Help me design a LED Emergency Light

[thegreatfixer]

hello i am looking to build several long lasting (30hrs) LED Emergency Lights as bright as a 5-10w LED or ~25-60w incandescent

my core materials are

Li-ion 18650 cells pulled from laptops (from all my dead laptop packs i never found even 1 18650 that will not run my Cree T6 headlight for at least 1 hour at full power)
or
6v 4.5ah SLA

i like the newer 5630 leds but will use anything ( i thought about just using 12v 5630 strips but they all use resistors and it seems like a waste of power

i thought to use 42x 5630 e27 lights that can be bought for $5 and redrive then
but i do not know what voltage they are running now
or some other 5630 disk module

i would like a auto on function when power goes out and a cut off when battery power is too low

if they work well i will need 20 -100 of them

thank you

 

[Esko]

I am afraid I can't help you much, but, 5-10W for 30 hours? 150-300mAh? You are going to need some 20-40 li-ion 18650 batteries per light (or 5-10+ SLAs per light), you are going to use cells from dead laptop packs (assuming 2000Ah/cell) and there would be some 20-100 lights like this (perhaps a few thousand 18650 batteries in total)? It sounds like a huge safety risk. Are you sure that this is the way you want to do it?

 

[AnAppleSnail]

+1 on huge safety risk. If the cells already got to end of life in one life, have been tested to be of awful condition (Unable to supply about 1 amp for an hour), and have been scavenged and bodged together, I certainly wouldn't trust them in an emergency. I wouldn't trust them to sit on my shelf!

To output 10W of power for 30 hours requires 300 watt*hours, or 100 of these crummy cells. 18650 cells weigh about 40g each, so this would be ten POUNDS of bad battery. However you wire them, they will be unbalanced and suffer damage in each charge cycle.

Eneloops weigh 26 grams and hold about 2.4 watt*hours of power. You'd need 125 Eneloops for this energy, and have a much safer, lighter, more reliable power source. Of course, it'd be expensive.

I suggest that you use the lead-acid battery, just because it's less likely to endanger you and others. It will also be more reliable, unless you also get your lead-acid batteries out of a junk heap. Most batteries are less than reliable once they are 3 years old, don't hold voltage, or don't deliver the energy they used to.

 

[DIWdiver]

Gotta agree on the safety issue, but he said they WILL run the T6 (at 3A, I assume) for an hour. Maybe you missed the double negative. That would make them around 10Wh each (which means they are in pretty good shape), so he'd need 15-30 of them, not 100. Even 30 of them is 1.2 kg or 2.64 lbs, while the eneloops would weigh 3.25 kg, or 7.15 lbs.

Really, though, cells of different capacities, makes, ages, and treatment should not be assembled into a pack unless you're planning on doing some destructive testing. There's way too much chance of reverse charging one .

Also, since you probably are looking for very high reliability in an emergency light, I would definitely recommend a pack that was properly spot-welded, not soldered by hand.

An SLA battery that's well cared for can last well beyond 3 years, but they definitely don't last forever. Then again, neither do LiIon or NiMH.

So I agree in the end, the SLA is the best choice.

The one thing you should definitely do no matter what choice you make, is to test it annually, if not more frequently.

 

[thegreatfixer]

thanks for the answers

is there a rule of thumb for led inefficiency between the old DIP leds VS. the newer SMD like 5050 & 5630 or running some Cree chip i am sure it can be done maybe i do not need 5w of led light

when i say 5w i am referring to a cheapo 15x 5630 e27 for $5 on ebay or 7.5W 42x 5630
in the ebay world they are called 6.3w 15x 5630 or 9w 42x 5630 both seem ok and i am sure the Cree are only better

and its true every 18650 i "salvaged" from a "DEAD" laptop packs has run my great t6 headlight for more then 1 at full brightness and runs for more then 2 hours but noticeably dimmer the light not having a auto off i stop it and recharge it
then www.ebay.com/itm/121161815811



i can tell you that i have customized (off the self) emergency light that 2x 20w florescent tubes on 3x 6v 4.5ah SLA batteries for ~10 hours and since it basically has only 2 more SLA added it keeps the over charge & auto shut off circuit in tact

i thought what not get better results with leds

thanks

 

[DIWdiver]

Something is wrong with your numbers. You say 2x20W for 10 hours. That's 400 Wh of load. The batteries are 6V, 4.5 Ah, which is 27 Wh. Three of them is 81 Wh. How can 81 Wh of source supply 400 Wh of load? The efficiency would have to be almost 500%! That's 6-7 times what the actual efficiency probably is.