Replacing 18650 cells in a laptop battery pack.

Greetings to all,

Recently my laptop's battery has been performing poorly, buying a new battery pack is totally out of my consideration since they are really expensive. Hence i opend up the battery pack to check if the cells inside can be replaced with a new one. Here is waht i found out, the pack accommodates three pair of sony 18650 Li-Ion cells with the capacity of 2200mah.

Began surfing the internet to check if i can find any one selling these cells nearby my location, found out that some customs confiscated UltraFire li-ion battery(BRC 18650) with capacity of 3000mah are being sold for amazingly cheap price. After a little research about the cell i found out that these ultrafire cells (length 68mm) are 3mm more in length then the sony cells (65mm) currently present in my laptop, this is a big difference as the space in the battery case is really tight, also found out that the difference in length is due to the protection PCB present in Ultrafire cells which can be easily removed & without the PCB the cell will be exactly 65mm in length.
(note: Sony cells currently present in my laptop do not have protection PCB)

I would like to know whether its a nice idea to replace my sony cell with ultrafire cells? will there be a bad effect if the capacity of ultrafire cell (3000mah) is more then sony cell (2200mah)? Is it ok to remove the protection PCB in ultrafire cells?

I'll deeply appreciate any comments, recommendation or help.

Best regards,
Lubnan.S

 

You should buy a battery. Batteries are NOT consumer serviceable!

If you try to "manufacture" one in your garage, you're not only likely to damage your laptop, but it could create a potential danger of personal injury as well.

 

The ultrafire cells are longer because they have a built-in protection circuit. That is useful if you are charging them individually in a wall charger or something like that. If you peel back the plastic wrapper a tiny bit you can see the circuitry and just rip that off the end of the battery. It provides no benefit to you in your application since its function is built into the circuitry within the battery pack. In this way those cells will fit just fine.

One problem though is if you have a Dell. Their laptop circuitry will never allow you to recover more charge capacity even if you replace the cells. However, the ebay dell batteries from china are reverse-engineered and get rid of this problem, facilitating user-replacement of the cells.

Sike.

 

Thank you for the useful Info, Fortunately I dont use DELL laptop, the battery pack I want to mod is from a Lenovo 3000 G530 Laptop.

What about the capacity increase from 2200mah to 3000mah, will there be any positive or negative effect on the laptop & the circuitry inside the battery pack of my laptop?

 

While I know Dell works that way, I can't say for sure if any other manufacturer does or doesn't. You should ask specifically in the Lenovo forum or google it.

The ultrafire cells do show increased capacity, but that is only realized under low loads. At higher loads, it doesn't show increased capacity over other cells in the class and in fact some might have better capacity in those instances. You should google those ultrafire cells and find lots of forum posts detailing testing comparisons. Figure out the cell configuration and average power draw for you laptop and go from there.

 

Cool, this sounds like something I could try. I've been thinking about it for a while. The replacement battery for my old laptop is $70 on eBay, so if I want it to ever be a portable computer again I'll have to replace the cells. Can you post pics if you have a camera and you end up doing this?

I used to build batteries for r/c cars, so this would be a step up, but I need to expand my knowledge anyway. This could be a really useful skill to learn, and I might as well learn on an old junk laptop

I'll give it a try this week or next week. Good luck to you!

 

If anyone is interested, Sanyo makes some 2600mAh cells with built-in protection circuits that are the same size as normal 18650's (65mm).

 

If you have built R/C batteries this is the same. The only hard part is opening up the case. I thought I damaged the 'lid' irreparably when I opened it up, but it closed back together firmly and securely anyway, no glue required.

IMO though I think it might just be easier and as cheap/cheaper to get an ebay battery. A good reason to diy though is to get the best cells and therefore capacity in there.

 

Thank you, your info is very helpful.

We do have some local shops selling the cells you mentioned above, they are really expensive, to be specific, three pairs of sanyo 2500mah cells costs exactly the same as a brand new battery pack for my lappy.

Hi,
If I do the operation, i will definitely post the pictures & details for you.
It's just that i am a little worried about doing this because my laptop is just 1.5 years old & fear negative effects on it after i replace cells in the battery pack.

 

You have nothing to worry about as long as your battery still outputs the same voltage when you're done assembling the battery. Make sure you connect everything exactly how it was before, and since you're replacing the bad cells with similar ones, your laptop will be fine.

Don't worry about the mAh rating screwing anything up. It's just a measurement of power output duration. So the more mAh your cells have, the longer your battery should last. Depending on the quality of the cells you buy, you might actually end up increasing the battery life of your laptop.

 

Thank you for your supporting post.
I'll go & check tomorrow whether those confiscated ultrafire cells I mentioned about earlier are still on sale. If i manage to get my hands on them, I will start the project right away. Will keep updating.

If you have any comments or info about Ultrafire 18650 3000mah cells plz feel free to post.

 

I wonder if this article might be of some help to you:
Inside A Lithium-Ion Battery Pack : How Notebook Batteries Work and Why They Explode

 

Thank you for the useful link, I did go through the complete page & it sure is useful. Anyways, i will purchase the cells tomorrow & update.

 

Indeed. Let me know why you receive your patent. Then I'll post a full retraction.

 

If you are looking for help with finding 18650 battery`s or any other information try the forum below.

Flashlight Electronics - Batteries Included - CandlePowerForums

 

HI,
Unfortunately for me the operations did not go well, the new arrangement of cells just refuses to fit in the battery case, the reason, increase in horizontal length by around 3mm because of the solders, it seems spot welding is required.
I did try to force the cells in the case, but then the case expands & refuses to get in the battery slot in my laptop.

No options left but to buy a new one.

Best Regards,
Lubnan

 

You hit on a key point “Spot welding” that is one of the reasons why I never recommend for people to build their own packs. You should never solder wires on lithium batteries (or any batteries for that matter); the direct heat is not good for them.

 

Can you take a picture please?

 

Sorry, I cant.
After i failed to put the cells in the case, i decided to put old cells back in the case by soldering the connections (earlier the connections were spot welded), the same thing happened, the old cells also wont go in because of increase in width by several mm from the solders.

 

You need to buy batteries that are already have tags/tabs spot welded. Usually come in pairs joined together, but the tabs can easily be cut leaving you something to solder to without damaging the cells.
LIR-18650-FT Lithium-Ion rechargeable cell with tags
I have rebuilt a number of batteries with higher rated cells than the original ones, they work fine apart from under reporting the time remaining

 

Thanks for the Superb Post, but unfortunately its too late, i already ordered my self a new battery pack.
Thanks anyways.

 

Not too late for me, thanks