18650 lithium cell need help understanding risks

[infringer]

Okay,

I have read tons of info on these cells. And while there is an inherent danger to using different cells for different applications I am curious about something that really need to have some solid evidence on.

I have a drill battery pack and it contains some INR high discharge cells which are "designed for power tools" and I have some laptop cells that are designed more geared for capacity rather than high discharge.

Are you supposed to use them no you are not according to what I have read and I am not telling anyone to do it either this is strictly theory.

Now here is the other key element of the battery pack you have the battery control system.

Is it not true that the battery control system is designed to monitor health of a battery while in use or while being charged in all cases?

If this is so than would the odds be that explosions would not result from using this battery in my drill the BCS does not know chemistry it just knows battery voltages, and temps I know this is true.

I have a feeling that someone will chime in and say something to the order of don't do it if the BCS fails than you are screwed or it's your life or whatever do not do it but the real question is if the BCS fails in any occasion I have seen the battery does not work and if there were some quirky thing that would go wrong and allow the battery to keep running it would do the same thing no matter which cell you put into the pack right?

The IMR or INR based cells may be able to tolerate it a little better but in truth how much of a percentage safer would you be in that case using a high discharge or not my guess is your safety would be roughly the same in any case if all of the safety fails just enough to let this occur you may have a very small percentage of a chance that your battery being an imr/inr is going to save you because it all boils down to well boiling point the electrolyte is going to vent out no matter what at the same temps right?

So would my theory be correct or is there something more to this that I am missing ? I am not asking for someone to tell me its OK I just want to know if I am understanding what I am reading correctly.

DO NOT TRY THIS IT IS ONLY THEORY AND DISCUSSION!

Results are pretty ugly when these things go. They look like this:

[infringer]

Re: 18650 lithium cell need help understanding risks

Specs of drill battery are as follows:

Nominal Capacity*1 1,300mAh / 18A
Nominal Voltage*2 3.60V
Charge Method Constant Current Constant Voltage
Charge Voltage (V) 4.20
Charge Current(C) 0.5
Discharge Voltage (V) 2.50
Discharge Current (C) 0.2
Dimension (mm)
Thickness / Width / Length 18.0 / – / 65.0
Max Weight (g) 43.5
Remark NCA

[infringer]

Re: 18650 lithium cell need help understanding risks

laptops batteries are rated at a 4amp discharge from what I am reading.

[infringer]

Re: 18650 lithium cell need help understanding risks

Little ohms law might be of the order here...

Resistance calculation R = V/I

Voltage calculation V = IR

Current calculation I = V/R

To me the discharge rate seems to be safe for operation unless my calculations are incorrect?

[infringer]

Re: 18650 lithium cell need help understanding risks

I'm going to go out on a limb here and suspect that a lot of the hazord may be hype from the rare instances of bad cells people are pushing the warnings as regurgetation to cover themselves from liability due the the over publicized events that took place during the explosive lithum summer resulting in lots of recalls. Which is fair I would do the same and adhere to the warnings but we are discussing theory here while use is likely impractical for the application and I would not use them I want some solidity and would like to know the error or holes in my theory? Please do help further my education on this subject.

NOTE I STILL DO NOT SUGGEST USING IMPROPRER CELLS AS WELL THIS IS ALL JUST THEORY AND SPECULATION I AM NOT AN EXPERT AND ANY FURTHER OPINONS SHOULD BE TREATED AS THEORY AS WELL DO NOT USE IMPROPER CELLS IT IS DANGEROUS!

[domas]

Re: 18650 lithium cell need help understanding risks

Well there is a lot of theory here. Lets be clear on what are you going to do.

You have a li-ion cell based drill. The cells are toast there but the controller is fine. You want to use some laptop battery cells you have around (p.s. i have 5 or 6 of them for same purpose, powering other electronics) leaving the original controller? If both batteries are 4.2V charge voltage, as there are some 4,1V versions (haven't seen any myself anyway), nominal voltage 3,6/3,7 can be different, you are good to go. Yes typical laptop cells would not like to be discharged to 2,5V/cell but:
a) those are used batteries you done give a flying fuck about
b) if their capacity is getting low at 3V you should feel that the drill is getting weak and should stop using it until recharge. But you have to confirm my hypothesis, if tool is actually feeling weak at this point with a multimeter

Li-ion cells are dangerous while overvoltaging, e.g. >4,2V/cell, over-current (e.g. short circuit), and physical damage (causing short inside, therefore over-current). Else you are good to go, and undervoltaging the cells is dealing with their lifetime, not safety.

[budm]

Re: 18650 lithium cell need help understanding risks

http://batteryuniversity.com/learn/a...oltage_cut_off

[kc8adu]

Re: 18650 lithium cell need help understanding risks

most of the packs run 2 or 3 and some even 4p.so the load gets shared among the paralell groups.
i rebuilt some makita packs with panasonic 2900's and have beat them up good.
like running the drill near stall for long periods.
no problem.
but if you do this and it imitates a roman candle i am nor responsible!

[infringer]

Re: 18650 lithium cell need help understanding risks

of course this is just theory furthering my knowledge and making sure I am understanding what I read thank you all for the affirmations on my theory... While I plan on using the correct cells for safety reasons of not getting my hand blown off or starting the house on fire as has happened I think it is good to have an understanding of battery storage technologies in this day and age.

[domas]

Re: 18650 lithium cell need help understanding risks

http://batteryuniversity.com/learn/a...oltage_cut_off

i do not think that this is applicable for li-ion cordless tool controllers, is it? I have a feeling that their controllers are way less complex. Aren't they?

