the weak point in the converter Mark is the DC side not the AC as you noted.
We can all pull up to 50 amps AC thru our external power cord, or using the
generator. However when you are working with a converter that converts
120volts AC to 12 volts DC problems quickly appear because of the resistance
in the toal DC circuit.
The relationship between voltage and amperage is not exactly like you
described. The proper relationship is: Current = voltage/resistance, and
power = current squared X resistance. Using these relationships we can see
that it is the total resistance in the circuit that determines the current
draw. The voltage out of the battery is determind for the most part by the
internal resistance of the cells.
Since the resistance of the circuit is the critical factor and since we
cannot change the internal resistance of the battery (short of replacing the
battery) and the internal resistance of the converter(it is determined by
the manufacturer), we can see that the resistance between the battery
terminals and the input to the converter is the critical factor.
Most designers I believe say that there should be no more than a 1/2 volt
drop between the battery and the input to the converter.
The resistance of this cable link than is determined by two things, material
and length. copper has a lower resistance per cross sectional area than
aluminum so we should use copper, and use stranded copper not solid.
If one remembers that our engine starters draw between 65-90 amps no load,
than one can quickly see that we are asking a lot from our converters when
running 100 amps (1200Watts) from our house batteries. They just were not
designed to do that for long.
Look at your cable running from the house battery to the front of the coach
(0#)and use one like it for the cable between the battery and the converter.
a 4 gauge wire will not work unless you want to melt it.
>> I think you will only be drawing 18 amps. 1800 watts / 110 volts
>> = < 18 amps
>> Darren
>
>Assuming 100% efficiency of the inverter. Can't happen. 80-85% maybe.
>
>Check the mfgs specs for current draw at rated voltage, and then remember,
>voltage goes down, amps go up.
>
>Mark Grady
>
>> -----Original Message-----
>> From: owner-gmcmotorhome
>> [mailto
wner-gmcmotorhome]On Behalf Of Darren Paget
>> Sent: Friday, December 18, 1998 11:02 PM
>> To: gmcmotorhome
>> Subject: Re: GMC: inverter cable size
>>
>{snip}
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
