My laptop is about 6 years old and it’s battery holds 8 Samsung cells in a 4S2P setup.
I have opened the battery case (yes I damaged it a bit but I think it is still usable) and I could see that at least 1 one the cells of one of the parallel set is probably damaged. I can see some rust at the + pole.
I want to replace the cell but probably I’ll have balance problems and probably the remaining old 2600mAh parallel pairs cells won’t have the 5200mAh capacity whatsoever.
So, I was thinking of 2 options.
1 - Replace the pair which one of the cells shows some rust by one single 3400mAh cell.
2 - Replace all 8 cells by these same 3400mAh cells, increasing the overal capacity of the battery.
Each option presents cons to me.
Option 1 will probably bring balancing problems to me and probably will decrease the life cycle of the unmatched cells overall (1x 3400mAh plus 6x 2600mAh with decreased capacity from 5200mAh to probably under 340mAh). Also, I’m not sure about this but I’ve been warned that removing/dessoldering the old cells in wrong order might block the charger controller and also soldering the cells back in wrong order might also do the same to the charger controller)
Option 2 is probably safer, better, increases overall capacity but the main con is that it’s a way bigger investment.
The other thing is that I’m completely ignorant about which brands or unbranded cells might be the least crap.
I’ll wait for advises before going forward!
Thanks
Psy
And Another quesiton I would like to ask is if is there any specific order I should dessoslder the old cells in order to avoid blocking the charger controller?
Oh really? Only flashlights?
Oh maybe I got the wrong idea about the forum, then… I thought this was a dedicated forum to rechargeable batteries in general!
I have bought the cells from a shop which I was said by some support guy (or girl) to be authorized Panasonic merchant (reseller I suppose) and the price is not that different. Each cell was about 2.34€ because I got a discount cupon and I bought 2 packs of 8 cells. Also I think they are with 30% off. Normal price would be 3.35€ (26.77€ per pack of 8 cells). I hope I was not scammed!
I’ll be adding a second voltage supply to try to trick the charger controller so that odds of blocking it becomes lower. I have a solder station (Ersa i-con Pico) and multimeter (Brymen BM869s) at home. I’m an electronics and programming enthusiast so I like to do this kind of stuff, but to be honest I still have a lot to learn!
There is no such thing as an authorised Panasonic battery merchant. The merchant just has exclusive sales (be it Panasonic, Sony, Samsung, LG or other) within a territory. They sell complete components. Lithium Ion cells are made for OEM and never sold directly to the public. They are too dangerous for tinkering and will explosively burn at the smallest short/misuse. The company would be liable to lawsuits. Panasonics/Sanyos (now known as Murata) in the 3400 mAh capacity are sold 4.27€ at lowest cost. Anything else lower are probably fakes. There are many counterfeits from China (>90 % of what you see on Alibaba or eBay). You post a link to a Chinese site but then state you purchased from an authorized dealer. You are giving wrong data to go on.
As for engineering a power pack, that’s up to you. There’s much more than simple resistances in a current regulator and termination voltage.
I’m not gonna bother with you. The name (oh that’s cute replacing ‘O’s with ’0’) , the lack of info (where from Europe?), and the construed repair/replacement of a laptop battery is not my handle. Best you take up with an engineering teacher or tutor.
Not to further frustrate your efforts, but if you plan to go about taking apart the battery pack using a soldering iron, you’ll be in for a bad time.
The reason being that (at least in all the laptop batteries I’ve disassembled) those cells aren’t soldered to those strips - they’re spot-welded.
That means you won’t be able to go about melting the connection - the simplest course of action would just be to snip the strip.
Well, I bought the batteries from someone who told me what I said here. So, if I’m lying, I’m lying by someone else’s mouth. So, yes, it was a Chinese shop and yes I was told they were authorized merchants. If it is a lie, it is not my lie! I just sold the fish as I bought it.
I’m not about to engineer a battery pack. I’ll just try to keep voltages at those spots at the same level so that the charger controller won’t see a voltage too low and lock the charging feature for safety reasons.
I’m from Portugal, by the way, if you’re so interested…
That’s why I bought cells with the tabs already spot-welded!
I can’t do anything about the bought cells. They are already paid and on their way. So, I’ll try to do it anyways. I’ll take some safety measures when I’m about to start this!
Either way you came to the right place PsySc0rpi0n. This forum has a very broad userbase, thus it is easy to find some helping fellow with the right expertise or skills.
Here's some advice:
Regarding the battery controller, at least in genuine batteries it is safe to remove in my experience. You need to remove power first, this means you must start disconnecting the circuit board either by the positive or the negative pole, V+ or V−, then proceed in order to the other side: either V+, V3, V2, V1 and V−, or V−, V1, V2, V3 and V+. For more details check this post of me at Karosium: Hacking the bq8030 with SANYO firmware.
As others have said it is more than likely that those cells you bought are fake. This is not necessarily bad because they can be perfectly fine high capacity cells from some good chinese li-ion OEM, like BAK (I found a BAK 18650-34T cell under an NCR18650B wrap, check this).
Glad you bought cells with tabs. I solder “untabbed” cells with Bi50Pb32Sn18 low temperature solder alloy (see Rose's metal). An aggressive flux is also required for steel.
Water and lithium do not mix so water will not put out a lithium fire and is likely to add fuel to the fire.
Have a bucket to throw it into to take outside but beware, the fumes are extremely toxic
I completed the task yesterday. I took the advises of having a metal bucket and some pliers to pick up the cells, if needed, and drop them in the bucket.
