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Increase the capacity (runtime) of your laptop battery.

Picture of Increase the capacity (runtime) of your laptop battery.
Is your laptop battery dead?
Is the runtime not long enough to get you through the day?
Do you carry one of those huge external battery packs?

This instructable is intended to show how one may replace the dead li-ion/li-poly cells of a laptop battery and how one may increase the capacity of the battery by adding extra cells.

The reason why adding extra cells to the internal battery is suggested compared to carrying around an external battery pack is that for the same amount of cells in an external pack, the laptop can run significantly longer if those cells were used internally.
 
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Step 1: External battery pack? Rip it apart and never think of using an external pack again!

So what's the voltage rating on your internal battery pack?
What's the rating on your power brick?

Lets use my tablet computer as an example.

The battery pack is rated for 3.7v * 3 cells or about 11volts. However, the power brick outputs 20v.

I've bought external battery packs before and have calculated how long it should last using watt hours instead of amp hours. However, that was wrong. The battery pack would need to output 20v in order to power my tablet, thus the battery cells used to increase the voltage does not attribute to the amp hours, which is indicative of how long the battery pack should last. Thus, a difference of 9 volts is significant. That's about 2 li-ion cells wasted just to match the voltage.

Another problem with using external packs is that the laptop would think that it's connected to an outlet, thus is not so weary of watching how much power it drains. The power brick for my tablet outputs 2.5 amps, thus it is possible at times my tablet is drawing 2.5 amps from the external pack. However, the internal batt pack only requires an average of 1 amp per hour.

So what would one do in order to increase the runtime of one's battery pack? Forget the external pack, just add more cells to the internal one.

Step 2: How laptop batteries work

Picture of How laptop batteries work
Laptop batteries are complicated pieces of equipment. They are somewhat redundant as well. There's a 'smart circuit' in the battery pack that monitors the conditions of the battery cells, however, it does not do what a lot of people say it does.

The image below is a typical smart circuit. It has four wires running out of it: ground, power, and two 'intermediary power' wires (actually the ground wire is just the tab on the right).

Lithium cells output about 3.7 volts. Like all batteries, in order to increase voltage, they are connected in series. However, charging a "pack" by adding power through the positive node and negative node of the whole battery pack is dangerous. They are not guaranteed to charge evenly (refer to resistance in series in a physics text). This means one cell may overcharge and explode, which is very bad especially since it's lithium. The intermediatary power wires are sandwhiched between every series connection of the battery pack so that it monitors each individual cell.

Now on to the nitty gritty. Most people would say not to mess around with the smart circuit, and they are correct. But if handled correctly, it won't be a problem. The core of the smart circuit does not control the charging cutoff and output cutoff when the gauge goes to 100% or 0% (older model laptops do, but not anymore). The smart circuit merely lets the enduser (laptop user) know how long they have before the battery runs out and let them turn on special options such as hibernation in order to save their work. Charging and discharging cutoff is done by a secondary monitoring circuit that monitors a one of two states called "end voltage" or "end amperage". So for those who believe that they must charge and discharge their batteries once a month or so to "recalibrate" the battery are wrong; it only recalibrates the gauge, not the actual capacity of the battery. That is, if one is missing about 20% of their battery capacity due to the gauge being offsetted, the only reason why one would need to recalibrate is because they want to utilize the hibernation/shut off option when the capacity reaches too low. If one were to turn that option off, one can use the battery pack until it drains fully, completely ignoring the fact that the battery meter is flashing 0% (Because the meter does not control the battery's cutoff point, just the computer's). However, if the li-ion cell is dead/dying, no number of charge and discharge cycles can bring the battery back to life; the cell is physically dead (so forget about the term 'digital memory loss').

