andreholgersson avatar image
andreholgersson asked

ArgoFET and Voltage sense wire?


I have two battery banks, and want to separate them with a ArgoFET. My alternator has a voltage sense wire that i guess is used to measure the actual voltage as close to the battery as possible. To my understanding the regulator tries to keep the voltage as high as possible without cooking the battery. Where to I connect that wire? To the start battery, or the service bank?

Argo FET
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1 Answer
benm avatar image
benm answered ·

It is different for every installation where to connect this.

Cable length and cable size will give different results.

If connected to the starter battery, the starter battery is probable very quick full, this means the house battery gets a lesser good charge.

If connected to the house battery probably the voltage on the starter battery gets to high.

Many times the cable to the house battery is longer, therefore more voltage drop in this cable, compare to the starterbattery. cable to starter battery, which is shorter, lower amp flow, therefore lower voltage drop.

As example, what can happen that with the sensor on the house battery, and voltage on the house bank is 14.0V. If the voltage drop in the cable is 0.6V as example. The alternator output is at that moment 14.6V.

Maybe to the starter battery there is No voltage drop, because the starter battery is full after 5minutes, this result in 14.6V on the starter battery.

Later in the charging process, 14.4V on house and 15 V on starter, this means your starter battery is cooking, or even exploding.

In most cases it is cheaper, to don't use a Fet based isolation, have the alternator only charging the house bank, and use a Orion 12/9 to charge the starter battery from the house bank.

Or even a better solution:

Use a external alternator regulator, like WS500 for the house bank. This will give a 3 steps charge profile to the house bank, which result in a better charge profile for the house bank. With lifepo4 even more important to have a correct charge profile. A better charge profile, will give a longer battery life.

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