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-   Archive through February 21, 2008 (http://www.wakeworld.com/forum/forumdisplay.php?f=550830)
-   -   What size alternator do I need? (http://www.wakeworld.com/forum/showthread.php?t=544003)

trickyboarder08 02-10-2008 8:42 PM

ok, so I have bought 4 wetsound XS650s for the inside of the boat I also purchased a wetsound 10' free air sub. Not sure what it called. I forget easily. I also am planning on adding one more of these 10's in the near future. <BR>I will have Cadence Marine Amps for everything. One cadence amp to run all 4 of the XS650's and 2 seperate Cadence Marine Amps to run both the 10' subs. In the future I want to put a pair of Pro60s on the tower so I will need another sub for that. So what size alternator will I need?

trickyboarder08 02-10-2008 8:44 PM

o, and I have a 83' ski nautique 2001 if that helps any.

mlb75 02-11-2008 2:55 PM

it really depends on the current draw of the amps you're using (you didn't mention model numbers) and how often you're going ot be cranking it up to max volume. BTW there's no NEED for another sub just because you add another set of tower speakers the rider won't hear the bass from in the boat (unless you go with way more that a couple tens, no offense to 10tens).

denverd1 02-11-2008 2:58 PM

<!--attachment: Alternator_calcs-347874-544265.xls*mime_msexcel.gif*application/vnd.ms-excel*17.4*Upload*Alternator_calcs%2d347874%2exls --><center><table border=1><tr><td><img src="http://www.wakeworld.com/MB/Discus/icons/mime_msexcel.gif" align=left alt="application/vnd.ms-excel">Upload<br><a href="http://www.wakeworld.com/MB/Discus/messages/65921/Alternator_calcs-347874-544265.xls" target="_blank"><b>Alternator_calcs-347874.xls</b></a> (17.4 k)</td></tr></table></center><!--/attachment--> <BR>i haven't actually used this sheet, just saved so keep that in mind.

denverd1 02-11-2008 3:00 PM

looks like you can adjust a combo of *amp draw, battery capacity and *alt current. <BR> <BR>(Message edited by denverd1 on February 11, 2008) <BR> <BR> <BR> <BR>(Message edited by denverd1 on February 11, 2008)

polarbill 02-11-2008 5:23 PM

Use that worksheet. That is pretty cool. Oh yeah, the company I work for sells a lot of marine OEM units. I had an 87 nautique with the 351 in it and it had a motorola style alternator on it. We have up to a 105 amp brand new marine unit that should bolt right in.

rodmcinnis 02-14-2008 3:27 PM

There are a couple of serious flaws in the alternator cacl worksheet. <BR> <BR>Unless your alternator has a "smart" multi-stage regulator you won't get rated current out of the alternator at "zero load" for very long, a few minutes maximum. The standard voltage regulator will start reducing the current as the voltage comes up. By the time the voltage reaches 13.2 volts the alternator may only be providing 20% of its rated output. <BR> <BR>If you have a smart regulator (not common) then the regulator will hold the alternator at full output until the voltage reaches 14 volts, at which point the battery should be 80 to 90% full. <BR> <BR> <BR>A second flaw is that the charge characteristics of a battery are not so simple. THe higher the current rates, the less the efficiency. It will take a lot longer than 1/2 an hour to recharge a 50% battery even if the alternator puts out a full 100 amps. This is also hard on the battery so you really don't want to do that. <BR> <BR>The "bulk" charge will only take the battery up to something between 80% anbd 90% full. After that it needs an "absorbtion" phase that holds the voltage and slowly decreases the current to get the battery to 100%. A standard alternator used in this type of application may never fully recharge your battery. <BR> <BR>Another thing to keep in mind is how you are going to spin the alternator. Larger alternators put a larger load on the belt. There is a limit to how much energy you can transfer from the belt and trying for too much will make belt life short and wear out bearings (because you have to make the belt really, really tight!) <BR> <BR>100 to 120 amps is about the most you can get out of a single V-belt. To go above that you need to change pulleys and have double belts. I am not sure what the limits are on a serpentine belt. <BR> <BR>Rod

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