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.

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.

Comments

[kingdalle]

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]

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.

[gmichaelt]

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]

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.

[boostergold1]

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]

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]

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?

[erixpc]

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]

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]

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]

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)

[Noblenutria]

Hey Harrison Ford could help me with this instructable.

[Noblenutria]

If your battery is mostly discharged when you start doing surgery on it it wont catch on fire even if you short it.

[charlieb000]

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.

[tgrundle]

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?

[tgrundle]

I forgot to say that the external batteries would be in parallel with the internal ones.

[bechard]

i want to replace my batteries with some srt of self chargeing device for ex. the magnet motor coud i do this and how?

[bechard]

.

[rmckinney]

Did you have to cut a hole in your battery casing in order to the smart circuit, then?

[Ted_lens]

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?

[martinlass]

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]

These two sites have what you are looking for:
http://www.all-battery.com/
http://www.batteryspace.com/

[grimgroper]

 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]

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.

[grimgroper]

 so would it be possible to build the pack with its own smart circuit?

[xeijix]

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.

[grimgroper]

 okay yep that makes sense, so will i be able to use a different laptops smart circuit or will i have to use the same one as in the laptops original battery? i will connect some sort of relay circuit with a capacitor (to make an uninterrupted switch between batteries) to disconnect the internal battery when the external one is connected. this would e between the smart circuits and the laptop. i didnt understand, does the smart circuit control the recharge?(would i be able to recharge the second set of cells with a separate charging circuit rather than through the laptop, perhaps more powerful charger... )


thanks for you help..
its hard to find some one willing to give out advice on laptop batteries.
 

[xeijix]

Sorry that's not what I meant. Simply stated, you just need two laptop batteries. When one runs dry, swap it (of course the replacement laptop battery will be your super huge one).

For uninterrupted switching, that would depend on whether your laptop supports hot swapping laptop batteries (some lets you swap when you place the laptop on standby). If not, you'll need to find a way to do it. Something like this: www.engadget.com/2008/02/04/hotswap-laptop-batteries-let-you-keep-the-juice-flowing/ might work(although in the picture, the person has a dedicated input for the laptop battery during swap, in our implementation, we will use the replacement laptop battery to charge via the laptop charge port). You'll just need to purchase a voltage up converter to reach the correct voltage level for the laptop's charging port; and connect that circuit directly to the voltage out of the laptop battery.

So to swap, you would plug in the replacement battery via the laptop charge port; remove the used-up laptop battery (at this point the laptop will get its energy from the replacement battery); put in the replacement battery; remove the cable from the replacement battery to the laptop charge port.

As for a more powerful charger, in the scenario I've just described, you would need to charge through your laptop or a special external battery dock that the manufacturer may (or may not) sell. www.amazon.com/External-Laptop-Battery-Charger-Inspiron/dp/B001LWWHOI something like that (although that is specifically for that laptop model)

[y2j514]

So I went about doing this before I found your instructable.  I was replacing my dead cells from a tutorial I found online.  They did not however warn about the smart circuit needing power.  It was disconnected for over 2 weeks.  When I put the new battery pack in windows detects the battery at 0% and if i remove the AC power it turns off immediately (like you said the gauge is wrong).  Is there anyway to fix this?!?!

Thanks!

[xeijix]

did you turn off the battery warning action option in the battery manager window? Typically, the laptop is forced to hibernate when its below a certain battery level. If you turn that option off, you should be able to leave the laptop on until the battery actually discharges. Once you do that, recharge the battery while leaving the laptop off. Then repeat the discharge. Repeat over and over again and hope that the smart circuit resets. If the data stored on the circuit isn't corrupt, it should reset. If not, you won't be able to fix it unless you happen to have extensive knowledge of how to program the smart circuit with the proper values.

[y2j514]

I tried this.  Ran into a tiny snag.  You can not simply tell windows to "do nothing" for a critical battery - well that is you can not do it through normal means.  I found this online, and it allowed me tell windows to do nothing if the battery reads critical.  I then disconnected the AC and the laptop just died, its not communicating with the battery at all =(
What are my options?


To change the 'Battery->Critical battery action->'On battery' setting to "Do nothing" using powercfg.exe

1. activate the power scheme you want to modify.
2. open an elevated command console (windows key, type 'cmd' in start menu, press "ctrl+shift+enter", click 'continue')
3. execute "powercfg -setdcvalueindex SCHEME_CURRENT SUB_BATTERY BATACTIONCRIT 0"
4. your current power scheme will show "Battery->Critical battery action->On battery: Do nothing" despite the option being unavailable in the drop box.

[xeijix]

Have you actually tried charging the battery while the laptop was off before hand? It's very likely the cells are physically depleted. If you're sure the cells have some charge, then I don't know what else you can do. It would seem like your circuit is fried. It doesn't make sense that it would immediately die if you unplug the AC if there is charge in the cells. The smart circuit only prevents you from turning the laptop on if the circuit reports that its empty. Technically, once you're booted into windows and you disable the critical battery action, it should definitely continue running until the cells actually run dry.

[y2j514]

One trillion percent sure there s a charge.  Had it plugged in for a night before booting.  My multimeter reads a voltage.  When windows boots, it says the battery is at 0% and NOT charging.  Has to be the smart circuit.  Ill try connecting the known to be working old cells and see if it works suddenly.

[y2j514]

Didn`t work!  Guess the bloody chip is corrupt.  Aside from ordering a new battery, is there anywhere I can purchase a new working circuit board? =(

[xeijix]

sorry dude, like all manufacturers, the circuit board is trade secret (although its not really) the point is, they don't like selling these sorta stuff to end users.

[cyz980313]

u said we could use lithium polymer battery, but the lipo batteries are really dangerous. if u over charge them, they'll catch on fire. i know because by r/c car was destroyed because of li po batteries. so i suggest that u delete that suggestion!

[xeijix]

I'm sure you mean well, but ALL devices nowadays use either lithium polymer or lithium ion. Either one will catch on fire if overcharged as I've explained in the instructable. It's up to the user to be safe, and I've given enough warnings.

[hansonsux]

There are classic lithium ion cylindrical cells, and Lithium-Polymer (Lipo).   Lipo's are actually safer as they contain less flameable liquid electrolyte.  As with RC stuff fires - I think it's more of these batteries taking alot of abuse.  Overheating, Overcharging, shorts, damaged in crashes, etc.  No way they should explode that violently in normal use in some of the pictures I've seen.  People have been holding Lipo's now to their face (cell phone) for some years now.  Explosions are rare, despite the media hypeing the few cases when defecticve batteries have gone off.

[j-]

Inspired by this guide, and ignoring all safety warnings, I expanded my laptop's battery using some old dell battery packs.
sites.google.com/site/keyboarddriver/

[masterchrisx3]

nice tablet pc what kind is it?