Hi all need some advice when connecting cb direct to car battery so far have wire with inline fuse connected to positive on battery negative connected to chassis of vehicle .... One question do I need to put an inline fuse in the negative cable connected to chassis read mixed reports .. helpppppppppp
Hi there golden yrs yes you only need a fuse on the active (red) wire but if you have it direct to battery then you need to turn it of each time you stop or you may flatten the battery.
Me being a amateur radio operator ( VK3SVG ) with a full licence . All of our radio equipment that is used on 12 Volt, there are fuses in both the positive and negative DC lines AND to connect both DC lines to your battery. Reason being that a lot of radios will draw +20 Amps on transmit. So with my understanding if the radio has two fuses in the DC power cables, the manufacture would have a reason to as why. My guess would be to allow the transceiver to pull max current @ full power and not rely on a poor earth that could reduce the amount of RF power that the transceiver would be capable of transmitting. Also the reduced voltage could destabilise the transmitter.
On another note, in a past life i used to install car audio, small and big systems. One job that i was asked to have a look at had 3 x power amplifiers and auxiliary batteries in the boot, sub speakers etc. Had to trace a problem of intermittent noise that was hard to trace. Ended up the previous installer had used the car's chassis as a earth for the whole system. It was only when i replace the main power feed cable with new cable from the main battery to the DC to DC converter in the boot to keep the batteries in the boot fully charged. This cable had both the Positive and Negative cables in the sheath.
A fuse is inserted into a circuit on the 12V side to protect the wiring should a short circuit or overload occur. You don't want the wiring to catch fire. Putting a fuse on the earth side of the circuit is useless because by the time the current gets to this point, the voltage is effectively zero at this point. Putting a fuse in the circuit is more likely to give troubles later on as it is another point of failure.
If it blows on earth side ? Just means the appliance is still a live . Not a big issue on LV DC . . Btw a sheathed wire souls only be earthed at one end . Or it becomes a conduit and prompts RFI . How they wire EFI ECU's .
As far as I know the fuse in the negative lead is for lightening strike protection. Not necessarily to protect the equipment but to protect against the thing catching fire or exploding. An RV is unlikely to suffer lightening strikes, boats are a different matter, but the manufacturer is covering their butt by saying it should be fused on both power cables. I would think the amateur radio would have a rather large antenna and this could become a lightening rod in some circumstances, so another case supporting the lightening strike protection
T1 Terry
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If it blows on earth side ? Just means the appliance is still a live . Not a big issue on LV DC . . Btw a sheathed wire souls only be earthed at one end . Or it becomes a conduit and prompts RFI . How they wire EFI ECU's .
I can't see any need to connect a fuse to both wires, I have always connected to the positive side near the battery and have blown a few over the years ,and once the positive side has been isolated by the blown fuse there's nothing there at all in the circuit to cause problems as far as I can tell...
Me being a amateur radio operator ( VK3SVG ) with a full licence . All of our radio equipment that is used on 12 Volt, there are fuses in both the positive and negative DC lines AND to connect both DC lines to your battery. Reason being that a lot of radios will draw +20 Amps on transmit. So with my understanding if the radio has two fuses in the DC power cables, the manufacture would have a reason to as why. My guess would be to allow the transceiver to pull max current @ full power and not rely on a poor earth that could reduce the amount of RF power that the transceiver would be capable of transmitting. Also the reduced voltage could destabilise the transmitter.
This is exactly what I have done too (vk2fbuz) and all other installed extras have been wired direct to the batteries with no body or chassis earthing.
If you have a lightning strike ? I highly doubt a 20mm to 50mm wide fuse with prevent damage .. These suckers come from the clouds .. Lol
Electrickery will always find the easiest path and there is sure to be an easier path than a 50mm arc gap. Remember the lightening strike goes from the ground to the clouds, not the other way around
T1 Terry
__________________
You can lead a head to knowledge but you can't make it think. One day I'll know it all, but till then, I'll keep learning.
Any links to any sites or products is not an endorsement by me or do I gain any financial reward for such links
