Laptop 18650 circuitry help needed

[RepProdigious]

Hey all!

My laptop battery died on me! When fully charged it would run down to about 97% (lets say 3 minutes) and then my laptop would turn off...... On my spare battery all is fine. So i decided to take the thing apart to see whats what!

Now, ive opened up a battery in the past but as soon as i saw the scary li-ions i got scared and stopped... Now after all ive learned here about working with cells i got brave enough to go on, and i got all the cells de-soldered and seperated.

All cells (after my laptop decided to die) had a resting voltage of more or less 4.1 volts, this voltage does not significantly drop after an hour or so! All cells can sustain a 1A current no problem and dont heat up when doing so. So in my book the cells are good (but please correct me if im wrong). So that leaves the circuitry as the culprit.....

Now my big question is; How much can a non electrical engineer check and/or fix on a piece of circuitry like the one that regulates a notebook battery? I have a DMM and quite a bit of 'electronics-street-smarts' :laughing: I'm very intrigued by those chip-thingies but i dont really understand em to be totally honest (i only do 555 timers )

Here's a pic on the circuit in question..... On the back there's a single thermal-couple and the four connectors to the cells: One for each side of the cell-pack and two in between the parallel cells (2p3s).

 

[Stereodude]

I'm not quite sure I'd draw the conclusion that the cells are good. AFAIK, that circuitry doesn't do much on the discharge side other than monitoring functions, so I'm not sure what might be occuring unless some of the protection circuitry is incorrectly detecting a fault and disconnecting the batteries from the load when it shouldn't be.

 

[RepProdigious]

I'm not quite sure I'd draw the conclusion that the cells are good. AFAIK, that circuitry doesn't do much on the discharge side other than monitoring functions, so I'm not sure what might be occuring unless some of the protection circuitry is incorrectly detecting a fault and disconnecting the batteries from the load when it shouldn't be.

Well, thats the feeling i have, that perhaps there's something funky with the protection circuit........

The batteries are still as full as the power-meter on my laptop would suggest. And what could be broken on an unprotected cell if it holds a charge, keeps up good voltage over time and can sustain a nice current draw and be charged without getting warm? Is there a test im missing here?

 

[cityevader]

I just took apart an old laptop battery and they are all over 4.1v. But four of the six when put into my ROP hi for testing die in a minute. The other two will go for over ten minutes until the Mag is too hot to hold.

All cell voltages started out the same.

 

[RepProdigious]

I just took apart an old laptop battery and they are all over 4.1v. But four of the six when put into my ROP hi for testing die in a minute. The other two will go for over ten minutes until the Mag is too hot to hold.

All cell voltages started out the same.

Well, since 18650 cells are not too expensive anymore i think ill just order me 6 brand new ones and see how they hold up in the pack. And if that wasn't the problem...... well you can never have too many batteries! lovecpf

 

[kramer5150]

5 ways I evaluate laptop 18650 pulls
Over-discharge, Measure cell voltage straight out of the pack. Less than 3.5V and I toss it.

Current delivery, Any cell that delivers over 2A is sufficient for my needs. Most of the Sanyo and panasonic japan cells deliver ~2.55V to my most current hungry P60 host. This particular light draws 3A with an IMR18650.

Self discharge, This is the hard one. I charge/discharge the cell a few times (just by using it). Then charge it once again and place it high up on a shelf... out of sight out of mind. I come back ~4-5 weeks later and measure cell voltage. If its less than ~4.10V I toss it.

Capacity, I approximate this 2 ways. My hobby charger "measures" (approximates is a better term to use) this and gives a reading on the diagnostic display at the end of the charge. I already know the cell delivers 2.55A in my P60 host. With Sanyo 18650 cells the capacity is around 2400Ah, so I should get 50 minutes per run. I simply use the light, anything substantially less than 50 minutes and I know its no good.

I have also had a few cells (like one in every ~25), not reach a full 4.2V peak. For whatever reason they only peak out at (say) around 4.05... and stop there. VERY DANGEROUS condition... because my chargers keep trying to charge the cells... blasting them with current. The cells get SCORCHING hot, if left unattended (ask me how I know...LOL). So... you should be on the lookout for these "runaways"... and always monitor your charging. Any cell that can not accept the full 4.2V at any time gets tossed.

