Buried Treasure...

Charging clamp for batteries, bought very cheap at harbor freight, make sure the clamps are plastic so you don’t short out the battery, put a metal screw on each clamp and use.

This post by Comfychair forever changed the way I look at (and use) my drill press:

I wanted to bump this thread, in hopes more people would share their discovered “buried treasure” here.

In the midst of a PM conversation about identifying laptop packs for scrounging, I said this:

Okay, I’ll be blunt. Watt-Hour is a bullshit number.

All I (we?) care about is AMP-hours, because the amperes delivered over time is what’s important in an LED flashlight. When the manufacturer only gives you WH, that BS can be converted to a useful number, i.e. AMP-Hours by the Power Formula.

The point of using the math here is to know if you’ll be getting 6 or 9 18650s from a given Laptop Pack, and roughly what Capacity (in AMP-HOURS) you can expect from each 18650.

When they give you the AMP-Hours Capacity, you don’t have to bother with useless, BS Watt-Hours.

We haven’t even moved on the concept of ‘C’ (“Charge” or “Coulombs”) yet, which tells you how much Current a battery can flow (e.g. “1C”, which would be ~2.5A in your #A pack) in a given instant. That’s much more important that Watts, because if you have (e.g.) a 2.5A driver, which runs at 50% efficiency, your 18650s will need to deliver 5A to run it. This means your #A pack batteries will discharge through it at a 2C rate, which isn’t that hard, but 2000mAH 18650s (1C = 2A) may not please you since they’ll need to deliver >2.5C, which is asking a lot from LiIon. In other words, a discharge rate of 1C will usually give you the “Amps” for an Hour from the Amp-Hours rating, but 2C may not give you quite half the time, and anything over 2C will probably not last very long between charges.

To be plain, your #A pack’s 18650s, at 2550mAH rated Capacity, will deliver 1C, which is 2.5A, for 1 hour, or 2C, which is 5A, for half an hour, or 0.5C, which is 1.25A, for 2 hours.

This will tell you whether the pack you want to buy/scrounge is going to be worth it. If the 18650s inside will be called upon to deliver >2C, you may want to pass on it.

And yes, I know 50% efficiency is too low, and even 2.5C isn’t too high, but I just used easy numbers to make the Math plain. If you want “ballpark” numbers, figure 90% Efficiency and 2.5C max rate (which means your 18650s won’t last half an hour!!).

The bottom line is, what matters is ‘how much current’ for ‘how long’, and Watts is a BS distraction which won’t help you understand. Amp-Hours (Capacity) and C (Ampere Delivery Rate) are what’s important here.

If I was wrong, I’d appreciate correction, if what I said make this easier to grasp, I’d like to share it.

Mostly I just wanted to bump this thread…

Thanks for reading.


Why not just use the search function for keywords?
Works for me

It can be very difficult to come up with the correct keywords sometimes. Other times there are no keywords that are both relevant enough and unique enough to pull up the post.

As I stated in the OP. Thank you for the reminder.

I just wish there was a button I could use to “fav” a post. Then I could just skim my list of faved posts to find stuff.

Post #8 here - Review: Versatile bicycle flashlight holder

Identifications for PAM280x family boost controller chips such as PAM2801, PAM2803, PAM2805, PAM2806:

via Post #37 in the “Ultrafire LZZ-06 AAA light with pocket clip 0.9-4.2v” thread

This would cover the controller for lights like the DQG clicky AAA and the Fenix E05.

Was re-researching for laptop pack calculations, found this post from last October

[(Total Pack Capacity (mAh) * # of cells in pack) / # of parallels] / total # of cells = mAh per 18650 cell.

So 4800mAh pack, of 9 cell, 3 parallels.

[(4800*9)/3]/9=1600mAh per cell.

(Note: that is a brand new never used battery pack)

From the same thread

Let’s take your example of a 6 cell pack rated 11.1V, 48Wh. Now 48/11.1 = 4.324Ah = 4324mAh. And 11.1V/3.7V = 3, so the pack has 3 cells in series, so 6/3 = 2 cells in parallel; thus 4324/2 = 2162mAh/cell. So they’re probably 2150 mAh cells, indeed 11.1 * 2.15 * 2 = 47.73Wh, which rounds to 48 Wh, as rated.

