How to increase UPS backup time - WILL THE INVERTER OVERHEAT with larger battery ?

UPS is made to supply power for only several minutes, as it quickly overheats and shuts down. In this video, I explain a workaround of using very LOW power for hours. But if you need more than approx. 50W power then you must buy components for a solar system that are actually made for a constant supply of larger power. You need an inverter from 12V to 220V, they go up to 3KW and need a battery charger. Also, you cannot use a car battery, but a deep cycle battery because a car battery is also made for a very short power supply, just to start the car. If it empties under 50% it cannot be charged again, while the deep cycle battery can discharge deeply and be re-used. With solar components, you do not need solar panels, but charge from the grid, all else is the same. You can power the whole house, the battery capacity is the only limit. But inverters with a higher power, over 1kW, are expensive, of course
Again,
You can connect to UPS as big a battery as you want under the condition that the power load is small - about 50W. This seems little but is sufficient for 7 surveillance cameras. This is not sufficient for a desktop computer. If you measure the temperature of the transformer under tour full load, as it is shown here - then you are pwrfectly safe. If you need more power than buy an inverter for a solar system, more ezpensive than UPS, but suited for gigher loads over long time.
Here, the UPS battery BACKUP TiME was increased by exchanging a 7Ah battery with 26Ah.
BIGGER BATTERY - LOWER LOAD !! It is tempting to simply replace a minuscule 7Ah battery from a cheap UPS with a much bigger one! Why not 30Ah, or 100Ah or 200Ah? But is it safe, will it overheat and burn down the house???
I measured the UPS temperature during battery charge and discharge, see what happens!

The baseline transformer temperature was around 50C. Overheating is considered when the transformer reaches 65C. I will soon extend this study by testing higher loads on this UPS to see at which % load it actually reaches 65C. I expect that UPS will overheat at a much lower point than its declared load of 380W because the backup time is greatly extended here with a bigger battery. So the rule is: BIGGER BATTERY - LOWER LOAD !!!

Deep cycle battery was used in this video as car batteries can only be partly discharged without damage.

Have in mind that generally, UPS setups are made to endure 50% of their rated power for only several minutes. they can endure a small load, at about 10% of their rating for a very long time. But if you want to power several hundred watts for a long time it may be best to buy solar setups (not necessarily with solar panels) just a 200AH battery and a transformer of 1000-2000W sinus and this could power a desktop for a whole day. But this is even more expensive than UPS.

Another video shows what happens when the load is gradually increased    • UPS load test - how to choose UPS cap...  
Load over 15% disproportionally shortens the backup time and causes overheating