Single wire alternator question
- Thread starter BAFRAID
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If you are going with more output like 90 amps I would rewire it with larger gauge wire and a fuse. Painless sells a nice kit. The purple wire feeds your horn relay.
This is what I use. https://www.painlessperformance.com/wc/30700
This is what I use. https://www.painlessperformance.com/wc/30700
What I did was leave the original alternator wire. I cut the lug off and soldered the purple to the black. That way the horn relay was fed as intended. I then laid the painless wire and taped it into the original harness all the way to the bulkhead area. I mounted the painless fuse block near the bulkhead and wired the alternator harness to it. I then ran power off the battery terminal of the starter relay to the painless fuse block. I also am running a converted ammeter that is now a voltmeter.
wish4hemi
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Here is a picture of the wiring at the bulk head.
BAFRAID
She’s looking like a Super Bee again!!
Thank you!!!! Perfect
BAFRAID
She’s looking like a Super Bee again!!
Would 150 amp fuse work? Or, does it have to be 200 amp?
It would be dependent on your alternator's output. So lets say your new alternator is 100 amps with heavy enough wiring a 100 amp fuse should be fine. I would prefer to go a little heavier at 125 amps.
BAFRAID
She’s looking like a Super Bee again!!
Thank you. I know in the painless system they give you a 200 amp breaker. The alternator that I have is a power master performance 90 amp 12 V output. Max is 90 A idle is 50 A
You would be fine. The painless kit is overkill in some aspects. The thing of it is it does not cost that much for over protection. You can wire it and then downsize the fuse if needed.
BAFRAID
She’s looking like a Super Bee again!!
I got a small 150 amp breaker that I’m going to put on. The way you wired it back into the car, does your amp meter still work? One article I read had it wired directly to the battery which bypassed all of that and left the amp meter not working.
I converted to a voltmeter. So to answer your question no it would not work. However your car will be a lot happier and safer with it by passed. There are cheap volt meters that can plug into a lighter socket if you want to monitor the system. If your dash is still out find a company that can supply a volt meter.
Nacho-RT74
Well-Known Member
Thicker wire to reach the amm and offer a better path than the bulkhead. The weakest point is the bulkhead. Once the bulkhead is saved, the rest of the system will be in peace and safe, including the ammeter ( believe it or not ), with a high output alt
The alternator actually don't need a fuse. Not saying you can't install one, but is actually don't needed. The only source to feed a short is the batt. Once the short happens all the power will be sucked by the short and that will stall the engine, but the batt keep sourcing, hence the reason why the fuse link is just in batt side. Once blows everything will stop.
BTW your alternator will never put 150 amps on a car with regular loads. That kind of output is selected to guarante the iddle capacity which is the big fail on stock alts. But you can fit either 150 amps alt or 500 amps alt, will just put out the load the car requires. If you car requires 50 amps, your 150 amps or 500 amps alt will feed just those 50 amps.
On stock form, our cars don't suck more than 25-50 amps depending on what you have turned on: lights, A/C Heater blower, ignition system, Radio, wipers... and quite often some 8-15 amps peaks with cigar lighter, powered windows, blinkers.
then if you begin to add electric cooling fans, fuel pump, EFI system, big stereos, this average load is increased. And everything must be sourced from alternator, not from batt if the ammeter is still connected
and a discharged batt won't suck more than 30-40 amps on the first instance to get recharged if is allmost death...
The alternator actually don't need a fuse. Not saying you can't install one, but is actually don't needed. The only source to feed a short is the batt. Once the short happens all the power will be sucked by the short and that will stall the engine, but the batt keep sourcing, hence the reason why the fuse link is just in batt side. Once blows everything will stop.
BTW your alternator will never put 150 amps on a car with regular loads. That kind of output is selected to guarante the iddle capacity which is the big fail on stock alts. But you can fit either 150 amps alt or 500 amps alt, will just put out the load the car requires. If you car requires 50 amps, your 150 amps or 500 amps alt will feed just those 50 amps.
On stock form, our cars don't suck more than 25-50 amps depending on what you have turned on: lights, A/C Heater blower, ignition system, Radio, wipers... and quite often some 8-15 amps peaks with cigar lighter, powered windows, blinkers.
then if you begin to add electric cooling fans, fuel pump, EFI system, big stereos, this average load is increased. And everything must be sourced from alternator, not from batt if the ammeter is still connected
and a discharged batt won't suck more than 30-40 amps on the first instance to get recharged if is allmost death...
