1200mA HIGH QUALITY Li-Ion charger discussion thread.

[VanIsleDSM]

I see my original thread was closed. I was just trying to gauge interest, and I thought there would be no better place to gauge interest of electronics than the electronics forum, I didn't mean for my thread to look like a FS ad, sorry for that. Just thought I would keep it all in 1. From now on this thread can be the ongoing discussion about my progress and such. I'll start a thread in the Marketplace with the list of people who want one as soon as I can (I just registered for the Marketplace, but I got no confirmation email, so need to work that out first)

For those who want to see the original thread, it's here:

http://www.candlepowerforums.com/vb/showthread.php?t=199573

Or if you don't want to bother I'll give you the summary. I'm building my own charger that will hold anything from 18650s to 16340s (34mm to 70mm long, 10 to 21mm wide) seen here:

Max charge current of 1200mA, adjustable down to 1000, 750, 500, 250, and 100mA.

Each battery bay is completely separate from one another and controlled by it's own electronics.

Charges to 4.2V within 0.5%

Preconditions deeply depleted cells.

Automatic end of charge, battery monitoring, and automatic recharge.

Continuous temperature monitoring of each and every cell.

Here's the datasheet for the IC I'll be using for the charger.
http://ww1.microchip.com/downloads/e...doc/21893c.pdf 0.11751955



My first update in this thread is that the electronics were ordered last night, they shipped this morning and they should be here by Monday.

I'm just designing the PCB right now. Stay tuned!

 

[Rommul]

Why aren't the holders wide enough to hold Emoli 26700 as well as AW C Cells?

 

[3rdrock]

 

[VanIsleDSM]

Why aren't the holders wide enough to hold Emoli 26700 as well as AW C Cells?

That's a funny way to make a suggestion.

Nobody has mentioned it yet.. I think if I was making a charger specifically for those batteries, I would probably be looking for something with a 2A charge rate. It would ad quite a bit to the cost of the battery holder if I made it big enough to accept those cells.. although I could look into another holder design that would be slightly more expensive if there was enough interest do it.

The marketplace thread is now open, you can find it here:

http://www.cpfmarketplace.com/mp/showthread.php?t=179626

 

[DM51]

The marketplace thread is now open...

I will therefore close this one and the discussion can continue there.

Edit: Following submissions received, I am reopening this thread.

Would the OP and members please note that all SALES discussions mnust take place in the MarketPlace, not here; and that DESIGN issues, including SAFETY considerations, should now take place here.

 

[cy]

let me get this correct... you don't own any li-ion cells... yet you are building a li-ion charger to sell.

have you done this before?

As for my testing, I'm wondering if someone has a Li-Ion cell they could donate to the cause. I actually don't have any of my own..

http://www.cpfmarketplace.com/mp/showthread.php?t=179626

 

[adamlau]

Are you still looking for 18650 test cells?

 

[cy]

have you looked a Pila chargers? New style Pila chargers are very high quality and properly terminates a charge and reasonably priced.

there's a number of reasonably priced quality li-ion chargers, including multi-channels available...

don't want to insult you but .... your comments indicate that you have little to no experience with li-ion usage, including charging li-ion cells.

please correct if this is not the case...

Being unsatisfied with chargers on the market, I took it upon myself to make my own.

There's also a safety timer for the whole operation. But I'm not too certain what to set it to yet. at 1200mA how long will it take to charge an 18650? 3 hours, maybe 4? maybe I'll set the safety to around 5 hours, what do you battery gurus think of that?

 

[VanIsleDSM]

cy, you are correct.

However I don't need any experience with Li-Ion cells to build a Li-Ion charger. The chip is completely pre programmed with the proper charging algorithm .. I'm not doing anything too special by putting it together with passive components to make it work.

One thing I do have quite a bit of experience with is electronics.. mostly I build LED drivers for fixed lighting. but have lately decided that I need a monster CREE torch.. so first I made some 3-4CREE buck drivers that work off 6 Li-Ion cells.. but then after looking around more I see I'd be quite out done. So I decided then that I needed more.. I now have 9 CREE R2s and I've built a ~35-50.4V buck driver that takes 12 Li-Ion cells in series and drives the 9 CREEs in series at ~96% efficiency. Adjustable from 1.2A to 60mA. I have a few extra of these drivers around too.. but I'm bench suppliless at the time.. I need to get another so I can finish all the testing to them and get efficiency numbers from all different input voltages and drive currents. Then I'll offer a few of those at cost to some CPFers too.

