Just a few pictures I wanted to share of my P42A 52V 8.4ah pack I made as a range extender for my ebike

13s3p with DMEGC 26E cells,30A bms,made to power a small inverter for a computer

Hi everyone. I tried to replace the cells of a dead power tool battery but some of the spot welds i did fell off right away and others are fine. I use a diy MOT spot welder with adjustable pulse time from 20 (1 mains cycle) to 200ms. I set it to around 80ms and the first few welds were fine (no discoloration and some strength) but then on the other cells they just started falling off right after the weld. I tried increasing the pulse time but that only overheated the strip. I tried 3 different strips with no success (finally did it but had to do a lot of welding). Only where i welded 2 strips together the connection is really strong. (And on different cells too). So could be the current too low for this 18650 cells to weld? I currently have 4 turns of car jumper cable on the MOT and probably can do one more to increase the voltage/current but im worried if that could potentially destroy the triac bt139 (16A continuous)? The datasheet says it can hande a lot higher currents for the first mains cycle but the MOT probably also have really high starting current. (I measured around 45A and i also use a "soft start" optocouple which turns on only on zero crossing of the mains). I need more suggestions how can i improve my spott welder? Will I have any problems with the current welds or potential risks? I think i can pull them off if i try.

Hey guys, I've come into the ownership of a few thousand LG 18650 MJ1s from medical equipment that was being taken out of service.

The batteries themselves are all basically new because of the warranty period of mobile batteries.

Im currently going through testing them all and grouping them by capacity, resistence, etc.

Is there a market for these in Melbourne? Would anyone be interested in buying them once Ive completed the testing? What kind of price per cell am I looking at?

They seem (so far in testing at least) to be in fairly good shape across the board.

Thanks guys.

Edit because I was asked: I should have around 9000 MJ1 18650s. As well as some Samsung INR18650-29E (probably a few thousand of those)

(This doesnt mean all of those will pass testing)

Hi everyone,
i just bought this thing and i'm trying to understand how to group my cells by capacity inside it.
It takes 8 21700 unprotected cells, and as far as I understand it doesn't manage them individually.
Is anyone familiar with this board ? i can post a more detailed picture of the board if needed

What should I improve?

How strong should the weld points be? I think I can still peel the nickel strip off, but it definitely leaves small craters on the battery.

This is a 13S5P pack. I am planning to add another nickel strip on top to connect all five cells together on both sides. Is this considered good practice?

I have some TP4056 charging modules and trying to charge some 2200mAh batteries, the charging module turns the blue light on (which means charging is finished) but the batteries never reached 4.2v. Most of them stopped at 4.16v. I have tested multiple of the same module and different batteries from different sources, all finishes charging at 4.16v.

Hi, I wanted to get a custom 14s6p pack. But I'm wondering if a 20s4p pack would have less sag due to less heat in the wires, even though it has 4 less total cells, I'm not sure if it's enough to offset it

So I did a lot of searching to find some 18650 and 21700 plastic insulator rings for the positive side (between raw battery and cell wrap) and wasn't happy with costs of the 21700s and the general lack of options. At this time I have some insulators coming via slow boat from the eastern mainland.....

In the meantime, it hit me.... I have a 3d printer, so I took out the calipers and gave it a whirl.

These are printed in PLA, but I may use PETG for the final choice.

Has anyone done this before? If so, did you find them to be equal to purchased insulators?

Thickness was made to .5mm as the .25mm measured wouldn't print very well.

With the .5mm I get a printed ring that comes out to .4mm with ironing the top layer (only 2 layers)

P.s. pardon the blur of the plate photo, my hands shake badly

Edit: clarity of insulator placement

Hi everyone,

I have been working on BatteryRealData.com as a place to compare real 18650 and 21700 cell behavior with the claims in the manufacturer datasheets. I think the public version is ready for more people to test, especially on phones.

The site currently includes 371 published discharge tests, 36 cylindrical cell models, and 35 manufacturer datasheets. You can compare discharge curves, usable capacity, voltage sag, temperature, energy, and written test reports. There are also simple pack-current and runtime tools.

The BRD Score is intended to measure how well a cell performed against its own datasheet claims. It is not a ranking based on the largest advertised current or capacity number.

