Thursday, Mar 13, 2003 at 23:03
Two minor points
1. All mains powered items with remote controls will never be truly "off". They require a source of power to run the reciever for the remote control and other "backup" items (clocks/last channel/volume/brightness/etc. memory).
2. The preferable way to run an inverter IS WITH THE ENGINE(ALTERNATOR) running charging the battery across it. This MAY cause induced interference in some electrical equipment attatched to the inverter depending on the type of inverter used. Sinewave
inverters wil be less likely to cause interference than square wave, but are a little less eficient due to the power dissipated to "round off the corners" of the output wave. You will not "force" 90 amps into a circuit drawing 20 amps, The fuse is there to protect the battery if the inverter develops an internal short or is heavily overloaded, just as the alternator fuse protects the battery if the alternator develops a short .
One other formula you may like to play with that will explain 90 amp assumption as false:
Using your 12 volt 20 amp inverter consumption 240 watts (realistically a "200 watt" inverter),
Ohms = volts/amps
or ? = 12/20
? =0.6 ohms
but you suggst "forcing" 90 amps through it
0.6 = ?/90, transposing (multiply both sides of the equation by 90)
0.6 x 90 = ?
? = 54 volts!! from a 12-14 volt alternator?
The other more realistic assumption is that the resistance changes with the load (ie. dynamic), therefore to get 90 amps through the 12 volts you would have a resistance of 0.13333 ohm and have a load connected of 12 x 90 = 840 watts, or over 4 times the rated load for your inverter. If your inverter had a 20 amp fuse then it would blow the fuse to save itself and/or the battery.
For clarity of explanation inverter efficiency has been disregarded.
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