Step 3: Parts list

Parts:

Soldering gun
Solder (but of course)
SAND (A MUST)
BIG METAL CAN WITH LID (A MUST)
fire extinguisher (somewhat a must depending on how careful you are)
wires
alligator clips
Laptop
dead battery
undead battery (zombie batteries) I mean, new lithium ion or lithium polymer cells (make sure you know which your battery uses)
duct tape (geek's best friend)

Other things as you see fit (second hand soldering helper, wire cutters, wire strippers, etc)

Step 4: Preparation/setup

Picture of Preparation/setup
IMG_1707b.jpg
diagram.jpg
Safety preparations

-put sand in can (picture below)
-place fire extinguisher someplace close

Battery preparations

-if you're just replacing your dead cells with new ones, obtain the same number of cells. As for choosing the capacity, bigger is better.
-Note how the cells are connected in series and parallel, and solder your new battery pack the same way.
-NOTE: do not remove dead battery cells from battery pack (explained later on)


-if you're increasing the capacity of battery pack, obtain nth times the number of cells in your battery pack (an original pack of 3 cells can have 6,9,12 cells, etc)
-for every series connection in the original pack, you can add cells in parallel. (a pack with 3 cells in series can accomodate 6 cells (pairs in parallel) in series. That is, two in parallel, and attach those pairs in series, etc) any number of cells in parallel is ok.
-NOTE: once again, do not remove the original cells from the battery pack.


My battery pack below has 3 sets of 4 cells in parallel, which are connected in series. (note: parallel groups are separated as left, middle and right. ) Wires are also connected so that I can solder the new pack to the smart circuit easily.

Step 5: Safety first: test the darn thing

Picture of Safety first: test the darn thing
IMG_1716.jpg
I've seen some people who've posted how-to's for replacing laptop cells immediately replace the cells seal the battery and use it. This is extremely dangerous, unless you want to cook your lap. The quality of the cells purchased is unknown, and needs to be tested. (manufacturers of laptop batteries quality test their batteries before shipping them off. And sadly, sometimes a batch can go undetected)

-So, attach alligator clip w/ wires to the new pack and bury it in the sand (don't forget which clip belongs to which wire)

-Here's the tricky part (yet another thing other how-to's messed up.) The reason why I said not to disconnect the original (dead) cells from the smart circuit (which I inadvertently did. Don't worry, it was my test battery) is because the circuit requires a constant power supply or the smart circuit guage messes up. You might wonder why worry about the gauge if it doesn't contribute to charge and discharge cutoff. This is because the laptop requires a signal from the circuit before the laptop will turn on (in case the cells are thought to be drained and draining more, even for a second can kill the li-ion cells. Or simply, something's wrong with the battery). So, connect the new pack to the circuit before disconnecting the original battery cells.

-However, what if you're using alligator clips, which is a temporary connection? How can you disconnect and solder on permanent connections? Either, solder on the new connections while leaving the clips connected, or you can even use a power brick with about the same voltage as the whole battery pack (a 11.1 v pack actually ranges from 12.68 v to 7 v so a power brick at 12 v is ok). But remember to add a resistor between either the anode or cathode of the power brick and the circuit, so you won't kill the circuit board. (Not connecting intermediate pins should be ok, I haven't tried. If you worry about this, you can reuse your dead cell as a temporary power source while soldering on the new pack.)

-Plug in the battery circuit into the laptop and place it FAR AWAY from the battery pack. Test the battery pack. Charge is first, then completely discharge it, then charge it again. This is when you should watch over the battery pack intently, because it might explode (sand should stifle the fire, but immediately unplug the battery from the laptop.) The fear here is the type of secondary circuit used to monitor end states. End Voltage type circuit is ok, but end amperage is no good. If you can tell what type you have just by looking at the circuitry, then you're in good shape, but if you can't there's always the fear of an explosion. From my experience, the circuit is typically end voltage.

Step 6: Completion

Picture of Completion
-If your battery doesn't explode/catch on fire, that means the circuit is good/the cells are good.
-Solder it permanently to to the circuit, and fit it back into the plastic housing if its the same number of cells, if not be creative and line the cells up so it fits nicely below/behind/etc your laptop. Use duct tape or if you have, shrink wrap it with rubber shrink wrap.
-And remember, be careful around rechargeable lithium batteries.

