Battery bank and inverter sizing
Hi all, I recently installed a new solar panel on my camper that is capable of 9.8amps at full sunlight. The controller is a MPPT type that seems to work well and keep my batteries charged up. I ha...
Forum Discussion
An inverter on standby only draws a fraction of an amp, but with time, this can be more AH than you can afford. Many inverters have a remote on/off switch on a telephone -like wire to bring inside the rig so it is convenient to operate instead of trying to get at the inverter, often mounted where you can't get at it easily.
The extra draw on top of the TV's draw on the 1500w inverter vs a 300w (due to efficiency curves --nothing to do with the standby draw) won't matter, because the inverter is only on when you are using it. Not enough time to build up AHs.
The battery drops its voltage under load and the inverter "sees" the battery voltage. When that hits 11v the inverter alarms. The bigger your battery bank, the more load it can take without hitting 11v,
Also the battery state of charge works the same way. If your load will drop the voltage by 1.0v, then if you start with 12.7, voltage will drop to 11.7 well above alarm.
But if you start with the batts at half full at 12.1v, then your voltage will be 11.1 right off. With the load now running, the voltage will drop more as amps are drawn, so your 0.1v margin disappears quickly and there you are at 11v with the alarm sounding.
Point being, with the two 12s and the 1500w inverter, if you had proper fat wiring inverter-battery, you could indeed run a smaller ("700w") MW briefly (but maybe long enough for the job at hand), but with two 12s only if they are near full to start with.
With four batts you can be near half full and still stay above 11v at the start
The extra draw on top of the TV's draw on the 1500w inverter vs a 300w (due to efficiency curves --nothing to do with the standby draw) won't matter, because the inverter is only on when you are using it. Not enough time to build up AHs.
The battery drops its voltage under load and the inverter "sees" the battery voltage. When that hits 11v the inverter alarms. The bigger your battery bank, the more load it can take without hitting 11v,
Also the battery state of charge works the same way. If your load will drop the voltage by 1.0v, then if you start with 12.7, voltage will drop to 11.7 well above alarm.
But if you start with the batts at half full at 12.1v, then your voltage will be 11.1 right off. With the load now running, the voltage will drop more as amps are drawn, so your 0.1v margin disappears quickly and there you are at 11v with the alarm sounding.
Point being, with the two 12s and the 1500w inverter, if you had proper fat wiring inverter-battery, you could indeed run a smaller ("700w") MW briefly (but maybe long enough for the job at hand), but with two 12s only if they are near full to start with.
With four batts you can be near half full and still stay above 11v at the start
