A couple of clarifications/corrections I think...
Quote:
Originally Posted by Oneilkeys
While you may have a 240 amp hour capacity, remember that you only get to use 120 amp hours before you drain your battery down to 50% - as low as you want to routinely draw down to, if you do not want to kill your batteries.
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Don is using FOUR T-125 batteries... These are 6V flooded golf cart batteries rated at 240amps EACH - so assuming a serial/parallel connection - he will have 480amps of 12v available... The 50% comment is right on (though golf cart batteries are meant for deep discharge and can likely take a little more - 50% is still a safe number for long life of an approximate $600 investment) - so 240amps available...
Quote:
Originally Posted by Oneilkeys
For a 36 amp draw for 8 hours down to 50%, the calculator says you need 750 amp hours of batteries. For a 28 amp draw over the same 8 hours it would be about 3/4 of that.
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Using the calculator - IF you had a solid 28amp draw all night - as Oneilkeys said - you need almost 600amps (584).. (the 75% number he referred to) *BUT* I wouldn't expect the fridge to run continuously unless someone is staring inside it with the door open all night - so the question is how much does it run??
(or what is the current battery capacity - and we can probably extrapolate from there how much longer you will get...)
IF it ran half the time (still excessive in my mind) - your average load would be 14 amps - and need 292amps to make 8 hours... driving under the 50% line (would have enough for 6 hours staying over 50% - double your current performance of 3 hours.)
If it ran 25% of the time (probably more reasonable) - your average load is under 10 amps and you should make 8 hours using less than 50% of the capacity. (10 amps would need 208amps 12v to make 8 hours)
Probably not much you can do to reduce the draw of the the fridge - but if your lights aren't all LED - that can help reduce draw significantly when using lights (your 36amp number)
Quote:
Originally Posted by Oneilkeys
28-36 amp draw is a lot. My small Axis draws less than 20 Amps with the A/C and everything else except the microwave.
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28-36amps may be a lot if it were 110v.. but at 12v, the amps will be much higher to get the same watts (watts = volts * amps).
A 20 amp draw at 110 volts generates 2200 watts... To produce the same wattage at 12v is just over 200 amps.
Don's 28 amp draw at 12v would be under 3 amps at 110v.