18650 Li-Ion Batteries

Madness

New member
I'm thinking of swapping from Ni-mh batteries to Li-Ion so that I can have a larger capacity battery pack. this will enable me to have longer duration or run at brighter settings.

I have a question for the more technically minded. If I use protected 18650 cells in parallel, will my lamp cut out suddenly or will the LED stop working before cut off voltage is reached? I'd prefer to use protected cells to avoid overcharging.

Also, can anyone recommend a supplier of decent 18650 cells or even 20650 cells?
 

Olaf

New member
Do you want a separate protection for each cell? That would not be how I'd design it, but should work. Parallel cells with a single protection might be a better choice.

Once the batteries are nearly empty, the behaviour of your light very much depends on the control circuitry. Do you have a simple resistor, a linear regulator or a buck converter? (I assume you've checked that the input voltages are compatible?)

As for batteries, the "supplier" is maybe less important than the battery brand. I don't think there are many fakes of quality brand batteries around, because reputable manufacturers just print something like 3400mAh onto their cells, while the people faking cells would usually write 6000 mAh onto theirs, which appears to be more lucrative. Good cells are for example Panasonic NCR18650B (3400mAh), if you can get hold of any of the rumoured and more recent NCR18650C or even NCR18650G you would be pretty much on top of the line. For some reason you'll find plenty of them at e-cigarette shops for not much money...
 

royfellows

Well-known member
Olaf said:
if you can get hold of any of the rumoured and more recent NCR18650C or even NCR18650G you would be pretty much on top of the line.

Yes, NCR18650G are what I am using in my new power packs. Truly state of the art tech. However, they are OEM so unprotected, I use my own electronics, dual chip to support high discharge in the bat cookers.
You should be able to source some protected retail re wraps, probably under the Panasonic brand. Sanyo and Panasonic are now same people.
(y)
 

Madness

New member
royfellows said:
Yes, NCR18650G are what I am using in my new power packs. Truly state of the art tech. However, they are OEM so unprotected, I use my own electronics, dual chip to support high discharge in the bat cookers.
You should be able to source some protected retail re wraps, probably under the Panasonic brand. Sanyo and Panasonic are now same people.
(y)

You're spot on Roy. I found some protected Panasonic cells at Batteries Plus.

Now I need to source a holder and something waterproof to house them in.
 

Pitlamp

Well-known member
I don't understand sparks very well but I do know that I've tried various sorts of 16850s and most have been utter rubbish. Their quoted capacities have been a joke.

My conclusion is it's very much a case of buy cheap buy twice (or in my uninformed case, several times).

However, these:

http://www.amazon.co.uk/dp/B00NNEHL8E/ref=pe_385721_37986871_TE_item_image

. . . have proved to be excellent. They're expensive but worth every penny in my opinion. I'm sure folk who know more about this subject could quote better cells at cheaper prices but these above ones work well and I'm happy with the several sets I bought for a high drain job (bright diving lamps).

 

Duncan S

New member
Pitlamp said:
I don't understand sparks very well but I do know that I've tried various sorts of 16850s and most have been utter rubbish. Their quoted capacities have been a joke.

My conclusion is it's very much a case of buy cheap buy twice (or in my uninformed case, several times).

However, these:

http://www.amazon.co.uk/dp/B00NNEHL8E/ref=pe_385721_37986871_TE_item_image

. . . have proved to be excellent. They're expensive but worth every penny in my opinion. I'm sure folk who know more about this subject could quote better cells at cheaper prices but these above ones work well and I'm happy with the several sets I bought for a high drain job (bright diving lamps).
I bought unprotected versions of these 18650's, also from Amazon.
My capacity tester indicates a genuine 3400mAh - very good cells :)
 

Benfool

Member
Wowza John, they are incredibly expensive. I too use lots of 18650s for dive torches. I always by them from here:
https://m.fasttech.com/p/1141104

They are exactly the same cells you've just linked from Amazon, but cost less than a third of the price! Take a couple of weeks to arrive though :)

B
 

royfellows

Well-known member
Interesting to note, I am getting 200 lumens for 18 hours then diminishing output up to 24 hours or more from a 2 cell pack using the NCR18650G. This is from a Dragon D800 lamp.

The pack weighs 180 grams, and yet I still see people underground with cables hanging down their backs. Out of curiosity I weighed a length of cable of that length and it came in at more than my batteries!


 

Madness

New member
royfellows said:
Interesting to note, I am getting 200 lumens for 18 hours then diminishing output up to 24 hours or more from a 2 cell pack using the NCR18650G. This is from a Dragon D800 lamp.

The pack weighs 180 grams, and yet I still see people underground with cables hanging down their backs. Out of curiosity I weighed a length of cable of that length and it came in at more than my batteries!

If you are getting 18 hours out of a 6800mah battery pack (2 x 3400mah) that equates to 377ma per hour of current usage, or am I getting this wrong? So I assume that the LED is being driven at 350ma? What LED gives 200 lumens at 350ma? I intend to make a new insert for my Oldham and 200 lumens for 350ma sounds a good deal. Obviously heat disipation is the main issue with an Oldham headset.

 

Duncan S

New member
Roys specs seem in line with my Phaethon lamp.
I get 300 lumen for 12 hours using a pair of identical looking Panasonic 18650 3400mAh batteries.
The lamp uses a pair of Cree XML-2 U2 3C; 300 lumen is no where near their potential :)
 

royfellows

Well-known member
Right, answers.
The cells are the 'rumoured' Sanyo 3500 mAh, and actually many give more than this, there are figures on the manufacturers data sheet.

