minimum size of battery cable

[tresi]

Interesting that the chart skips right over 6,2,1, and 0 gauge.

[In-Tech]

Interesting that the chart skips right over 6,2,1, and 0 gauge.

That chart leaves a lot to be desired and isn't the one I have blown up on my wall at the shop. It was a google quicky.

[user-23911]

it's not just the battery that's receiving the amperage. It's all of the accessories.

When you put the battery into the back (front engine), the accessories are still powered from the front.
It's only the battery that's in the back so it's only the battery charge current and the starter motor current that the cable feeds.


That's why I mentioned "properly" in my last post.

[n2xlr8n]

it's not just the battery that's receiving the amperage. It's all of the accessories.

When you put the battery into the back (front engine), the accessories are still powered from the front.
It's only the battery that's in the back so it's only the battery charge current and the starter motor current that the cable feeds.


That's why I mentioned "properly" in my last post.

A load is a load, unless there is a switch in there someplace removing the load from the alternator circuit.

Please explain, as I'm not terribly versed in automotive charging circuits, and I have a 200A alternator going into my Ranger build.

[gnicholson]

it doesnt matter if you put the battery in the front in the trunk or on the roof you still have to have enough amperage to keep the battery charged and supply all the running electrical accessories .if the battery is located in the trunk and the charging cable from the alternator is attached to a heavy 1 ought or better battery cable at the starter then a 4 guage cable is probably enough for a 200 amp alternator as it will only be about 3 ft in length. If you use a separate charging cable that runs directly to the battery then you need a 1 ought cable

[user-23911]

it doesnt matter if you put the battery in the front in the trunk or on the roof you still have to have enough amperage to keep the battery charged and supply all the running electrical accessories .if the battery is located in the trunk and the charging cable from the alternator is attached to a heavy 1 ought or better battery cable at the starter then a 4 guage cable is probably enough for a 200 amp alternator as it will only be about 3 ft in length. If you use a separate charging cable that runs directly to the battery then you need a 1 ought cable

You've fitted a 200A alternator?
Your electrical load hasn't changed.
It's still the same as it was with the old alternator.


It will only supply the required amps at most and no more.


The battery is normally fully charged.
When you use it to start the engine, you suck out a few amps which need replacing (the volts go down, volts x amps = power in watts, then x time = energy).
That will normally happen over the first 30 sec or so then the battery voltage rises to it's "float level" normally about 13.8 to 14.2, the battery current decreases to close to zero.


As for the accessories..........headlights as an example.
Lets say 130W for simplicity.
At 13V that's 10A.
That's how much they draw.......doesn't matter if the alternator is rated at 60A or 200A, it doesn't change.
That 10A will travel from the alternator directly to the headlights, not through the battery.

The alternator is NEVER going to make 200A. Not in this case.

Lets say you added more lights........2600W of lights in total, no other load.
Then at 13V your alternator SHOULD be able to keep up and supply 200A. You'd need to upgrade the wiring to the headlights though. NOT the battery. If the alternator can't keep up then you'll be drawing current from the battery and the voltage will drop to 12.0 or less.
But your alternator will only make that 200A at a certain RPM and probably won't hold the volts up at 13 either.


That's why you NEED to know how the alternator is rated, in terms of RPM, volts and current.
Because it won't be what you think it is.

[stealth]

it doesnt matter if you put the battery in the front in the trunk or on the roof you still have to have enough amperage to keep the battery charged and supply all the running electrical accessories .if the battery is located in the trunk and the charging cable from the alternator is attached to a heavy 1 ought or better battery cable at the starter then a 4 guage cable is probably enough for a 200 amp alternator as it will only be about 3 ft in length. If you use a separate charging cable that runs directly to the battery then you need a 1 ought cable

I'm betting there is a main disconnect switch mounted with battery in trunk. This requires running long wire from alt. to switch or it will not shut car off. (Alt will supply power with battery switch turned off with engine running)

Why run 200 amp alt?

[peejay]

10 gauge, really? This chart will get you in the ballpark. Always overbuild wire size unless weight is a factor.

And if weight is a factor, lose the weight somewhere else!

[Fireonthemountain]

I agree with Joe on most of what he is trying to tell you, and most 200 amp alternators are not 200 amps, and besides this taking a normal alternator and trying to build it to many more amps is asking for failures do to extreme heat they were never designed to deal with in the first place. 110-130 amp factory alternators are plenty for power hogs, if everything else works fine.

But lets tackle this from another angle and that is voltage drops and check the voltage at the battery, and up around the engine with the engine off, and then with it running at max electrical loads (heater, amps, all light). This will spot problems and no theory is needed. Just the facts Mam, just the facts, as Joe friday use to say.

Now a tip, for all the would be detectives of electrical problems, especially on remote batteries and that is voltage drops and GROUNDS. I had a big voltage drop between my remote battery and my engine compartment and I was using large welding cable on the positive post to the engine. All connections were good and clean. The ground wire was also large welding cable, but not quite as large running to the engine from the battery, but it still showed a large drop in voltage of 1/2 a volt. So I decided to try something and hooked up one lead from my jumper cables, to the negative at the battery and then the other end to bare metal in the bed of my truck. Poof, and the big voltage drop vanished nd only 1/10th remained. I then added a second large cable ground wire about 18-24 inches long, from the negative post to the bed of the truck and screwed it in. Voltage drops of a 1/10th of a volt are normal, but not 1/2 a volt or more.

200 amp alternators are generally not needed, and they are not usually a real 200 amps, but good voltage always is or should be. So the question should be what are the volts, and are they here, and are they all getting there. Bigger alternator amps and bigger batteries are not usually the answer nor bigger cables. Number one problem is corroded and/or bad battery connections on all vehicles.

More volts are more important, in my view, than more amps, and making sure they get there.

[Paul Rig]

If you run a car with no battery, the voltage goes high and the higher the rpm the higher the voltage with amperage relatively remaining steady in line with the power supplied by the field voltage the heat generated is based on load ie wattage being used by the car. this didnt really matter with old cars as they were pretty insensitive to voltage as its wattage that drove them.
Unregulated power in new vehicles will kill electronics.
When you have high current draw like when cranking- the length, diameter of the cable, as well as fine multi stranded stranded copper all come into play.
Battery in boot small gauge cable, voltage and amperage drop excess power turned into heat, starter motor barely cranks on a full charge.
That battery in boot is probably extra heavy duty large capacity. which then turns into a nightmare for the alternator to keep in a fully charged condition. great for the first few start stops of a cruise night but eventually you will be looking for someone with jumper leads because the alternator couldnt keep it at 14 something volts to keep it charged.