Milwaukee M18 dead battery

[ukracer]

I can't find the old 12 volt irons we used but this is what they use now apparently.
Can't see any on UK eBay sadly but I would think they are available in the UK somewhere.

 

[GafferTapeKing]

Does the RC charger do a full cycle, managed discharge before recharge ?


That's a name I haven't seen in a while, Weller!

I used to borrow a mates Weller heat gun to solder PL259 coax connectors.
Trouble is buying that and two 18650s would be slightly more than a new battery pack

Expert Soldering Gun 100W 240V - 8100UD​

​

 

[ukracer]

Does the RC charger do a full cycle, managed discharge before recharge ?


That's a name I haven't seen in a while, Weller!

I used to borrow a mates Weller heat gun to solder PL259 coax connectors.
Trouble is buying that and two 18650s would be slightly more than a new battery pack
View attachment 316842

Expert Soldering Gun 100W 240V - 8100UD​

​

Don't use heat guns for cells. They just don't get hot
enough..

"correct procedure in using both big tip and temp, as a cell sinks heat fast thence a lot of thermal inertia is required to stand a chance of raising the battery terminals to solder fused temp quickly, minimizing overall thermal transfer (if the heat source is removed immediately, of course)."


taken from here... https://budgetlightforum.com/node/52417?page=1

 

[Turbo]

I buy the cheap ebay BMS boards and fit them to bricked batteries, they seem to work just fine for years after

I have 2 batteries that I rebuilt using those ebay BMS boards & they are running ok, though those copy boards are based on the early Makita BMS boards and do not monitor every pair of cells so they are not able to properly balance charge all the cells.

 

[Turbo]

rc charger ?

I fed the two low ones 5v at 200ma, CPC lists the charging voltage as 4.2 so maybe the cells are baked now rather than a bit low.
Maybe I should have looked up a charging voltage before that but I didn't know the cell type.
Hindsight is great.

The specs on them are impressive, peak current of 25A, I can see how these micro jump packs can step up to cranking an engine and still fit in a pencil case.

I have an Imax B6 clone & I've used it to balance charge li-ion battery packs. As well as the charger you will need a set of banana leads plus croc clips, a long balance lead & make up an adapter with a balance plug on one end & magnets attached to each wire on the other end. (the magnets are the easiest way to attach the balance wires to the battery)

Li-ion should never drop below 3v & absolute max 4.2v, you will get a longer life battery if you restrict it between 3.5 & 4.1v, some tools are only charged to 4v!
If it drops below 2.5v the battery shuts down & usually is bricked! There are videos on youtube about recovering these cells but I've never been successful & even if they do work again they are unlikely to hold a decent charge.

 

[Turbo]

I would not recommend anyone try to solder directly onto Li-ions, they are quite sensitive to temperature & its very easy to overheat them. Nicad & Nimh were quite robust but not Li-ion. I learned that the hard way on the first Li-ion battery I built. It charged ok the first time & ran the tool until flat but it would not charge again. Opened it up & all the cells I soldered onto directly had failed!

Lesson learned, I bought one of these spot welders.
https://www.ebay.co.uk/itm/124699978724?hash=item1d08b2abe4:g:AdQAAOSw5jVgiQBZ

Did the recommended mods to it but was initially disappointed by in not having enough penetration using the recommended battery size. Then I swapped to a 075 car battery & it will happily weld 0.15 nickel strip onto 18650's.

 

[julianf]

Its been a while, as it wasn't my only battery, but I'm about to buy another tool, so thought it was about time to fix it.

As per my other thread, the spot welder let out the magic smoke instantly, so i resorted to the soldering iron. To change the management board, there's no heat anywhere near the cells anyway (although it was still factory spot welded on two of the connections that need re-joining)

The photo below shows the end of the first charge cycle, so that's certainly more of a result than its seen since it went bad, and i assume its now fixed.

Thanks to all for the help.

 

[sako243]

Some Li-ion power tool batteries contain one or two large MOSFET transistors on heatsinks, which cut or enable power to/from the cells. There are no components on the PCB of this Milwaukee battery large enough to switch the 20- to 40- Amps involved, so the board only monitors voltages, and balances and temp-checks the cells. The 20-odd volts should always be present at the outermost two terminals. The PCB will use one of the other terminals to signal the tool to shut down on low voltage, and probably to control the charger too.
It should be possible to charge the battery using a generic ( Radio-Control ) charger, and to test it under load ( 2 x 12v headlamp bulbs ) across the outermost two terminals.

Q5 and Q4 are plenty big enough to handle that current if specced appropriately. I've had SOT style packages rated at almost 100A if you design the PCB appropriately. It's fairly easy to get sub milli ohm Rds(on) FETs and if they're switched hard on or hard off then minimal power is dissipated in the package.

 

[gordon stephenson]

I posted a while ago, Milwaukee 18v battery showing faulty in charger, Flashed the two outer battery contacts for a few seconds with a "9v" battery, worked a treat and has taken charge ever since, (saw it on youtube)