Very Fast Charging

I've learned from bitter experience, more than a few times, that if it moves, it breaks. It doesn't matter what moves, how it moves, or how it's protected, moving devices and 3rd world users are a dangerous mixture. For testing, I suggest you give your gravity, hand crank, wind up, or foot powered generator to a 4 or 5 year old to operate. If it survives intact, you may have a chance[1].

Any chance you can disclose what device(s) you plan to power?

The only thing that NiMH cells hate are over temperature, over charging, over pricing, and very low charge rates. Some mention in this thread was made about high charge rates. Here's EEVblog on an 8A charger:

It is difficult, if not impossible, to slow-charge a NiMH battery. At a C rate of 0.1 to 0.3C... etc. Actually, the problem is not charging but rather when to stop charging. The EoC (end-o-charge) algorithm used just doesn't work with slow charging which means you need to use a timer or something. Knowing when to stop charging with a hand crank generator source is going to be a real challenge as EoC is usually detected by a drop in terminal voltage, which could easily be produced by a slowing in hand cranking. Timers don't work because you never know the SoC (state-o-charge) to determine how long to charge. You might get away with a coulomb counter, but that will need some data storage to deal with aging cells.

In the past, I did some experimenting with 750 ma-hr AA NiCd cells and fast charging. I could charge a AA cell in about 6 min at 12C (9A). The NiCd cell would start to get warm at about 90% of full charge. I could do the same with NiMH, but it would begin to get hot at about

75% of full charge, making such fast charging a potentially bad idea. I still have the scorch marks on my Formica workbench from these tests. [1] Long ago, I worked on a man-pack HF radio for "civilian" use in the jungle. The prototypes survived various MIL-SPEC environmental tests. We shipped a batch to the jungle for field testing. They were eventually returned with an amazing variety of failures that had not be considered. For example, the telescoping antenna was not made to be raised and lowered 1,000 times per day by a bored operator. Various rotary controls were not meant to be "wound" up like a clock. Security screws were demonstratively not very secure. Batteries were not made to be left in the hot sun until they bulged and leaked electrolyte all over the inside of the radio. Insufficient room was left for painting the tribal colors on the case. So they painted over the instructions and warnings. All the projecting lights were bashed in because the operator assumed that they were push buttons. If there's a way to break it or steal parts off it, the 3rd world users will find it.

--
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

On a sunny day (Thu, 26 Nov 2015 17:02:00 -0800) it happened Jeff Liebermann wrote in :

And where to stop discharging. I am going to test those lipos we were talking about with an old car headlight, I get about 3.17 A (IIRC measured it a few days ago) from a 3.7 V lipo na 50 W 12 V light, As somebody here pointed out those lights make a good current source. But I need some power MOSFET to switch it off at 3.1 V or sit there next to it.. It is a variant of your PC processor heatsink with cooler. Need to order some more power MOSFETS.

Sorry for hijacking the thread ;-)

There are a zillion existing battery protection boards cheap. I haven't looked in detail in a while. To get the current you want, you may have to replace the FET with something bigger.

Only if you consider I ~ sqrt(V) to be a constant current.

A JFET is my idea of a minimalist constant current source.

Or zero once the bulb blows for over voltage.

There was a physics exam question involving series and parallel bulbs once where the approved answer as provided by the examiners was wrong. I turned up to our examiners final meeting with pages of algebra proving it and a more practical member of the group turned up with a plank and the circuit nailed onto it.

We agreed in the end that we would mark as correct either the answer taught in the syllabus or the true correct answer based on physics.

--
Regards, 
Martin Brown

On a sunny day (Fri, 27 Nov 2015 01:14:12 -0800) it happened mike wrote in :

Thanks, way cool, gotta get some.

I may try that

Lighting primarily. I'll design some minimal radios at some point too.

All that is a non-issue when using a partial charge

There are people like that and there are people that try to keep what they have working. Having worked, saved and bought is a great attitude changer - though as you point out, not for everyone.

NT

On a sunny day (Fri, 27 Nov 2015 10:08:46 GMT) it happened Jan Panteltje wrote in :

Ordered 2 of these:

Sevral reasons:

1) voltages seem correct 2) has 4A 3) has discharge limit 4) I can understand the Chinglish and it makes sense

Note that some other cheaper or bigger ones specify up to 3V as top limit... Or other strange voltages, could be translation, but this seems to make sense.

