Guide: replacing and upgrading laptop batteries

Aim:

• Replacing the lithium-ion cells inside a battery pack.

Advantages:

• Lower cost vis-à-vis full pack replacement (roughly 25-50%, ymmv).
  
• Increased capacity vs. the original pack (from +21% up to +55%, depending on original).
  
• Environmentally friendly (or 'less not-so', rather).

Disadvantages:

• Time
  
• Burning down the house

Tools:

• Soldering iron
  
• Multimeter
  
• Box cutter or rotary tool (dependant on pack)

Background info:

Laptop battery packs may seem to vary from brand-to -brand and model-to -model. However, they all contain the same li-ion cells inside, either 18650-type (18mm x 65mm) or pouch-type, both 3.7V nominal.

The main differences are:

1. Type of cells; 18650 or pouch.
   
2. Number of cells in parallel.
   
3. Number of parallel cells in series.
   
4. Total number of cells (x parallel * x series).
   
5. Capacity of each cell.

We'll elucidate the difference with a few examples along the way. Ah, and this guide is for 18650 types specifically. Everything applies to pouch type as well, but unfortunately pouch form factor is not standardised, so hunting down matching cells is rather tricky.

Step #1: Draining the battery

Run the laptop on battery until it has close to zero charge. This is just a precaution; it will minimise the consequences of the dremel/cutting operation. If you happen to cut/slice through the cell's container then it will short the cell's wrapped layers, causing a bit of heat/fire and such . Really, just be a little careful, that's all.

Step #2: Opening the pack

If you're fortunate then it's a simple plastic clip design which can be pried open using nothing more than a screwdriver:

Spoiler: cheap Acer pack

Spoiler: cheap Acer pack, configuration

Replacing these with 3400 mAh cells ( highest capacity currently available) would increase total capacity by (3400-2800)/2800 = +21%. Cheapest stock battery pack, and the only one available, is $34.20 (using mere 2,200 mAh cells ... ), which we can compare to the alternative options:

1. 4x 3,400 mAh cells for $33.00 -> +55% mAh, -3½% $
   
2. 4x 2,800 mAh cells for $24.22 -> +27% mAh, -30% $

So it's a win-win; save money and increase capacity at the same time. Of course, not all replacement packs will have less capacity than the original, but it is not uncommon, either; check the specifications before ordering any pre-assembled battery pack.

Anyway, we're still at step #2, so let's open a two-halves-glued-together pack:

Spoiler: opening pack using a rotary tool

This, especially, is where a drained battery is useful. The cells are very closely packed to the edge, so it's quite a small feat to damage them, thereby causing a short. The hot plastic can get a bit smelly, btw. Box cutter will not have that problem, but then you'd better have some bandages ready ...

Spoiler: glued-type pack disassembled

The white goo is normal; it keeps the cells firmly in place, preventing any rattling noise.

Spoiler: configuration; two cells in parallel

Spoiler: configuration and capacity, old and new

This is an example of 2x cells in parallel and each 2-cell placed in 3x series. The advantage of parallel over a simple dual series design is that a failed or poor cell can be bypassed with its direct neighbour, saving the series. Disadvantage is that the parallel set will be as weak is its weakest member, since the lowest capacity cells will cap out before the rest and this will prevent the other cell(s) from charging to full capacity (maximum safe charge voltage is reached). If you can be bothered to make an accurate measurement of each cell you've bought, then it's possible to position them in the most optimal way:

Spoiler: battery pack, 3x parallel, 4x series - cell positioning

Of course, it doesn't matter where you place each worst cell within the parallel pack, as long as the worst ones are distributed amongst all four parallel sets. This specific configuration is from an M18x R2, btw, but many DTRs will be similar.

Step #3: Choosing new cells

First consideration:
Batteries are a pain to solder properly, although you can get away with sanding the surface first. However, it is much, much easier to order cells that have tinned tabs soldered to the ends in advance (assuming they've used proper equipment). Cost isn't much higher, so unless you can't find cells with tabs for a decent price; don't bother.