The emitters are Cree XP-Ls which are the most efficient bang for bucks currently available, and actually beat the XM-L 2 by a narrow margin.

The lamp uses 7135 linear drivers which are not the most efficient, but roundabouts and swings are in my opinion best choice for low voltage, ie parallel cells. However, there is zero Vf drop on the circuit due to the use of MOSFETS for reverse polarity protection rather than Schottky's or horrible standard RF diodes. (This is down to the kindly advice of Mr Mike)

There is some technical stuff on my website www.ledcaplamps.com and data sheets can be downloaded from the manufacturers, Cree inc and Sanyo

The battery protection is by the now standard Seiko chips, but in paralleled arrays to stand higher currents and give a reliability edge.

General advice, avoid any Li Ion cells with "Fire" in the name like the plague. Trustfire used to be reasonably good but have now gone down the drain, while the cost of quality cells based on OEM Sanyo/Panasonic has fallen dramatically.
 

royfellows

Well-known member
sorry forgot
Its 400 mA standard mode on the D800, calculated output is the 200 lumens, D1800 is 200mA on 2S beam emiiters, and 60mA on 2S downlighters. Emitters are XP-Ls on all except the D1800 downlighters which are XPG 2 s.

My experiments indicate that best output at very low drive currents are from XP-G 2s, some people my disagree.

Hope that all this is helpful
 

Olaf

New member
Madness said:
If you are getting 18 hours out of a 6800mah battery pack (2 x 3400mah) that equates to 377ma per hour of current usage, or am I getting this wrong? So I assume that the LED is being driven at 350ma? What LED gives 200 lumens at 350ma? I intend to make a new insert for my Oldham and 200 lumens for 350ma sounds a good deal. Obviously heat disipation is the main issue with an Oldham headset.

How about looking at Watt hours rather than Ampere hours?

Say we have the 3500mAh at nominally 3.7V, i.e. two of them have about 25.9 Wh in total. Draining this in 18h means roughly 1.44W constant power. With the specified 200lm at 1.44W you are at roughly 139 lm/W, which is not far the manufacturers claims for the latest and greatest LEDs. In fact, Cree claims up to 200 lm/W for the XP-L, and presumably the gap is at least partially explained by Roy's use of linear regulators (7135) and can be reduced a bit with the use of a Buck converter.

Furthermore one should maybe add that at 200mA, the diagram in the datasheet for the XP-L states a forward voltage of roughly 2.65V. If the LED's start to fade out, this means the batteries are drained so far, that they can't even deliver these 2.65V any more. Presumably the protection circuit kicks in once a level of 2V is reached. One should hasten to add that while it is safe to discharge LiPo's to such a level, you should make sure you recharge them within 24 hours, or they might never reach their 3500mAh again. A safer cutoff voltage would be 3V, but I'm not sure up to which voltage you have to discharge to get the claimed 3500mAh out of them in the first place...
 

royfellows

Well-known member
Olaf said:
Presumably the protection circuit kicks in once a level of 2V is reached.

2.5V

Also, thing to remember about 7135 chip setups is that once input voltage falls to level of, or below, forward voltage of LEDs, they will go to direct drive. As I said, roundabouts and swings
Dont like buck circuits for low voltage, maybe just me.
 

Madness

New member
Thanks for explaining things. The electronics side of diy lamp building is the most complicated bit. I can basically solder a driver to an LED and connect it to a battery. After that it starts getting complicated.

My current Oldham insert is basically two Cree XP-G2. One runs at 350ma with a flood optic, the other at 700ma with a reflector giving more of a beam. The main downside of this is that it hasn't got a really low setting. I've not found a compact multi mode driver that works with 4 x 1.2v Ni-mh cells. That's another reason for changing to Li-ion cells, there's a better choice of drivers.
 

droid

Active member
Benfool said:
Wowza John, they are incredibly expensive. I too use lots of 18650s for dive torches. I always by them from here:
https://m.fasttech.com/p/1141104

They are exactly the same cells you've just linked from Amazon, but cost less than a third of the price! Take a couple of weeks to arrive though :)

B

Fast-Tech are a good company to deal with. Pretty useful if you're into vaping too....
 

royfellows

Well-known member
Of the HK sellers, Kaidomain is quickest deliverer, usually 2 weeks, DX is not too bad, FT is slowest. Look out for Euro stock as its from Sweden and delivery pretty good.
There are also some others and new boys on the block, but the above are the big 3, I deal will all the above and get treated very well. I don't mess them about with petty complaints and if I do reject something they are very quick to look after me.

The quality of stuff has improved tremendously but not the Li Ion cells. While the "fire" brands have nosedived their price on quality Sanyo/Panasonic has come down, and they are absolutely genuine. My burn times are on lab test not estimated which proves the cells.

My electronics are bought in from the HK sellers but heavily modded. I try to keep a margin, for instance my Dragon D1800 pulls about 1.9 amps on max but the PCB is rated for 3 amps.

In the past, some of the stuff was atrocious, drivers circuits which were little more than resistor circuits with a PWM for instance, but a lot of junk has disappeared.

Descriptions are more accurate now, with more tech info and honest feedback.

The big thing I have though about their torches and bike lamps etc is the habit of parallel wiring the LEDs. They use generic components, nothing seems to be specialised. Typical of their high powered torches is say 6 LEDs all parallel wired and sharing 9 amps from a generic driver, so they getting approx 1.5 amps each, with some getting more than others as internal resistances will vary slightly. The finished product will appear on eBay claiming something silly like 10,000 lumens.
:LOL:
 
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