Building this charger is, electronically, a walk in the park. I should have the electric components by tomorrow. Follow my thread, I'll be updating as I go with pictures of everything. If you don't think you know what I'm doing by my work I post.. then by all means raise a flag.

 

[SilverFox]

Hello Cy,

What do you think of his choice of charge controller chip?

Tom

 

[Alan]

However I don't need any experience with Li-Ion cells to build a Li-Ion charger. The chip is completely pre programmed with the proper charging algorithm .. I'm not doing anything too special by putting it together with passive components to make it work.

No offense, this is exactly what most junior Chinese engineers are thinking and they manufactured hundreds of thousand of them. Yes, most of them charge OK and only a few fraction of them get into unexpected accidents when the cell reacts differently and beyond the limited knowledge of these engineers on li-ion cells. To them, it may be only a 0.1% failure rate but the consequence of this 0.1% could be serious if not fatal due to the nature of li-ion.

May be I'm paranoid but selling li-ion charger to public is very different from doing experimental projects that building 9A driver for mulitple LEDs.

I apologize if I am a bit too harsh or too paranoid.

Alan

 

[SilverFox]

Hello Alan,

While I agree that people (including engineers) make mistakes, it has been my experience that almost all of the problems are generated from those who are trying to control production costs. It is not unusual for a production manager to make an "engineering" decision based on cost analysis, rather than heeding the original engineering findings and limitations.

I respect that your work experience, culture, and day to day dealings with manufacturing may be different from mine.

By the way, what do you think of his choice of a charger controller chip?

Tom

 

[jtr1962]

By the way, what do you think of his choice of a charger controller chip?

Since nobody else answered this thus far, to me it seems like a great chip except for the fact that it is a linear regulator. This means it requires a power supply fairly close to the voltage of the cells being charged to prevent overheating. For single cell charging 5V is good, 4.5V would be about ideal. If used with a 5V supply, a schottky diode to drop the supply voltage to the chip by 0.3 to 0.4 volts would be a good idea. It would also provide reverse polarity protection as a bonus.

A better but more expensive way to do this would be to have a switching pre-regulator to allow operation on more common 12V supplies. Also, the current requirements from the supply would be less. For example, a four bay charger requires 4.8 amps at ideally 4.5V. A 90% efficient switching preregulator could deliver this while drawing only 2 amps from a 12V supply (or ~1.75 amps from the 13.8-13.9 volts from a typical automotive cigarette lighter plug). Power bricks of over 4 amps at 12V are commonly available fairly cheap, making it possible to power an 8-bay charger. Also, by preregulating at 4.5V, heat buildup in the charger IC is kept to an absolute minimum.

 

[VanIsleDSM]

If you haven't read through datasheets and put together your own drivers or controllers, and you're telling me I don't know what I'm doing... well.. you don't have any feet to stand on as far as I'm concerned.

There are chips exactly like this one in your ipod, your cell phone, your PDA your camera.. you name it.

The chip is pre-programmed.. the only things I have control over are, the charge current, 4.1 or 4.2V charge, charge timer, and what colour of LEDs I want to use.

Please.. look into the common schematic on the datasheet.. it's basically the same as I will be building it.. read through that datasheet, and then tell me a failure mode you see could pose a problem.

If all you have to say is "Li-Ion batteries are dangerous and you probably don't know what you're doing" Then please... take a seat.

/rant



SilverFox, Thank you for asking a worthwhile question.

jtr, Thank you for criticism that actually has thought involved. I agree a switching regulator would be best.. but the amount of components and complication that would add would be too much. And if I stick with linear I have no EMI to worry about. 5V supplies in the form of computer PSUs are very cheap and plentiful. Using a schottky diode would be a good idea if you needed to move to heat away from the chip.. but I don't. Each chip will have a heatsink thermal epoxied onto it, and each chip is equipped with a thermal throttling that reduces charge current to stop the chip from overheating.. you can actually connect these to 12V in a pinch and just use a lower charge current to keep the Pd down on the chip.. but it'll never melt down on you no matter what. Using a 5V supply the Pd isn't very bad..