Second consideration:
We want unprotected cells; most packs are cramped, so there's only room for true 65mm variety. The protection pcb adds ~2mm and those, usually, won't fit inside this casing. It is also unnecessary; the battery's control circuit has its own overcharge/de-charge protection. If for whatever reason you happened to have ordered protected cells then it's easy enough to remove the tiny pcb and wire (use knife/pliers).

Third consideration:
Order any capacity you want, just don't mix different capacities, used cells or brands. Of course, higher capacity (up to 3,400 mAh) will be more expensive, but not linearly so; entry-level cells generally have a poorer price/quality ration than their high-end counterparts. Mind that anything over 3,400 mAh is an outright lie and cells cannot be had for $0.95/piece unless they're either used (and re-wrapped with fresh plastic) or have 1/10th the capacity claimed. Expect $5 to $9 per cell, depending on capacity.

Spoiler: background info for capacity-upgrade situations

In case you're replacing an x mAh cell pack with higher capacity cells; the battery pack doesn't actually know the capacity of the cells. It has a factory-preset Wh value in its firmware which is used along with current pack voltage to estimate the current charge level. This is merely an informational-type of application and is irrelevant to the charge cycle. What happens during charging is that the system (pack+laptop) will supply a variable (and increasing) voltage plus a fixed current (in mA). While it's doing so that will increase the cell's internal resistance due to the higher charge level. To overcome that additional resistance and deliver the same mA's, the pack will keep stepping up the variable voltage until it reaches ~4.2V, which is considered 'full'. At that point the charging current will taper off to zero (part of the protection circuit). With higher capacity cells it will simply take longer for the sets to increase resistance and, thus, voltage; charge time will be proportionally longer. The mAh/Wh report you'll see in HWiNFO or other tools will be wrong, though, since that information is part of the battery pack's fw. Consider lowering the %-left warnings to compensate for the increased life-span away from the socket.

Step #4: Removing the old cells

Use pliers to strip off the existing tabs; they'll separate easily from the cells. Optionally there'll be a few 'bypass wires' (or whatever they're called ...) interspersed in-between two cells or parallel cell sets:

Spoiler: bypass wires

Their purpose is to speed up the charge cycle; one cell or set may overheat or be near-full, so a different set can be charged alternately. De-solder the wire from the tab and, optionally, make a simple sketch to remember where each was going (hence the different colours). If you got cells with tabs then you may disregard the existing ones; the new tabs should be long enough to bridge cell-to-cell and connect to the bypass wires.

You may also run into this thing:

Spoiler: battery pack - thermistor

It's called a thermistor, the purpose of which is to measure the cell's temperature and, in case of overheating, prevent thermal mayhem (slow down charging). After finishing the new battery pack simply reseat it snug against the replacement cell.

Step #5: Soldering the new cells

At last; the fun starts. With a parallel set it may be easier to solder each set before assembling the full pack:

Spoiler: soldered cell sets (x3)

So I've just solder one cell's tab to the other's and plan to use the second tab for further assembly. Important bit here is that we want to test each set before soldering them together:

Spoiler: checking voltage of a set - 1st measurement

Spoiler: checking voltage of a set - 2nd measurement

Now, if our soldering job was awry then you'd find different voltages. Unless ... they just happened to have been identically charged to within 0.01V. Cross-checking the negative end of one cell with the positive side of the other would rule out that possibility as well; if the soldering joint was off then you'd measure no voltage whatsoever.

Next thing is to assemble the sets and recheck total voltage (the sum of all sets):

Spoiler: checking voltage of the pack - 1st measurement

Spoiler: checking voltage of the pack - 2nd measurement

Looks good. Of course, you'll want to check in-between as well to make sure the bypass wires are connected properly. These too have soldering spots on the battery pack's pcb, so there's plenty options to check your work. With everything checked the pack can be re-assembled. Most likely it'll take a little force to get everything to fit (factory assembly is pretty exact), but if it's loose; consider a bit of padding with electrical tape to make sure the cells will stay neatly in place.