I would appreciate direct criticism from people who actually use these cells. If a comparison is misleading, a datasheet boundary is unclear, a chart needs more context, the mobile layout gets in the way, or a feature is not useful, please tell me.

https://batteryrealdata.com/

Cell library and datasheets: https://batteryrealdata.com/cells/

Comparison tool: https://batteryrealdata.com/compare.html

For transparency, BatteryRealData is a project from DIY500AMP.COM, and DIY500AMP sells some of the cells included in the database. Test results are not guaranteed to be favorable, and commercial testing requests do not buy a positive conclusion.

Manufacturer datasheet limits remain the limits for pack design. Tests beyond those limits are laboratory evidence only, not operating recommendations.

What would you add, remove, or change first?

I am trying to balance a M18 12ah high output pack

cells are 3.6v 3.8v 4.1v 3,5v 4.1v

At first I connected my 5s balancer to it but nothing happened which was weird cause the cells have power and the balancer works I tested it on a different one.

I connected 1s to my xtar VC8 charger to fully charge it and it seemed to work but after I disconnected it jumped immediately down to 3.6 ish volts every time

Now I'm just going to say the cells are bad but why would the balancer not work

It supports

Cells at 2.7-4.5v so it's not like the cells where too discharged

Rather spend less, but I also want something that wont give me a hard time or / and make my life easier, I was looking at the awithz units, but im not sure which one to pick, im just starting out and want to make myself a better ebike battery in the near future, is awithz p20b going to be sufficient without causing me to many issues or should I get a bigger unit from them? ty

So I know identifying cells can be a bit difficult, with some brands not fully putting their branding on cells, but I'm pretty sure I've been done here.

I paid £60 for a 10s2p hoverboard pack branded Samsung from what I thought was a reputable source ( not AliExpress, eBay or Amazon), a hoverboard online shop. When I went to fit them I've peeled off the blue plastic wrap to see the cells are branded Tesson.

This isn't a branding that Samsung use or are rewrapped Samsung's are they?

A friend wanted more runtime with his DeWalt grinder, so I tried building a pack with the most capacity possible, one that doesn't heat up much under heavy load, while retaining maneuverability.

Cells are Eve 50PL, capacity and IR-matched for a 5S2P configuration according to Cell Saviors pack builder.

I use 0.1x10mm copper for the series connection and 0.1mm nickel-steel for the parallel. It also doubles as the nickel part of copper-nickel sandwich.

Works great on the powertools and accept charge from the original charger.

No runtime test result as my friend haven't had the opportunity to test them yet

Have a bunch of dead/dying M18s.

Rebuilt the first (5.0 XC) with JP30 cells. Charged all cells to 3.70 before spot welding.

Pack had same flashing single red light (flashes 8 times) as before rebuild; charger (genuine Milwaukee regular, non-rapid) lights up solid green. OK; no problem - heard this could occur.

Tried:

-Put battery in tool, trigger, then right to charger, no dice

-Put battery in and out of charger multiple times, no dice

-Leaving in charger for a few hours, no dice

-Connect the J2 terminal and main BAT- for a few seconds, then onto charger, no dice

-Discharge all cells to ~ 3.2 volts and balanced (found last post (resolution) in this thread: M18 5.0 battery issue : r/MilwaukeeTool), no dice
-Tried jumping Pins 2 and 4 on the HD1 pad, no dice

Only item of note this appears to be an older battery (2015 date on BMS) I did find some posts indicating the M18 BMS needed to remain powered to avoid permanent brick; but these posts were all older than 2021. They mention a 'test point' which is needed to remain powered - assume this is somewhere on the pcb ,for example:

"Ive found its EXTREMELY difficult to repair an m18. They have a spot on the pcb that must remain powered, and if you break that bus to get at the cells its a wrap for that bms pcb. So if you do a lil more digging there is a way to keep it powered, but you are a bad man if you can do it. It only cost me one pack, I think I could do it if you wanna donate. This time Ill solder a lead to the test point after a proper tinning"

It' just odd that even with 16V at the main terminals, the charger is solid green like it's fully charged. From what I've found, sounds like new BMS time. Anyone have any;

1. Thoughts if this one is just dead at this point and I need to swap to new BMS
2. If anyone has experience with different year M18 batteries behaving differently in this regard, before I go wasting time on the next one?

