Andrew Leigh
Member
Hi,
I am using an old PSU as an inverter. I would like to calculate the Ah rating of battery required to give a certain life.
From what I have read the fridge being powered (electric element) has a duty cycle of 50%. The power consumption of the heater is 160W so in theory this means I will be consuming 80W per hour on average? The other knowns are that the inverter is fed by two 12V 11Ah batteries in series and that the no load current is 180mA and an output of 240V. The Fridge will need to operate for the duration of a 6 hour road trip.
Question 1 - Two 12V 11Ah batteries in series = 24V @ 11Ah or 24V @ 22Ah?
Question 2 - I would like to establish the efficiency of the inverter. I am not looking for an nth degree calculation here but ± 5%. I was thinking of connecting a load, measuring the voltage and current on the LV and HV sides then calculating the power. The difference between the power in and power out I was thinking would be what is being consumed internally and therefore the inefficiency?
Question 3 - I do not think that I will connect 220V to the PSU input when power is available. The batteries I plan using are going to be of sufficiently larger capacity and therefore may not charge correctly. Will need to measure the charge current before a final decision is made. If I do not connect the 220V supply this should not cause any damage?
Question 4 - When 220V power is not available at the input to the PSU, the PSU has a standard feature which is a buzzer that sounds at a too regular frequency. I have not located this yet but would think that it could be desoldered from the board without any negative effects?
Finally would the rough formula for the Battery required look something like this;
Ah = Current at 24V side when under load * Time Required
So assuming a 15% inefficiency then the current draw will be 7.84A * 6h = 47Ah
Thanks
Andrew
I am using an old PSU as an inverter. I would like to calculate the Ah rating of battery required to give a certain life.
From what I have read the fridge being powered (electric element) has a duty cycle of 50%. The power consumption of the heater is 160W so in theory this means I will be consuming 80W per hour on average? The other knowns are that the inverter is fed by two 12V 11Ah batteries in series and that the no load current is 180mA and an output of 240V. The Fridge will need to operate for the duration of a 6 hour road trip.
Question 1 - Two 12V 11Ah batteries in series = 24V @ 11Ah or 24V @ 22Ah?
Question 2 - I would like to establish the efficiency of the inverter. I am not looking for an nth degree calculation here but ± 5%. I was thinking of connecting a load, measuring the voltage and current on the LV and HV sides then calculating the power. The difference between the power in and power out I was thinking would be what is being consumed internally and therefore the inefficiency?
Question 3 - I do not think that I will connect 220V to the PSU input when power is available. The batteries I plan using are going to be of sufficiently larger capacity and therefore may not charge correctly. Will need to measure the charge current before a final decision is made. If I do not connect the 220V supply this should not cause any damage?
Question 4 - When 220V power is not available at the input to the PSU, the PSU has a standard feature which is a buzzer that sounds at a too regular frequency. I have not located this yet but would think that it could be desoldered from the board without any negative effects?
Finally would the rough formula for the Battery required look something like this;
Ah = Current at 24V side when under load * Time Required
So assuming a 15% inefficiency then the current draw will be 7.84A * 6h = 47Ah
Thanks
Andrew