Step #6: Re-assembling the pack

With a clip type casing there's little to do, but the glued-on casings don't take a lot of effort, either:

Spoiler: all hail duct tape!

Spoiler: resealed pack in place

Pretty much lean towards one extreme end of the function vs. form spectrum (duh ... ). Use black/matching tape if the looks bother you ...

Step #7: Testing the new pack

Run something like Battery Eater Pro to confirm it's all working as expected:

Spoiler: battery runtime stock (reader's test)

If you're smart, you'll make a 'before' and 'after' plot for comparison. Even better would have been a plot of the stock battery when it was still new and as it was used in your specific system configuration. Didn't do either, of course ...

Happy tinkering !

 

Excellent! @t456 so, bottom line changing the battery controller when reassembling is just a gimmick?

 

Indeed, there's no reason to as it doesn't know what cells are inside the pack. Think of it as filling a cup with an unknown volume; it will keep doing so until it reaches the brim. You might think it at least knows how much juice it has supplied, but this too is an unknown due to loss/heat.

One reason to change it would be the Wh report to the OS, even if that has no functional consequences for the device. Could make it claim 500 GWh for example; it'd say '0% left' all the time, even at full charge. Not sure what happens with the cycle count value, though. This is a fw number that is used to estimate 'battery wear' and ticks off a cycle for each full->zero charge cycle (or 2x half, say). Yet, this too is a 'cosmetic' value, same as the Wh's. Perhaps there's a way to reset it to '0 cycles', but disconnecting the cells (cmos reset-ish) didn't do anything for my battery pack:

Spoiler: wear level battery pack

Again; cosmetic. It charges to 75 Wh all the same, but if it bothers you then consider rewriting the firmware. A proper reason to use that would be to lower Vmax (maximum charge voltage). According to these test every 0.1V drop (-15% max. capacity) doubles the cell's lifespan:

Spoiler: BU: cycle life at elevated charge voltages

However, most laptops these days have a 'battery preservation'-type of driver, which does the exact same thing; limit Vmax. Funny thing is that the stock Vmax is really an overclock; one that helps sales by inflating the battery run time in the product specs. and reviews. Perhaps NBC could take that into account by listing the Wh + run time based on 4.2V charge, instead of whatever top-off charge the manufacturer has deemed appropriate.

 

this may apply to the *usual* laptop batteries but the panasonic batteries have a part and design made of unobtainium that make cell replacement an exercise in futility .
... according to a couple of other members ...
just saying that there may be some clarification needed at the beginning .

 

How so? They keep their stamina fine so far and appear quite genuine, to boot:

Spoiler: Panasonic NCR18650B - wrapper

The charge voltage is regular 4.2V as well, so nothing really special otherwise, save the capacity. Of course, they're not cheap, so any offer that seem too-good-to-be-true, likely is. Bought a rather cheap pre-assembled pack once; never again ...

Please note that the guide is for soldering pre-tabbed cells, not soldering straight to bare cells. Wouldn't even consider attempting that without proper tools; move/shift once or twice and the connection breaks.

 

i should have clarified this a bit better ...
to the best of my knowledge , the battery packs for the toughbooks (say CF-30 , CF-31 , etc) contain a chip that must be re-written or replaced if/when the cells in the pack are swapped out .
according (again) to a couple of members over in the panasonic forum (at this website) , no one has come up with a replacement chip or re-programing method (codes and software) .

this has been a topic of discussion over there and i have asked the question myself .
replacing the cells has been tried by other members and it was a failure .
it appears that the battery pack and the laptop *talk* to one another (i am betting primarily for safety) .
as the panasonic packs are rather spendy , one can imagine that others have tried in earnest to thwart the design .

this may or may not apply to other brands of comps and their respective battery packs ... however ...
i am certain that panasonic/matsushita is not the only company to have *smart packs* for their products .

again , i mention this only to help prevent the uninitiated from stumbling down the path of futility .

