I’m conducting a run-time test in the kitchen at the moment. It involves a 3 x CREE LED light I’ve recently bought, a broomstick to mount it on, a fan and a stopwatch. The Mrs says it looks like a cannabis factory and is not all that amused.

Anyway. If I establish, for example, that the battery will do 1 hour with all three LEDs on, does this mean that I can reliably say it will do 3 hours with only one LED on?

Also, can this logic be extended across the three power settings so I can juggle these effectively and not be left, literally, in the dark!

I know cold weather will reduce run-time, and can adjust accordingly. It’s the logic I’d like to confirm.

Go on, please give me answer. You can take the mick in doing so if you like, I’d just like to know for sure!

Right then, you miseries!

The light will do over an hour and twenty minutes on full chat. Which means the alarming immediate shutdown after 40 minutes the other night must have meant I has shaken the connector loose, although I find this difficult to believe.

Still, at least I’ve got an idea now.

I was just about to post a really long post about too many variables : heat, resistance, ambiguity in your question, what drivers, batteries in parallel, chargers etc.

But as you’ve call us miseries, I just deleted the whole thing. So there!
Stupid question in the first place. 😉

Anyway – what happened and to what light? How long have you had it?

You having a conversation with yourself?

Works better if you have two log ons

Your logic is reasonably sound.

Simple answer…Buy a Troutlight with endurance batteries… 8)

Sorry. Can we class that as a ‘mini flounce’ and say no more about it, please?

Just so long as my basic logic is ok, then I’m ok. Runtime will be affected by temp, but I have taped the battery bag over a bit to help with insulation against cold.

Anyhow, I shouldn’t have too much trouble doing a 2.5 hour night ride if I juggle the settings a bit.

Sorry again for the mini flounce.

if it’s a new light you’ll prob find that the battery gets better after a couple of cycles

I’d be surprised if it actually turns off some of the LEDs – more likely to run them all at lower current (and so would depend on what that current is fixed at)

By the way, it was a 3 x cree xml t6 from Amazon, so I’m not expecting too much.

The light just cut out on a rough-ish descent after about half an hour on one LED and about 20 minutes on three. I was a little perturbed, but not massively as I always run a headtorch as well.

I think I checked the connector at the time, but as that final run down the hill dumps me out 200 yards down the road from my house I might not have. I was a bit knackered as I always razz it a bit at night as they are mostly solo rides and you have to outrun those werewolves.

If anyone has any other explanation I’d be glad to hear it.

What robhughes said ^^

Batteries are rated in amp hours, or Ah. Which means a 5Ah battery will supply 5 amps for an hour. In theory it would supply 10 amps for half an hour or 2.5 amps for two hours, and this is generally a reasonable guess. The problem is that batteries don’t perform as well under higher current drains, so you’ll get a bit less than half the runtime if you double the current.

As above, batteries do improve after a few full cycles. My L&M commuter light was quite poor for ages until it was run in.

Also, LEDs get less efficient the harder you drive them. So if you put them on full for say, double the lumens, they’ll use more than twice the current and last less than half as long. Or, to put it another way, if you use them on half power you’ll get more than twice the life 🙂