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Old 03-10-2017, 04:42   #106
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How to shutdown the alternator ?

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Originally Posted by stormalong View Post
That is only true with an internal regulator. An external regulator would still energize the field. It there is no alternator output what do you hope to accomplish by shorting to ground?
His alternator has an internal regulator. Shorting should accomplish the OP's stated goal of shutting down the alternator without using energy from the engine.
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Old 03-10-2017, 06:00   #107
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Re: How to shutdown the alternator ?

Mechanical option: add a 2 grove pulley so you can turn rotation on and off via belt tension.

Not the scientific test mentioned early in this thread but air conditioning in a car reportedly consumes 1 mpg at 65 mph.

I am considering eliminating my starter batteries to make space for two more lead acid house batteries. Starting would be accomplished by one of two jump packs with emergency starting via house bank. If I'm ok with the minor inconvenience any reason this approach wouldn't succeed?
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Old 03-10-2017, 06:21   #108
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Re: How to shutdown the alternator ?

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Originally Posted by transmitterdan View Post
His alternator has an internal regulator. Shorting should accomplish the OP's stated goal of shutting down the alternator without using energy from the engine.
His solar is set for 14.8V his alt is set for approx 14.4V plus it will drop regulated voltage by 0.01V for every degree rise in temp above the 20C (68F) baseline. If the solar is doing its job the alt would be off anyway, except for some bulk periods. Because the system voltage on the bus, dictated by the solar controller, will be above the alts limiting voltage, the alt regulators only is to turn off the field.

These Hitachi alts can still self excite even with the L terminal disconnected or the lamp burned out... The "L" terminal helps excite it at low RPM but they can still self-excite when it gets to a higher RPM.

There are numerous options:

*Open the alt and tap into the brush circuit and insert an On/Off switch. Takes about 30-45 minutes. (least expensive, less than $20.00 in materials, no risk of alt self exciting)

*Open the alt and bypass the internal reg and use an external reg with an On/Off switch. (more expensive, more complicated, requires alt temp sensor and a regulator that can limit field output such as the Balmar ARS-5 or MC-614)

*Run the alt to the safety battery then use a simple ON/OFF switch and constant duty / heavy duty solenoid to parallel to house when needed. A simple ON/OFF battery switch could also be used for paralleling and is likely already there. Safety battery will always be at or near 100% SOC so load on engine is likely not even measurable or essentially zero. (inexpensive to moderately expensive, simple and straight forward)

*If concerned about continual absorption to safety battery simply insert one leg of a diode isolator in the B+ path with a switch to bypass the diode when full regulation voltage is necessary. (medium expensive, slightly more complicated)



If the OP is discussing an external rectifier he is certainly capable of tapping into the brush circuit to install and $8.00 On/Off switch and some wire....
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Old 03-10-2017, 06:32   #109
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Re: How to shutdown the alternator ?

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I am considering eliminating my starter batteries to make space for two more lead acid house batteries. Starting would be accomplished by one of two jump packs with emergency starting via house bank. If I'm ok with the minor inconvenience any reason this approach wouldn't succeed?
Start from House and save the jump packs for emergencies.
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Old 03-10-2017, 11:35   #110
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Re: How to shutdown the alternator ?

Thank you Mainesail for the very good summary of options available to shutdown the alternator or disconnect it from the house battery.

As the OP, allow me to say that if you are still searching for the answer: I am convinced, switching off the field is safe, works everytime, before or after you start the engine. You probably don't need to go any further than post # 108 from Mainesail.

And you probably don't need to waste your time on the rather suspicious alternative options we have been debating lately, unless like me you feel the need to educate yourself, and are ready to be asked for public apologies if you go to far
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Old 03-10-2017, 11:50   #111
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Re: How to shutdown the alternator ?

Rom,

No need to apologize. If people cannot discuss technical topics for fear of offending someone then "they" have won.

But you are right that cutting the field wire will shut it down.
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Old 03-10-2017, 20:46   #112
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Re: How to shutdown the alternator ?

Excellent to see an OP acknowledge that the horse is well and truly dead.

Maine Sail he da man!
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