Laptop Battery Types
This page documents the different types of battery chemistries used in vintage laptop computers.
Sealed Lead Acid
Some early laptop computers used Lead Acid batteries, the same type used in automobiles. They were an unideal choice for several reasons, including their weight, energy density, and the fact that they do not perform well when frequently fully discharged and recharged. As of February 2026, only 7 laptops listed in the database used this battery chemistry, the last being the IBM ThinkPad 500, which released in June 1993. Even then, due to some issues that cropped up, the ThinkPad 500's battery was recalled and replaced with a NiMH battery.
Rebuilding Lead Acid Battery Packs
Most of the time, you can simply source a "close-enough" off-the-shelf replacement that will work in the laptop with little work. An exception applies for the aforementioned ThinkPad 500, and the Apple PowerBook 100, which both used small form factor cells which are no longer manufactured.
Nickel Cadmium (NiCad)
Nickel Cadmium was the most common chemistry used in early laptops, being most common from the 1980s through to the early 1990s, when it was phased out in favor of NiMH chemistry. The last laptops to use NiCad batteries released in 1995.
For their time, NiCad batteries worked as a decent option in laptops. They had a better energy density than lead acid, handled full discharge cycles better, and were generally smaller and lighter. The biggest problem with NiCad batteries was the "memory effect", a chemical effect which caused the capacity of the cells to drop if they were repeatedly recharged after only being partially drained. The effect could be mitigated by fully discharging and recharging the cells periodically.
Throughout the first half of the 1990s, NiMH technology improved and replaced NiCad in laptops. NiMH offers very similar characteristics to NiCad, but has a higher energy density and does not suffer from the memory effect.
Rebuilding NiCad Battery Packs
NiCad laptop battery packs are typically completely "dumb" batteries, meaning that they do not have an internal BMS. This means that it is simple to break the pack open and replace the cells, without having to worry about any problems with the BMS. In 2026, NiCad cells are for the most part no longer manufactured, mainly due to environmental and health reasons, as cadmium is toxic. Luckily, NiMH cells are a "close enough" direct replacement that you can usually just swap NiCad cells out for NiMH with no problems. At worst, the NiMH cells may have a shorter lifespan than they should do to the slightly different charging characteristics between the two chemistries. This will vary laptop to laptop.
Properly rebuilding any laptop battery will require the use of a spot welder. You can purchase a decent battery spot welder for less than $100 on Amazon. Never attempt to directly solder to battery cells, as the prolonged heat exposure will likely damage the cells, and at worst may start a fire (although NiCad and NiMH cells are far safer than Lithium Ion).
Nickel Metal Hydride (NiMH)
As mentioned in the previous section, NiMH chemistry replaced NiCad chemistry throughout the early 1990s. It offers similar characteristics to NiCad, but has a higher energy density, does not suffer from the memory effect, and is more environmentally safe due to not using cadmium. While superior Lithium Ion chemistry became available in laptops starting in 1993, NiMH remained in use for many years due to the higher price of Lithium Ion cells. The last laptops to use NiMH batteries released in 2005.
Rebuilding NiMH Battery Packs
Rebuilding a NiMH laptop battery is typically a straightforward process. Usually, you can just crack the case open and replace the cells. NiMH laptop batteries were available in both "smart" and "dumb" configurations, meaning that the smart batteries used a BMS to monitor state of charge, while the dumb batteries did not. In most cases, even smart NiMH batteries can be rebuild via a simple cell swap. NiMH cells are still manufactured, and direct replacements can be found for all of the types I've seen used. The most common type you'll find is 4/3A (also known as 17670), with A and AA also being common.
Properly rebuilding any laptop battery will require the use of a spot welder. You can purchase a decent battery spot welder for less than $100 on Amazon. Never attempt to directly solder to battery cells, as the prolonged heat exposure will likely damage the cells, and at worst may start a fire (although NiMH cells are far safer than Lithium Ion).
Lithium Ion (Li-Ion)
Lithium Ion chemistry first became available in laptops starting with the Toshiba Portege T3400 in 1993. From there, it slowly took over NiMH throughout the 90s and into the 2000s as Lithium cells became cheaper. Lithium Ion chemistry offers superior energy density to NiMH, and is still the dominant chemistry in use today.
Leaking Cells
While it is commonly stated that Lithium Ion battery cells do not leak unless physically damaged, this is not true of cells that are 20+ years old. When dealing with vintage laptops, it is actually relatively common to encounter leaking Lithium Ion cells. The worst offenders are the red Sanyo cells from the 1990s and early 2000s. These are nearly always leaking. Panasonic cells from the 90s and 2000s can also leak, along with 2000s era Sony cells. Of course, like any leaking battery, you should wear gloves when cleaning up any leaked electrolyte.
