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Old 15-02-2010, 18:04   #1
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Sure Power Isolator

Anybody know anything about Sure Power Isolators? I have a model 1202.

My main question is whether this model robs me of a 1/2 volt of power during charging? If so, I plan on upgrading to a Yandina combiner.
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Old 15-02-2010, 18:26   #2
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If your regulator is sensing the voltage at your batteries it really doesn't matter if your isolator drops 1/3 or 1/2 of a volt. If you are sensing the voltage at the alternator, then move your sense wire.
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Old 15-02-2010, 18:39   #3
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Any diode such as the one you mention has an inherent voltage drop of between .6 and .9 V. It really makes no difference where the sensing wire attaches; the voltage drop will occur regardless. You can easily see this yourself by measuring the voltage both at the alt and again at the batteries while the engine is running.
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Old 15-02-2010, 19:18   #4
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Well, of course the diode will drop the voltage if there is current flowing through it. You are right, the voltage drop will be there. However, if the voltage regulator senses the voltage at the battery, it will compensate for that voltage drop. Your batteries will receive the correct charge and all will be well. If the voltage regulator senses the voltage at the alternator, it will not compensate for the voltage drop across the diode and the batteries will be undercharged.

Diode isolators are a valid way of isolating battery banks. The caveat is of course where the regulator senses the voltage. Some people think that diode isolators are less prone to failure and of course they are less expensive than other types of isolator. I don't see any reason to replace a diode isolator while it is still working.
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Old 16-02-2010, 05:00   #5
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For the sake of discussion, lets say the alt output is 14v. The isolator cut's that to 13.5. The sensor tell the alt to raise the voltage to 14.5v. Would the isolator then cut that voltage some amount and then the sensor tells the alt to kick it up again, and on and on? Pretty soon the alt is putting out 15 volts to achieve the 14 volts you asked it to provide. Would't this be a stress on the alternator and a waste of some of the capacity of the alternator in the form of heat dissipated by the isolator?

Remember, the 14 v is just an arbitrary number I'm using for illustration, not the actual voltage I'm trying for
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