 

I have tried and failed at rebuilding a Panasonic battery pack. I am VERY experienced with electronics. Many forum members have tried recelling Tougbook batteries. They all have met with failure.
The issue is that the chip is a smart chip similar to what is in an ink cartridge. Not only does it read the voltage and temperature of the cells, it monitors the usage hours / recharge cycle count. If you refill an ink cartridge without resetting the chip, The printer does not know the cartridge is full. Same thing with a Panasonic battery.
Even with new cells, the chip THINKS they are old cells and will lock out the battery. You will not gain any runtime.
You must reset that chip so it knows that they are new cells.

 

Alright, thanks for the heads up, both of you . Too bad it's such bad news.

Fortunately, cycle count does nothing to my batteries; peak voltage and real battery life are unaffected by its excessive wear 'value'. Terrible shame about the Thoughbooks, though, especially considering it's Panasonic ( gods-of-batteries, no less) doing this . Thinking about that ... they are in dual business; laptops plus batteries ... Would be nice to find out if other brands do the same; the only other example would be Sony. Will pimp a 4 yr old, $200 HP (or something) next week with $50 worth of batteries, let's see how that goes.

Hm, has anyone de-soldered the fw eeprom of a brand new battery pack, replaced cells later on and rewritten the stored, fresh .bin back to the eeprom?

 

Do you have the eeprom reader and such?
I have a CF19 battery that worked, but was so-so. I will donate it to the cause.

 

Yes, if it has a fairly low cycle count than it should help 'the cause'. Only need the pcb, of course, so envelope shipping is fine.

Hmm ... actually ... even a used-but-usable-pack might be good, too; read rom on day x, wait/wear/cycle the battery for a few days, read rom again. The roms' hex compare should show the exact address of the cycle count byte. Can do that using my own battery easy enough, then run a battery life test on high% wear and, on the same day, one with the rom modded to 0% wear. Likely there's a fw checksum, calculating that for the mod may be the hardest part. Tempting, this ...

 

Pm started.
I will donate a working battery or two to the cause.

 

additionally ...
i have looked high and low , in sunshine , rain and darkness ...
i have found no relevant information on "chipping" or re-programming a few different types of smart batteries .
and yep , i know that sony is *very* protective of their "stuff" when it comes to their products (i was warranty repair for them for more years than i would care to admit) .

the sony camera batteries are smart types ... at least they were a few years back .
heh ... protective ... a guy made an after-market microphone that mated to the "hot shoe" jack ...
it worked and was about 1/4 the price ...
sony brought suit against the guy/company and it was pulled off the market .

i mention this as an example of the length and extent that a company may/will go to "protect" their product(s) .

 

excellent guide but why picture are not showing guys?

 

Don't know why they disappeared ... the links were simply gone . Re-uploaded them and made a backup on Internet Archive's WayBack Machine, just in case.

As to the possible issue with battery pack's firmware values overriding charge levels; planned to make a guide to overwrite the eeprom's firmware, but someone already posted one on Tech|Inferno a month or so ago. Site is down right now, but search there in case the refreshed pack doesn't charge to max capacity.

 

thanks mate for your quick response. Your awesome as like your guide.

 

@t456, excellent, excellent guide, you ought to make this a sticky.

My battery wear is nearly at 50%, and I get a third the battery life out of my machine as I used to do (at one point, I got seven hours of screen-on time; now, I hardly get two hours). I'm on the verge of purchasing six Samsung INR18650-35E 3.5 Ah cells for this, as well as a multimeter, soldering tool, dremel tool, etc. Have you found a way to reprogram the W230SS battery chip to reflect the newest values? Oh, and is it possible at all to slooooowly open the W230SS battery pack instead of slicing it open? I want to try to be able to put everything back together without duct tape (heh)...

 

Going to re-pack mine again too, but this time not with the ubiquitous Panasonic NCR18650B.