-Update: I forgot to mention. Depending on the type of "smart" fuel gauge, adding more cells won't change the 'estimated hours left' displayed by the laptop, this is because the number of hours might be a fixed range. One might think that even if it's a fixed range, the number of hours left or % capacity left might be proportional to the actual number, however, depending on the type of circuit used to count the "electrons" (some use ic's called electron counters), it might assume the capacity to be fixed as well, thus the estimated capacity won't be proportional, just truncated. However, from my experience, the capacity gauge stops at about 7%, until the physical battery drains until 7%, so it still effectively alerts the user when the battery is drained after below 7%.

-Update 2: At first I thought my smart board fuel gauge circuit was of fixed capacity, but after a few complete discharges, it recalibrated. Now it knows the capacity of my new pack and estimates accordingly (ranges from 9 - 8 hours total runtime depending if I'm constantly using my secondary hard drive accessed via USB and/or lcd backlight levels)
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JewelA16 months ago

t is only dangerous if you don't know what you are doing. Laptop batteries can take A LOT before they actually become dangerous.. Shorting them out, or deliberately placing them in a fire or anywhere hot.

If you want to Increase the capacity of the laptop battery,you could buy a 9 cells or 12 cells battery from here.

Hi there, Unfortunately, I could not replace mine. It seems the contacts has been welded to the board. I do have a soldering iron. Could someone advice? Thanks.....
xeijix (author)  keni_matukoshi6 years ago
I'm assuming the contacts are fairly long. If you have some needle nose pliers and perhaps something to wedge the contacts on the cell side, you can rip the contacts off of the cells. You can solder on wires to the freed contacts. If you can't rip them off, you can always cut off the contacts, but giving yourself enough contact space for soldering.
Hi, thanks for the quick reply. I did try this the whole night only to find out the battery pack's board has to be troubleshoot/tested for failure and eventually the main powerboard on the laptop ...(darn!) Can anyone lead me someplace for troubleshooting the battery pack's board? By the way soldering lead and steel don't solder well, I ended up having a longer batt than the package... and reslodering...
xeijix (author)  keni_matukoshi6 years ago
you need flux and need to heat the tabs a bit longer. I don't understand what you mean by troubleshooting. Are you saying the battery pack isn't working? If the smbus controller is dead (not powering the laptop correctly) you really need a jtag programmer and knowledge of the communication protocol to fix that, which isn't worth it. I would suggest getting another 'dead' battery and playing around with that. That is what I did in actuality. I got someone to donate their dead battery.
Oh, well, it's too late for me now. I just missed the part where you have to keep power in the smart circuit.

"smart circuit can't be disconnected from a power source"

And the new li-po cells are just lying around since 2009.
nice tablet pc what kind is it?
xeijix (author)  masterchrisx35 years ago
motion computing LS800. It's been discontinued though.
imark77 xeijix1 year ago
like all the good ones ( and win XP, 2K, Mac 10.6 ) they all get discontinued.
i have a acer TravelMate C110, discontinued, needs a new battery ( not a no-name one ). but that's what ebay is for after all.
TO EBAY!!!!!!!!!!!!!
Any reason why I couldn't use protected cells instead of unprotected? From what I've read about the protection circuits it doesn't sound like it would interfere with the charging/discharging process assuming I increase the total capacity.
xeijix (author)  seabeepirate2 years ago
There are many reasons why it's a bad idea to use protected cells. For one, the smart circuit has two layers of protection: electron counting which gives you the estimated battery life, and the normal protection which handles extreme cases of overcharging and underdischarge. By have another layer of protection, you're going to confuse the electron counting part of the circuit, effectively (possibly) ruining the tracking and the laptop will never boot on battery alone if it thinks there's 0% left. The second reason is that the smart circuit was designed with the cells in mind; by introducing the protection circuit in the cell, you're effectively changing the design of the smart circuit. Unless you understand how the smart circuit works and have analyzed its function with the additional protection circuit, most likely something is going to be screwed up.
Found this url on an EE page explaining the battery/charger requirements for laptops with some additional information included. http://electronics.stackexchange.com/questions/31618/why-do-many-laptops-run-on-19-volts
Xeijix, Thanks for the detailed explanations. Possibly a stupid question or 2.... why 19volts input for a 11.7v battery charging circuit? (is the overhead used to pwer the laptop so charging and laptop operations can happen simultaneously?) Or is that entire 19 volts being sent to the battery charging circuitry?

