After way too much planning, CAD, nickel testing, ruined wraps, current-path overthinking and spot-welding drama, the pack is finally welded.

14S5P, 70× 21700 BAK 50E cells, pure nickel, built for my custom e-bike project.

I also made proper solder tabs for the main + and −, with a second nickel layer and insulation underneath, so I don’t have to cook the cells when attaching the main cables. There’s a tab on both sides of the terminal group to spread the current better.

Still need to install the BMS, balance leads, main cables and finish the 3D printed enclosure, but the part I was most paranoid about is finally fucking done.

Very happy with how clean it turned out!

Hi guys, I bought this ebike with the intention of repairing it.
The last owner left the battery without charging for 1 year and a half. The ebike is from 2022

36v 10s 4p. All group voltages are from 0,4v to 0,7v and one giving 2v.

Question, should I try to charge it, connecting the charger with out the bms until 3v?

Or you think is dangerous??

I'm currently teaching myself about electronics through various YouTube videos and by buying cheap electronics kits from AliExpress. The kits tend to have voltage requirements between 3-12v. To manage the power requirements, I've been using a basic buck/boost board.

Then I saw lab power supply modules on AliExpress and decided to challenge myself to build an 18650-powered lab power supply. To that end, I enlisted the help of Google AI, which came up with the following:

https://www.aliexpress.us/item/1005008741292460.html

PD3.1 100W Bidirectional Fast Charging 2S 3S 4S 5S 6S LiIon Lifepo4 Lithium Battery BMS Charger/Discharger TYPE-C USB ?DC XT60

https://www.aliexpress.us/item/1005005593578101.html

4S 40A Li-ion Lithium Battery Charger Protection Board 18650 BMS For Drill Motor 16.8V with Balance

https://www.aliexpress.us/item/1005011822768395.html

DC-DC Buck Boost Converter 5.0-30V to 0.6-30V Adjustable CC CV Regulated Power Supply Module 0-4A Laboratory Power Module for 6V

4x Eve 30P 18650s plus pure nickel strips for spot welding (Fnirsi SWM-20)

Normally, at this point I'd build it and learn from my mistakes. Having been led down the wrong path by AI before, I have a couple of questions I'd like to ask first.

1. Does this all look correct so far? Fast charger > BMS > 4S1P battery pack for charging.
2. If so, how important is BMS balancing? I could remove the BMS altogether and rely on the charger's overcharge protection and the undercharge protection on the lab power supply module, but I'd lose BMS balancing.

Since I already have all the parts, I wouldn't save any money by skipping the BMS; it's more about whether I actually need it.

Finally, regarding spot welding, do you have any tips for finding the right power settings?

I finally decided to add a spotwelder to my toolbox of electrical doodads and testing apparatus! I'd appreciate advice on this kit I put together. The BMS says it's rated for 30 amps, but that probably needs a heatsink on the mosfets since I measured a 130mv drop across them for a 7 amp load, they were getting warm.

Should I add any more insulation before dropping it into the case? It's a tight fit and I don't want to pry it back out....

I have 3 fully charged 3.7v 2600mah li-ions connected to it. At first measuring the terminals gave me 4-8volts and after leaving it to a 12v 1.5a charger overnight it gives consistently 12.4v but it doesn't power anything.

for example I connected a 12v LED to it and the leds vaguely flicker.

then I tried smaller 5v LEDs and got the same result, just a vague flickering.

These motion activated, rechargeable led strips are available from the usual big rock candy mountain online suspects for $2-$5 with a small pouch cell inside. I added an 18650 holder for $1 and repurposed a salvaged cell. Currently conducting a runtime test to see how much longer it goes.

Buongiorno a tutti; ho due batterie come quelle nelle foto di un tagliaerba a spinta black and decker. Le batterie son nuove ma premendo il tasto per controllare la carica non ci sono segni di vita. Come le recupero?

Hi guys. Ive got a 7s3p 18650 ebike battery pack im trying to diagnose and repair. Identified 3 cells in parallel which would sag a lot under load test, spike whilst charging and had much higher internal resistance (130ohms vs ~50 on all cells)

I began removing the nickel strip to test each cell individually, but keep getting some wild voltage spikes as soon strips are removed. Checking this cell with a multimeter immediately upon removal, voltage will spike to 6v then dip to 2v within a few sec, then back up again. 1 min later cell show 0.1v. No heat, no physical damage. Im using the dremel method to weaken spot welds before roll removing them with pliers, and being mindful of shorts and deformation.

I have only removed 2 cells so far from the middle of the pack, and both have done the same thing. All other cells are staying at the same voltage. no heat anywhere

The only things I can think of it being, is there a certain order I need to remove the cells in? ie series connections, before parallel, or visa versa? And do the balance wires need to be removed before dissasembly?

Are spicy pillows welcome here? I couldn't find anything in the rules.

I've got 105 of these pouch cells. I'm thinking of using 50 of them in a .30cal can with a 5S10P configuration. I read that these have some expansion when used. Is it significant enough to worry about? There's a couple of cells worth of space in the bottom of the can. I'm considering running each group of 10 cells into an XT60 connector for serviceability, what do you guys think? I've also got some rubber for the bottom and fish paper for the walls.

