Greengear

lionelhutz

Interesting article. They are correct about solenoids switching can produce voltage spikes and have the idea behind using ohms law to calculate voltage drops correct, but they make their point by saying a piece of 1/0* wire has 0.1 ohms of resistance. Who uses about 1000' of 1/0 wire for the circuit from the battery to the junction block?

* I'm assuming they mean 1/0 wire because 0/0 wire doesn't exist. It's either 0 or 1/0, as in the gauges go 0, 00, 000, 0000 or 1/0, 2/0, 3/0. 4/0.

lionelhutz

That's not the issue. I looked that scope up when you posted it and it said 35V peak then you get a 10x probe which should allow it to measure up to 350V peak.

The probes have a little adjuster in the connector base. Make sure you connect the probe to the compensation terminals and then adjust the probe (with a plastic tool) until you get a clean square wave.

Richard454

1/0-Probably what they meant.

However- if you figure the ambient temp the wire sees under the hood- .1 Ω might not be too far off for a 15-20ft run in a car.

Richard

lionelhutz

I meant 1000' in the last post. 10' of 1/0 is around 0.001 ohms. I highly doubt it gets hot enough when used in a car to make the resistance rise to 0.1 ohms. Maybe 0.0011 ohms or something like that.

Antz81

I think if your using 1000' then you're probably going to find you have bigger problems than the resistance.

Greengear

DblTrbl

I agree that the .1 ohm number in the article used is too high. More like .001.

The basic principles they discussed are sound, but they do not include the alternator which is producing much of the needed power. My battery is in the rear of the car, so I'm not sure if the alternator ground is more of a player than the battery ground.

And what about the battery fuse? That's a fairly high resistance.

I also agree about the no "butt splices"

Richard454

I get it-using the 1000ft versus 100ft- big difference.

BUT- the point being is the ambient temperature in a car under the hood- changes things. Not only resistance in the wire- but what about alternator performance- more ripple? What about chemical reactions in the battery(under-hood vs in the trunk)?

It might be small- but in the real world- it adds up.

Just like the percentage interest I receive from my savings account- might seem to some it really doesn't matter- but at the end of the year- big enough to get a 1099 on it- so yea- I'm not going to discount it.

Richard

Big2Bird

If done correctly, I.E. crimped with the correct tool, soldered, and insulated correctly, they are fine, and quite often necessary.

Antz81

I agree. I've only seen splices fail due to extreme mechanical stress or because they weren't done properly. If properly done even years later with large currents they can be thermal imaged with no temperature increases at the splice.

DblTrbl

I'm talking about unsolderd mechanical butt splices. If done correctly, yes. But how many people you know don't have the proper tools or experience for good connections? The right tools can be expensive.

I've seen my share of loose butt connectors. I've also seen some cold solder joints, but fewer.

If you're going to solder it anyway, no need for a crimp connector. My 2 cents.

DblTrbl

Getting back to the original thread. Sorry I don't have any real measurements because my wiring is far from stock.

So I'm stuck with theory. As we modify our cars with stockish wiring and add more electrical loads, you're going to see more ripple. The alternator, as a 3 phase bridge rectifier supply is going to create ripple. Roughly 14% of the output voltage. The battery acts as a filter to smooth this out. As the alternator is required to produce more current, the battery will be less and less effective as a filter. The distance between the battery and the alternator, the battery condition and the gauge of the wires from the battery to the alternator all will affect the battery's filtering ability. If you're reading more than 14%, then there is a good chance it's a PWM load or inductive kickback possibly from the coil(s), maybe electric fuel pump or electric fan.

If one of the 6 diodes in the alternator is shorted, I would guess you'd see some ripple also.

My apologies again, only theory. My non standard wired car should be running again shortly. I'll do some measurements for comparison with huge load shifts. I'm curious now.

Big2Bird

I think the weather is really bad timing for this thread.

mrvette

Never had my but connected, but the on the other hand, the connections never loose until they came.....

how ever, on my wife's damn hated 01 Focus, I changed alt some years ago, and so it was checked out fine, turns out a bad solder connection to the tab from the freeking FACTORY failed, and the output wire was just hanging there next to the firewall, never noticed it somehow due to funky design....so out alt in place after wire was soldered by ME.....then the alt failed a couple weeks later, back to AZone and got another under lifetime warranty......PIA, HATE THAT CAR!!!!!

as for ripple, just rund the fans main current off the alt out stud and get hell over it, I don't bother with PWM controllers, I let the computer decide to turn on/off the fans, KISS principal certain asspects of crap just don't need to be over engineered......only trick I MAY consider is maybe putting the fans in series and when temp needed, switch to parallel be cute, but I too lazy....

Greengear

Big2Bird

Can you do it again across the battery posts, and ground to starter post?

Greengear