Increase the Capacity runtime of Your Laptop Battery
Introduction: Increase the Capacity (runtime) of Your Laptop Battery. The battery pack is rated for 3.7v 3 cells or about 11volts. 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. 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). 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. (note: parallel groups are separated as left, middle and right. 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. 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)I’m assuming you have an A+ or similar type certification? Why not just do a search for re manufactured laptop battery, isn’t that the proper way that A+ techs work? Would cost you about the same in buying new cells hacking apart the battery etc. It is fairly easy to find outlets to temporarily connect power and swap out for a full battery. In fact will be much safer(Risk of fire/explosion/insurance etc.). Assuming you follow all of these guidelines, if you haven’t shorted out the PDB on the pack and you haven’t damaged the charging circuit in the laptop you’re golden. But assume you temporarily managed to shock the PDB. It will no longer function and you can kiss your laptop goodbye! Most of these PDB boards have IC’s that are proprietary, and illegal to hacking so it is best to either replace with a new PDB that matches your laptop or go through proper channels to obtain a new battery.
I understand that laptops now have reduced battery life but for the most part a spare pack is as easy to replace than hacking apart an old one. Because once you take it apart you have to test each cell individually to test the charge capacity(Beyond the scope of this instructable). If any one of them is out of balance the whole pack is bad. Assuming you find a few good cells, do they match the capacity of your new cells? If not then the charge will always go to the least common denominator and that’s the amount of charge given to your laptop. You are better off just buying a new one and not wasting time. Good Luck, Peace Out brothers.
critterfluffy 2 years agoReply
Motion Computing Tablet. I have 2 of those. They really are amazing and I recommend them to anyone who has a couple bucks and some time. They are old so not powerful but the screen is godly accurate for drawing and such.
LydiaT2 2 years agoReply
I’d like to see you take that through an airport and try to board a plane. Being red, it looks like dynomite.