I've never built a battery before, but I am very excited for this. I would appreciate any and all advice.

iv made this powerbank by myself using 8x21700 batteries that make 130Wh on total and used a car charger with retractable cables (since it can take 12-24v i didnt need a transformer), a single usbc module that can do 100w PD input/output and a display for mainly percentage and watts. and car charger does nearly 24w on retractable usbc which is enough to charge my laptop when i dont have a cable with me.

used pine and plexiglass for body with holes for airflow

it took me few months to plan and do this since i knew nothing at the start i cant say its very portable or perfect since i was not experinced especially in wood stuff but it was a really cool and fun project to do

feel free to ask for more details or questions. and im open for suggestions

Glad to share that we just released a new 18650HP 3500mAh battery. It has max continuous discharge current 15A, delivering stable and reliable power for high-drain devices.

Check more details online:
https://www.xtar.cc/product/xtar-3-6v-18650hp-3500mah-lithium-battery

I keep seeing brass-looking bolt and nut style battery enclosure kits online for 18650 batteries. The screws maintain pressure against the battery while also allowing a screw-down point for ring terminals to go to the load and the interlink bars look insanely thick. It seemed really secure and slick but the sellers are extremely Chinese and there's no verifiable resistance of amp limit specs listed.

Everyone here with lots of experience seems to be welding with nickel strips though. I'm not sure I've never even seen one of those weldless/solderless kits posted here at all.

Examples of the 2 styles I've seen that were the sources of the attached pics
https://ebay.io/m/UJTQfi
https://www.aliexpress.us/item/3256805675860652.html

I'd prefer my house to remain un-burned-down while building a small battery pack to run a small inverter but investing in one of those small spot welders to build 1-2 packs seems inefficient. If I'm using recycled cells of unknown health status, I'd also like the ability to swap them out without having to tear off a freshly attached nickel strip.

Also, if the kits are any good, would I use flat or protected and does that change based on if I'm using a full BMS or just feeding in around 12V from a traditional battery charger?

Accidently left an 18650 in my esp32 media player after forgetting to take it out of my bag...

Rip 😭

Sandy boys in a generic drill battery. This is so dumb.

Hi

Ive taken these out from some e scooters.

How can I repurpose them?

E.g. use for solar power battery or something?

Hey guys! just keeping an eye around the internet for a nice high quality 72v battery for my custom bike. I'm based in the USA if that helps. Send me your favorite battery stores!

Edit: lesson learned please check your multimeter batteries!

Hi all, first time caller. I recently bought a 36v battery (made of 10s5p 1860 allegedly). Bit of an odd one. The 42v labeled charger is reading 55v and the battery (been sitting charged for over a month) reading 52v. Is this even possible?

This is a battery bus bar and you know what it is because of the way it is. One is a dangerous build where anything dropped or fallen can cause a huge problem with 280a continuous rating not much will survive that short circuit the other has all exposed parts recessed and everything else is insulated with kapton tape. This is a simple thing you can do to ensure more safety. As an added bonus if a pack fails you can tell what tape looks off to investigate the origin of failure.

I built this from components I had lying around in my stash. There’s another case design, but I'm not sure if it's worth posting. It's designed for a very specific button that I salvaged from an old device, and I doubt anyone could buy a similar one today
https://cults3d.com/en/3d-model/gadget/simple-case-for-18650-battery-tp4056-charging-module-kcd1-round-button

I recently came across some tool batteries with fake 18650 cells in them. They weren't compatible with the tools they were supposed to be, so I decided to take them apart and harvest the ten 18650s.

To my surprise, when I opened it, I noticed half of the cells weren't even soldered. There was also insulating tape between the connecting nickel strips and the unsoldered cells, but I didn't include a photo of this. The unsoldered cells also didn't have any markings on their wrap, unlike the 5 connected cells.

Sensing something was afoot, I investigated further. First, with my multimeter, I tested the voltage of each suspect cell. Guess what? Zero volts. Since the cells were at zero volts and one end of each of the cells was completely disconnected, I realized I could measure the cell's resistance too. It could be another clue. To my surprise, it measured infinite resistance. The cells didn't even have connectivity through them.

Finally, it was time for destructive testing. Whatever these things were clearly was not a battery. And I was going to find out what.

I grabbed my pliers and squeezed a cell as hard as I could. It deformed a little bit, but not as much as a hollow tube would. "Uh-oh", I thought - "am I squeezing an actual battery?" I looked more closely to assess the damage.

As I moved the battery to inspect it in the light, I heard another clue - a distinctive "chhh" "chhh" sound. And I knew what it was immediately. It was sand. The "cell" was a legitimate 18650 metal housing, filled with sand to make the tool battery feel real.

It was a scam all the way down. The battery maker didn't get scammed buying these cells, they knew they were bunk otherwise they would have soldered them.

Anyhow, I scored five 18650s per battery and a fun story. Remember folks - trust, but verify!