Power Draw

[David_Doan]

So, I was working on this little spreadsheet for my wiring diagram, to see how much draw each circuit would have. The table below (which amazingly just pasted in from excel) shows what I found so far. In each case if I found varying results, I just used the worst case.

Wipers, Heater, and Ignition are unknown. Wipers I will test when I put mine back together. Anyone have any idea what the average draw for the points ignition is? After a lot of googling, I found nothing.

Component	Watt	Amps	Number	Total Draw
High Beam	65	5.4	2	10.8
Low Beam	55	4.6	2	9.2
Brake Lights	21	1.8	2	3.5
Tail/Parking Lights	5	0.4	4	1.7
Flashers	21	1.8	2	3.5
Wipers				0.0
Heater				0.0
Dash Lights	2.2	0.2	6	1.1
Ignition				0.0
Fuel Pump		4.5	1	4.5
License Plate	6	0.5	1	0.5

(Fuel pump is a Carter P60504)

 

[dklawson]

Average ignition current can be guestimated using the basic formula V=IxR. In this case, with the engine running your system will be at about 14.5V and a standard coil has a nominal resistance of around 3 Ohms. So the current ( I ) would be 14.5/3 = 4.8 Amps. However, the coil resistance may be lower, immediately after the points close there will be an inrush current that is much higher than 4.8 Amps, AND the current is only flowing while the points are closed making the average lower. In short, there are a lot of transients making it nearly impossible to determine an average current for the ignition system.

If you are designing fusing for the car, ignition systems typically are not fused. If you are sizing an alternator/generator, use the 4.8 Amp figure as extra capacity is a good thing.

 

[David_Doan]

Thanks Doug, that makes sense. I've converted to an alternator so I know I'm OK there. I'm laying out the fusing and wire sizing. I know the original Bugeyes had some stuff that was not fused - like the ignition - but I see no reason not to use a fuse going forward.

 

[58Custom]

Fuses? From the looks of your list one small wad of aluminum foil or a .22LR round will suffice.
































:wink-new:

 

[David_Doan]

Finished the wiper motor. Draws about 3 amps