snafu

Additional output voltage = additional output current. That's Ohm's Law as it applies to DC circuits. Voltage * Current = Power. More Power at the output stud = more power wasted as heat. The heat is the enemy. As DC Power is the manufacturer, they have a pretty good idea of the power capability of their alternators. They're simply telling you - Hey Mr. Customer, we don't recommend that sort of behavior with our products as it will shorten the life of the unit. They are correct. By how much? I guess you'll find out.

Nice to see solid advice given here.

As to your original question, your system is simply not large enough to warrant the need for either. However, a larger alternator would offer additional current wheres a 2nd battery would provide additional play time with the engine not running - double if the batteries are of the same group size.

As has been stated here, any upgraded return path to anything in the charging system in such a vehicle must pass through the RVC ring. [This is a hall effect sensor.] The ring tells the ECM the charge state of the battery and the regulation of the alternator is managed via that data.

This isn't so straight forward on this vehicle. Best to contact the guys at Mechman and ask their advice. In addition, as SD says, more voltage isn't always better. Car batteries like 2.4V per cell at maximum. That's 14.4V for a traditional 12V battery with 6 cells. More voltage will shorten the life of the battery - unless we're talking deep cycle marine batteries . . .

We made a BUNCH of 3/0 AWG custom cables for Ron's Gen 3 Dodge Diesel Truck. We also set him up with a lime green 370A Mechman alternator. He did all the installation per our guidelines. He supplied his own battery terminals and red wire covering . . . He brought it by and we put the carbon pile on it. Now, this thing is kinda' like D'Amore's honeybadger - it don't give a shit. The results were mighty impressive. The screen shot I captured was at idle (800 rpm). We also measured the voltage drop between the alternator and the battery which we had the carbon pile connected. The sun was in the absolute wrong spot at that time so the photos with the meters was washed out, unfortunately. However, who would like to guess the difference in voltage measurements between the two meters, given the following? 315A - at operating temp, at rpm Meter 1 - red to Alt output stud and black to case of alt Meter 2 - red to battery (+) and and black to (-) terminals on passenger side battery This is known as a voltage drop analysis when you look at the difference of voltage between any two points in a circuit. Ideally, we like to see such measurements differ by less than 3%. This shows us if the circuit is optimized or has room for improvement. Keep in mind that any voltage drop is voltage loss, and is converted to heat vs work. So, guesses? And by the way, all alternators have losses due to heat when mounted to an engine in an hot engine bay. We like to see that 15% or less under load while the alternator is at operating temp. So, this Mechman unit delivered the goods as always.

CE AUTO ELECTRIC SUPPLY CABLE Meets or exceeds full AWG (American Wire Gauge) specifications. Is made of Pure OFC (Oxygen Free Copper) and tinned for corrosion resistance. Has a soft, flexible 600V PVC oil resistant jacket. Is dry rated for between -40 to 105 deg C, wet rated for up to 75 deg C. Is BC-5W2 Marine Compliant. Yep. Be sure you're comparing apples to apples when shopping for cable sir. Just the tinning adds 8% to the raw material cost.

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Still got it but it's likely going up for sale soon . . . Since the last post, I've put maybe 8k on the clock.

What you didn't tell us is what kind of vehicle this is. Many, and I mean many, late model vehicles have all kinds of challenges facing you in the digital domain that must be undone or normalized before installing new gear - equalization contours designed to make $3 speakers sound like $30 ones, fully active systems with each component having a narrow bandwidth of operation and / or delay, multiple position contours overlaid on top one another, etc. In addition, you could have some impedance mis-matching with your interface which could cause frequency response irregularities, etc. So, share a bit more.

And now . . . it's in full color! Check out this example I did for a positive battery cable assy for a builder that prefers to use all black cable. The red battery boot keeps things sane when it comes time to break out the booster cables. The smaller 8 AWG auxiliary cable goes to the under hood power center. https://ceautoelectricsupply.com/custom-cable-builder/ If you've not tried it by now, then check it out. Design a cable, take a screen shot of it, post it up here, and tell us what it's for. You can literally do this in minutes!

Thank you sir!

Ready. Willing. Able. We build the very best cables in the industry, bar none. I'll stake my reputation on it.