Simple Electrical advice Needed

Submitted: Wednesday, Jan 07, 2004 at 14:12
ThreadID: 9554 Views:1531 Replies:7 FollowUps:4
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Hi folks ...
As you will soon see, I am no auto electrician.
I have a 2 pin marine fitting professionally installed to run my Engel car fridge, which works well. It is connected to my second battery in my 80 Series Landcruiser. I would now like to fit a 12v plug next to it. This is a job I can handle, but I have no idea on wiring things in parallel or series (whatever that may mean).
Can I position the 12v plug next to the marine plug and just run my wire "postive to postive and negative to negative" from the marine plug. I will be using it to power my laptop and possibly recharging my battery powered spotlight. It is a convenience thing.
Many thanks ... especially as an auto electrician wanted $90 to do this, and I have the wire and the plug!
Safe travels
JackNo trees were harmed in the making or sending of this message.
However a great number of electrons were terribly inconvenienced.
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Reply By: Big Trev - Wednesday, Jan 07, 2004 at 14:30

Wednesday, Jan 07, 2004 at 14:30
Jack, when you say as running red to red and black to black, that is commonly called running in parallel. Yes that is OK to do, I am no auto-elec, but have done all the 2nd battery stuff in my 4X4 and have never had any problems. Just be sure that the wire from the battery to the back is fused, and it a good size and quality as you will have power loss over distance.

I have my 2nd battery hooked up in parallel with a manual isolator (as recommended by a very good auto-elec) and everyhing is good.
AnswerID: 42061

Reply By: Moose - Wednesday, Jan 07, 2004 at 15:02

Wednesday, Jan 07, 2004 at 15:02
I'm not an auto elec either but I think you need to be careful with spiking as the laptop may be suceptible to it as the Emgel cycles on and off. I may be way off the mark but I'd be tempted to put in separate wiring directly from the battery. However I'm happy to be corrected by someone who knows more than I do on this subject.
AnswerID: 42065

Follow Up By: bruce.h (WA) - Wednesday, Jan 07, 2004 at 15:52

Wednesday, Jan 07, 2004 at 15:52
i have to agree with moose always run computors off of a different line to other equipment as the continual turning on & off of your fridge can destoy your computor. i found this out the hard way after our computorrecieved $6500 worth of damage due to power spike ,our computor now run on a compltetly seperate line from the metre box with serge protection at the box & at the plugs so the extra spent now may save you the cost of a new lap top
regards bruce
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FollowupID: 304515

Follow Up By: jeff-wa - Wednesday, Jan 07, 2004 at 16:58

Wednesday, Jan 07, 2004 at 16:58
Because the laptop would be running off an independant power supply (probally worth $70 dollars or so) It is probally not that bigger deal.
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FollowupID: 304537

Reply By: Rick Blaine - Wednesday, Jan 07, 2004 at 15:19

Wednesday, Jan 07, 2004 at 15:19
well at last a question that I can answer..... yes you may wire them up in parralell as you suggest. I do prefer to put in a seperate illuminated switch though. I had to entirly rewire the rear section of my Jack as the wiring wasn't capable of handling the load of the Waeco fridge and the other stuff in the back of the Jack. You should also use an auto circuit breaker on any " extra wiring' they cost about $6-7 and do reset themselves, far more convenient than a fuse. also make sure your wire is dresigned to carry the amperage that you will need and alow a 20% safety margin. I'v set mine up to carry 30 amps and the wire is relativly thick but believe me the last thing you need is a wireing melt down behind an innaccessible panel when you're on the road.
AnswerID: 42068

Reply By: Mark - Wednesday, Jan 07, 2004 at 15:21

Wednesday, Jan 07, 2004 at 15:21
Wiring red to red and black to black is correct from the original 2 pin plug .

I assume the original 2 pin plug is already fused where it connects to the battery, so there is no need to add another fuse in the circuit (but make sure there is a fuse on the original 2 pin socket, if not, get one installed).

As for spiking, its not really too much of a worry on a laptop as the 12V actually charges the laptop battery and the battery runs the laptop. Thus the battery acts as a surge protector for the laptop.

Cheers

Mark
AnswerID: 42069

Reply By: Martyn (WA) - Wednesday, Jan 07, 2004 at 15:44

Wednesday, Jan 07, 2004 at 15:44
Jack,
If the cables are coming from your main battery you could splice into your live lead and run the earth off to a suitable location to save connecting both wires to the original plug. As mentioned make sure your fuse ratings are correct.Keep the shiny side up
AnswerID: 42071

Reply By: Ray - Wednesday, Jan 07, 2004 at 18:08

Wednesday, Jan 07, 2004 at 18:08
Hi Jack,

You should fuse both ends of the positive lead between the batteries. There is the possibility of either ending grounding and if it's not fused the potential of a fire.

Ray
AnswerID: 42094

Follow Up By: Mark - Wednesday, Jan 07, 2004 at 18:57

Wednesday, Jan 07, 2004 at 18:57
Only need to fuse the battery end, and as close as possible to the battery. Everything downstream of the fuse is then protected .

There is no extra protection provided by fusing both ends, just makes looking for a blown fuse harder.

Cheers

Mark
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FollowupID: 304556

Follow Up By: Ray - Wednesday, Jan 07, 2004 at 19:01

Wednesday, Jan 07, 2004 at 19:01
Mark,

What I was saying is to fuse both ends of the battery. ie a fuse should go in close to battery one and then close to battery two. This will protect the main wire that joins them both together.
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FollowupID: 304557

Reply By: Phil G - Thursday, Jan 08, 2004 at 10:36

Thursday, Jan 08, 2004 at 10:36
I'd run a separate cable. Your Engel instructions will tell you to do this because other power drains on the came cable will cause voltage fluctuations which damage the Engel's compressor.
AnswerID: 42195

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