Long lasting emergency lights?

Alter them so they only come on when the circuit is switched on. Just like a normal light. Unless you leave lights on 24/7.

you probably won't find any. The standard specification for emergency lights is 3 hours.

I've not seen emergency lights that work that way

Either they are non-montained, so they charge when the circuit is on, and light up from battery when the circuit is off, until the battery runs out.

Or they are maintained, so they are on (from mains) when the circuit is on, and remain on (from battery) when the circuit is off.

Some are convertible between maintained and non-maintained mode by removing an internal wire link, I have used this type in a dark cupboard in conjunction with a "wardrobe door" switch, wire N/C contact of the switch where the wire link was and it will believe there's a power cut and come on whenever I open the door.

But I've never seen any that will stay off when the mains power goes off, ready to be turned on from the battery when wanted ...

yup

that's what ours here are rated for

the PP's scenario is in the realms of fantasy

the use case is that it's the fire that burns out the electrical circuits that causes the emergency lights to be required

You could just double up the nicad batteries in the LED ones.

Or fit a buzzer so that if the power goes off during the night you get woken up and can stay awake for the rest of the night.

Or fit one with a DP relay to the smoke detector so the mains is removed AND the LEDs are connected ONLY during a fire alarm.

Owain

I thought multiple batteries in parallel generally leads to uneven charging, hence circulating currents within the batteries?

I'd say it not that difficult to mod one?

As the OP says, an emergency light which runs itself flat when not needed seems a bit pointless to me in a domestic environment. In commercial premises you'd likely evacuate in event of a power cut, so a different requirement.

Andy Burns formulated the question :

No. The possible problem is unmatched batteries - all should be the same age, voltage and capacity.

It is even more of a problem where they are used in series.

take a chance...

Why?

Has said in previous posts a lot of his guests use candles.

I have a collection of electric candles (originally bought for stage use), but they're quite fun for carol singing.

Do they need to be on when people are asleep in bed. I'm sure there used to be motion sensing emergency lights on sale. Brian

I am sure Altai used to sell emergency lights with built in PIRs that only came on both with power off and pir seeing movement. CPC used to have them, please tell me I'm not dreaming. Brian

Emergency lights are specified to last about 3+ hours runtime. (more than long enough to allow an emergency evacuation)

You would be much better off with an LED torch by your bedside. A simple modification to bridge the switch with a ~1M resistor or two means you can even find it in total darkness (and see by it once dark adapted).

I have a couple of emergency lights - one in the kitchen and one in the dining room since those are the places where being suddenly plunged into total darkness could be most annoying. I was able to increase the batteries in them from 1.3Ah to 4.5Ah after a bit of careful measurement but that was more because it looked like the physical enclosures had been originally designed to take the larger batteries.

George Miles snipped-for-privacy@gmail.com posted

... and if the emergency lights all coming on doesn't wake anybody up, and if nobody who wakes up during the night notices that the emergency lights have come on ...

Eh?

If you're going to be that unlucky, you might as well not bother with emergency lights in the first place.

Think I'd prefer passive luminous tape. Wonderinmg what happens after a period of time with that low load on the battery. I suspect the low glow will still be present but all you get when you switch the torch on will be a brief pulse of light or a very short runtime. The dim glow lulls you into a false sense of security that the batery is OK.

One next to the CU is a good idea as well. I don't think the management would pass having a normal emergency light in the living room, kitchen maybe. The little battery powered motion sensor lights are a very good solution for both of those locations and can be used as a torch to break out the proper backup systems.

You could increase the capacity of the supplied batteries for longer run time. Or install a UPS to feed the light - so on power failure the UPS will supply mains to the light and it will stay off. When the UPS runs out of juice it will drop mains to the light and it will take over!

(Having said that, you are dealing with two unlikely events power failure and a fire. You would have to be particularly unlucky to get both to happen within a timing window that would cause a problem (i.e. the fire needs to be more than 3hr after the mains failure, but not before daybreak)

Change the bulbs in them to LED.

Mike

Ones you buy nowadays have LEDs - the size of battery has, consequentlyt, been reduced - and the price.