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Author Topic: Power using Rigrunner  (Read 6812 times)
KG5ELA
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« on: September 27, 2015, 08:42:59 PM »

This is a little different question from the normal about power for a mobile install. I know that there is a difference in opinion as to whether you should run the negative from the battery or from a chassis ground. I want to do a install using the Rigrunner 4004 USB to give me other options for running power inside my truck and give me the ability to charge some of my devices from the added USB ports. What are your thoughts about running power using the Rigrunner with regards to the negative/ground?
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Tim
M0GVZ
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Posts: 388




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« Reply #1 on: September 28, 2015, 04:39:15 AM »

Exactly the same.

Look at how the vehicle is wired. None of the electrics are connected directly to the battery negative terminal. At best if there is one it is directly to the engine. The main negative wire from the battery goes directly to the chassis/body. All wiring negatives for all the vehicle electrics connect to grounding points at various points on the body/chassis. You do that so in the event of a fault in the main negative wire from the battery to the body you don't end up with all the current for every device running off electricity flowing through the component that has a direct connection to the battery negative terminal.

If the manufacturers of the vehicle don't do it, neither should you.
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K0BG
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« Reply #2 on: September 28, 2015, 10:46:48 AM »

Not too long ago, almost all vehicles had battery connectors with two wires attached. One was for the starter, the other for accessories. Whether or not any given device was connected to the chassis ground or the accessory ground depended on the manufacture.

Nowadays, almost all vehicle incorporate some sort of battery monitoring system. Sometimes the load detector is in the main fuse box, but more and more, it is built into the negative battery connector, or a separate Hall device surrounding the negative lead.

In any case, you do not want to bypass the load detector, no matter where it is located. Using the chassis is the only alternative, but there is a small caveat. The negative lead needs to be very close the the battery's ground, if not the same place. If for example you use the chassis via a seat bolt, aside from the extra voltage drop, you have a chance of creating a ground loop. While you might get away with it, most of the time you can't. As alluded to above, the sensors for the various on-board devices are grounded in specific places. Create a ground loop between them, and you can have a real problem, like non-working ABS!

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KG5ELA
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« Reply #3 on: September 28, 2015, 01:49:45 PM »

So the Rigrunner should have the negative connected to a ground near the battery but the rig would be fully connected to the Rigrunner? By the way, I have read a bunch on your website K0BG. It is an excellent resource.
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Tim
M0GVZ
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« Reply #4 on: September 29, 2015, 04:33:12 AM »

Yes that's correct.

Look at the following picture of my car. Its the strut tower on my Mondeo. Bottom left hand corner next to a bit of dry grass is the negative jumper point with the main negative terminal from the main battery. Above that slightly to the right is my main negative wire for all my radio gear so its connected electrically to the same body panel the main negative from the battery is. I use a serrated washer to cut through the paint and make contact in addition to what the bolt provides. Braid is the bonding for the bonnet (hood) of the car. Again there's a serrated washer under it.

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N3QE
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« Reply #5 on: September 29, 2015, 06:05:44 AM »

For small loads like USB charging, it is hard to see how the chassis ground could be inadequate.

If you are also running, say, an amp through the Rigrunner, then it is likely you would benefit from dedicated negative wire to battery terminal.
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KG5ELA
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« Reply #6 on: September 29, 2015, 02:15:05 PM »

It will mostly be my mobile unit which according to the manual pulls about 8.5 amps max. Obviously the USB is not going to be much at all. Not sure what else might be there, possibly a connection to a power inverter to run a laptop. At some point maybe even a HF rig. I just figure if I am going to put it in I am going to make it like it is working at its max, then I have a lot of overhead.
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Tim
K0BG
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« Reply #7 on: September 29, 2015, 02:53:38 PM »

I should have questioned this before, but what about fuses? RigRunners are nice devices, but they need to be master-fused near the battery connections. The fuses and holders are not supplied with them! And, they must be fused with the appropriate-sized fuses, which depends on the load. The wire feeding the RigRunner needs to be able to handle the imposed (proposed) load, with a minimum of voltage drop (≤ .5vdc). Obviously, if you're going to add a 100 watt transceiver later, you need to plan that now, not then!
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KG5ELA
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« Reply #8 on: September 29, 2015, 08:22:26 PM »

So even though the Rigrunner has its own fuse for the incoming voltage it needs to also be fused near the battery? I have looked at the wiring requirements. The supply to the Rigrunner is going to be 8 awg. Depending on where I bring it in the length would be between 6-12 ft long. The wire from the Rigrunner to the transceiver will be 12 awg. The only real problem is figuring out exactly where to mount the Rigrunner. I am looking at under the dash somewhere. I just have to look at it.

