I checked how long a 300-watt incandescent lamp connected through a 12-230 inverter to a car battery can burn.
Many people think that the capacity in ampere hours written on the battery is always the same. And it is enough to know what current the load consumes in order to calculate how long it can work, powered by this battery. In reality, everything is more complicated.
The energy that the battery can give depends on the load. The greater the load, the less energy the battery will give. All lead-acid batteries (both car and small, for UPS) always indicate the capacity at 20 hours discharge (that is, with a discharge current of 1/20 of the capacity in ampere-hours for 20 hours, for example, for a 60 Ah battery, this is a current of 3 A).
For the experiment, I used a cheap car battery ERA 75 Ah, made in Poland. The battery is new, it was fully charged before the experiment.
A 500-watt inverter with a modified sine wave was connected to the battery. Its efficiency at a load power of 300 W is 92%.
Power analyzer G.T. POWER Rc 130A (https://ammo1.livejournal.com/502657.html).
A 300 W incandescent lamp is connected to the inverter.
A minute after switching on, the voltage on the battery was exactly 12 volts, the current was exactly 30 amperes.
After 30 minutes, the voltage dropped to 11.72 V, the current rose to 30.3 A.
An hour later, the voltage is 11.18 V, the current is 29.52 A.
After 1 hour 7 minutes 40 seconds, the voltage dropped to 9.6 V and the inverter shut down.
The 230 V 300 W lamp worked for 1 hour 8 minutes, while the battery produced 36.423 Ah.
After turning off the inverter, the voltage on the battery instantly increased to 12.03 V. Instead of a 300-watt incandescent lamp, I connected a 12-watt LED lamp to the inverter and continued the experiment. The current consumption from the battery was about 1.3 A, the power was 15.8 W.
Before turning off the inverter, the lamp worked for 8 hours and 5 minutes. In total, the battery delivered 48 Ah.
Conclusions:
The temporary power supply scheme for a summer cottage with a car battery and an inverter is quite working.
With a constant load of 300 W, the battery will be able to deliver about half of the nominal capacity.
If the constant load is small and only sometimes the more powerful load is turned on, the battery will be able to give more energy.
Using a 24 or 48 volt inverter and two or four car batteries can be more efficiently due to the fact that the batteries will work in a more gentle mode and will be able to give more energy.
© 2021, Alexey Nadezhin
For ten years I have been writing every day about technology, discounts, places of interest and events. Read my blog on the site ammo1.ru, v LJ, Zen, Mirtesen, Telegram.
My projects:
Lamptest.ru. I test LED lamps and help figure out which ones are good and which are not so good.
Elerus.ru. I collect information about domestic electronic devices for personal use and share it.
You can contact me in Telegram @ ammo1 and by mail [email protected].