How to remove protection circuit from 18650 batteries.

Did a quick tutorial on how to remove the protection circuit from Ultrafire '4000mAh' 18650 batteries.
I'm not sure if these are the same circuit configurations for other brands.

Purpose

The primary reason to do this to this battery is to stop the protection circuit from activating when high current loads are put upon the battery.

See how it affected my lasers here: http://www.youtube.com/watch?v=fyrsh3psIN4

Here's a animation i whipped up



The secondary reason is to reduce the length of the battery for what ever reason. e.g. the host you selected doesn't quite fit the battery and you need every mm you need!



Length comparison between protected and unprotected




Step 1.

Remove the plastic wrapping from the battery.



Wrapping removed





Step 2.

Remove plastic washer and/or metal positive terminal (this one fell off when i remove the washer, it wasn't secured properly, a good idea would be to solder it on).





Step 3.

Remove protection chip connections.
I did this by wiggling the 2 connections loose, you could cut them if you wish.





Step 4.

Remove plastic ring that is glued to the negative terminal.



Step 5.

All done!

Nice! This wont reduce power right? just decrease the length?

So why do you need to reduce the length...
Are proper sized Batteries not available...
Or are you just making do with what you have...:thinking:

Not sure if I'm missing something...
You didn't mention why you did the battery mod..


Jerry

elnicodor said:

Nice! This wont reduce power right? just decrease the length?

Click to expand...

That is correct if anything it would increase the available power, cause the chip can restrict current flow.

lasersbee said:

So why do you need to reduce the length...
Are proper sized Batteries not available...
Or are you just making do with what you have...:thinking:

Not sure if I'm missing something...
You didn't mention why you did the battery mod..


Jerry

Click to expand...

I did not do this to reduce the length, it was done cause the protection circuit was being activated when i turn on my laser(s) due to the current flow.

Umm, so the circuit was protecting your cell and you just removed it?

Exactly how much current does (did) your laser draw from that cell?

Im with BShanahan14, sounds like a good fix but it could also potentially damage the cell form to much draw. Maybe you need to upgrade your batts

Ra1nfade said:

Im with BShanahan14, sounds like a good fix but it could also potentially damage the cell form to much draw. Maybe you need to upgrade your batts

Click to expand...

It doesn't bother me, these batteries should be able to handle all the current a 1W laser pulls from the battery.

BShanahan14rulz said:

Umm, so the circuit was protecting your cell and you just removed it?

Exactly how much current does (did) your laser draw from that cell?

Click to expand...

Yes, if i short the battery out, its my problem. The only real problem i would face would be over/under voltage but that can be managed.

Im not sure, it was tripping while feeding a flexdrive at 1A so im assuming ~1.5A.

Fiddy;

Now, you understand why I don't like "cheap protection circuits".

Good job on your removal instructions. The cells will perform better without the circuit.

The very best new UL listed "brand name" cells are just now hitting 2900-3000mah.

Your cell is actually quite a bit less than 4000mah.

The Ultrafire 4000 is probably closer to 1800mah from the testing I have seen.

That loose positive terminal probably added some additional resistance to the cell.

Also the nickel strap from the positive terminal is only a thin heat shrink away from a short.
It should be insulated where it bends around the positive end.

Some boost drivers I've seen, are sensitive to excessive voltage drop (IR) in the cell,
and the driver will shut down in that case.

Let us know how the lasers work after your cell rework.

LarryDFW

Edit: Since I posted this, it has been reported that Seiko (Japanese) does make a protection circuit used in "quality" protected cells.
I have never seen one in dozens of protection circuits I have looked at.

Haha yes i do, i always had this quote by you in the back of my mind:

"questionable quality" circuit board.

Click to expand...

Yeah 1800mAh sounds about right for them.

Have you played with the Panasonic NCR18650 2900mAh & the NCR18650A 3100mAh yet?

Cheers!

Fiddy;

I am testing several of the 2900mah Panasonics . . .

as well as the 2800mah Samsungs.

The Samsungs so far, have the lower IR (internal resistance).

Edit: Test results in 1st Sticky thread in this topic.

Larry

interesting stuff, will be looking forward to seeing the results!

LarryDFW said:

Some boost drivers I've seen, are sensitive to excessive voltage drop (IR) in the cell,
and will shut down in that case.


LarryDFW

Click to expand...

This is the only reason I ask about how much current laser is drawing. Boost drivers will pull more current from the cell to convert into higher voltage, and at higher currents the cell voltage sags more. This is why if you set your boost driver to 1A, your tailcap current will be higher than that. How much higher depends on what voltage your load drops when being pumped with 1A.

Dug up this thread while looking for a source of high current single cell protection circuits. Will look for ICs made by seiko later. I did want to comment on Fiddy's cell above, just a random thought, really.
What if the protection circuit's main function is to make sure the battery discharges at a low rate to ensure that it makes it closer to the advertised mAh rating?