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what size wire to use for 30amp 12v circuit ?
In article ,
"Lynn Coffelt" wrote: The Ancor calculator Matt mentioned is about right. Things to keep in mind are that a 25 foot length of wire is only good for 12.5 feet of distance..........out and back, right? And the type insulation is worth considering, particularly if it's going to be near any heat, oil, sunlight, etc, etc. Remember also that under emergency conditions (no alternator turning) there isn't going to be that comfortable 14.7 volts to fall back on, but something like 12.3 or 12.4 from a good, recently charged battery. Lots of high class SSB radios will start jumping frequency or channels with 11 volts at the radio, and the tuner will also be trying to retune everytime you holler "Heeeelp" in the mic. Welding cable is worth considering. Fine, cable laid wire with good tough neoprene jacketing. Terminals deserve good swedged tools, and wicking a little solder in after the swedging is super around salt water and batteries. Old Chief Lynn I agree with "Old Chief Lynn" here, if the appliance we're discussing here is an MF/HF SSB Radio. The thing that needs to be understood is that Battery Voltage at the terminals is NOT Voltage at the back of the Radio, or at the PowerAmp DC Terminals, especially at the 20 to 25 Amp draw of a 100 to 150 watt Peak Envelope Power Radio. It is commonly understood that for each volt dropped from 13.6 VDC at the radios PowerAmp DC Terminals, you lose 50% of your PEP Power. So if your at 13.6 Vdc you get your 150 PEP, and at 12.6 VDC you get 75 PEP, and at 11.6 Vdc you get 35 PEP and below 11.0 VDC the internal Voltage Regulators drop out of regulation and the radio goes OFF. So any voltage drop associated with the wiring between the battery and the radio at the the Demand Input Current of the radio, effects the available output power. How many times have I seen a radio that receives perfectly, but dies whenever you press the PTT and modulate the Mic. LOTS. This is one of the reasons that the Powersupplys for FVSA (Fishing Vessel Safety ACT) and SOLAS requires that any batteries used for powering these MF/HF SSB Radios be on or above the same deck as the Radio, and Battery Condition be certified each year by a Discharge Test, in the case of SOLAS Required Vessels. When FVSA was out for Public Comment, there was a bit of a uproar about this requirment, as no one had that type of power system aboard, but it was made LAW anyway, and most of the fleet installed the required battery under the wheelhouse floor, right behind the wheelhouse on that deck, or on top of the wheelhouse. These locations will tend to keep the wire runs short, and any installer woirth his Salt, should and would DOUBLE the wiresize on the MF/HF SSB Radio that any table stated would be good enough. Most of the vessels I Inspected had AC PowerSupplies, or DC/DC Converters running from Ships Power of 120Vac or 32Vdc and Power leads of a foot or two, before the FVSA, and we just added an 8D battery between the two. Bruce in alaska -- add a 2 before @ |
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