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Once again, incorrect assumptions. The alternator output to its connected load (the car and all its accessories), is not fused for this reason: an alternator will destroy its diodes if not connected because the generated voltage will exceed the diodes PIV (Peak Inverse Voltage) rating. The purpose of the fusable link is to limit the short circuit CURRENT, supplied by the combined contribution of the battery and alternator, to prevent a catastrophic failure of the wiring harness to ground, should the insulation become damaged due to heat, accident, or incorrect hook ups.
One should base their alternator's load, using the diversity factor not the total connected load in amps. The diversity factor is based on time the of the largest load at 100% is on or in use, plus 50% of the second largest load for 50% of its on time not the total connected load, and the remaining loads at 30% This is how electric utilities determine the load. In a car, not all available components are on at the same time, why size for the absolute maximum. Just my opinion of course (based on sound electrical engineering principles not guesstimates or suppositions).
BOB RENTON
Nacho-RT74
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For the same reason you install a batery able to crank up the starter motor ( 150-200 amps maybe ? ), then feed the brake light on cluster after that ( maybe .30 amps ). Battery will feed whatever the device conected will suck and must be able for both, and won't feed its full load capacity all the time. So the same to the alt for all the car trying to keep the batt out of the game as much as posible.
Just like you plug a hair dryer ( 10 to 15 amps ) on the wall outlet, then after that you charge your phone on same outlet ( .5 to 1 amp amps maybe ? ).
Damn!
I'm out... once again.
Just like you plug a hair dryer ( 10 to 15 amps ) on the wall outlet, then after that you charge your phone on same outlet ( .5 to 1 amp amps maybe ? ).
Damn!
I'm out... once again.
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What language are you speaking? Starter motors typically draw or consume 300+ amps at 12 volts (nominal), but during the cranking event, the battery terminal voltage drops to 10 0 - 10.5 volts due to the battery's internal resistance, due in large part to Ohm's Law.
Batteries do not suck anything. Batteries are rated in CCA (Cold Cranking Amps), CA (Cranking Amps) and AHr rating (Amps / hour or a given amperage for a given amount of time), beside voltage and physical dimensions.
Your statment "So the same to the alt for all the car trying to keep the batt out of the game as much as posible", means what? As long as the battery is connected to the circuit, its "in the game". As far as which device (battery or alternator) furnishes the voltage and current, refer to Kirchoffs Law of voltage.
Your other statment re a hair dryer..."Just like you plug a hair dryer ( 10 to 15 amps ) on the wall outlet, then after that you charge your phone on same outlet ( .5 to 1 amp amps maybe ? )". Makes no sense. It's like comparing apples and oranges.
You best bet is to study Kirchoffs Laws, to understand and apply them to your statements, rather than unrelated meaningless analogies. Understanding is based on sound engineering principles and practices not on incorrect assumptions.....if you lack knowledge or understanding of a subject, all you need to do is ASK.
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You two need to get a hotel room somewhere and fight it out and see who comes out the door...
451Mopar
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You both have good points. You don't want the alternator output to go OPEN / unconnected. On external regulated alternator the alter may output high and unregulated voltages that might damage the alternator diodes (depending on what voltage they are rated for.) The external regulator will also be applying maximum current that it can to the alternator field windings (this will happen when the regulator senses the ignition voltage is below the regulators set point. Either alternator open or short in alternator out or ignition sense. I am not sure how an internally regulated alternator would react to no battery load, but I would think the alternator output is going to be very noisy?
The fuses are not sized by the alternator current output, They are sized by the wiring gauge in the harness they are protecting.
With a short-circuit at the alternator, you are not protecting the alternator, but the wiring harness going to the alternator (sourced from battery.)
Alternator output should be routed to the battery, and then vehicle power taken from battery. A common point with low resistance. large wiring or bus bar is nearly the same as directly from the battery, but if you loose the battery connection, and the only the alternator is supplying power than the output is going to be noisy, maybe with high voltage spikes depending on the capacitor in the alternator (and any other capacitance in the connected circuit.)
As mentioned above, it would be rare that a 100+ AMP alternator will be operating at maximum output, unless you are operating a bunch of electrical accessories.
Usually 4AWG is good from alternator to battery is the cars actual constant electrical loads are < 100 amps, and a 100 Amp mega-fuse (slow-blow) will protect the 4 AWG wire.
