ho alternator

What do i need to take into consideration when i go to install my HO alternator? It is a direct bolt on custom alternator that is (supposedly) going to put out ~200 amps at idle and ~300 amps at speed. Do i need to add anything special (besides the Big 3 upgrade) to protect my system from such a drastic change in the charging system? 2006 Mitsubishi Galant, yellow top up front kinetic 2000 in the rear with isolator.

There is no change to your charging system. It is the same voltage and your loads take their usual current. You need the Big3 from the alternator to handle its increased current (whether to battery and/or body/chassis/car-electricals; the current from the battery should not change). As an FYI to counter the majority of information out there.... There will be more current available to recharge the battery and hence possibly exceed its rated maximum recharge current even more than usual, but this is a common occurrence and AFAIK, no vehicle charging system employs current limiting (to suit the battery - which is academic anyhow - ie, high current is used to recondition the battery). Besides, healthy batteries quickly recharge to point where their recharge current is within specified limits. (But show me a current sensing and limiting system and I'll start to address people that go on about that crap.)

Thank you oldspark

No probs. Be sure to let us/me know if either battery fail - especially the Optima. Reason: add to battery stats. (FYI - I usually recommend retaining the standard cranker (ie, flooded battery) in dual-battery systems. If the cranker fails prematurely, keep that in mind.)

Is a standard battery superior to a yellow top for my application? I still have the original sitting on a rubber mat somewhere in the garage. I never originally planned on the whole 2nd battery, alternator upgrade thing...I just can't stop myself from upgrading everything. System started as a H.U. upgrade, then a single 10" pioneer premier w/ an MB quart amp for cheapness. I've since spiraled out of control, and have forced myself to stop after this "one last upgrade," but we shall see if that lasts. (I'm already eyeing some new components to replace the door speakers that I just replaced 6 months ago.) /wrists

Superior? That depends on definition. The problem is that AGMs do not like supplying high currents. Flooded batteries tend to be more self protecting (due to their higher internal resistance (typically double that of wets)). So is superiority one that lasts longer (eg, several years between replacements) or one that provides more current to your starter (who cares?). On the secondary side it's usually a no brainer because either it's internal which means it must be "sealed" (AGM or Gel else in a sealed & externally vented enclosure), or low resistance as desired for pathetic 12V audio amps (which for some IMO unknown reason have PSUs that usually do not behave like true SMPS and, for some even vaguer reason, are placed in the amplifier itself!). If you have an AGM in the front, its benefit may be academic if the resistance to the load (amp) is high - especially thru resistive fuses, distro-blocks, long cables etc. And if an AGM has low resistance to a big thumper (eg. 3kW), then caps may prevent premature AGM failure. The lot does depend on what is desired (eg, SPL, or dipless thumps, or long play times with engine off) and the set up (location, distribution, temperatures, music or dynamic type). Although the choice of yellow tops surprises me when for cranking AND thumps, high-discharge rates are desired. But then again, I wouldn't chose Optima anyhow. Keep it as is for now, and keep your original on float else monthly to 3-monthly top up charges. (And maybe exercised every 6 months - ie, in the car for a crank and drive.) If an AGM packs it in, use your old as the cranker. BTW - I'm usually a bit cranky (love the pun?) about high-powered audio systems AND dual battery setups etc. But my general ill feeling towards the bad info "out there" has recently peaked due to a revisit of general web sources. (Bring back hard copies!!) Hence my slur at the current PSU-in-amp topology which will be split once the current market has been $ucked dry. (That's $ as in s, not f!)

How can the stock cable be safe to carry 300 amps to the battery?

It isn't. That's why I mentioned the Big 3, though in retrospect that should have been highlighted. I was considering it more from the "system" POV (my bad). Many think that a bigger alternator "pumps" more energy/current in to the system - which it doesn't. (It can supply more energy/current, but it cannot "pump" - only voltage can do that.) And I should check this site's Big-3 - I think of it as battery ground to chassis and engine (that's 2) and alternator to battery +12V... But assuming typical modern wiring which include an alternator-battery fuse, and undersized alt-battery +12V should not be disastrous. However, undersized grounds will be. Failed grounds can and often blow every voltage sensitive device in the vehicle - ie, battery, audio, ECU, etc. Thanks gstacks!! I'll PM bored`n`def to make sure all is understood. Bad oversight on my part. And as for these damned (and alleged) Rookies correcting and value adding to us older expert Old Farts - well, I am eternally grateful! Welcome "Rookie" Esq. PS - PM to bored`n`def sent. He(/she) should reply to this thread...

So what your saying is 160 amp stock alternator and a 270 aftermarket alternator can use the same Alternator to battery cable.?

Voltage doesnt change but the amount of amperage changes. 

http://custombatterycables.com/technical_data.htm

This is a chart someone refered to me. 

No - the voltage drop will be 270/160 = 1.7 times greater. Plus if the existing cable does not handle 270A, it will melt and flame - unless the fuse blows first. Hence make sure the Big3 are upgraded or suitable - you do not want a ground cable to fuse!! Your linked cable data seems strange - they reckon a cable can carry MORE current at HIGHER temperatures? Isn't it LESS current in hotter surroundings - ie, you have to DERATE fuses and cables for increasing temperature? POST EDIT - J378 is for marine use, but it includes temperature DERATING comments - ie, higher temperature means LESS current. Either I misread that custombatterycables table, else their.... ..."Quality" and "Excellence" has some new meaning... (LOL) But I'll leave cable ratings to others hereon. I never use cable tables - I design using a max allowable voltage drop and hence I select the cable based on total path resistance, and my allowable voltage drops have always been far less than allowable cable current (ie, thermal) ratings.