I am looking at the Nitecore D4 Digicharger/Four Channel Universal Smart Battery Charger/LCD Display and GYRFALCON All-44 4 Channel Digital Battery Charger.
What do you recommend ?
I read where 26650 have a higher capacity than 18650s.
Andy
"IMAX B6AC V2 Professional Balance Charger/Discharger (US Plug)" $44 for the built in 117VAC version or: $29 for the 12V DC input version. I have one of these.
It's basically a fairly universal programmable charger that can do almost anything. If you're building a series wires battery arrangement, you add a JST-XH "balance charger" wiring connector and you can safely charge LiIon cells in series. For high current, use XT-60 connectors:
I haven't used either of the chargers you mentioned, so I can't offer an opinion.
Yep.
18650 1500 - 3600 ma-hr 26650 3300 - 5200 ma-hrI'm still waiting for you to disclose the maker and model of your tail light so I can calculate runtime for various batteries.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
The 26650 is twice the size of the 18650, so sure, it _should_ have a higher capacity.
I posted it in that thread.
Here it is again.
Andy
The numbers give a rough idea of size.
18650 :- 18mm diameter, 65mm long.26650 :- 26mm diameter, 65mm long.
Hardly twice the size.
Andy
It has more than twice the volume.
16540 mm^3 vs. 34510 mm^3
That's make sense.
Andy
It looks like I will need some battery holders also ? I saw some connectors included.
Andy
yeah, capacity is closely related to the volume occupied by the battery.
the numbers indicate the size of the cell.
18650s are 18x65.0mm (18mm diameter 65mm tall) where as 26650 are 26x65.0mm, which is just over twice the volume. so with the same technology inside the 26650 should last more than twice as long.-- This email has not been checked by half-arsed antivirus software
Thanks. I didn't see your reply:
Two ways to grind the runtime. I could estimate the current drain based on the efficacy (lumens/watt) or I could dig for the specs. I'll do both.
The box says 150 lumens output. Oops, they cheated. The 150 lumens is for flashing in an unspecified mode with an unspecified duty cycle. Full max continuous output is only 90 lumens.
The better LED's deliver about 100 lumens/watt. 90 lm / 100 lm/watt = 0.9 watts I'm going to ignore losses through the lens for now. Also, note that the red color is well down the from the peak sensitivity of the eye (yellow-green).
The 18650 cell can produce 1500 - 3600 ma-hrs. I'll use 2000 ma-hr because I'm lazy. At an average cell voltage of about 3.6V, that's: 2.0 amp-hrs * 3.6V = 7.2 watt-hrs. The light consumes 0.9 watts, so the estimate battery life is: 7.2 / 0.9 = 8.0 hrs Actually, it's less than that because the battery cannot be fully discharged without also killing it. My guess(tm) is you'll loose about 20% of the available power resulting in: 0.8 * 8.0 hrs = 6.4 hrs Two 18650 cells in parallel will deliver twice the runtime or 12.8 hrs. Is that enough opertaing time?
As usual, the manufacturers specs do not include current drain or power consumption. It does show that there are 6 modes, all of which draw less current than the full brightness needed to produce 150 lumens. The data sheet also claims that the run time is 2 to 210 hrs. Sorry, but without either some measurements or specs, I can't calculate the runtime in the other modes. If you have time, measure the duty cycle of the various other modes and max power current drain.
My testing of junk 18650 cells showed and average of about 900 ma-hr. Laptop battery salvaged cells were about 1800 ma-hr. 2000 ma-hr assumes you're using brand new quality cells. If you use the two junk Ultra-Fire brand cells in your photo, you'll get about 2.7 hrs.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
XT-60 connectors are what I use for most everything. The 60 means 60 amps. It's certainly overkill for a tail light that draws maybe 500 ma from the battery. However, it's nice having the same battery connectors for everything, so that I don't need to juggle adapters.
One of my better mistakes was buying the wrong 18650 battery holder. There are two types. One is made for a "button" + terminal. The other is made for a battery without the button. The individual cells sold on eBay are usually the button type. The stuff I salvage from laptop battery packs do not have the button. In general, the battery holders that have a coil spring on one end will take button top cells. The ones with leaf springs on both ends are for cells without the button top.
If you're using more than one cell, it's tempting to buy dual cell holders. It won't work for your derangement because most of them are wired for 2 batteries in series, and not in parallel. You will probably end up buying individual 18650 cell holders.
These should hopefully work because they specify that it takes a button top cell:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
It won't work for your derangement because most of them are wired for 2 batteries in series, and not in parallel.
I re-wired it and made it parallel. :-)
I hate wasting anything.
Andy
12 hrs is plenty.
I ride about 1 hr. at nite.
Andy
ALmost exactly twice the size. ..OK, 4% larger than twice.
pi * (r) ^2 * L
3.14* (18/2)^2 * 65 = 16,500 mm^3 3.14^ (26/2)^2 * 65 = 34,400 mm^2 34,400mm^3 / 16,500mm^2 = 2.08
Yes, but you should be using the inside cell dimensions, not the outside for calculating the volume of the actual cell. The stainless steel jacket does nothing for the production of useful power. I couldn't find any specs for the ID, but I would guess(tm) that the wall and insulator thicknesses total about 1.5 mm each. Same with the end caps. Therefore, the cell volumes, using the inside dimensions, are:
3.14 * (18-3.0/2)^2 * (65-3.0) = 3.14 * 15^2 * 62 = 43,800 mm^3 3.14 * (26-3.0/2)^2 * (65-3.0) = 3.14 * 23^2 * 62 = 103,000 mm^3 103,000 / 43,800 = 2.4 times-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Perfectionist eh ? :-)
Andy
What is the discharge function for ?
Is it for measuring the actual capacity ?
Andy
Yes. Unfortunately, the IMAX B6AC V2 and other RC (radio control) style chargers will not produce impressive graphs suitable for posting on web sites and forums. For graphs, I use an older West Mtn Radio CBA-II battery analyzer: which attaches to my Windoze XP computah via USB. Charge and discharge testers like the IMAX B6AC V2 charger will only produce a single number for the capacity. It will not show what happens between full charge and full discharge and are not very accurate. I prefer graphs, like these: which offer far more detail and are much better for comparisons.
Unfortunately, the CBA series of discharge testers has a design problem. Instead of using a Kelvin bridge to sense the voltage at the battery, it does so where the battery leads attach to the PCB. At high currents, the voltage drop across the battery leads will produce strange looking graphs. Other than tearing it apart and using an Xacto knife to modify the PCB wiring, the 2nd best fix is to insure that the battery wires and connections are very low resistance. This is my fix to improve clamping pressure:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.