screwdriver mod.

[kc8adu]

i suspect many here have these power screwdrivers too.
stand by for the full mod.will have usb charging too.

[eccerr0r]

Re: screwdriver mod.

I have a cordless drill whose batteries are dead, tempted to replace the NiCd cells with a homemade Li-Ion pack...

I have another cordless drill that has a working Li-Ion pack but the contacts to the battery have gotten so resistive it doesn't work anymore, Using a "good" connection with clip cables, it works just fine. Grr... Need to redesign contacts or something...

[momaka]

Re: screwdriver mod.

An unprotected 18650 Lithium battery driving a DC motor?! WOW!

I don't need cordless tools anymore, so I have retired/modded all of my battery-operated stuff to run off of some kind of adapter.
Like this usually:
https://www.badcaps.net/forum/showpo...5&postcount=48

[kc8adu]

Re: screwdriver mod.

will be protected when complete.
i got some good boards that can take the lra of the motor.
even if i went direct it would be ok as long as i have good charger control.
by the time it hits less than 3v under load its going to perform poorly anyway.
and 18650 cells are essentially free here so i dont really care if i shave a few cycles here and there.real danger is overcharging and recharging after draining way too low.like 0v by leaving iy on.tool has momentary switch.

[mutant]

Re: screwdriver mod.

Yeah charging is the most important. Did that with mine but used 2 rcr123 cause I had so many of them. The original nicads are now dead and a new one is just way too expensive. I get the same power except not quite as long and they keep a charge for longer periods of non use.

Glad you still put those tools to good use momaka.

[momaka]

Re: screwdriver mod.

and 18650 cells are essentially free here so i dont really care if i shave a few cycles here and there.

Yeah, I guess I could have done quite a few stuff with mine as well. But I just don't feel man enough to open up a lithium battery (mostly worried about it starting a fire in my house more than anything else). I had maybe 10 old laptop battery packs - none of which would take a charge, but I'm sure they had at least a few okay cells in them. Most were old P3-era Dell, so good quality cells (Sanyo, Panasonic, etc.). Actually, two of them got revived just by leaving them in my laptop - those are the only ones I kept. All the others I sent to the recyclers because they didn't want to "wake up" and have been sitting too long without being charged.

Glad you still put those tools to good use momaka.

Thanks.
Well, I don't use that drill a whole lot - it just seems quite a bit underpowered compared to my dad's 2-speed 600W Ryobi corded drill . But when I have nothing else, I do fire it up.

The one "tool" that I converted that I use the most is my camera. Normally it uses 4x AA batteries, but it drains them FAST! Can't defeat my 5V 2.8A power adapter, though .

[domas]

Re: screwdriver mod.

I have 3 li-ion mods around me. Of course, all of them ghetto, all unprotected.
1. ATX fan wired to small timer circuit on 6 li-ion cells that is forcing steam out of the bathroom. there was nofan before, just an ineffective ventilation line
2. Bosch Cordless drill. Used to have ni-cd/mh (can't remember) pack, dont have it anymore, there are 3 flat laptop battery cells under it. Functions as a stand
3. Dewalt impact wrench. Should have nicd/mh pack under it. Has 6 cell laptop batteries in a 2/3 of the 9 cell battery box (shape was better). Works as a stand as well.

Always charging using a smart charger

didn't bother to take a picture pf bosch. and yes i do use tape in ghetto mods. "It aint ghetto if you did not use any tape?"

[Kiriakos GR]

Re: screwdriver mod.

all unprotected

On eBay you may find 14,4 12A controllers very cheaply.
And for 2-3$ dedicated ones for single cell, dual cell and even more configurations.

When the reliable solution are cheaper than one ice cream why not following it so to prolong Li-ion serving life.

[domas]

Re: screwdriver mod.

nice, love those mods. Yes i know there are controllers, but my main concern is not overcharging (i use smart charger /w balancing circuit), not over discharging (i can feel when the tool is getting weak at 3V/cell) and as well as kc8adu I do not really care too much ;-]

My problem is that I am more afraid of short circuits inside the pack due to failed wiring inside, thus I would prefer using controllers for individual cells, so they are as close to cells as possible.

Question 1: if there are 3 cells in series, is it still okay to use 3.7/4.2 protection circuit on each cell? because thats the voltage differential over each cell, i don't think i need 3 12.6 circuits, do i?
Question 2: I am sure that the inductive kickback of my cordless drill will kill the protection circuit.. Any simple solution for that?

[clearchris]

Re: screwdriver mod.

Q2: I usually use an MOV. The trick is to make the clamp voltage high enough that the MOV is only active when the voltage is high enough to fry the circuit. Too low, and the MOV clamps all the time, you use the life up. When that happens, failure mode is flames. that's why I always epoxy a thermal fuse on the back. Thermal fuse probably not required though.

[Kiriakos GR]

Re: screwdriver mod.

Even in my 14,4 12A for four cells, its one cell is wired back to controler PCB, and he does the combining of all four.
In Li-Ion cells, simple math as 2+2=4 it does not work that way.

[domas]

Re: screwdriver mod.

I am not sure if you got me right.. my question was if i could use http://www.ebay.com/itm/9pc-2A-singl...item3f32b97401 for each cell and avoid using a single controller for the whole pack?

[Kiriakos GR]

Re: screwdriver mod.

I have no experience of how single controllers behave in series, I got only for dual and quad cells / 7.2V & 14.4V.

My prediction is that they work in series for handling the load, but in charging you have to do that individually.

[domas]

Re: screwdriver mod.

yes yes - my charger will take care of that. I have balancing cables going out of the pack

I guess there is nothing wrong in using single controllers

[Kiriakos GR]

Re: screwdriver mod.

Any charger not able to hold it voltage inside the range that controller tolerates as max charging voltage, will lead the controller to cut off and battery will not charge.

[domas]

Re: screwdriver mod.

typical protection controllers have cutoff voltage at 4.25V / 4.30V
have never seen more than 4.23V/cell on my charger (assuming that the values shown are correct)
even if it would be the case, it would happen at close to 100% of charge.

But if i try one day to do so, i will post it here how it works

[kc8adu]

Re: screwdriver mod.

getting good bms for single cells can be fun.rdson of the mosfet is often higher than ir of the cell.thats why i chose to protect for charging only.ptc in cell will protect against shorts/stalls.and individually protected cells series just fine.like in flashlights.first to lvd kills the whole stack.

[domas]

Re: screwdriver mod.

interesting perspective, i see.

So typical cylindrical cells have PTC's inside? I mean unprotected li-ions from laptop battery

[Kiriakos GR]

Re: screwdriver mod.

All Li-ions from laptop battery are controlled from the master controller in their pack.

[kc8adu]

Re: screwdriver mod.

yes each cell has ptc in the + terminal.

interesting perspective, i see.

So typical cylindrical cells have PTC's inside? I mean unprotected li-ions from laptop battery