Note that since nearly every Lithium Ion battery uses a smart BMS controller, the cell pack is nearly never wired up directly to the battery contacts, which is the primary way that leaking NiCad and NiMH battery cells cause corrosion to the laptop. Because of this, you don't really see any laptops getting damaged by a leaking Lithium Ion battery pack, and unless it's letting off a smell (the Sanyo cells do, they let off a sweet smell), you often won't be able to tell if the cells are leaking unless you crack the pack open.
Rebuilding Lithium Ion Battery Packs
Unlike NiCad and NiMH, rebuilding Lithium Ion battery packs is a very delicate process which requires a high level of knowledge to do safely. The increase in difficulty comes from two main factors: the increased danger of Lithium Ion cells, and the increased complexity of Lithium Ion battery management systems (BMS).
Safety
You probably know that shorting out any battery cell is a bad idea. That being said, shorting a Lithium cell is much more dangerous than shorting a NiMH cell. If you short out a NiMH cell for a prolonged period, it will get hot, become damaged, and eventually it might let the magic smoke out. Obviously, you don't want to do this, but a brief short circuit will not cause anything to blow up. By contrast, a fully charged Lithium Ion cell can reach thermal runaway and ignite after as little as one second of being shorted. Additionally, if a Lithium Ion cell gets accidentally punctured, it will also likely explode. For these reasons, extreme care and precaution must be taken when working with Lithium Ion cells. You should treat any charged Lithium Ion cell as if it is a little bomb. Note that Lithium Ion cells are much safer when discharged. More than just being careful while handling and installing the new cells, you must also be very careful when choosing how to wire up the pack. For example, if you leave out a piece of insulation behind where a nickel strip makes a 90 degree turn over a battery cell, the pack will work fine for several months, but then due to the friction of the nickel strip rubbing against the edge of the cell, it may pierce the insulation of the cell, short the cell, and start a fire. You have to really know what you're doing when assembling a pack to avoid scenarios like this. Pay very close attention to how the wiring and insulation of the original pack was designed.
BMS Issues
Many Lithium Ion battery management systems have internal firmware flags which can lock down the BMS if it detects that something isn't right. These flags, known as Permanent Failure (or PF) flags can be triggered for a variety of reasons, including if the BMS detects a cell failure, or often if the pack voltage drops too low. If the BMS you are working on trips a PF when the pack voltage drops too low, then disconnecting the original cells will immediately trigger a PF and brick the BMS. While not all battery controllers do this, you're bound to run into one eventually, so if you're going to be rebuilding Lithium Ion batteries, you will want to obtain the proper hardware and software to be able to communicate with and reflash the BMS's firmware. I plan to add more information on this process in the future.
Prismatic Lithium Ion
Standard Lithium Ion cells, like 18650s, are cylindrical. From the late 90s through the early 2010s, many smaller laptops which were too thin to fit cylindrical cells used Prismatic cells instead, which are rectangular cells housed in a rigid enclosure (this is in contrast to Lithium Polymer cells, which use a different chemistry and are not typically housed in a rigid enclosure). The standard type of prismatic cell used in laptops was the 103450 cell. These cells seem to still be in production as of 2026, but their modern use cases are limited and it is nearly impossible to obtain them outside of China. As such, if you need to rebuild a battery pack which uses these cells, you will have to find a Chinese distributor to buy them from.
The two companies that are currently manufacturing them are Panasonic and Molicel. Molicel's current 103450 product line includes the ICP103450CA and ICP103450DA. Panasonic's current 103450 line is the NCA103450, which is the highest capacity available at 2350mAh. However, it achieves the higher capacity by using a different chemistry (LiNiCoAlO2) which has a lower rated discharge cutoff of 2.75V. If you are unable to modify the firmware of the BMS you are installing these cells into to change the discharge cutoff, you will only get around 1800mAh of capacity out of the cells. The Molicell ICP103450CA cells are 2000mAh and have the standard 3V cutoff. The ICP103450DA has a higher 2150mAh capacity, but does not have an internal fuse.
If you do a google search for 103450 cells, you may find listings which show what claim to be a Lithium Polymer replacement for 103450s - don't buy these, they don't work well at all in place of actual prismatic cells. They're also unsafe as a replacement in packs designed for prismatic cells, since they have no rigid enclosure, which increases the risk of a puncture. Li-Po cells also expand more during charging then prismatics do, so a pack designed for prismatics may not have enough space inside for a Li-Po cell to expand and contract, which could cause a fire (not leaving enough space for this expansion is part of why the Samsung Galaxy Note7 batteries exploded).
Lithium Polymer (Li-Po)
Most modern laptops use Lithium Polymer cells, which are thin and flat. They saw use starting in the 2000s, and today have replaced both standard cyclindrical Lithium Ion cells and prismatics in modern laptops.