Also, do I need to fuse both wires? I keep forgetting to say it is a 2008 Nissan Frontier.
« Last Edit: September 29, 2015, 10:40:01 PM by KG5ELA » Logged

Tim
AC4RD
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« Reply #9 on: September 30, 2015, 04:04:52 AM »

So even though the Rigrunner has its own fuse for the incoming voltage it needs to also be fused near the battery?

You don't NEED a fuse in the line very close to the battery.  But if you ever have a short, even a brief one, further down the line, you'll really wish you had put that fuse near the battery.  Don't ask how I know this, OK?  :-)
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KG5ELA
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« Reply #10 on: September 30, 2015, 05:06:50 AM »

How do you know? ;-)  So the Rigrunner has a 40 amp fuse for the incoming voltage, what should I use near the battery?

Just out of curiosity though, what would a fuse at the battery provide over the incoming fuse at the Rigrunner? If the wires shorted wouldn't the Rigrunner fuse be sufficient?
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Tim
K0BG
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« Reply #11 on: September 30, 2015, 05:44:33 AM »

Go to my web site and read the wiring article.
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AG5BC
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« Reply #12 on: September 30, 2015, 06:25:51 AM »

How do you know? ;-)  So the Rigrunner has a 40 amp fuse for the incoming voltage, what should I use near the battery?

Just out of curiosity though, what would a fuse at the battery provide over the incoming fuse at the Rigrunner? If the wires shorted wouldn't the Rigrunner fuse be sufficient?

All the positive lead has to do is come in contact with any metal part of the car body that's tied into the ground between the battery and the RigRunner, which means practically any metal part. The fuses in the RigRunner would be bypassed and you'd have a short across the battery, which turns your positive lead into a hot, glowy, burny thing for a short but brilliant lifetime. A fuse near the battery on the positive side protects this from happening.

As for having a fuse on the negative lead near the battery, this protects any component being used from bearing the brunt of a current surge if the battery cable from the negative battery terminal to the car's ground connection fails. (Sure, the fuse would blow, but how much damage might occur to your hardware might be inflicted by having an entire car's worth of juice go through that lead before the fuse fails?)

Alan's website is highly recommended reading for mobile installations of ham equipment.

Brian
AG5BC
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KG5ELA
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« Reply #13 on: September 30, 2015, 07:44:12 AM »

Yes, I have read Alan's website. It's a great source for information. Sometimes if things are presented differently, or if I think of it differently, I understand. Your description helped to make it clear to me. That being the case, I am thinking that for the fuse near the battery should be a higher amperage than the ones in the Rigrunner, but not necessarily by a lot. I am thinking maybe a 60 amp fuse for that. The ground wire from the battery goes to the engine block. Can I just connect it there or should I run it to someplace else and connect the fuse there?

By the way, anyone have ideas on a cheap crimper for 8 awg? If I am only doing a couple of these I don't want to spend a tone on a crimper.
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Tim
K0BG
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« Reply #14 on: September 30, 2015, 09:06:32 AM »

Don't go cheap on a crimper!

Everything in a power path from the source to the load should be kept as resistance free as you can, for two reasons, both elated to voltage drop. This requires a larger gauge of wire than most folks think. In other words, it is not the current carrying capacity of the wiring we're worried about—it is the total voltage drop. The rule of thumb is to keep the drop to less than .5 volts, under full load. Part of that calculation is the voltage drop across fuses, fuse holders, connectors, and even solder joints if used. And if some of those connections are crimped, they must be properly crimped, both for resistive loss and mechanical strength. Cheap crimp tools make lousy connections.

All of this relates to putting your best foot forward. If you want to go cheap, that is your choice. But I don't do that! I expect my gear to come on every time I hit the switch, and to work as they should. They do, in part, because I don't go cheap on anything I do.

« Last Edit: September 30, 2015, 09:16:15 AM by K0BG » Logged

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