0.8V x 1.2A = 0.96W... that will easily be dissipated by the heatsink.

Using a 4.5V supply would be great, but it would have to be deadly accurate to keep the charger working. 10% wouldn't be good enough. 4.5V is the bare minimum input voltage.

If you didn't want to use a computer PSU you could buy a 5V supply.. they're pretty cheap.

here's a 3 amp unit for $11, good for 2 bays.

http://www.powersupplydepot.com/prod...oduct=17430+PS

8 amp unit good for 4 bays at $15.

http://www.powersupplydepot.com/productview.asp?product=17432+PS

12 amp unit good for 8 bays at $17

http://www.powersupplydepot.com/productview.asp?product=17433+PS

 

[cy]

no one is saying you don't know what you are doing... just that you might consider charging a few li-ion cells, then use it a few cycles to learn what common issues are.

to answer silver's question about the chip... not familiar with this chip. but all the factors safely controlling a li-ion charge are there including low voltage cell conditioning. especially if temp sensor option is taken.

one limitation is 1.2amp charge which would match 18650 charge for .5C. typical charge rate is 1C for li-ion cells, assuming one is using a quality hobby charger like Schultz or Triton.

larger cells will not achieve .5C with 1.2amp limitations.

If you haven't read through datasheets and put together your own drivers or controllers, and you're telling me I don't know what I'm doing... well.. you don't have any feet to stand on as far as I'm concerned.

There are chips exactly like this one in your ipod, your cell phone, your PDA your camera.. you name it.

The chip is pre-programmed.. the only things I have control over are, the charge current, 4.1 or 4.2V charge, charge timer, and what colour of LEDs I want to use.

Please.. look into the common schematic on the datasheet.. it's basically the same as I will be building it.. read through that datasheet, and then tell me a failure mode you see could pose a problem.

If all you have to say is "Li-Ion batteries are dangerous and you probably don't know what you're doing" Then please... take a seat.

 

[MrAl]

Hi there,

Just to note, we built a charger that works up to something like 3 amps
a short while back. It's a custom design with more than one ic chip,
so it's a little more involved, but it's good for the much bigger Li-ion
cells when you want to charge fast.
The project schematic and details appear right here on CPF although
someone would have to do a search.

 

[VanIsleDSM]

no one is saying you don't know what you are doing... just that you might consider charging a few li-ion cells, then use it a few cycles to learn what common issues are.

to answer silver's question about the chip... not familiar with this chip. but all the factors safely controlling a li-ion charge are there including low voltage cell conditioning. especially if temp sensor option is taken.

one limitation is 1.2amp charge which would match 18650 charge for .5C. typical charge rate is 1C for li-ion cells, assuming one is using a quality hobby charger like Schultz or Triton.

larger cells will not achieve .5C with 1.2amp limitations.

Please explain how charging a few Li-Ion cells would help me build a charger? There's no other way I can put the thing together, it wouldn't change anything.

1.2A is not a limitation in the world of affordable chargers.. it's double the usual. 1C is only recommended for smaller cells, for larger cells like 18650 0.7C is the recommended max charging rate.

MrAl,

I'd be interested in looking at that thread. Do you have any idea what I should search for to try and find it?

P.S. I'll charge some cells when I'm finished building the first charger

 

[ProofTech]

...The project schematic and details appear right here on CPF although someone would have to do a search.

Here it is.

 

[VanIsleDSM]

Thanks ProofTech.

cy, as I already mentioned to SilverFox, the first charger will be dedicated to testing. michelkenny has been kind enough to send me some old cells he doesn't use anymore. After I'm done with it I plan to do a pass around for anyone who wants to scrutinize it..

 

[cy]

if you had basic charging knowledge ... don't think you'd be taking that stance.

Please explain how charging a few Li-Ion cells would help me build a charger? There's no other way I can put the thing together, it wouldn't change anything.

1.2A is not a limitation in the world of affordable chargers.. it's double the usual. 1C is only recommended for smaller cells, for larger cells like 18650 0.7C is the recommended max charging rate.

P.S. I'll charge some cells when I'm finished building the first charger