches because they are always dependant upon human operation and, as you say, have the potential to kill your alternator. In time it will wear and may break before make and that damages the alternator. I would not fit one and would never advise anyone to fit one. I would suggest a good quality split charge relay wired as I describe or a voltage sensitive relay (Blue Sea do one), again wired as I describe. My own split charge relay with a 60amp Paris-Rhone alternator is a Lucas that looks much like the Durite ones that are known to be problems. It has worked for 10 years so far without a problem. The relay that has the best name is the Albright SW180-2 relay. KIS - and try to avoid human operation. I do not see how in effect disconnecting the domestic bank from the alternator would make the alternator unusually hot or damage the starter battery UNLESS you have a battery sensed alternator or some other advanced charging gizmo measuring the domestic battery voltage. Tony Brooks

antares
antares

Posted: Wed Sep 12, 2012 3:58pm

Post Subject:

Tony, Thanks for the advice and yes I did have a battery management system which ,on the advice of the engineers who reconned. my alternator,has now been disconnected. I will now have a re-think! Regards Vic Moses

Tony-B
Tony-B

Posted: Wed Sep 12, 2012 5:28pm

Post Subject:

The A127 can have a variety of regulators fitted with the regulated voltage being different. If your regulates at 14.2 or more then the advanced controller will not produce a major benefit providing all the cables on the circuit are large enough and the connections in good order. If it is less than that then either change the regulator or the management system will be of benefit. Far too many engineers seem to think that such systems can damage the alternator but the vast majority of alternators are self regulating for current so they simply can not burn themselves out (even into a dead short) providing the fan is the correct one for the job, there is adequate cooling air around the engine and the engine is spinning it fast enough. The latter may be a potential problem in your case. If you do reinstate the controller please make sure it's sensing cable is connected to the battery that is fed directly from the alternator. If this had been done on your boat the alternator would never had gone to full output and stayed there. TB

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