Energizer Ultimate Lithium in SK68 flashlight - Page 1
Forum section: electronics / beginners

author: Peabody
author_rank: Super Contributor
timestamp: September 12, 2021, 06:37:29 pm
content: The Ultrafire SK68 flashlight sales material says it will take a 14500 rechargeable Li-ion or an alkaline AA, with the former giving more brightness. But I would like to use the Energizer Ultimate Lithium AA, which is a non-rechargeable battery, nominally 1.5V. Is there any reason why this wouldn't work? Should I expect longer life, at least twice as long as alkaline?

author: Rick Law
author_rank: Super Contributor
timestamp: September 13, 2021, 07:38:45 pm
content: Hey, since you said it works with an Alkaline AA which is 1.5V already, so a lithium 1.5V AA should work fine.But... it wont be as bright as using a 3.7V lithium rechargeable.According to specs on the Ultrafire site, the flash light has a 7W LED. That is, 1.89Amp at 3.7V or 4.67Amps at 1.5V. The Energizer Ultimate Lithium AA at 1.5V can't put out 4.67Amp.According to the spec sheet for the EnergizerL92Ultimate Lithium, it can do 1.5Amp continuous, and 2Amp pulse (2 seconds on, 8 seconds pause). The best you can do (continuous) is 2.25W for that 7W LED, less than 1/2 of what you would need to drive the LED to max brightness. Looking at the spec sheet's graph, starting discharge at around 1.25A max, you have a nice discharge curve up to 1000mAH. This suggest at 1.5A, it wont last 1000mAH (otherwise they would have shown the nice performance even at max-continuous discharge).On the other hand, a lithium rechargeable 14500 at 3.7Vcanshould be able to discharge at 2Amp readily and have max brightness a lot longer.With an UltraFire being not exactly what one would call a premium brand, I would bet the LED emitter in it isn't name-brand either. I doubt you would get 300 lm even with a 3.7V lithium 14500 anyhow -- but it would be a lot brighter than what the 1.5V 1.5Amp AA's can do.Can you unscrew it and take out the driver PCB? A look at the PCB would be very telling.EDIT:I use 18650 a lot but I don't actually have a 14500 so I am projecting my experience with 18650 to the 14500. Lacking actual experience, I reworded that "can discharge at 2Amp readily" to "should be able to discharge at 2Amp readily"

author: james_s
author_rank: Super Contributor
timestamp: September 13, 2021, 08:03:02 pm
content: It will work fine. The AA lithium primary cells are actually a bit more than 1.5V but they are much lower voltage than Li-ion like the 14500 type you mention. 14500 is just the physical form factor but most of the rechargeable ones are Li-ion. They are very much like the common 18650 cells only smaller.

author: Peabody
author_rank: Super Contributor
timestamp: September 13, 2021, 09:46:12 pm
content: I've ordered a three-pack, but they won't arrive for a few days.https://www.amazon.com/gp/product/B07BDGD8KRI just thought that the primary lithiums cost about twice as much as alkalines, but my understanding is they last much longer. Plus, their voltage holds up better as they discharge. So, short of using Li-ion rechargeables, it seems the primary lithiums are the best alternative. I'll be using one of these, but the other two are for friends who I think would do better not having to mess with recharging, at least initially.

author: james_s
author_rank: Super Contributor
timestamp: September 13, 2021, 10:42:00 pm
content: The main advantage of lithium primary batteries is they have a very long shelf life and rarely leak, so they're good for things like emergency flashlights that are rarely used. They also work better at very cold temperatures than other types so I've seen wireless weather stations recommend them for the outdoor unit.

author: Rick Law
author_rank: Super Contributor
timestamp: September 14, 2021, 12:04:55 am
content: Quote from: Peabody on September 13, 2021, 09:46:12 pmLithium is best recharged by a good recharger and shopping for a recharger could be difficult. For me, temperature monitoring is a must-have.The Nitecore NL1475R (750mAH@3.6V) has aninternal chargerand micro USB slot right on the battery. You only need to buy a micro USB cable, plug it into the slot on the side of the battery and off you go charging. The top side of the battery has LED indicator to show charge state. That is about as easy as it gets. It can also be charged by external chargers, which ever tickles you.I have to say, I have not use any Nitecore products myself. I consider Nitecore a good brand. This battery is so interesting I almost want to buy a 14500 flash light just so I can try out this battery... But I already have a drawer-full of 18650 flash lights...

author: Rick Law
author_rank: Super Contributor
timestamp: September 14, 2021, 12:58:16 am
content: One final thought, and this one is an important one - that is why I made it a separate reply instead of tagging on to the last one.Battery makers tends to push the limit on size, a bit too fat and/or a bit too long.With lithium rechargeable, particularly the protected kinds, length could be a problem. Some may push the length limit a bit too far.Your flashlight no doubt will have a spring holding the battery in. The spring can be cut short a little to get some extra but there is a limit. So do check the size of the battery to make sure it is not exceeding by too much.

