Battery switch with AFD (Alternator Field Disconnect) ?

[Boo2]

Hi,

I'm starting in on sourcing the bits for wiring the engine battery for Sunrunner's new engine installation (a Nanni N.38 diesel). I have come across references to possible damage to engine alternators if you switch off the battery while they are running and also a putative cure in switchs having AFD (Alternator Field Disconnect). Can anyone tell me what this is about ? Are these switches advisable for modern engines or is the whole issue a relic of the past ?

Thanks,

Boo2

 

[VicS]

Hi,

I'm starting in on sourcing the bits for wiring the engine battery for Sunrunner's new engine installation (a Nanni N.38 diesel). I have come across references to possible damage to engine alternators if you switch off the battery while they are running and also a putative cure in switchs having AFD (Alternator Field Disconnect). Can anyone tell me what this is about ? Are these switches advisable for modern engines or is the whole issue a relic of the past ?

Thanks,

Boo2

Its about interupting the field current before the main switch contacts open.

Read all about it here http://www.bluesea.com/articles/91

Note it can only be ( easily) used if the alternator has an external regulator.


Two alternative solutions:

Switch via the "both" position if changing batteries while the engine is running ........ Only the skipper is allowed to operate the battery master switch!


Take the alternator output direct to one battery, charge the other via a VSR