Quote: Originally posted by J_Clarkson on 14/5/2007
Quote: Originally posted by MudIark on 14/5/2007
Quote: Originally posted by J_Clarkson on 13/5/2007
....... but in answer to your question, the fridge draws approx 10A and your battery is rated at 110Ah so in theory if the battery is fully charged it will run the fridge for 110/10h = 11hours.
This is true only while the battery contains 12 volts, once it goes below the fridge will draw more current dropping the voltage quicker and increasing the amperage and so on. Therefore the 11 hours very soon becomes a lot less hence the reason the battery will flatten overnight
Actually it won't. As the voltage drops so too will the current, its ohms law.
Ohms Law yes you are right BUT......
120 watt fridge at 12v draws 10 amps (120/12=10)
the same 120 watt fridge now with 10 volt supply (120/10=12) - now drawing 12 amps
At 8 volts (120/8=15) - now drawing 15 amps
at 6 volts (120/6=20) - a massive 20 amps
Wrong ...
The stated wattage applies only at the stated nominal voltage, and anyway, when a leisure battery voltage drops below about 11.8v the current will be practically nothing so it will never be running at your stated 10v anyway.
As I said before, take the voltage below about 11.5 and the battery becomes a door stop.
Quote: Originally posted by J_Clarkson on 15/5/2007
Quote: Originally posted by MudIark on 14/5/2007
Quote: Originally posted by J_Clarkson on 14/5/2007
Quote: Originally posted by MudIark on 14/5/2007
Quote: Originally posted by J_Clarkson on 13/5/2007 ....... but in answer to your question, the fridge draws approx 10A and your battery is rated at 110Ah so in theory if the battery is fully charged it will run the fridge for 110/10h = 11hours.
This is true only while the battery contains 12 volts, once it goes below the fridge will draw more current dropping the voltage quicker and increasing the amperage and so on. Therefore the 11 hours very soon becomes a lot less hence the reason the battery will flatten overnight
Actually it won't. As the voltage drops so too will the current, its ohms law.
Ohms Law yes you are right BUT......
120 watt fridge at 12v draws 10 amps (120/12=10)
the same 120 watt fridge now with 10 volt supply (120/10=12) - now drawing 12 amps
At 8 volts (120/8=15) - now drawing 15 amps
at 6 volts (120/6=20) - a massive 20 amps
Wrong ...
The stated wattage applies only at the stated nominal voltage, and anyway, when a leisure battery voltage drops below about 11.8v the current will be practically nothing so it will never be running at your stated 10v anyway.
As I said before, take the voltage below about 11.5 and the battery becomes a door stop.
Dont worry about, I have been an electronics engineer for 20+ years after finishing my degree in Electrical and Electronic eng.
If you don't believe me then try it, just hook a battery with an ammeter in series across the grey plug and watch the current fall over a few hours but don't ruin your battery.
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Topic: Running Fridge on 12v
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