Found out something while analyzing the battery firmware; the cut-off voltage is not only set by the fw, but also by a physical battery protection ic (example). Problem is that these are not programmable and are often set to a conservative value of 3.3V. This is a bit of a waste since most can be discharged further and there's still power left down to 3.0 or even 2.7V. The consequence of this choice is that we cannot get the full discharge from these cells and have to consider only the capacity down to 3.3V:

Spoiler: LG 18650 D1 3000 mAh vs. Samsung ICR18650-35E 3500 mAh

So the 3000 mAh LG actually has 25% more capacity than the 3500 mAh Samsung after it is deployed in the battery pack. We might swap the protection ic for a different chip, of course. Ordered a bunch of these LG's already, but thinking about this ... perhaps I'd better find the protection ic that was used and order a 2.7V substitute. There is a small risk that the discharge is too much for the AC circuit to handle and that it will struggle charging it when the cells are down to zero.

Mind that this has nothing to do with the reserve charge level set by the OS, which will permit entering sleep mode for a while and grant some leeway in the ' now-where's-that-adapter-gone-to' window.

Yes, found the values with the help of @Khenglish 's excellent guide (see his thread on TI):

Spoiler: Battery firmware, Clevo W870CU and P150HM

Spoiler: Clevo W870CU 4450 mAh (stock = 3900 mAh)

This is dry run (no cells) of a W870CU (3 cell pouch type), but it's all more of the same. Amazingly, there's no checksum anywhere, so updating these things is as easy as 1-2-3. By comparing the two it also looks like value 0x28-29 might indicate the software-set discharge level (factor 1.00 between both), but that will not help if the protection ic will not permit discharging below 3.3V. Haven't extracted the W230SS's yet, but it should be identical. Also, in hindsight it was silly of me to de- and resolder this tiny chip (a 0.5mm pitch TSSOP8); the middle pins of the battery connector are there to communicate the battery information and status over SMBus to the laptop. So we can simply hook up the DATA and CLOCK wires to the pins (#3 and #4 on the W230SS, respectively) and solder 3.3V and ground somewhere on the battery's pcb.

Sorry, no. It's glue all the way on this model, so ... either glue it back or duct tape it is. There's not enough room for tie-wraps, but you might use black tape, of course.

Thanks, appreciate it !

 

What is your guys' recommendation for which manufacturer of battery to buy? Panasonic, Samsung, ???

 

Those, Sony and Sanyo all make very good, reliable cells. The LG seems ok, too. Mind that a lot of the 'unknown' brands bin and re-wrap cells of actual manufacturers. Take care when buying; these should go for at least $4-5 each, the high capacity types for up to as much as $7-8. Anything less means used cells or a fake wrapper over a cheap, low capacity cell.

There's lots of scammers, unfortunately, so it pays to have a Li-Ion charger that can also measure capacity accurately. When the cells arrive simply measure each and file a claim if they're not the real McCoy. Check the various charger reviews for good ones. Got a SkyRC MC3000 and it works beautifully, but it is a bit of hassle to do normal charges with it, so have also kept the NiteCore D4 (there's also counterfeits of this model, so take care when buying).

 

Thanks for the reply. Looks like I need to get myself a programmer as well.

One question: why'd you set the battery current to 5A, though? That's assuming maximum power draw (10 A through each parallel cell, 10 A × 11.1 V = 111 W) in which case I probably wouldn't ever be using the battery at all, and be plugged in instead. Assuming a significantly lower power draw, we'd only be drawing roughly 1-2 A from each cell, in which case the 3.5 Ah cells look like a better choice (though not by much):
As you mentioned in the end, it'd be a good idea to source around for another chip with a lower undervoltage protection, for at most 3.0 V...

 

If you are looking for good cells or chargers check out this site for comprehensive reviews:

http://lygte-info.dk/

 

Hi,
I have my HP Pavillion laptop battery - that I replaced less than a year ago - almost dead. I would like to change its cells to a better / higher longevity cells. My dead battery has 3x2 Samsung ICR18650-26H cells. What can I exchange these cells with ? I don't wanna use the same cells as I really would like to upgrade my battery. These Samsung cells came with the battery I bought over the internet to replace my original dead battery about a year ago, unfortunately I don't know what cells that original HP battery had since I don't have it anymore. The original battery used to last up to 4 hours...which I was never able to achieve with this bad replacement battery. any advice please on a new cells choice ? Thanks,

 

Ask @t456 he is an expert.

