The 12v20AH lithium battery was used for a 35W hernia lamp and only lasted less than four hours. The

Look at the rated current and voltage of the xenon lamp. 35 W should be measured under nominal conditions. If the voltage and current are higher than the rated value, the power consumption will definitely increase if you want to extend the power consumption. time, you can try to change the voltage or connect some devices in series in the circuit to divide the voltage or limit the current

Also, you can calculate the parameters you provided:

Depending on your situation, 20AH capacity will take less than 4 hours, which can be estimated. Use a current of approximately (20AH)/(4H) = 5A

Calculate the current working power of your xenon lamp approximately 12v * 5A = 60W

S' there is nothing else between the power supply and the xenon lamp If you look at the circuit you can be sure that your xenon lamp has exceeded the rated power.

< p>Also need to look the tensionn to know. Because 100 W corresponds to power and 50 Ah corresponds to capacity, which is related to voltage. Assuming the voltages are all 50V, this can be calculated using the following method:

Time=50AH*50V/100W=2.5H

That is -say 2.5 hours