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Author Topic: Power cord fuses  (Read 6945 times)

KB1HJW

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Power cord fuses
« on: February 06, 2002, 03:07:33 PM »

I am in the process of setting up my rig power cord for quick switching between commercial and emergency (battery) power. All suggestions say to have the fuses as close to a battery as possible, however, the fuses are quite near the rig on the factory power cord (ICOM 706MKIIG). Because of that configuration, I have attached Anderson Powerpole connectors on the power cord between the fuses and the power source.

My questions are; Is this configuration adequate? Should I add fuses close to the battery in addition to the ones already in place? Do I gain safety and lose throughput by double fusing a line?
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ASTEFFES

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Power cord fuses
« Reply #1 on: February 06, 2002, 03:35:25 PM »

Having fuses close to the power source helps to ensure that a short anywhere along the power lines will blow the fuse instead of shorting the battery.

If the fuses are near the radio, for example, and you short the wires near the battery, there will be no protection to stop the short circuit from damaging the battery.

On the other hand, if you fuse near the battery then the short could only really occur between the fuse and the radio which would cause the fuse to blow.  The blown fuse protects the radio from any damage and the battery from exploding.

In car installations, you'll often see three fuses for a mobile radio.  One fuse on each power line near the battery, and a third located on the positive tail coming out of the radio, before the OEM connector that mates with the longer wiring harness.  This is the safest solution.

  -Adam, KG6JLG
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N8EMR

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Power cord fuses
« Reply #2 on: February 07, 2002, 11:25:15 AM »

You should be fusing on both source and destination. The Fuse at the radio does nothing if your short the power cord where it enters the firewall.
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ASTEFFES

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Power cord fuses
« Reply #3 on: February 07, 2002, 12:32:46 PM »

"That's what I said!"  Perhaps a bit less clearly, but yeah...
  -Adam
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KB1HJW

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Power cord fuses
« Reply #4 on: February 07, 2002, 01:32:19 PM »

I guess I was not completely clear either. I am not running this through the firewall of a vehicle. This would be for base operation emergency power. I intend to get a marine battery and have it available for power outages. The connection would be a short distance, probably in the 5 foot range. If it were used in a vehicle, it would be a separate battery from the vehicle battery, probably in the bed of my truck, with the power cord through the sliding window in the rear. Do the same suggestions prevail?
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K3AN

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Power cord fuses
« Reply #5 on: February 09, 2002, 10:14:38 PM »

You MUST prevent a battery short circuit of any duration.  The short can heat insulation to the point of melting, and possibly cause the battery acid to heat up to the point where it boils out of the vent caps. That's why the writers are saying to put the fuse near the battery.

You should also cover or otherwise protect at least one battery terminal. Your goal is to prevent any metal object, such as a dropped tool, from being able to contact both terminals.
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KC7YRN

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Power cord fuses
« Reply #6 on: February 22, 2002, 05:30:38 PM »

Everyone's right, it's a safety imperative to have fuses right at the battery terminals. Put them so close that you couldn't short the battery on purpose if you wanted to. You don't want to short the battery, but Murphy does.

Shouldn't be much loss of throughput until/unless the fuse holders corrode. I've seen automotive fuses spec'ed at maximum voltage drops of about 0.08 volts.
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