 

Yep, which I just did on his post, hope he will reply soon Thanks,

 

This is what you have. The higher the mAh the longer they should last. That is provided the cells you buy are not fakes and they are the mAh as listed.

Brand: Samsung
Model: ICR18650-26H
Capacity: 2600mAh Rated
Voltage: 3.63V Nominal
Charging: 4.20V Maximum
1300mA Standard
--- mA Maximum
Discharging: 2.75V Cutoff
520mA Standard
--- mA Maximum
Description: Pink Cell Wrapper
White Insulator Ring
18650 Form Factor

 

Personally, I would go with these Panasonics.

They are considered one of the top cells out there as far as I know.
Listed as 3400mAh

http://www.batteryspace.com/prod-specs/NCR18650B.pdf

 

Use the fantastic ' 18650 battery review comparator' to find good cells. The Panasonic NCR18650B is still a nice choice, adding +20% capacity at the default cut-off voltage (3.00V):

Spoiler: Samsung ICR18650-26H 2600 mAh vs. Panasonic NCR18650B 3400 mAh

But Samsung has a new 3500mAh cell, which even surpasses the Panasonic:

Spoiler: Samsung ICR18650-35E 3500 mAh vs. Panasonic NCR18650B 3400 mAh

The picture is actually a little different; the Panasonic claims a 4.35V charge voltage, whereas 4.2V is regular and what the laptop battery pack would normally charge with. Increased voltage will increase capacity for all batteries, so that would be apples and oranges. Longevity will be decreased by the higher voltage, so it's a trade-off.

If you want the increased capacity then you have to reprogram the firmware. You might also lower the cut-off voltage to 2.9V or 2.8V, but this risks a hard-to-charge battery when it has been drained completely and left passive for days or weeks before recharging. Not all chargers can handle that; in a laptop that would be a motherboard limitation rather than the adapter's.

 

Very interesting, wasn't aware about all these details. Where can I find these batteries on the market ? Genuine batteries not the fake ones. Also, what about high drain and regular batteries, I read that high drain, even when they have a lesser mAh they still last longer than the regular batteries.

 

Also, how do we re program the firmware to increase the capacity of the battery ? I quite did not get this point ! I do understand that decreasing the cut off the voltage will let you run longer on the battery, but still did not get what you mean by reprogramming the firmware !

 

You

1) buy a hardware programmer because if you brick that EC, the power button won't even work.
2) learn Linux.
3) learn how to disassemble the EC firmware.
4) learn what to change after disassembling it
5) recalculate the checksums.
6) reflash and watch your PC be bricked because you messed up on a checksum
7) redo the checksums and this time don't forget about the POST startup checksum (fails=permanent brick again).
8) HW flash the bricked EC again.
9) Cry in jubilation because you finally got the SHA-1 and other checksums correct and your laptop just belched.
10) profit.

 

Or just leave it the way it is and just replace the cells with no re programming I guess this will work too...

 

@t456 @Shawn @Falkentyne being experts on the subject, please kindly look at my battery dilemma and share your opinion.

 

I'm no expert. I know nothing about this stuff. I just type to you what I read on other forums

 

Haha, it's not that bad, really.

The battery firmware is part of the battery pack itself, not the bios or ec. For some pointers on how to rewrite it see here and here.

Sure. Won't have the benefit of the extra mAh's when using better cells, but longevity will increase greatly since you're not charging it to full capacity.

As for buying genuine products; $5-7 is a normal price. Also check negative reviews and buy a li-ion charger+tester if you can; measure the mAh's and ask for a refund if they're way off. Mostly it's ' no questions asked' and you can keep the fake product. Charger is also useful to recycle the old cells in a flashlight (or drop them in an 18650 power bank).

Ok.