Maybe the gearing could be in the form of string, inspired by the button on a length of thread toy we used to make, a bit like this...

For example, a bicycle wheel with two lengths of string passing through the spokes at 180 degrees apart. Tension the string and wind the wheel lots of turns to somehow lift a weight or bend a bough. On release, the wheel spins and you somehow tap off some energy.

Just an incomplete thought...

Cheers

--
Syd

Cyclists have an advantage over other athletes - they move faster, and the faster-moving air travelling across their bodies evaporates more water, and cools them more effectively, than happens with runners.

It turns out that the maximum sustainable human power output is limited by the waste heat generated, and cyclists can dissipate enough extra heat to be able generate more sustained power than anybody else.

Stationary bicyles are useless (unless mounted in a wind-tunnel, which has been done).

--
Bill Sloman, Sydney

Putting a 13V lead-acid car battery in series with a 220V bulb decreases the bulb's current by 3%. Adding a second battery in series drops the charging current another 3%.

Yes, in the bush, that's rough-science constant current.

JFETs, besides being unpredictable, and unobtainable in the bush, make extremely poor lines-operated lead-acid battery chargers.

Which never happens, since the bulb is used at less-than-rated voltage. The lower-than-rated operation, instead of blowing, makes the bulb last a very, very long time.

Here are some actual data from a 2.5V .5A flashlight bulb (I didn't leave time for the bulb to reach full temperature)--

.74V 293mA

1.08 353 1.45 394 1.72 433 2.1 478

Confirming that i ~= k*sqrt(V), sqrt(2.1V/.74V) * 293mA = 493mA.

Cheers, James Arthur

Interesting. I'm wondering how to turn that into a working mechanism.

Motor + gear at top with shaft vertical, and strings attached. Weight could be bar shaped so it doesn't rotate. Maybe a very low speed motor like a stepper would work with that, otherwise the discharge time would be much too short.

NT

On Fri, 27 Nov 2015 11:45:53 +0000, Syd Rumpo Gave us:

You should. When the prospective users have a surplus of kids hanging around doing nothing, they need something to keep the kids busy. It will probably be your light.

Have you searched for the available products? Third world lighting is a big need: Bamboo wind generator lighting: Don't forget the bottle light. No power required: Or, just buy the book:

However, before you do all that, I suggest you get some of those solar powered lawn lights, that run a single white LED, turn off ALL the lights in your house, scatter them around as needed, and try to function at night using them as your sole form of lighting. I actually did that about 10 years ago. I won't spoil your fun by disclosing my results.

Also, consider the cost of interconnect. Yep, that's the two copper wires going between the gravity or solar power source and the LED. In the 3rd world, many projects have failed because someone stole the copper wiring to melt down and sell. I'm not sure how this idea will play out, but it's worth considering.

What type of radio? Nobody listens to the radio. HF programming is all religious recruiting. AM/FM broadcast is mostly commercials. What they want is internet, TV, satellite TV, and especially cellular. The problem is not the design, or even the cost. It's the method of payments. Micropayments, pay as you use it, microenterprises, and creative loan finance are popular:

I see. You want to ship oversized batteries that utilize only part of their available capacity. That should go over rather badly with those funding your project. Please note that battery powered device manufacturers like to squeeze every last watt-hr out of their batteries so that they can advertise long operating times.

Incidentally, you're still stuck with the problem of determining the EoC (end-o-charge). The NiMH negative delta-V "peak" in the terminal voltage only appears at full charge, not at half charge. Also, hand crank and gravity powered charging is rather erratic, and will do nicely to hide a small negative delta-V peak. A battery pack coulomb counter will work, but adds cost and complexity.

Go to the local recycler and look at what gets tossed. Look especially at the cell phones, which represent the epitome of todays throw away economy. What I find are fairly new looking devices that work and can possibly be fixed, mixed with devices that have been beaten to death by their former owners, with very little in between. The difference is that the nearly new stuff was either poorly designed or suffered infant mortality failures, while the abused devices were mishandled and not designed to last forever[1]. Consumers are much the same everywhere. They "consume" which often means they don't care if the device survives. It's often easier to replace than to repair or even to keep clean. If the local relief agency passes out gravity lights to anyone that wants them, then the light is likely to be abused.