As the pwer brick supplies pwer to the computer, does the input simply split --with some current going to the charger circutry and some going to the battery? Is it possible to access that split and tie directly to the power feeding the cpu, avoiding the charge circuit completely? You indicated there is indicator message of some sort sent from the chargin circuitry to the computer regarding the state of the battery or "it won't turn on". Are all computers charging setup like the one you described here or are there differences such that I could have a recently mfg'd computer that would have a completely different charging circuitry design and function and your article would not apply to it? My Dell M70 (2005) computer runs with no battery in it. Is that bad for the computer? Does your description and explanation of the wasted cells in a 19V pack apply in this case? Where is the "extra" pwer gojng? Thanks for the very informative explanations, instructions, and the focus on safety!
k
gdaley3 years ago
hi.

do u know where the 3 wires from the circuit board in a laptop battery go in correspondence with the battery series? i replaced the cells in my gateway mx 3560 battery, thought i remembered wher the wires went, but the battery will not power the laptop at all despite reading 62% charged. also they will not charge past 62%, leading me to think i have maybe 2 cells not wired correctly or 1 of the 3 wires from the board are not in the correct place. any help most appreciated.

thanks, glenn.
kingdalle3 years ago
Hi, great post! I understand that the smart curciut needs constant power, but connecting it to new batteries, will there be any? Are the batteries charged from the manufactorer? Otherwise it will do no good in keeping the circuit alive when the removing the batteries. Thanks
xeijix (author)  kingdalle3 years ago
The new cells have to have some charge. The cells are completely dead and unrevivable if its charge is 0V. Also keep in mind the lowest voltage the cell should be at is 2.7 V (discharged) and the highest is about 4.23 V (fully charged). They should not deviate under or over those two values.

The new shells should have more than 2.7V of charge because if its close to 2.7V you'd be at risk of having bad cells.
gmichaelt3 years ago
If you can add a string of cells to an existing battery (in parallel, as described), it would seem reasonable to suppose that you can also remove a string once you've ascertained that the recent additions are, in fact, in it for the long haul. The implication of that supposition is that once you've added (and verified) cells as described in this instructible, you could go back and excise the original cells, moving the additions directly into the casing where the originals were. Correct? Caveats? Qualifiers?
xeijix (author)  gmichaelt3 years ago
That's how I swapped my cells out. However, how long do you plan to leave the original set of cells connected (when will you excise the cells)? I ask this because if you don't match the capacity of the parallel cells, you risk damaging the a set of parallel cells (of course, I'd be concerned with the new cells not the old ones)

Also, I would not charge and discharge the pack if you haven't excised the old set of cells because charging mismatched cells (even if the capacity is matched, but one set is older) also risk damaging the cells.
Hmm... i have always been suspicious when my battery was holding a charge for several hours one day and then the next it quit working all together immediately as i was working on it. What a joke. Does this mean i didn't have to waste my money on a replacement laptop battery?
xeijix (author)  boostergold14 years ago
So it just stopped working? How did it stop working?

Can you boot it up with the battery then it runs out of battery after a few usecs/secs/minutes?

Can you boot it up with battery and power supply in place, and when it fully boots, can you run on battery only (ie. unplug the power supply)?

Sounds like the smart circuit just died although I've never encountered such a thing before.
vo_danh xeijix3 years ago
I also have the same issue as Ted_lens. I opened mine up and all the batteries are 4v . (some are 3.98v). What is the cutting point on voltage that they will work or is my circuitry bad?