Thank God it wasn’t needed although some mistakes I did created a few sparks maybe twice.
Well, for my first time, I think it wasn’t bad at all. I didn’t set the house on fire, I think I haven’t damaged any of the cells but to be honest I made a few noob mistakes.
Mistakes that might have blocked the charger controller.
1 - I was said to disconnect the cells, one by one from ground to V+ and then connect the new ones in reverse order. I kind of forgot that and disconnected one old pair and connected the new pair right away and repeated the process from ground to V+. So I didn’t follow that advice exactly. Stupid of me. Don’t ask me why.
2 - When connecting the new pair #3 (the one before the last at V+ end), I connected it in reverse polarity, so it started heating and when I noticed it and disconnected it, I measured the temperature with myultimeter temp probe and it read 47°C. So até least it reached about 50°C for sure.
3 - Probably the most serious mistake due to the fact this was my first time and no experience whatsoever. I didn’t know how to proceed with the tabs, so I removed a small black rubber they have and soldered first the 4 pairs with those tabs placed in an X. Then when I wanted to connect the wires from the circuit I ended up bending the tabs close to the cell body to be able to solder the circuit wires to the tab resulting in melting the cell wrap creating momentary short-circuits and some sparks. But honestly I was the only way that came to my mind to work with those tabs. Remove black rubber, solder them to the other tab and due to their position, they were soldered in an X position. Then I bended them close to the body of the cell so that I got the flattest surface possible. After that I soldered the circuit wires and as the tabs were touching the cell body, the heat melted the cell wrap and the tab torched the metal plate of the cell body.
Not needed to say that the battery casing is unusable and will have to come up with some idea to be able to use the battery pack if it’s still usable.
I wouldn't say completed, I'd call that a minor disaster instead. But you get the experience. ;-)
If you aren't willing to opt for a low melting solder path, the super reduced available space inside those battery cases forces you to wrap cells with polyimide film or so (I bought some super cheap more or less recently here, btw).
Needless to say, I advice you to undo all the blunder and try to recondition the case.
Clean and set the cells in parallel for self-rebalancing. Rewrap the cells too. And discharge them down to ≈3.92V maximum, so they rest without getting stressed.
Oh! Wait, you said you @#$% the battery controller. That is bad news, pretty bad. Unless you can harvest and transplant some other usable and compatible controller board, you are forced to diagnose, possibly repair something like a fuse and even reprogram the microcontroller chip. Good luck.
Yes, I completed the task. Completed is the correct term here, yes because I finished all the tasks. Now what you might want to say is that is probably an unsuccessful completed task. That I can take and will admit but I’m still on the process of knowing if it was successful or not by letting the batteries work for a full cycle or 2 (charge, discharge, charge, discharge) for calibration purposes, I guess.
But yes, there is the very real possibility that I might have blocked the charger controller. But I’ll wait to see what comes out after the charge/discharge cycles if it even charges.
I turned off my laptop and connected the battery pack with the new cells. Then I tried to turn on the laptop but it didn’t turned on. Then I plugged the laptop charge cable and turned the laptop on and waited it to reboot. My SO says the same about the battery as it was saying before with the old cells but it is also saying “Charging”. So, I guess I have to wait to see!
And btw, I think I wont redo all the work again just to wrap the cells in film. If they work like they are now (which I doubt), I guess I’ll wear them down and as I have a second 8 pack of the same cells (yes, I purchased 2 packs by mistake), I might try to do a better job with this 2nd pack. We will see…
Did you checked the voltages of all battery segments? I understand I may be a picky or perfectionist individual, but laptop packs do not have any calibration mechanisms. In my rebuilds I did not even allow 1 - 2 mV of drifting apart, and prior to assembly I carefully charged all cells in parallel to same voltage, then set the team in series and slowly discharged them to a set voltage point to obtain a cell ranking. You then complementary team cells for maximum pack balance: 1 + 8, 2 + 7, 3 + 6 and 4 + 5.
Albeit good in any case LoL that may be a bit over the top for cells with great consistency.
Well, about calibration, that was what I read from an article in BatteryUniversity site. They explain there how smart batteries work and why and how they need calibration.
If you want, please take a read here and let me know your thoughts.
I have measured all batteries individually and they all were in the range of 3.77V and 3.75V,so I mixed them in order to have the best and closest average value of about 3.76V (by mixing 3.75V with 3.77V) when packing them in pairs.
The problem is that I think I can’t read any voltage at the output plug of the battery case. So either there is bad contact between that plug and my measuring probes or there is really a blocked and/or damaged circuitry in the charger controller. I’ll try again later today after work.
Well, looks like somehow the battery pack is broke.
It’s not charging but weird fact is that if I measure the voltage at the battery pack contacts I can only read the correct votlage if I touch it with my fingers.
Here is what I’m trying to say. An image worth a thousand words, I guess.
Watching a video rotated 90 (or whatever) degrees usually is uncomfortable for most people, especially for those who on top of this need to figure out what you are doing in it.
Check if there is some bad contact in the connector. Could you also explain why is the oscilloscope showing an AC waveform?
You are quite good criticizing… The problem is that I on’t know how to rotate the video in Youtube Channel options.
I am trying to demonstrate that the scope/multimeter only reads any meaningful voltage when I touch with my fingers (with my bear feet on the floor or better in the wall) in V+ of this battery pack.
Anyways, I don’t think there is any bad contacts as I have checked this behavior several times. As for the AC waveform, it’s probably my scope picking up my house mains 50Hz frequency.