It is fine to go with larger size wire because it will have less restive losses, but it will weigh more, cost more, and routing is more difficult.
What I am trying to say, For example, you have a 100 Amp alternator, and your electrical loads are normally < 60 Amps.
You could wire the alternator with 8AWG wire and a 60 Amp slow-blow fuse (or fusible link) at the alternator output, but not a 100 Amp fuse.
Although the alternator could supply the 100 amps if there is a short between the alternator and battery. The wire is not rated for 100 amps of current and will melt after a short time.
Also as pointed out above, if there is a short, normally the battery is the source supplying the power. A battery fuse (if even using one) is going to be very large so the starter circuit does not blow the fuse. Single ought (1/0) welding cable normally used in battery relocation is good for 300 Amps for a few minutes.
A 300 Amp Mega-Fuse can withstand short high currents around 1,000 Amps for about 1 second (non-derated.) At normal temperatures and say 400 AMPS through the 300 AMP mega-fuse, it would take a few minutes for the fuse to blow. It looks like a 250 Amp fuse may be a better selection?
I'm no expert, but I would need to do more research on wire size to fuse rating, and length/temperature derating (although most wires are fairly short compared to most derating graphs.)
https://www.littelfuse.com/~/media/...bolt-down-fuses/littelfuse_mega_datasheet.pdf
The fuses are not sized by the alternator current output, They are sized by the wiring gauge in the harness they are protecting.
With a short-circuit at the alternator, you are not protecting the alternator, but the wiring harness going to the alternator (sourced from battery.)
Alternator output should be routed to the battery, and then vehicle power taken from battery. A common point with low resistance. large wiring or bus bar is nearly the same as directly from the battery, but if you loose the battery connection, and the only the alternator is supplying power than the output is going to be noisy, maybe with high voltage spikes depending on the capacitor in the alternator (and any other capacitance in the connected circuit.)
As mentioned above, it would be rare that a 100+ AMP alternator will be operating at maximum output, unless you are operating a bunch of electrical accessories.
Usually 4AWG is good from alternator to battery is the cars actual constant electrical loads are < 100 amps, and a 100 Amp mega-fuse (slow-blow) will protect the 4 AWG wire.
It is fine to go with larger size wire because it will have less restive losses, but it will weigh more, cost more, and routing is more difficult.
What I am trying to say, For example, you have a 100 Amp alternator, and your electrical loads are normally < 60 Amps.
You could wire the alternator with 8AWG wire and a 60 Amp slow-blow fuse (or fusible link) at the alternator output, but not a 100 Amp fuse.
Although the alternator could supply the 100 amps if there is a short between the alternator and battery. The wire is not rated for 100 amps of current and will melt after a short time.
Also as pointed out above, if there is a short, normally the battery is the source supplying the power. A battery fuse (if even using one) is going to be very large so the starter circuit does not blow the fuse. Single ought (1/0) welding cable normally used in battery relocation is good for 300 Amps for a few minutes.
A 300 Amp Mega-Fuse can withstand short high currents around 1,000 Amps for about 1 second (non-derated.) At normal temperatures and say 400 AMPS through the 300 AMP mega-fuse, it would take a few minutes for the fuse to blow. It looks like a 250 Amp fuse may be a better selection?
I'm no expert, but I would need to do more research on wire size to fuse rating, and length/temperature derating (although most wires are fairly short compared to most derating graphs.)
https://www.littelfuse.com/~/media/...bolt-down-fuses/littelfuse_mega_datasheet.pdf
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Acceptable current draw for a Chrysler starter motor of this era is 165-185amps.
- The alternator/generator attached to the engine should be designed and built to supply enough power to keep the battery charged even when all the accessories are on - lights, wipers, heater, defroster, radio/stereo, everything (otherwise, driving with everything on would kill the battery after some time).
- The alternator is also designed to run with the load of the battery in the electrical system. The battery is considered a load as it is being charged by the alternator. Removing this load (the battery) could damage the alternator or the external voltage regulator. In our cars you can remove the battery (not recommended) and the vehicle will continue to run as long as the alternator is doing it's job. I have been forced to do this numerous times.
- I get the analogy! The battery is plenty capable of supplying huge amounts of current at any given moment, the point is that the battery will only supply what current is asked for or "sucked" from it to supply the load at any given time.
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