How long would this last?

[CathJ]

So blackout on Friday night made me realise just how dark it is with no lights. I don't like using candles, but battery-powered lanterns and torches aren't going to last long before the batteries go flat.

I saw an Eveready LED desk light at PnP today; it uses one of those big square batteries (a PP9), and you can have either the standard 20 LEDs on, or you can switch it to power saving mode and only use 10 LEDs. The question is, how long might it last on one battery?

 

[medicnick83]

Wait a few days till the next 'outtage' and let us know

 

[CathJ]

Wait a few days till the next 'outtage' and let us know

Gee, thanks.

Actually, that's not a bad idea - if I go ahead and buy it, knowing my luck, we won't have an outage for ages

 

[Moederloos]

Get a rechargable light from a camping store.
Good for 8 hours or so I believe.
Get two or three and run them "in series" for longer outages.

 

[CathJ]

Is there a way, in general, to calculate how long something will last on batteries?

 

[BobbyMac]

Is there a way, in general, to calculate how long something will last on batteries?

Yeah.

Step 1. Insert batteries into device
Step 2. Check stop watch is reset to zero
Step 3. Switch on device
Step 4. Push stopwatch starter button.

Now here's the tricky step:
Step 5. Stop the stopwatch when device no longer exhibits any behaviour attributed to its power source.

Not very Scientific, I know, but accurate to within a second or two.

 

[CathJ]

Yeah.

Step 1. Insert batteries into device
Step 2. Check stop watch is reset to zero
Step 3. Switch on device
Step 4. Push stopwatch starter button.

Now here's the tricky step:
Step 5. Stop the stopwatch when device no longer exhibits any behaviour attributed to its power source.

Not very Scientific, I know, but accurate to within a second or two.

Ah, but I said "how long something will last", not "how long did something last"

But after googling, and finding some hectic looking formulas, I'm thinking that that is actually the easiest way to tell.

 

[Aphrael]

Those rechargable lights that Moederloos suggested are a good idea. I remember having one as a kid ... this is going back about 20 years We'd plug it in, in the lounge in the morning and I'd take it to bed with me at night

 

[Rockford]

The rechargeable ones with LEDs are the best and can last through the night I have found. I bought some at a camping shop. The fluorescent ones are no good - they last about half the advertised time, and hour to an hour and a half in my experience.

 

[Hein_JHB]

LED's will last long with rechargeable batteries.

I got a few of the white LED's and 2 of the 1W High Power LED's