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Old 09-16-2020, 11:03 PM   #21
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16ACE27's Avatar
Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 14,356
THOR #7035
Originally Posted by Beau388 View Post
A typical charger puts out a max of 50 amps @14.2 volts. A F-53 V-10 alternator has a max output of 175 amps @ 14.4 volts, take away 30 amps for the engine and computer and you have 145 amps potential for the batteries almost 3 times what a charger has. The bulk charge times will quite short because of the extra amperage and the absorptive charging time will also be shorter because of the much higher bulk charging amperage.

In other words the charger will drop to absorptive mode ant about 80% total charge where the alternator will change to absorptive charge mode at about 90% of full charge. Remember the alternator is built to bring a starting battery up to full charge as soon as possible, where as the charger is built to preserve battery life by charging slowly.
You are correct about the alternator's charging capability vs a converter's charging capability, but the alternator's voltage regulator reacts to the state of charge (SOC) of the chassis battery, which normally drops to maintenance voltage after about 15 minutes of charging. So taking into account the alternator is only putting out 13.1 to 13.5 volts, and the voltage drop across the relay and wiring to the house batteries, it will take much longer to bring the house batteries to a full SOC since they are not being charged at the full capability of the engine alternator.

This is the same issue Travel Trailer and Toad batteries have when trying to be charged from the engine alternator, though not as bad depending on the length of the wire run to the house batteries, and the reason many install DC-to-DC voltage converters/chargers at the trailer/toad end.

Ted & Melinda
2016 ACE 27.1
2016 Chevy Sonic Toad - Selling
2020 Chevy Colorado Z71 Trail Runner Toad
2024 Chevrolet Trax 2RS - Soon 2B TOAD
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