Laptop works fine plugged in. On battery it dies within a few minutes. Is this repairable? Do I have to buy another used cheap battery and steal the circuitboard? Are my batteries just too low if the requirements on voltage stability is too sensitive?
erixpc4 years ago
Being off the grid for 8+ hours sounds exciting. Instead of strapping on extra bulk and weight to the laptop battery pack, what do you think of adding a 4 wire pig tail connector (http://www.etrailer.com/Wiring/Spectro/9653P.html) to the existing pack and then connecting that to the DIY external pack with all those li-pos? Would that work? How long does it take to fully charge your 15 cell set-up?
xeijix (author)  erixpc4 years ago
A few things to note. You can't use any of the old lipo/lion cells. The wire from the battery cells to the laptop battery pack can never be disconnected. (you can probably put in some fail-safes in case it does get disconnected, but it's not something you can make a habit of. Every time you disconnect, you risk screwing up the smart circuit)

Mine takes around 8 hours to charge so I just leave it charging overnight.
erixpc xeijix4 years ago
Got it. Don't mix old wth new. All batteries should be new. Got it. External pack to cut down on bulk and weight is fine but don't use the pig tail connector. Solder the cord directly. Thank you.
xeijix (author)  erixpc4 years ago
Yup exactly. Just one thing to remind you, you shouldn't take out the old cells until you soldered on the new cells, this is because the smart circuit can't be disconnected from a power source. (Just think of where the bad/good guy needs to replace an artifact with a dummy artifact before the pressure switch activates a trap)
Hey Harrison Ford could help me with this instructable.
Noblenutria3 years ago
If your battery is mostly discharged when you start doing surgery on it it wont catch on fire even if you short it.
charlieb0004 years ago
you said "connect the new pack to the circuit before disconnecting the original battery cells. " thats a little dangerous, no wonder you say bury in sand!!
the circuitry with the battery controls the charge speed because the cells heatup if charged to fast, and you are anticipating a blow up!
id recommend having a series resistor between each connection to the old battery (excluding GND) to limit current.
tgrundle4 years ago
Would it be possable to connect wires to the positive and negitive of the batteries ( before the smart circuit ) and run them to a connector in the side of the pack that way you could plug in/ unplug your extra batteries (circuit still has power for batteries in pack, external batteries can be added/ removed as needed, external pack can be connected to supply power to smart circuit while changing batteries in pack). And if so would the computer need to be off when adding/ removing external batteries?
I forgot to say that the external batteries would be in parallel with the internal ones.
bechard4 years ago
i want to replace my batteries with some srt of self chargeing device for ex. the magnet motor coud i do this and how?
bechard4 years ago
.
rmckinney4 years ago
Did you have to cut a hole in your battery casing in order to the smart circuit, then?
Ted_lens4 years ago
1st of all, great instructable! your instructable and some other sources made me confident enough to rip apart my broken laptop battery...here is the deal:
My toshiba batterypack broke down a while ago... symptoms were:
- battery only had power for +-10 minutes
- batterypack drew large amount of current when charging, resulting in 2 blown adapters before i found this out.

So I ripped this thing apart and found 6 us18650gr cells inside. these cells are unprotected and wired to some electronic board like a lot of batterypacks are. So i ordered 6 unprotected replacement cells which are being shipped to me right now.

however further testing of the old cells made me doubt whether the cells are faulty, or maybe if the circuit-board is defective.
- all old cells read out +-4volts without load
- under load they all give me about 3.7 volts.

could it be possible that the circuit-board screwed up here instead of the individual cells? would be uncool since, in that case i might have ordered some useless batteries. Could anybody share their thoughts on this?
martinlass4 years ago
Hi xeijix,
Great Tutorial!

Can you tell me where you got the replacement Lithium batteries for you LS800? I have hunted the internet like a demon and I cannot find anything that seems suitable except the AA size.
Martin
xeijix (author)  martinlass4 years ago
These two sites have what you are looking for:
http://www.all-battery.com/
http://www.batteryspace.com/
grimgroper5 years ago
 great tutorial!! i want to build one that will fit in my back pack and connect via a second cable.. so it will be huge, possibly 20 cells.

what would happen if they were unevenly discharged? say i unplugged the laptop drained the internal battery then plugged the back pack one in after. visa versa.
xeijix (author)  grimgroper5 years ago
definitely don't do that. The circuit board needs to keep track of the charging and discharging of the cells. And if you're connecting cells in parallel that are unevenly charged, that won't be good for the cells. On top of that, some of the energy stored in the charged cells will go towards charging the depleted cells.
 so would it be possible to build the pack with its own smart circuit?
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