Electrical help needed!

MBI Houston

MBI Houston

Senior Member
I am an electric novice. I am planning to put a 12v power outlet in my Coupe so that I can charge a cell phone, camera, and mini speakers. How would I determine what amperage fuse I should put on the line between the outlet and the battery. Or should the fuse be on the negative side. I have a 12v negative ground system.

Thanks for your advice.
marshall
 
I'm certainly no expert, but I converted my Tudor to 12 volt 30 years ago. Just went through an experience with rewiring the A with a new loom set up with signal lights. Best advise I can give you is to look at Les Andrews' Volume 2. He gives a step by step instructions that are excellent. I have a fuse block on the starter with a 30 amp fuse. Using a 60 amp Delco alternator with an internal regulator. You will need a ballast resister on the 6 volt coil and one also on the horn and electric wiper if you have one. I kept the 6 volt starter and have never had any problem but it does spin the engine. Good Luck
Rick
 
I just put in a 6 volt pos ground to 12 volt neg ground plug in my coupe. I wired in a little box that does this for you. You can buy these units at most of the parts suppliers. It works great. But be sure you wire the correct pos and neg wires to the correct pos and neg plug hook ups. I wiped out my plug for my GPS because I had them switched.

Sorry did not want to spoil this posting but thought it might be interesting for someone that wants 12 volt neg in the car without having to put is a 12 volt system.
 
Great point about watching for the negative ground since all the current devices are set up this way. As far as how big of fuse, the fuses are there to protect the devices, so it depends on the load. As stated above 10 amps is a great size and very common.
For those who want to figure out for themselves, use ohm's law. Power = current x voltage or P = I x E. If you have a 10 amp fuse, this is the max current (I). Your new voltage is 12 VDC (E). So 10x12 = 120 watts (P) of power available.
 
How do we always get off track and not really answer the question. Read the thread again, he ALREADY has a 12V system installed, all he wants to know is how big a fuse to use for the 12V outlet/power point he wants to install.
Sorry if I ranted.
Paul in CT
 
"Sorry did not want to spoil this posting but thought it might be interesting for someone that wants 12 volt neg in the car without having to put is a 12 volt system."
__________________
 
Look at the wattage of the device you're going to plug in. To determine the fuse size. Volts X amps = watts. therefor if you know the wattage and the volts(12) the formula is watts divided by volts equals amps. then you know the size of your fuse. Now find a wire/amperage guide and select the proper guage wire (size).
 
clocey said:
Great point about watching for the negative ground since all the current devices are set up this way. As far as how big of fuse, the fuses are there to protect the devices, so it depends on the load. As stated above 10 amps is a great size and very common.
For those who want to figure out for themselves, use ohm's law. Power = current x voltage or P = I x E. If you have a 10 amp fuse, this is the max current (I). Your new voltage is 12 VDC (E). So 10x12 = 120 watts (P) of power available.
Click to expand...

Actually the fuse is there to PROTECT THE WIRES, not the devices which are VERY low draw and to protect the kind of devices you refer to you would need a number of, say .2 amp quick blow fuses. The 10 Amp fuse should protect the wiring sufficiently as Tom recommended. You could count on the sensitive electronic items listed as being destroyed with internal shorts long before the 10 amp fuse blows, but that should not have to be a consideration in this instance.:)
 
To run a cell phone charger or a GPS unit, all you need is a 1 amp fuse. You could bump it up to a 3 amp fuse and have plenty of protection.
 
MBI Houston said:
I am an electric novice. I am planning to put a 12v power outlet in my Coupe so that I can charge a cell phone, camera, and mini speakers. How would I determine what amperage fuse I should put on the line between the outlet and the battery. Or should the fuse be on the negative side. I have a 12v negative ground system.

Thanks for your advice.
marshall
Click to expand...

You never want to fuse the "ground" or return path. The problem is that the fuse could open up and the attached device could attempt to "pull" a ground or return path via a route that was never designed to handel the current. This is a bigger issue in for example a 2-way radio, that has an antenna attached, and draws high current on transmitt. This return path issue can also occure when the case (assuning it is conductive) touches a part of the car that is grounded. This issue has the nasty habit of letting the smoke out of the electronics, and we all know that all electronics run on smoke, because everytime you let the smoke out they never work again!!:D
 
Bruce nailed it with the statement that the fuse protects the wires. Sorry I skipped over that VERY important detail. I had that in mind when I stared typing, but lost it with everything else.
 
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