Li-Ion recell, anyone dipped their toes?

[Ian X]

I baulk at paying £200 for a battery pack used on a still current Hilti tool and fancy a tinker in time that might be occupied holding the sofa down. I re-celled the four B72 NiCd packs for my still going strong Hilti TE5-A drill but have never attempted a job on a Li-Ion based pack. Anyone?
I know I could just use a pack case to hold a cable running to a pack of any sort slung over my shoulder but fancy using the tools as single items rather than a rig. They are a WSR 36-A recipro and a circular saw with metal cutting blade. The saw is a no for using a corded battery, the recipro I could just about live with a pack on a shoulder strap.

 

[xmetal]

It can be done but whatever you do, be careful how you handle the cells. A lot of Li-Ion individual cells don't have protection built in to them and can be dangerous if shorted.

 

[Ian X]

Whatever you do, don't short them out. A lot of Li-Ion individual cells don't have protection built in to them and can be dangerous if shorted.

Indeed the existing cells are unprotected Samsung 15Q from the 18650 family.

 

[xmetal]

Panasonic cells are good ones to go for. I got some Panasonic cells direct from Amazon as it avoided the chances of getting inferior copies from iffy sources. It's quite common with inferior brands to find they to break an old laptop battery apart and repackage the working cells.

 

[roofman]

Ime leaning back to Ni-Cad after a spell with li-ion as the way they just go flat without a warning really anoys me.With the Cad,s you get a warning and know not to climb a 3 storey ladder with the drill and a hundred screws to zip in

 

[xmetal]

Indeed the existing cells are unprotected Samsung 15Q from the 18650 family.

A useful comparison test here for 18650 cells.

 

[knighty]

I've done loads with li-ion cells

if you solder them, try to keep them as cool as possible

and make sure you buy decent cells, there's a LOT of fake ones around, and a lot that lie about the cells capacity

they're safe to handle, just don't try to cut them in half or anything silly like that (as if you would)


not looked at the hilti packs, but there'll be a number of cells inside some i parrallel with each other, and then those in series with some others

so something like

3 cells together in parralel
connected to another 3 cells
connected to 3 more

etc. etc.

if it's 18v it'll probably be 4 lots of cells in parallel
(which is really 16.4v max but they fudge the numbers to make things 'user friendly')

 

[ukracer]

I've done loads with li-ion cells

if you solder them, try to keep them as cool as possible

and make sure you buy decent cells, there's a LOT of fake ones around, and a lot that lie about the cells capacity

they're safe to handle, just don't try to cut them in half or anything silly like that (as if you would)


not looked at the hilti packs, but there'll be a number of cells inside some i parrallel with each other, and then those in series with some others

so something like

3 cells together in parralel
connected to another 3 cells
connected to 3 more

etc. etc.

if it's 18v it'll probably be 4 lots of cells in parallel
(which is really 16.4v max but they fudge the numbers to make things 'user friendly')

What I fail to grasp is how to charge them. To try and solve that issue I purchased a cheap pack from erbauer and took it apart...it was chaos inside with just one circuit board for all cells.

 

[xmetal]

What I fail to grasp is how to charge them. To try and solve that issue I purchased a cheap pack from erbauer and took it apart...it was chaos inside with just one circuit board for all cells.

I use a Xtar VP2 charger that charges up to two cells. It's one of the better makes of charger. There are some iffy chargers out there too.

 

[ukracer]

I use a Xtar VP2 charger that charges up to two cells. It's one of the better makes of charger. There are some iffy chargers out there too.

Yeah but I think my drill pack has 5 cells in it....

 

[xmetal]

Yeah but I think my drill pack has 5 cells in it....

One of these type of chargers might do for that then.

 

[ukracer]

One of these type of chargers might do for that then.

I have a few of these but when we ran RC cars we used NiCads and each cell was accessible so we could balance charge. I was not sure how lion took to being bulk charged..

 

[knighty]

What I fail to grasp is how to charge them. To try and solve that issue I purchased a cheap pack from erbauer and took it apart...it was chaos inside with just one circuit board for all cells.

charge them when they're in the pack or out of it ?

I assumed you'd be swapping cells like for like, so could just use the normal charger the drill or whatever comes with ?

not much point in trying to save old cells, once you're changing few, change them all - so no real need to test old cells (other than a quick voltage check with a meter for the sake of curiosity?)

