Easy Electrical Question.

[FargoZ71]

I've been seriously contemplating installing a system under the back seat, and running a 600~1k watt amp. Also looking to upgrade my truck from the clutch driven fans to LS1 electric's. Anyone know what I'll need power wise from a alternator and what I currently have?

[bill190]

Not so simple, you might need to redesign a portion of your electrical system...

 

You would basically need to see how much amperage you are drawing now from the alternator with everything on. This means A/C, headlights on high, fog lights, wipers, door open and dome light on, etc. Everything you would ever have on at the same time.

 

You would measure this with an amp meter (ammeter). And need an ammeter with enough capacity to measure all this. Here is one which is rated to 600 amps AC or DC for a little over $100...

http://www.testequipmentdepot.com/extech/c...eters/38394.htm

 

Some multimeters will say 200 amps AC and 10 amps DC or something like that. These are useless for automotive work. What you need is around 200 amps measuring capacity *DC*, so read the ammeter specifications carefully before buying.

 

Then you would need to know the amperage draw of the components you are installing. The fuses for a fan and 1000 watt speaker may be 40 amps each, but that does not mean they will be drawing 40 amps each. Should be something less than that.

 

So run the fan and measure with the amp meter. Then blast your stereo 1000 watt amp and see how much it draws. (1000 amps at 12 volts would be around 83 amps, but these come with a 40 amp fuse!) So the amperage draw would be less than 40 amps. Measure it with the amp meter.

 

Then you would basically know what the total amperage draw of everything would be with everything on at the same time.

 

Then see what the specifications are of your alternator. This might be fun because auto parts tend to just have part numbers and not electrical specifications (like everything else does in the world electrical).

 

Then if your existing alternator does not have enough rated capacity, you would need to see what other alternators are available to fit you vehicle with a rating above what you need.

 

Then you would be best to look at a factory electrical diagram (order from GM dealer) for your vehicle and see where fusible links are located in relation to the existing alternator wiring.

 

Then you would need larger wires going to the alternator to handle the extra amperage capacity if the existing wires are not large enough. This would include the ground wire from the battery to the engine block. And you would also want fusible link wire of the correct rating or an inline fuse of the correct rating as was installed with the factory wiring. This protects the alternator/automobile wiring in the case of a short.

 

Here are wire size amperage tables. This is the size of the copper wire inside, NOT the outside insulation size...

 

Wire gauge sizes for 12V wiring

22 - 5Amps

20 - 8Amps

18 - 10Amps

16 - 20Amps

14 - 40Amps

12 - 60Amps

10 - 100Amps

8 - 150Amps

 

Wire sizes conversion...

Metric to AWG

0.5 - 20

0.8 - 18

1.0 - 16

2.0 - 14

3.0 - 12

5.0 - 10

8.0 - 8

 

So now you would have a higher capacity alternator, large enough wires going to the battery to handle the load, and fusible link or fuse protection for those wires.

 

Next you would want to run the new electrical loads directly from the battery connections as this would be where you could tap into the added additional amperage (without overloading the existing vehicle wiring). Be sure to install fuses. A good rule of thumb is the amperage draw of the circuit is 80% of the value of the fuse. So the fuse will have a higher amperage capacity than what ever will be used. And use the size wiring which which will handle the rated capacity of the fuse (larger than needed).

 

You could use relays to power on these devices. Use "continuous duty relays", not intermittent duty relays. Then power to operate the relays could come from any existing circuit most likely as they do not use much power. But again use your amp meter to check the amperage draw of the relays, and the amperage draw of the existing circuits, and turn everything on for the circuit as described in the factory electrical diagram manual to measure the existing amperage draw. Use the 80% rule for each circuit and this will avoid fuse blowing problems.

[FargoZ71]

Not so simple, you might need to redesign a portion of your electrical system...

 

You would basically need to see how much amperage you are drawing now from the alternator with everything on. This means A/C, headlights on high, fog lights, wipers, door open and dome light on, etc. Everything you would ever have on at the same time.

