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Message: <blockquote data-quote="knukonceptz" data-source="post: 2286833" data-attributes="member: 548221">Did another test today but again my load was not as high as I previously had wanted. A quick over view 90A alt (stock wire) Standard car battery (Interstate MT-35) with constant 55A draw on 18ft of 1/0; nothing else. At idle start voltage was 14.47 under load voltage shot to 12.4(Front)/ 12.16(rear) instantly and continued to fall below 12V. This with only 55A at idle......cable should cause a .2V loss according to our wire calculators - those look to be spot on. Alternator only put out 40A at idle with the one battery. At idle the stock unit could not keep a 55A load above 12V, a HO alt will have similar issues on large loads.We added a second battery (SLA type posted earlier) - voltage stayed at 12.8 at the Front and 12.56 at the Rear (again we only did this at idle) There was a much slower drop this time.Next I might try at higher rpm with a smaller wire to demostrate resistance with the same 55A load, wont be this week though.At idle - the battery makes a big difference, keeps the voltage higher and stable. A HO alt, if it can make the 55A at idle would make a bigger difference (sustain 14V most likely) In some instances, your HO alt will not always meet the demads of the system at idle or even at max output.... It is at this point voltage will begin to drop and continue to fall until the battery reserve holds it from dropping further down (small reserve will drop quick, large reserve will maintain and slowly drop). The battery will always add support in the 12V range - If you drop to far, that is when you will damage the amplifier power supply.so its back to square one and comes down to what your needs and budget are. An SLA battery like I used is roughly $100-120, the HO alt will range from $200-$600 - best option is both, but thats not always realistic when the bills are due......</blockquote>

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