 

[ukracer]

charge them when they're in the pack or out of it ?

I assumed you'd be swapping cells like for like, so could just use the normal charger the drill or whatever comes with ?

not much point in trying to save old cells, once you're changing few, change them all - so no real need to test old cells (other than a quick voltage check with a meter for the sake of curiosity?)

I changed my Nicads for lions to see how they did back to back..

 

[Ian X]

This is good. Obviously a few of you have tried with these and Ni-Cd packs. Since my original post I have skimmed some of the data sheets of the main suppliers, Sanyo, Samsung and Panasonic. What is interesting is that power tool demands and vaping devices appear to have created a fork in specification. The cells in one of the 36v Hilti packs I wish to avoid paying full rate on replacement are Sammy 18650-15Q. If you take a look at the spec they are really no more than laptop cells from the early 2000's, laptops have become less demanding as the chip producers make more energy efficient backbones for motherboards.
Those cells are weaklings in comparison to the rated continual drain current and capacity of current replacements for the same type of work. 25R is in common use for similar work.
With the Ni-Cd it is very cheap (now) to buy 20 to fuel a 24v battery without regretting anything apart from time spent. I doubted the ebay candidates rated at 2800mAh that I rebuilt several Hilti packs with but they outperform the original product by a good margin and still provide considerable grunt after many, many charge cycles.
The stick in the mud for Li-Ion packs appears to be the balancing circuitry for the trickery employed in connecting cells in both parallel and series within a pack. I doubt the importance if all of the cells are similar but the emphasis is enough to sow doubt.

 

[Ian X]

Best thing about Ni-Cd is that they are really are dirt cheap, the only visible cost is time with a soldering tool. The clock ticks on every cell available to us, whether in use or laid up, inclusive of Li-Ion. A look at the British based rebuild outfits will tell you that none of them deal in Li-Ion. There are several companies in Europe that will sell you an exchange on them and some in the US.
My original post was to sound out people who have tried with rebuilding Li-Ion packs but the question of how much use you get for your money over time has caused me to question where I stand on the use per outlay scale.

 

[Ian X]

I made an inquiry to batterybro asking for advice on a suitable replacement for the Samsung 15Q. They replied and say the Samsung 25R is the cell of choice. Asked me what quantity I was after. Still thinking of a way of asking for 50 without them replying with lolololololol!
There really is only one way to find out if the control circuitry is going to play nice with a different cell load and I intend to find out after I have been busy with a pressing matter, literally a pressing matter.
Regarding the dearth of Li-Ion rebuilders I found a Belgian bloke on eblag who rebuilds all of the quality manufacturers Li-Ion packs including Hilti so it seems that possible has become certain as regards me and you doing the job if the fancy takes.

 

[knighty]

how are the cells wired up ?

for normal cell balancing, the balance board is pretty simple, it lets the cells charge as normal until either a set of parallel cells or the whole pack hits a max. voltage

any cells over a certain voltage get drained, slowly (normally just through a few resistors to make heat)

in use, the pack is charged till a cell hits the max voltage, charging stops, that cell is drained down a little bit, charging starts again


balance board also watches to see if a cell hits a min. voltage... if it does it cuts power so you don;t over-discharge them



and just to be tricky... some battery packs the board will only look for a min. voltage to protect the pack, and let the charger do all the other work (better system tbh, but needs more charger/battery connections)

some let the circuit in the battery pack do all the work and the charger is pretty dumb



but the good news is.... all these power tool battery pack circuits are pretty simple and won't care at all about the battery capacity, only the voltage :-)

 

[Ian X]

how are the cells wired up ?

The most pertinent and as yet unanswered question. I have removed the shell from the Hilti B36 pack type, looked at the construction and not recorded the connection sequence. Short of breathing my last I endeavour to complete this thread with a yes here's how I did it or hope you have more luck than me. I found that soldering 18650 end caps is very easy. I considered buying a cheapo spot welder but it really is not required. An 80W gun iron with nice old fashioned lead solder wire and Frys flux does the job without much fuss or heat inside the cells. I had the good fortune to have a Lenovo battery die last week, I stripped it and wetted the cells with solder, scothbrite rub and flux and all good.