 

You would measure this with an amp meter (ammeter). And need an ammeter with enough capacity to measure all this. Here is one which is rated to 600 amps AC or DC for a little over $100...

http://www.testequipmentdepot.com/extech/c...eters/38394.htm

 

Some multimeters will say 200 amps AC and 10 amps DC or something like that. These are useless for automotive work. What you need is around 200 amps measuring capacity *DC*, so read the ammeter specifications carefully before buying.

 

Then you would need to know the amperage draw of the components you are installing. The fuses for a fan and 1000 watt speaker may be 40 amps each, but that does not mean they will be drawing 40 amps each. Should be something less than that.

 

So run the fan and measure with the amp meter. Then blast your stereo 1000 watt amp and see how much it draws. (1000 amps at 12 volts would be around 83 amps, but these come with a 40 amp fuse!) So the amperage draw would be less than 40 amps. Measure it with the amp meter.

 

Then you would basically know what the total amperage draw of everything would be with everything on at the same time.

 

Then see what the specifications are of your alternator. This might be fun because auto parts tend to just have part numbers and not electrical specifications (like everything else does in the world electrical).

 

Then if your existing alternator does not have enough rated capacity, you would need to see what other alternators are available to fit you vehicle with a rating above what you need.

 

Then you would be best to look at a factory electrical diagram (order from GM dealer) for your vehicle and see where fusible links are located in relation to the existing alternator wiring.

 

Then you would need larger wires going to the alternator to handle the extra amperage capacity if the existing wires are not large enough. This would include the ground wire from the battery to the engine block. And you would also want fusible link wire of the correct rating or an inline fuse of the correct rating as was installed with the factory wiring. This protects the alternator/automobile wiring in the case of a short.

 

Here are wire size amperage tables. This is the size of the copper wire inside, NOT the outside insulation size...

 

Wire gauge sizes for 12V wiring

22 - 5Amps

20 - 8Amps

18 - 10Amps

16 - 20Amps

14 - 40Amps

12 - 60Amps

10 - 100Amps

8 - 150Amps

 

Wire sizes conversion...

Metric to AWG

0.5 - 20

0.8 - 18

1.0 - 16

2.0 - 14

3.0 - 12

5.0 - 10

8.0 - 8

 

So now you would have a higher capacity alternator, large enough wires going to the battery to handle the load, and fusible link or fuse protection for those wires.

 

Next you would want to run the new electrical loads directly from the battery connections as this would be where you could tap into the added additional amperage (without overloading the existing vehicle wiring). Be sure to install fuses. A good rule of thumb is the amperage draw of the circuit is 80% of the value of the fuse. So the fuse will have a higher amperage capacity than what ever will be used. And use the size wiring which which will handle the rated capacity of the fuse (larger than needed).

 

You could use relays to power on these devices. Use "continuous duty relays", not intermittent duty relays. Then power to operate the relays could come from any existing circuit most likely as they do not use much power. But again use your amp meter to check the amperage draw of the relays, and the amperage draw of the existing circuits, and turn everything on for the circuit as described in the factory electrical diagram manual to measure the existing amperage draw. Use the 80% rule for each circuit and this will avoid fuse blowing problems.

Holy Hell batman, you know your stuff, and it's too complicated for measely lil ole me.. I'm just looking to see if anyone has electric fan conversion + Sub system and if they had to upgrade the alternator / battery at all..

 

And for as much of a pain in the arse the electric fan conversion is starting to sound, i'm thinking just of getting a system.. so I should probably move this to the Audio forum. Thanks though man.

[bossier62guy]

I'm running electric fans along w/ some upgraded audio gear on my stock 105 amp alternator and I don't have any problems at all. Yes the alternator is being worked hard at times but it's been kicking along for quite sometime now. I haven't experienced any light dimming either. If and when the stock alternator takes a dive I'll upgrade it. Gor for it!