Which battery do I need?

Question

I need to run a projector (220W) for 6 hours or so outdoors and away from a power supply, if anyone could tell me which battery/power pack would be suitable I would very much appreciate it as I can't run a noisy generator. I have searched high and low but really I don't know what I'm looking for.

Stephen P · Accepted Answer

Start with a quick calculation:

220 W X 6 hours =  1320 watt-hours = 1.32 KWH

Adding inverter & other losses, you need a battery pack that can supply at least about 2.5 KWH.

At those kinds of power levels safety is a big issue. You have to consider fusing and preventing short circuits.

For a 12 volt battery, that amounts to 208 amp-hours minimum at whatever temperature the batteries are going to be at. (12 volt inverters are very common).

Here is an example of a lead acid battery (12 volt  245 amp-hour) that's $600 and 158 lbs
http://www.batterystuff.com/batteries/rv-marine/agm/8A8D.html

Plus you need the inverter & charger.

You could cut down the weight quite a bit buy using other types of batteries,  I'm not sure where you would find them though.

To get a picture of what you need, think of a stack of  160 alkaline D-cells, that's about how many it would take to get 2.5 KWH.

I suppose you could wire about 16  lantern batteries (6 volt alkaline  type 915A 26 amp-hr) together, that would give you about 2.5 KWH.

Which battery do I need?

1 Answer