Alternator ratings are kind of meaningless.<br><br>The number is the absolute maximum the alternator could even make. In a Lab, At super high rpm, when cool with devices asking for the maximum, through cabling that can pass it.<br><br>So long story short, a 165 amp alternator will likely never come close to producing that in an engine Bay. In fact some higher rated alternators cam actually produce less current at lower RPM than their less robust rated counterparts.<br><br>Basically unless you are powering 100 amps worth of electrical devices while trying to recharge a bank of deep cycle batteries, the higher rated alternator will likely charge the batteries no faster.<br><br>It might however deal with the heat produced better and last longer in such abuse. Alternators produce a huge amount of heat when asked to produce lot of amps. Making a cold air feed to the back of the alternator is highly beneficial to those asking a lot from their charging system, for battery charging at lower rpm's, and for longevity.<br><br>The batteries accept what they can at the voltage allotted by the voltage regulator. The higher the voltage, the more amps the batteries will be able to take.<br><br>The problem with vehicle voltage regulators is they are designed to prevent overcharging. They are not programmed to Ideally and quickly recharge deep cycle batteries tacked onto the circuit.<br><br>All vehicles will be slightly different depending on which lawyer and bean counters decided to overrule the engineer, and if the vehicle has a battery temperature sensor.<br><br>My Voltage regulator is in my engine computer. After start up, the alternator produces the maximum amps at the rpm provided until 14.5v is reached. Then to keep it from going above 14.5, the amps required to hold 14.5 deep tapering. The more depleted my batteries, the longer it takes to reach 14.5 and the more amps required to reach 14.5. If my batteries are full or within 10% of full, then very little amperage is required to bring them to 14.5 and it happens within seconds of start up.<br><br>At some point my engine computer decides it allowed 14.5 for long enough and reverts to 13.7.<br><br>While the batteries were requiring 45 amps to hold 14.5, they only require 13 amps to hold 13.7, so charging slows down greatly. They'd happily take over 25 amps for the next hour, but the voltage regulator and 13.7 volts will not allow it.<br> Sometimes this happens in 5 minutes, sometimes it takes 30 minutes I've even seen it at 14.5 after a 2 hour drive, but taking only 3 amps to hold them there. I am not sure what triggers or how it decides 13.7 is all that is needed. I've just decided it is what it is, and Oh well if the alternator is not working as hard as the batteries would like.<br><br>The DC to DC converters are trying to keep a steady 14.5 to the house battery, basically trying to overrule the vehicles voltage regulator. <br><br>Powering a Battery charger by an inverter running off the engine battery is a good way to keep the house batteries at 14.5 for as long as the batteries desire. Depends on the charger, and if Idling the engine to recharge the house batteries, the alternator might not be able to keep up, and the engine will be discharging while the house batteries are charging.<br><br>Since AC voltage drop is much less, this inverter battery charger strategy is often used when the house batteries are very distant from the alternator. Just place the charger near the batteries with a longer AC extension cord to the inverter, which should be close to the battery over thick cabling.
