Rebuilding E1705 battery pack with high-capacity cells

The highest capacity 18650 cells that I can find are Panasonic 18650 2900 mAh cells.

http://industrial.panasonic.com/www-cgi/jvcr13pz.cgi?E+BA+3+ACA4001+NCR18650+7+WW

9 of them have this power capacity:
3.7V * 2900 mAh * 9 = 96.5 WH, almost 100Watt-hour!
Significant improvement in capacity and runtime, double that over my current 6-cell battery.

Possible to use these? Any reason why it wouldn't recognize that capacity correctly?

Cost-wise, they come out to be about $11 each, or $100 so it's not cheap. maybe not even cheaper than OEM stuff. It doesn't seem possible to buy that high capacity cell pack off the shelf however, it seems they use 2600 mAh cells, not the highest that are almost 3,000 mAh each.

 

The mAh ratings of all 18650 cells are based on a 0.5A, or 500mAh, current draw. The lower current you draw, the closer to the advertised rating you will be. However, even at 500mAh, it would still be a little bit less. Those Panasonic 2900mAh cells have a slightly below average internal resistance of 60m-Ohm, so they will retain their true rating at a lower current draw around 0.5-1A, and at higher current draws of 2A and higher despite the amount of heat generated. P=I^2*R states that the less current draw, the less percentage of energy is lost as heat.

My flashlight draws about 750-800mAh, which would make the battery in your link very ideal for this use. My laptop uses an eight cell 4400mAh battery pack configured in two sets of four parallel cells with each cell rated at 2200mAh. My power supply outputs 120W, 6A at 20V, which means that my laptop would not be able to keep up when unplugged because the battery can only output 6A at 14.8v, which would already make the cells hot and battery life would drain quickly mostly due to heat. However, this is at theoretical maximum load. However, regardless the Panasonic cells would make a very good upgrade in this case.

Here are some comparisons at various current draws.

http://light-reviews.com/forum/viewtopic.php?f=9&t=513&start=20
http://www.candlepowerforums.com/vb/showpost.php?p=2970294&postcount=73

However, despite the excellent performance from these Panasonic cells, I highly advise that you avoid them for use as laptop batteries because they are unprotected cells, they do not have integrated PCB, and have a slightly lower voltage output at load compared to other 18650 cells.

The equation you used was assuming that all of the cells are stringed in series, and that you are using nine cells instead of six. Your Dell E1705 uses a six cell 11.1v 4400mAh battery pack configured in two sets of three parallel cells each. Each cell is 2200mAh just like the cells in my battery. 11.1 * 4400 = 48.84Whr. If you were to use the Panasonic cells, you would get 11.1v * 5800 = 64.38Whr.

 

It's my understanding that the individual cells do not have a protection circuit, they don't need one, as it's built into the battery pack. Which makes them less than ideal for use in regulated flashlights as they will drain them beyond recovery to the point of damage instead of cutting out at some point like 2.5V.

Pull any 18650 cell from a laptop cell pack and you will see that they are unprotected.

I did see these charts before and I got these Panasonic cells as they seem to outperform everything else. They are not designed to be used in devices but in a battery pack, which is why you see these tabs soldered into them.

I do have a modified Surefire torch that I use with 1x18650 Panasonic 2900 mAh cell with great success. The drop-in LED module I have runs regulated for 1 hour from 3.8V to 4.2V and below that runs unregulated with about a 2-hour tail so you actually see you need to recharge.

I just started using them, maybe on my 2nd cycle and cannot get them to charge to full 4.2V, as I found out I need to fully discharge them to 2.5V instead of constantly up-charging as I have been doing. They can take discharge to 2.5V.

I use the nice Pila IBC charger...

I also have a number of 2x18650 lites but for these I use protected 18650 cells as the cells can get discharged too much but still stay within regulation (3.7V*2=7.4v, but say in discharged state: 2.5V*2=5V)

Anyway, do you have any better suggestions?
Surely you are not suggesting these Ultrafire cells? Certainly these Panasonic cells have got to be better than the low capacity LG cells currently in it - what was it, 1800 mAh, or something close to it?