As for that PCBA...
I would start out by looking up the data sheets for each of those SMT components. Find out what each one is and what it does.

From there map out all the values for the caps, diodes, resistors..etc.

They usually are double sided PCBAs, with all the SMT components on one side. Follow the traces from point to point.



**edit**
AW has unprotected cells for $7... so in all honesty its hardly worth the effort... IMHO.

 

[Ray_of_Light]

Replacing dead 18650's in laptop batteries is the easiest part, if I can say so.

The most difficult task is to reprogram the EEPROMS. Some of the controllers have read protected memory areas, like the texas. If one cell go below a certain threshold, the battery is disabled forever. Other batteries, like Toshiba, have a cycle counter; above 500 cycles it disables the battery. All controllers measures the charge output power and upon the subsequent discharge cycle will discharge the battery only of that amount.
After replacing the cells, all that parameters requires a reset. Some controllers doesn't allow this reset.
In any case, you need a specialised software and an hardware interface. It is not a job for beginners.

Check this:

http://sbworkshop.com/

Regards

Anthony

 

[RepProdigious]

Well, i did indeed follow all the lines, measured all resistors against the value written on the parts itself and i managed to figure out what all the connectors do and indeed, my battery follows the SMBus guidelines (non switching, NTC with separate data and clock lines).

I currently have a batch of protected cells on route (for flashlights) and when i receive those ill give the circuit a test-run before i buy new cells to see if the circuit is indeed still good to go. I even read somewhere that some circuits die if they lose voltage, so you must keep the circuit under power when changing the cells.... but that sounds a bit too scary even for me and ive already disconnected everything so if thats the case than its too bad

But this got me thinking..... What if i go all franken and bought a bunch of protected cells and hooked them op to - for example - one of these babies:

http://www.all-battery.com/pcbfor111vli-ionbatterypack3cells-pcb111v65a32057.aspx

http://www.all-battery.com/protecti...batterypack3cellswith12alimit-pcb111v12a.aspx

Now that would be great fun! The protection circuit on the cells itself should keep bigger issues in hand (like overheating) and the circuit should make sure the cells get charged evenly.....

Only thing is that i must be pretty sure that my laptop will operate without any data and clock lines (the NTC value can easily be faked with a resistor).....

I only doubt if this would be a very wise undertaking :shrug:

 

[jasonck08]

The cells are probably bad. I took a pack apart that would last less then 5 minutes. When fully charged the cells were at about 4.1-4.2v. They did not seem to self discharge much by themselvs. I did a discharge test on them and most of them tested to around 100-200mAH! LOL! And they are rated for 2400!

Take a cell out, and pop it in a light and test the runtime (unless you have a proper discharger).

 

[Mugrunty]

I can post more tomorrow, as I'm off to bed and typing on my iPod, but I've had quite a bit of experience in repacking smart batteries. Not sure if you've heard of the SONY AIBO, but all of these robots use batteries that comply with the Smart Battery System and SMBus. I've repacked and sold a few packs and they have worked better than new. One model uses the bq2040 chip and another uses the bq2060. They also use 18650 unprotected cells.
I successfully reprogramed the eeproms, and reset the gas gauge chips. It's not impossible, but not easy either! Luckily, Texas Instruments has great datasheets on their fuel gauging chips and explain how to program the eeproms!

 

[RepProdigious]

The cells are probably bad. I took a pack apart that would last less then 5 minutes. When fully charged the cells were at about 4.1-4.2v. They did not seem to self discharge much by themselvs. I did a discharge test on them and most of them tested to around 100-200mAH! LOL! And they are rated for 2400!

Take a cell out, and pop it in a light and test the runtime (unless you have a proper discharger).

I put one in my fenix TK11 and it ran for an hour on high before i had to go to bed, after that is still had 3.99 volts (i started with 4.13)...... Seems fine, even a bit high actually...... Im continuing the experiment now (note to self 11:55!).

