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Shutting down alternator charging by cutting ignition signal

We have a catamaran with two engines, each with a Balmar 614 external regulator and a Balmar Centerfielder to manage the output from the two alternators. We have decided to direct the charging from the alternators to the LFP house battery. For the high voltage warning, we were considering interrupting the field current to shut down the alternators as this seems to be the standard solution. However, there are a few issues, including risking the alternator with an abrupt shutdown and the risk of a voltage spike on restoring the field current.

Philippe forwarded to us an email he received from Balmar a few years ago. In that email Balmar recommends interrupting the ignition to turn the regulator off, which turns off the alternator and should still leave enough current to keep the tachometer working. Best of all, we are using the built-in functionality of the regulator to turn the alternator off and on with no risks of any spikes.

Has anyone else done this?

Hi Foxy Kitty,

Thanks for sharing.  For other readers I copy here the original message from Balmar support:

"You do not want to disconnect the battery from the alternator until the regulator has been turned off. It is best to use the ignition wire to turn it off because if you disconnect the field then reconnect it will be at full field which will cause the alternator to go full on where turning the ignition on it will be a soft ramp up.  Having the sense wire on the alternator side of the switch helps but not the solution."

Let us know how it works for you.