I've found from intuition that:

3 cell = 3S1P [10.8/11.1]

4 cell = 4S1P [14.4/.8]

6 cell = 3S2P [10.8/11.1]

8 cell = 4S2P [14.4/.8]

9 cell = 3S3P [10.8/11.1]

12 cell = 4S3P [14.4/.8]

= 3S4P [10.8/11.1]

Might not be buried deep in the boneyard, but its easily overlooked.

oh snap…those could also work as impromptu shotgun light mounts too :smiley:

More BLF Gold:

Keywords: Ultrafire 501A Solarforce L2m 1xCR123 1x16340

People hunting for laptop packs might also want to know that any pack over 100Wh is subject to strict transportation regulations and so we are unlikely to see higher pack capacities. I wrote a bit about some of the implications of this for battery pack ‘upcyclers’ a few weeks back. A few highlights:

  • 12 cell packs are likely to be older and certain to be using lower capacity cells (<2,400 mAh).
  • The largest cell you are likely to find in a 9-cell pack is ~3,100 mAh.

On a related note, Dimbo-the-Binky, Wh is NOT a bullshit number. It actually conveys more useful information than just focusing on mAh.

Thats not to say your advice is wrong. Current delivery is pretty much always an important consideration alongside capacity, and for lights using direct drive, or a driver with a linear regulator, nominal Wh isn’t really an added consideration.

Nominal Wh is relevant for lights with a switch-mode regulator. I think most commonly these are buck converters, which switch the power flowing to an inductor to regulate voltage and current. The inductor can trade a reduction in voltage for a boost in current (which is smoothed by a capacitor). Wh is also relevant when a boost converter (like a joule-thief) is involved.

Further, true (measured) Wh may shed light on the shape of the discharge curve and hint at how much time a discharging spends above the target voltage when used in a light with a linear regulator. I haven’t done any tests on this yet, but in theory, two cells of different types (manufacturer, chemistry, design, etc) with the same nominal capacity and voltage could have different measured Wh capacities due to one delivering more of its initial current at a higher average voltage.

To Summarize:

  • mAh capacity is always relevant
  • discharge rate is always relevant
  • Wh is relevant when a switch-mode regulator is involved.

That’s my understanding, at least. I’m sure someone will be along shortly to correct anything I’ve got wrong.

Sounds like the Xtar MC1 chargers can have wide range of termination voltages (post #3102)

Here (Post 917), wight showed some basics for making a voltage divider for series cells.

This classic thread by drJones explains all about what happens, and especially what does not happen optically when you dedome a led. Not everything is easy to comprehend, but wether you understand it or not, or believe it or not, it is true and practically it helps you designing your mods and predict the performance:

Dimbo The Blinky wrote the below here. Works great. Now I can re-profile blades and reshape metal in a fraction of the time. Thanks Dimbo bro! :)

If you want to whittle steel, like whittling wood with your favorite pocket knife, get yourself one of these:

It’s nothing but a Carbide bar on the edge of a small steel bar. KISS. I picked one up on a whim at the local hardware store, to see if it would make sharpening lawn mower blades less of a chore. It worked.

For a giggle, to test it, I tried whittling the edge of a double-bit axe head I was in the process of re-handling… One stroke down each side of an edge made the old head (the axe, not mine!!) dangerous to work on!!

Needless to say, I’m impressed.

Not shilling, just sharing. This is a cool tool and it is small enough to fit almost anywhere you want it, and will get any metal you can find (even bar stock, I’d wager) sharp enough to skin a deer, without a lot of work. No, it won’t likely make an edge like you guys are discussing in this thread, but it will make an edge you can use to cut things, on anything metal and flat — and that right soon.

I only paid around seven bucks, so needless to say I went back & picked up a few. One of them is the only sharpening tool in my BOB now…

Hope this helps.


More buried treasure:

Just a little nugget of gold I found lying there…

Some good suggestions on soldering LED leads in well heat-sinked heads.

There is so much history and info here we need a forum archivist. BLF is THE library on how to mod. I still find myself reading posts from 5+ years ago.

You know, there’s always thread tagging. Not sure if it’s even an option with Drupal. Might be a plugin for it. But, that would also increase overhead and might be abused. Ok, nevermind.