 

Whoops, way too many tabs open again. Sorry about that. I got mixed up with the PCB circuit board independant from the cells themselves and the integrated PCB's on protected cells. Yes, you are correct. Laptop battery packs do not have the devices on the cells. No, I'm not suggesting the Ultrafire cells, especially the 3000mAh ones. They drain way too fast at higher draw. I'd still recommend you the Panasonic 2900mAh cells. I'd also take a look at the AW 2600mAh cells. I have a few in my older torches and in my robots and they ran extremely well. Tenergy also makes a few good ones as well. Their 2600mAh cells are more true to 2300mAh from my tests, but they still hold their capacity at higher draws.

I use a DSD TL-100 to charge my 18650's.

 

I already have AW's cells, including 18650 and 18500 cells. I had issues with 18500 mAh but 18650 have been pretty reliable. That's both the older 2200 mAh he had and the newer 2600 mAh cells..

Keep in mind that AW 2600 mAh cells are slightly longer than standard due to the protection circuit. So to rebuild the pack you would have to get non-protected ones. They are not substantially cheaper than Panasonic however, was it 8 bucks vs. 11 bucks each?

Question, can the laptop run off house power with the battery pack removed while I rebuild it?

 

Yes, your laptop can run off of house power with the battery removed.

 

Well this is good news. I suppose the only danger is if we get a power hickup for a second, the machine will crash.

I am going to order about 9 of them soon, there is actually a seller on Ebay.

The old ones I will recycle into my flashlights.

 

Here is a useful thread with pictures:

http://forum.notebookreview.com/showthread.php?p=2932783

BTW, My E1705 started showing this message some months ago saying that the battery should be replaced. I turned the mesg off but the cell pack is at the 3 year mark. I want higher capacity anyway.

 

Yeah, I remember that thread. It reminds me of when I was back in high school. We modded the board game Operation with more kick. Me and the guys used to gather all the Duracells we found lying around in the chemistry lab and ran them all in a series totalling ~40v if I can recall. Lunchtime was always a test of bravery.

 

I am a big fan of 18650 Li-IOn cells, I use them a lot in flashlights.

I have a flashlight with 1x18650 configuration that uses a Malkoff drop-in module, getting about 230 lumens for a couple of hours and then diminishing output. These Panasonic cells just keep on going and going.

If you look Whr, 1 18650 has 4 times the capacity of a NiMH cell or an Alkaline cell. Very impressive performance.

I have a lot of other batteries as well. The really cool thing is, if you suddenly need batteries in a TSHTF situation, you can take your laptop cell apart and get some.

 

Im interested in how this goes.

If the e1705 is anything like my old Inspiron 6400 (e1505), then inside the battery pack there is a chip that will not function once you disconnect the cells from it (safety mechanism). So you might have to wire in the new cells in parallel with the old cells such that the chip inside the battery is always powered. Just something to consider.

I also believe Dell's batteries may be more intelligent than most. After taking apart my battery and doing some research, I believe they incorporate a counter in the chip which deliberately prevents your battery from operating to it's full capacity after a certain amount of charge cycles, or after a certain time period (after warranty expires). This is why you will usually hear people complaining that their batteries one day went from being able to hold 2 hrs + to only 20 mins. More info here:

http://www.west-wind.com/WebLog/posts/365.aspx

If this is indeed true (which I believe it may be), then there is no point wasting your money to buy new cells for the battery and you would probably be better off just buying a cheap eBay battery which likely wont have this counter chip.

 

That's not true, that's some angry guy with a defective battery making things up.

 

If you look at the reviews for the e1505 batteries (and perhaps e1705), you will see a common complaint that the battery mysteriously fails within a month (or mere days) after the warranty is up. It happens way too often for it to be dismissed as a mere coincidence.

After I mysteriously had my 6400 battery go from being able to hold 3hrs of charge to 20 mins practically overnight, I read the article and decided to poke around the battery a bit. I managed to "jumpstart" one of the chips and get an additional ~2.5hrs of battery life from my cell which the BIOS had reported to be flat. I ended up frying the chip though after more experimentation, so I just bought a new battery off eBay instead of messing around with it. I still have the chip numbers if anyone who knows what they are doing might want to take a look.

 

I've got Dell batteries still kicking after as much as 10 years in some cases. None of my Dell batteries are under a year old.
All of them hold about the charge I would expect.
It's not impossible, but I find what you are saying hard to believe.

 

That's the biggest basket of bollocks I've heard in a while, nobb.