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Old 06-27-2016, 08:46 AM   #11
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A properly running DT will have no trouble starting in the cold.
One group 31 started mine in 10* weather with icicles hanging off the bus.
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Old 06-27-2016, 10:58 AM   #12
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If I understood it correctly, you've got the isolator (a simple solenoid plus controller?) near the main batteries and the voltage at its output "looks good." But the voltage at the aux batteries droops after the inverter has run for a while, even though the isolator appears to be on, alternator is on, etc.

Nominal resistance of solid copper (per hyperphisics) is 0.1563 ohm per 1000 ft, or 156 micro-ohm per foot. Working with rough numbers, you were seeing 13 volts at the isolator and 10 volts at the battery with about 10 amps flowing through the connection? That looks like about 0.3 ohms resistance between them to create that voltage drop. You mentioned copper-coated aluminum, but I can't imagine it's that much higher-resistance than pure copper. There has to be more than just the metal type and gauge going into this.

If you could draw us a schematic, label several nodes, and measure voltages among the nodes that could help. Test with and without loads, ie inverter loaded or unloaded, aux battery fully charged or somewhat discharged (this affects alternator load when the inverter load is off).
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Old 06-30-2016, 04:58 PM   #13
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welding cable 2/0 fixed the issue! batteries charge and my 200 amp alternator keeps everything running even at idle with the A/C on and a 1000 watt load on the inverter...

welding cable is a PITA to pull through holes but is nice and flexible..

no warm wires, no warm connections.. no massive voltage drops..

that other wire just wasnt conducive to conducting I guess...

-Christopher
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Old 06-30-2016, 05:26 PM   #14
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Quote:
Originally Posted by superdave View Post
you should use welding cable between the inverter and the batteries,the shorter the better. 2 or 3 feet, also you should have a slow blow 300 amp fuse.
Dave with the win!
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Old 06-30-2016, 05:39 PM   #15
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I just read this thread, good job! I was going to post something about "if the wires are warm, they're probably too small" but you found that out. ;)


Quote:
Originally Posted by cadillackid View Post
welding cable 2/0 fixed the issue! batteries charge and my 200 amp alternator keeps everything running even at idle with the A/C on and a 1000 watt load on the inverter...

welding cable is a PITA to pull through holes but is nice and flexible..

no warm wires, no warm connections.. no massive voltage drops..

that other wire just wasnt conducive to conducting I guess...

-Christopher
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Old 07-05-2016, 12:44 PM   #16
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Quote:
Originally Posted by cadillackid View Post
welding cable 2/0 fixed the issue! batteries charge and my 200 amp alternator keeps everything running even at idle with the A/C on and a 1000 watt load on the inverter...

welding cable is a PITA to pull through holes but is nice and flexible..

no warm wires, no warm connections.. no massive voltage drops..

that other wire just wasnt conducive to conducting I guess...

-Christopher
Can you do up a basic schematic of your system to coincide with the thread? Could be of good use to searchers in the future.
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