battery consumption

roadroamer

Full Member

Messages
33
Just a question to all the technical people that understand electrics, I have a 1000w air fryer running through an inverter, my question is how many 12v AH does it use for 15 minutes use? I have 300AH’s of lithium batteries and a 2500w inverter (said to be 95% efficient) sensible answers please or a chart that a simple person can understand thank in advance
 

wildebus

Full Member

Messages
2,237
Basic maths are this ...

1. Ohms Law == P = I * V - or Power (Watts) = Current (A) x Voltage (V)
Another way to say that is I = P / V (Current = Power / Volts)
so 1000W / 12V = 84A
if you lose 5% due in inefficiencies, add 5% to the current, so the current drawn is 84A *105% = 90A (I rounded up to 90A as 95% efficient is pretty optimistic)

2. 1AH = 1A drawn for 1 hour. so 90A would be 90AH if drawn for 1 Hour.
you are drawing for 1/4 of an hour, so AHs used will be 1/4 of 90A = 22.5AH

Those are the theoretical numbers. a 12V system is not actually 12V of course.
With a Lead Acid Battery system with that load, that Voltage would probably drop down to under 12V (and the lower the voltage, the greater the current to deliver 1000W - remember P = I * V).
With a Lithium Battery system like you have, the Voltage drop does not occur and your batteries will be greater than 12V (so there will actually be a lower current draw to achieve that 1000W and a corresponding decrease in AHs consumed)
 

roadroamer

Full Member

Messages
33
Basic maths are this ...

1. Ohms Law == P = I * V - or Power (Watts) = Current (A) x Voltage (V)
Another way to say that is I = P / V (Current = Power / Volts)
so 1000W / 12V = 84A
if you lose 5% due in inefficiencies, add 5% to the current, so the current drawn is 84A *105% = 90A (I rounded up to 90A as 95% efficient is pretty optimistic)

2. 1AH = 1A drawn for 1 hour. so 90A would be 90AH if drawn for 1 Hour.
you are drawing for 1/4 of an hour, so AHs used will be 1/4 of 90A = 22.5AH

Those are the theoretical numbers. a 12V system is not actually 12V of course.
With a Lead Acid Battery system with that load, that Voltage would probably drop down to under 12V (and the lower the voltage, the greater the current to deliver 1000W - remember P = I * V).
With a Lithium Battery system like you have, the Voltage drop does not occur and your batteries will be greater than 12V (so there will actually be a lower current draw to achieve that 1000W and a corresponding decrease in AHs consumed)
thank you wildebus that was explained in my language (simpleton) I now understand
 

Alf

Full Member

Messages
90
A simple formula I have always been taught.
The ratio of 12 into 240 =20, for every 1 amp at 240v you will draw 20 at 12v, 1000w roughly 4a so 80a at 12v

Alf

Just a question to all the technical people that understand electrics, I have a 1000w air fryer running through an inverter, my question is how many 12v AH does it use for 15 minutes use? I have 300AH’s of lithium batteries and a 2500w inverter (said to be 95% efficient) sensible answers please or a chart that a simple person can understand thank in advance
 
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