Instructables

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.
 
Remove these adsRemove these ads by Signing Up

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.
1-40 of 114Next »
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_matukoshi5 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)  seabeepirate1 year 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
gdaley2 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.
kingdalle2 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)  kingdalle2 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.
gmichaelt2 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)  gmichaelt2 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)  boostergold13 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?
erixpc3 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)  erixpc3 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 xeijix3 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)  erixpc3 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.
charlieb0003 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.
tgrundle3 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.
bechard3 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?
bechard3 years ago
.
rmckinney3 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/
grimgroper4 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)  grimgroper4 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?
xeijix (author)  grimgroper4 years ago
Not the way I imagine you want it. The only way you can do it would be to just make a huge battery pack that's in your bag or something, and have the cable connected to the smart circuit and contact pins of the laptop battery w/o any cells in the original battery chassis. Essentially its just a large battery pack but the place you store the cells would be away from the rest of the battery. However, you cannot severe the connection between the cells and the smart circuit.

Since you want to option of carrying a larger battery pack (or not), i suggest getting a second laptop battery and stripping that for its smart circuit and stuff. You'll still have to swap the batteries when the original is low, etc.
1-40 of 114Next »