I can post more tomorrow, as I'm off to bed and typing on my iPod, but I've had quite a bit of experience in repacking smart batteries. Not sure if you've heard of the SONY AIBO, but all of these robots use batteries that comply with the Smart Battery System and SMBus. I've repacked and sold a few packs and they have worked better than new. One model uses the bq2040 chip and another uses the bq2060. They also use 18650 unprotected cells.
I successfully reprogramed the eeproms, and reset the gas gauge chips. It's not impossible, but not easy either! Luckily, Texas Instruments has great datasheets on their fuel gauging chips and explain how to program the eeproms!

I'd love to hear about this...... If there's a cheap way to get this fixed that is guaranteed (to some extent) to work im all ears! But if its gonna cost me significant amounts of money i think ill just buy a new laptop because theres a nice eeepc on sale here in the Netherlands for 190 euro's shipped..... I can just keep using my current laptop plugged in and use the little netbook for traveling.

 

[RepProdigious]

I put one in my fenix TK11 and it ran for an hour on high before i had to go to bed, after that is still had 3.99 volts (i started with 4.13)...... Seems fine, even a bit high actually...... Im continuing the experiment now (note to self 11:55!).

Well, its 13:10 now and the measured 'open voltage' is 3.4V, so the cell is dead in my book, the cell is cold to the touch... Gives it more or less 2hr and 15 minutes... Sounds about right to me.....

Ill see how the others do, and ill try to charge this one......

 

[Mugrunty]

I'd love to hear about this...... If there's a cheap way to get this fixed that is guaranteed (to some extent) to work im all ears!

I'm not sure if it will be the money that stops you, but the time. Attempting this procedure with most likely require many hours of soldering, debugging, and programming....not to mention the testing you'll have to do.

Like Ray_of_Light said, you'll need a circuit to interface with the SMBus of the battery. I built a Philips I2C adapter shown here: http://sbworkshop.com/i2c.jpg

I actually used a slightly different adapter, and a program called Accplus...but that program doesn't seem to be available anymore. Accplus could also read an EEPROM using the I2C adapter through the SDA and SCL on the memory. This made it convenient, as I could write to the EEPROM and talk to the chip using the same program. I believe you can do the same with sbworkshop...except that the program is much more expensive ($159.95!). Accplus did the same thing, but was only $19.99 or so. I think you can get a limited three use version from sbworkshop for 15.95.

So essentially, you're going to need to do the following:

1.) Buy the necessary components to build the I2C adapter and have an available parallel port on your computer. (I got my components for free from school! )

2.) Have some sort of program that can talk to Smart Batteries and program EEPROMS.

3.) Replace the old crap cells with the shiny brand new cells.

4.) Use your computer to program the EEPROM with the correct values for the new cells.

5.) Reset the BQ chip so that it loads the new values from the EEPROM.

6.) Hope that whatever protection circuitry they used can be reset. Whether its with a stand alone protection chip, or using the function of the BQ chip...who knows.

7.) Read the data from the BQ chip and see if everything looks ok...maybe even do a test discharge/charge while reading data.

8.) Squish it all back into the case and hope it still fits your laptop.


Yup, so you'll have to be pretty good with surface mount soldering and all that jazz. I'm not entirely sure if it's worth it. It might be easier to just buy a new battery. In my case, the AIBO batteries were either no longer in production...or were selling for $150 or so. Since I like batteries, flashlights, and robots for some odd reason...I started this project for my own benefit and fun.

I'm sure I could help out a bit if you still decide to go through with it!

 

[RepProdigious]

Thanks for that great info! Ill play with the idea a little bit... Maybe ill just go out and find some new hardware (either a new battery or a whole new laptop/netbook).

 

[Battery Guy]

Thanks for that great info! Ill play with the idea a little bit... Maybe ill just go out and find some new hardware (either a new battery or a whole new laptop/netbook).

I think that is a good idea. Remember, your laptop gets used ON YOUR LAP! Messing around with rebuilding the battery pack or using off-brand replacement batteries is just not worth the safety risk.

Cheers,
Battery Guy