[budm]

Re: 18650 lithium cell need help understanding risks

http://www.powerstream.com/li.htm
http://liionbms.com/php/wp_lovtg_cutoff.php

[budm]

Re: 18650 lithium cell need help understanding risks

Good power tools will have good protection in the batteries pack (not just batteries in plastic casing and terminals) and in the charger. I open MAKITA batteries pack and it has PCB with lots of power MOSFETs and IC, etc. also.
http://www.siliconmethod.com/li-ion.html

[barry wilkins]

Re: 18650 lithium cell need help understanding risks

Hi I rebuilt a Makita 14 volt battery with 4 cells that came from a laptop battery .I would have liked to use 8 cells to give me twice the power ,but there were only 6 cells in the battery. The drill will work for about 5 mins. with these cells ,it draws 3 amps.
At the moment I am designing a charger after I have finished this ,I am going to look at some Sanyo cells from a UK supplier ,you can get some cells that are intended for high discharge rates of 10 Amps so I might go for them.

[budm]

Re: 18650 lithium cell need help understanding risks

I have yet to find out how to reset the chip so the Makita charger will recognize the rebuild pack.
http://www.candlepowerforums.com/vb/...-LXT-batteries

[kc8adu]

Re: 18650 lithium cell need help understanding risks

i just use a hobby charger.my triton2 eq does just fine.

[infringer]

Re: 18650 lithium cell need help understanding risks

http://www.overclockers.com/forums/s...d.php?t=467302

Interesting thread...

[kc8adu]

Re: 18650 lithium cell need help understanding risks

sounds like he is simply retraining the fuel guage chip.
worn out cells just get worse the more you mess with them.

[infringer]

Re: 18650 lithium cell need help understanding risks

yeah may be oddly I was able to recharge some cells that were showing 0v 4 out of 5 of them actually one of them would not go above 1.3v and started getting warm I monitored the thing with a meter and a IR thermometer the whole time it was charging just to be safe so hours of looking at batteries is not my idea of fun lol but my rig was primitive a meter and a 5v 500ma charger hacked up with some gator clips screwed to a hunk of 2x12 the voltage held at 3.6v and it is about 9hours that has passed so I assume the cells are still good and they just fell asleep well 4 out of 5 of them. We will see I got a 18650 usb charger on order from xtar to safely top them off using the word safely loosely cause I will have to pay attention to it and make sure it doesn't overcharge the cell I will likely charge inside of an old computer case just to somewhat contain anything that may happen from topping them off but the cells look as good as new or I would not have even attempted it.

Finally I will say that the cell will not take a charge if it shows 5 v and does not change when your leads touch the battery's anode and cathode.

Do not try this I take no responsibility for anyone trying this I did this in a well contained and safe area with a fire extinguisher near by that is suited for this type of fire. Do not try it at home!

[infringer]

Re: @budm

@BudM

The makita thing sounds like a fun project do you have any information or close ups of the board to look at?

I would bet it is an SMT chip that can either be replaced or reset somehow it depends how they do it if they blow a fuse in some OTP memory then you would need to find a way to put it into factory mode to reprogram the memory or it may not be possible at all and it may just have to be replaced I think it is a poor choice to do this it causes conditions that drive the costs skyward its not like we have an unlimited supply of lithium so there should be conservation laws in place for this type of thing...

Personally I think they should require all manufactures to provide swappable cells for their batteries using a socket like a AA socket this would not only make it cheaper to fix your battery but it would make it more safe with less incidents...

I guess I just don't get it they do stuff like this intentionally to make more money under the guise of safety when in truth you are making it less safe there will always be someone that will try I think they should standardize all packs and start selling cells call me ignorant or crazy but it makes since to me "in the name of safety"

Whats more dangerous then throwing a soldering iron to these cells?

Not a whole heck of a lot and its harder then heck to get the solder to stick correctly as well requiring you to heat it up several times sometimes even after a quick sanding.

Anyhow I am interested if anyone does figure out the whole makita pack issue I wonder if other packs use a similar protection measure cause I have a battery with perfectly good cells except for one and I replaced it with a good working cell it shows that it is charged on the charger but when I throw it in the drill it does not work I didn't have time to test and analyze everything but it appears to me that either the board is bad or something similar has happened ... It is a ryobi pack...

I'll have to look into this a bit more could just be a bad component I suppose but it is showing voltage out of 20.1v which should be good .... but like I said could be something I'm missing on the board that went south not too familiar with it all I just started looking into it within the last week good to know about makita packs no wonder they are everywhere being sold as parts units. INR IMR based batteries should do for most all drills might be a good source for working cells for other packs if you get annoyed with their business practices.

[selldoor]

Re: 18650 lithium cell need help understanding risks

Hi Clearly Infinger you have done quite bit of research into this, so you may be able to answer this query saving me hours?

I have just aquired for free a faulty tablet in which among other things the power socket had been broken and pushed completely off the board.

I have managed to rebuild the socket and fitted it to the board.

Battery seemed to be completely flat - not a flicker on my meter. Anyway It did not come witha power lead so I have tested it with a multivoltage walwart set at the correct voltage and polarity and it does power up the tablet and when powered down a led flashes red ( Of course I have no idea what that means but hope it is recharging. I have however bottled it in case I damage the battery.

Question is can I recharge a lion battery with this type of multicharger will the "control" be in the battery or does it have to have a "special" lion charger.

EDIT - May have answered my own query -albeit with another question.: The batteries are still in the tablet not being charged externally so does the tablet provide the "control" required