author: james_s
author_rank: Super Contributor
timestamp: September 14, 2021, 03:45:59 am
content: The problem is almost always the protection. Protected round cells are almost always ordinary cells that have a protection PCB stuck on the end. That adds about 2mm to the length.

author: Rick Law
author_rank: Super Contributor
timestamp: September 14, 2021, 05:00:02 am
content: Quote from: james_s on September 14, 2021, 03:45:59 amFatness too, also in the name of protection. Good cells' original wrapper has value. When I break down a battery pack to re-wrap, I keep the original Fujitsu/Sony/NCR wrappers on the cell rather than removing them. Add a flat-conductor strip from the anode to the protection board, perhaps some labeling on a strip of paper, then wrap the whole thing with an outer clear layer. All these add to the fatness.Length-wise, besides the protection board, likely on the anode is an added cap with a raised nipple. Even flat ends without nipple adds to the thickness. At some point, every 0.1mm counts. As I said in last reply, you can buy some leeway in length by cutting a bit of the spring off; but there is only so much spring you can cut while keeping the set up viable.When I was less experienced with doing that, I purchased thicker wrapper thinking it would give the cell better protection from scratches that may expose the metal. After having real trouble putting the finished re-wrap cell into a flashlight housing, I learned and begin using thinner outer wrap. The couple of real fat ones I made were stripped and re-wrapped with thinner outer layer.

author: Rick Law
author_rank: Super Contributor
timestamp: September 14, 2021, 05:02:58 am
content: Quote from: james_s on September 14, 2021, 03:45:59 amFatness too, also in the name of protection. Good cells' original wrapper has value. When I break down a battery pack to re-wrap, I keep the original Fujitsu/Sony/NCR wrappers on the cell rather than removing them. Add a flat-conductor strip from the anode to the protection board, perhaps some labeling on a strip of paper, then wrap the whole thing with an outer clear layer. All these add to the fatness.Length-wise, besides the protection board, likely on the anode is an added cap with a raised nipple. Even flat end-caps without nipple adds to the length. At some point, every 0.1mm counts. As I said in last reply, you can buy some leeway in length by cutting a bit of the spring off; but there is only so much spring you can cut while keeping the set up viable.When I was less experienced with doing re-wrap, I purchased thicker wrapper thinking it would give the cell better protection from scratches that may expose the metal. After having real trouble putting the finished re-wrap cell into a flashlight housing, I learned and begin using thinner outer wrap. The couple of real fat ones I made were stripped and re-wrapped with thinner outer layer.

author: richard.cs
author_rank: Super Contributor
timestamp: September 14, 2021, 09:02:25 am
content: Quote from: Rick Law on September 13, 2021, 07:38:45 pmI know it's outside datasheet specs but I am not so sure it won't. A good-quality alkaline AA manages 10 A short-circuit, so about 3.8 W per cell into a matched impedance load. Given one of the selling points of the lithium ones is supposed to be lower internal resistance I would expect them to do better than the alkaline.

author: Rick Law
author_rank: Super Contributor
timestamp: September 15, 2021, 05:08:38 am
content: Quote from: richard.cs on September 14, 2021, 09:02:25 amI agree, likely, it can put out more than specs for a little while, but for how much and how long is the big question.Here are a couple of photos of an Eneloop trying to give me more Amps than specs for a bit too long.

author: Peabody
author_rank: Super Contributor
timestamp: September 15, 2021, 03:50:04 pm
content: The flashlights arrived yesterday, and I tried them with lithium and with alkaline. Both worked fine, and I didn't really see any difference in brightness. Since it will also work with a 3.7V lithium rechargeable, I think it's possible it has a boost converter. If that's the case, then the lumens would be the same no matter what the power source. But that's just a guess. I don't have a 14500, but perhaps I can rig up an 18650 and see if that's brighter.The wide angle setting is not particularly bright, but about half way to the full spot gives good brightness in the spot. If you move it all the way to spot, you get a bright image of the LED.Edit: Well it would have to have a boost converter, wouldn't it? I don't think these power LEDs work at 1.5V.

author: Rick Law
author_rank: Super Contributor
timestamp: September 15, 2021, 05:21:34 pm
content: I would not expect a regular boost converter in there.On the cheap Chinese single AA/AAA flashlights, I've seen them use a joule thief like but single chip solution which requires just one external part: a small resister like inductor. It outputs pulses rather like the joule thief.It was about 5 to 10 years ago when I disassembled the cheap flashlight. May be by today with 5+ years of advancement, their solution would be a bit better.If you can disassemble it, post some pictures of your LED driver PCB.