How long would a 200W fluorescent last with a 60Ah car battery connected to a power inverter?

Question

How would I calculate what capacity battery I would require when I know the light wattage? These are standard 240V fluorescents

Answer 1

200 Watts at 12 volts is 16.7 amps. If you assume you could get all 60 Amp-hours out of the battery, you just divide the 60 Ah by 16.7 Amps and get 3.6 hours (dipakrashmi - check your math!). In reality, though, the inverter will waste some power, and you can't totally discharge the battery without damaging it, so you have to multiply that 3.6 hours by inverter efficiency and depth of discharge. Efficiency for a small portable inverter is probably in the .85 to .9 range. Depth of discharge depends on the type of battery. Use too much of the battery's capacity and the voltage may drop below a usable level, plus you will damage the battery so it won't hold a full charge. I wouldn't count on using more than 50% of the total charge of a car battery on a regular basis, or 80% of a deep-cycle battery. So for a deep cycle battery, assuming 90% inverter efficiency, you might get 3.6 x .9 x .8 = 2.6 hours. Cold weather will further decrease the power available from the battery.

Answer 2

12 hours is a good estimate in theory, however, there are a few important practical considerations.

1 - Power inverters are not 100% efficient, usually around 50% to 80% for a top quality one, this will cut down an estimate of the battery life to about 9-6hrs.

2 - Most batteries do not appreciate being discharged quickly. A battery that will provide 60 Ah at 1 amp. will only provide about 20 Ah or less at 10 amps, for example.

3 - The voltage of a battery *drops* in a logarithmic fashion, as its charge is expended. Inverters lose efficiency as the input voltage drops, and most will shut off at a certain point as a safety feature.

4 - Also, manufacturers will overestimate the capacity of their batteries, because they assume that most people wont bother to actually test them.

It's difficult to say exactly how much all of the above will decrease the performance of the battery(without more specific information...) I'll use a fudge factor of about 60%, reducing the estimate to 2-3hrs.....

From a purely theoretical standpoint, 12hrs is correct.

~W.O.M.B.A.T.

Answer 3

For this you have to know the voltage of car batteray. Typical value is 12 V.

200 w is the output of car battery.
200 = 12v*i so current is 200/12 = 16.67 A
The time it will last is 60/16.67 hours = 11.997 = 12 hours.

Answer 4

One 32 watt bulb will last about 2-3 hrs on full charge battery.

A small generator can putout 2500 watts which is about 70 bulbs for as long as you have gas or propane...

Answer 5

why would u want to ask this question