Good luck with your project.

[1] The average life of a cell phone is 18 months. A smartphone is 21 months (Recon Analytics).

--
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

I've been doing it (using solar LED garden lights indoors) the last few nights. It's great. Let's be clear--a 10mW light won't light up 200 sq. ft. to reading-standards, but it *will* light a 1 sq. ft. book quite well. It's fine as a personal reading light. 3mW is a bit spartan for a personal reading light, but still very serviceable.

As a room light, 10mW lights up the room well enough to not bump into people or things, which is an enormous luxury many people simply do not currently have.

The 10mW head off a garden light also illuminates the 5 sq. ft. in front of you to a decent standard, hand-held as a flashlight. That's pretty useful too.

This is why removing the head from a garden light is attractive. You can hand-hold it, put it in the sun by day, and bring indoors at night. More suitable packaging would increase its utility / versatility.

Good list. Now that you mention it, there was a world-wide non-profit devoted to bringing cheap LED lights to the third world, exactly NT's mission. That was several years ago--can't remember who / what. They had a LightingTheWorld.org website, or something like that.

LED garden lights full-cycle their Ni-xx cells nightly, thrashing the Ni-xx. An over-sized storage under shallower cycling would extend life enormously, which is a good thing.

Yep.

Cheers, James Arthur

The water bottle is useful but doesn't produce light. The rest are commerci al products which rules them all out. $10 a light for 1.4 billion people, d o the math and you see why. And that's just for a low power light. The prom otional blurb for the book, the less said the better.

A single 0.1mm strand has more than enough ampacity & low enough R. 3 for r eliability or a metre or 2 of 10/0.1 I can't imagine too many stealing. Les s than a foot will be external anyway.

something very simple, AM. It's a shame I can't use pfb at rf.

I guess all those commercial stations are going bust then

...in N. America

I'm sure they want all sorts of things.

It's one option. I'm more interested in approaches that don't involve ongoi ng payments. Any time you bring that kind of model in the cost goes up, up and up, because suddenly you're also paying for someone's business & profit .

The only things being shipped are paper & CDs. End users will use whatever batteries they can get. In most cases that's going to be ones with far more capacity than is essential, since those are the cheapest locally available options. The upside is we can abandon any form of charge control, it's no longer needed. Thus unit cost drops, not increases.

cheap means no charge controller. I like that. People will be instructed to check battery temp while they charge & stop if it heats up.

things are rather different in different countries of course. UK, Japan and 3rd world countries aren't like that.

oh yes, I'm not into that model.

thank you. It's all going well so far, but there certainly is a lot to do. Lighting is a tougher challenge than the other projects. Probably because m any have tried already.

NT

useful info. I've not yet encountered the product on my travels, but I'm sure I will.

yup. And it saves money by losing charge control.

NT

The water bottle is useful but doesn't produce light. The rest are commercial products which rules them all out. $10 a light for 1.4 billion people, do the math and you see why. And that's just for a low power light. The promotional blurb for the book, the less said the better.

A single 0.1mm strand has more than enough ampacity & low enough R. 3 for reliability or a metre or 2 of 10/0.1 I can't imagine too many stealing. Less than a foot will be external anyway.

something very simple, AM. It's a shame I can't use pfb at rf.

I guess all those commercial stations are going bust then

...in N. America

I'm sure they want all sorts of things.

It's one option. I'm more interested in approaches that don't involve ongoing payments. Any time you bring that kind of model in the cost goes up, up and up, because suddenly you're also paying for someone's business & profit.

The only things being shipped are paper & CDs. End users will use whatever batteries they can get. In most cases that's going to be ones with far more capacity than is essential, since those are the cheapest locally available options. The upside is we can abandon any form of charge control, it's no longer needed. Thus unit cost drops, not increases.

cheap means no charge controller. I like that. People will be instructed to check battery temp while they charge & stop if it heats up.

things are rather different in different countries of course. UK, Japan and

3rd world countries aren't like that.

oh yes, I'm not into that model.

thank you. It's all going well so far, but there certainly is a lot to do. Lighting is a tougher challenge than the other projects. Probably because many have tried already.

