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Current/Voltage Help?

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Opinions on a direct 0g run from alternator body to battery negative? i am currently being advised to do this. Did some tech flex / heat shrink work today on a couple of the pieces. Got the rest of wire for the second + run of 0g & three 0g in/out fuse blocks as well as a dual 0g in/out for the double run down to the back. Will use the block until i can get the battery. Things are progressing slowly but surely 😃

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Alt back which is its ground to frame or battery neg is a must for the Big4 upgrade.  Electricity travels on the path of least resistance.. 

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Agreed, but considering i will be doing a 0g engine body to chasis ground, is a direct 0g from alternator to battery still necessary or will it be of much help? 

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Necessary no but it does help... Especially with multi and big alt setups.  

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Since no one answered your question about the stock alternator amperage, I'll say it's very unlikely that a stock 80A alternator has secret potential to do 250A given a change of rectifiers. Output current of the alt is mainly limited by the output voltage of the alt, which is dependent on hard design elements such as number & strength of poles in the rotor, stator winding loops, spinning speed, etc. If more current was trying to be pulled than the rectifiers are rated for, they'd get hot and likely fail. They could act as a bottleneck yes, but one that leads to damage when it gets blocked up.

One other note, you can't take a resistance measurement in a live circuit. A multimeter works by injecting a known current, measuring the voltage, and then calculating the resistance. So if there's already a power source in the circuit, your reading will be off. If you really want to know the resistance of a particular point on the car back to the battery, you need to disconnect the battery and then measure resistance from your point of interest back to where the battery was connected to the frame.

Edited by k58.cross
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Thanks @poorfish88, those were my thoughts. Was just wondering if it went beyond just helping & was more of a mandatory step to take with an HO alternator. Will probably still run it 😃

@k58.cross Appreciate the answer bro. Apparently the guy who was doing the modification for me, after scrapping down the alternator, realized it was not a four coil but a three coil & said it was not the type that he could modify. At least not for the parts he had. i was a bit skeptical about getting that type of output increase but he & a few other seemed to be confident so i decided to try it.

i guess it worked out because now the plan is back to a Mechman 240A which i am pretty comfortable with. Hoping to have it installed before the start of next month. Can't wait! 

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The rectifiers themselves don't produce current, they only pass it along. They're one directional and will turn the AC into pulsed pseudo-DC. He must have been talking about changing out the stator winding. That could allow more current by changing the winding ratio between rotor and stator or bigger wire, yada yada. In any case, you're way better off buying a unit designed for a specific current than trying to upgrade a smaller unit. It's like if put a steel toe in a running shoe, sure your toes are protected, but the rest of the shoe is still soft and fragile.

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@k58.crossUnfortunately not. He even showed me the rectifier plate & i asked him if he was going to upgrade the stator or increase/strengthen the field somehow but he said no, it's just an upgraded rectifier with more/larger/higher end diodes etc. Does that make sense at all? If not then again, maybe thigs worked out for the best. Lol

 

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1. Toss amperage ratings for wire out the window. They're a thermal maximum but not necessarily always desirable. Figure out your target voltage drop for the system and run some math to figure out what's appropriate to run

2. Stock alts have really limited buildability. You're constrained by interior dimensions. They're also typically not designed to handle the heat output demands of powering a large system. i.e. internal fans and diode heatsinks. Aftermarket from reputable companies is recommended, but if you're on a budget, be careful with what you're doing. A busted alt can break a whole lot of shit. Err on the side of caution. If you need to keep it at 14.2v, I think you can turn on the headlights and that should bump it up? If not, let me know and I'll see what I can scrounge up for wiring diagrams so we can figure out a bypass.

3. Low RPM in general? Or dips low under alt load? My I had a 390a alternator in my subaru. The thing had a tiny crank pulley on it and idle output suffered. I found a CNC shop to tool me up a larger pulley. Other options include getting a plug in tuner of some sort to raise the idle. The old school cable stops won't work since your vehicle is drive by wire. Could you provide a bit more detail on why you want to raise your idle? Perhaps we can think up a solution

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