pack failed,the old cells were mediocre at best and the connections were only 8x0.15 nickel plate. doubled up the connections and replaced the cells with (reclaimed but near mint) Sony VTC5As. reinforced the output leads with 8x0.12 pure nickel strip and covered everything in kapton for fun

What would be your spot welder recommendation for the following goals:

• Occasional use, basically rebuilding 2-3 ebike batteries every 4-5 years (as needed) and the odd project here and there;
• I have no desire for maintenance, so battery-powered is out of the question; Capacitor-based or mains-powered (if that's even a thing) is preferable;
• I can design PCBs and solder components, but I'm not looking for another project (too many of those already 😂), I'd rather have something pre-built or requiring minimal assembly;
• The smaller the better;
• Ideally a BIFL item that's repairable and uses off-the-shelf components;
• Price point under $100; The cheaper the better as long as it works decently.

So far I'm leaning towards the K7-Pro or AwithZ UF20B, but I'm wondering if there's anything better on the market that fits those goals.

Thanks!

Im fairly new to robotics and have been trying to build a hexapod from scratch. I got a bunch of parts but wasnt careful enough to make sure they all work together. Ive now run into a problem where my my LiPo battery xt60 output will not directly connect to my UBEC input that is dupont input, is there any way to get around this? Any adapter? Or do I get another UBEC. Here are both of the parts, and im also confused about how to connect the UBEC directly to my servo tester as it has the 3 dupont looking output pins and also thicker looking output wires and im not sure which ones to use.

UBEC: Amazon.com: FEICHAO 8A UBEC Output 5V / 6V 8A Max 12A Input 7V-25.5V 2-6S Lipo / 6-16 Cell NI-Mh Input Switch Mode BEC for RC Helicopters : Toys & Games

Servo tester: Amazon.com: OGRC RC Digital Servo Tester/ESC Consistency Tester for RC Helicopter Airplane Car(Servo Tester,ESC Consistency Tester,RC Helicopter Tester Tool) : Toys & Games

LiPo: Amazon.com: URGENEX 7.4V 2200mAh Lipo Battery 50C High Discharge Rate 2S RC Batteries with XT60 Plug Fit for RC Car Truggy, RC Airplane, FPV Drone, UAV Quadcopter, Helicopter and RC Boats Racing Models : Toys & Games

Hello there

I’m starting to loose it with trying to dial in my AWithZ P60F spot welder. I'm trying to weld a sandwich of 0.15mm copper and 0.15mm pure nickel onto 18650 cells, but I cannot get consistent results no matter what I try.

Whenever I try to dial in the settings, it goes one of two ways often on the same settings. It either makes a weak weld with very tiny nuggets when ripping the strips off (often just under one electrode the other doesn't even stick) or just blows a hole through the strip and often the battery can (I tried on dummy cells).

The P60F is a powerful welder, so it definitely has the power for this thickness, but the inconsistency is killing my cells. I suspect it might be an issue with the stock pen. I tried switching the needles with spares but it is the same.
I upgraded to this welder from uf20b because that machine works like a dream it makes very consistent welds and is easy to dial in for lower thickness material. Meanwhile p60f has just been a nightmare, I haven't done any real work with it yet.

Has anyone tried to use to the WP240 multifunctional spot welding pen? I saw that it has adjustable distance between the pins. And possibly spring loaded tips?

Hey folks,

I'm building a simple USB charger for a friend's scooter using a single 18650 as a buffer. Goal: Charge the phone even when ignition is off. Scooter provides ~11-15V when running, so I'll drop that to stable 5V with a buck. Then I want an all-in-one module that handles:

- Charging the 18650 from 5V

- Boost to stable 5V USB output

- Load-sharing/UPS (seamless switch when scooter power drops - no phone disconnects)

- Protection (overcharge/discharge/short)

- Preferably dual USB or easy USB-A output

- Minimal wiring (just battery wires + input/output)

I've seen the usual TP4056 + MT3608 combos and basic power bank boards, but I'm looking for specific integrated modules (ideally with good load-sharing) that people have actually used reliably in similar portable/UPS setups. Bonus if it has a battery holder, LEDs, or display.

What exact modules have you used successfully? Links to AliExpress/Banggood/etc. or model numbers would be great. Also interested in real-world issues (heat, current limits with one 18650, vibration durability for vehicle use, etc.).

Thanks a lot!