NT

+++++++++++++++++++++++++++++++++++++++++++++++

First they need to elect all democrats so they can get all that stuff free.

True. However, an LED flashlight looks much better going through a light fixture than by itself.

Only free lighting qualifies? Is there something wrong with commercial products that are designed to be affordable?

The users don't pay the $10. Various relief agencies pay the bills and hand them out for free.

Cu 0.1 mm wire is about #38 awg which fuses at 2.6A. An NiMH battery can easily produce that. #38 awg is also good for 2.2 ohms per meter. A 2 meter loop will be

4.4 ohm. I have no clue what your light will draw but for all night operation, I would guess(tm) about 50 ma or about 10 mw lost in the tiny wire. Not much, but when you're playing with micropower, every milliwatt counts. Also, you won't like handling #38 AWG and neither will your users. It breaks quite easily.

Have you considered that it might be better to supply what they want and need, instead of what you envision they might find useful? Have you asked anyone from your prospective target audience? (Welcome to marketing). If you want numbers of RF media usage and listener statistics, give me a country and I'll dig it out for you. I don't have time to do the entire world.

Hint: Except for government funded projects, every venture eventually has to pay its bills or go under. I've lost count of the number of really good ideas and products that died because the proponents could not monetize their grand schemes. You can delay the inevitable through angel investors, charities, foundations, kickstarter, gofundme, government subsidies, and such, but not forever. Consider paying your bills a necessary evil.

You're quite correct about the advantages of monthly payments and pay as you go schemes being beneficial to the operators. But it's also beneficial to subscribers that have no other alternative and are willing to take the chance that large scale production will drive costs down, not up. If you believe that nobody else is allowed to make a profit until AFTER you have at least paid your bills, you're not going to get anywhere with any funding scheme (except government subsidies and maybe pyramid schemes).

They are most likely to get defective or dead batteries. It would be interesting to design an LED driver that works with dead or near dead batteries. Incidentally, it's been my experience that dead or half dead batteries like to bulge, leak, or belch gasses, depending on chemistry.

Incidentally, we have a local company selling high end radio kits to ham radio operators. Selling do-it-thyself kits is very different from selling completed products. I think you'll find that average customer has difficulties reading and following instructions, as well as lacking in basic mechanical and electrical skills. The third world equivalents, even less so.

Those may be the only options. I take it that you're assuming that a bank of over-capacity batteries is equivalent to one good battery? I haven't bothered to work that out, but it might be possible. One local eBike builder built a pair of battery packs out of discarded laptop LiIon cells. By borrowing my discharge tester for 2 months, he was able to test enough individual cells to build a workable battery pack.

The charge controller is there to keep the user from injuring themselves. If you hand them instructions that even under obscure circumstances will produce some kind of life or health threatening situation, you're asking for major safety problems and litigation. Yes, an automobile will run quite nicely without brakes, but it's generally considered that brakes are a good idea.

When ANY battery heats up, the damage is done, and it's too late to stop the charge. That's because it takes a while for the heat to go from insider the cell, to the outside, where it is detected by a thermistor or IR detector. That's also why using heating for EoC detection tend to kill cells, and has lost favor in most chargers.

I won't try to convince you otherwise. I suspect that you will only believe me after you find out for yourself. Please go to the local recycler and look at the stuff that comes back from users and decide for yourself.

You have a better model for fighting poverty and keeping the GUM (great unwashed masses) from destroying everything they touch? I'm all ears.

"Insanity is doing the same thing over and over again, and expecting different results" (Al Einstein).

Whenever I have what I think is a really good idea, the first thing I ask myself is "why hasn't someone else done the same thing"? I usually find that there's some kind of fatal flaw or major snag in the idea. Look over similar past project and see what and how they did it. Then, if you think you can do it better, do it. The really big hits in product design were usually not the first attempt and can often credit their success more to the sales and support structure surrounding the great idea, than to the design.

"We lose money on every sale, but we'll make it up in volume". (I forgot who said it, but they're probably out of business today).

--
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

powerprofiling.jpg

The top cyclists produce these higher power with lower body weight, so they can climb steep hills frighteningly fast