I was just wondering if anyone here has ever added a protection circuit to unprotected batteries. I've seen cheap PCB's and solder strips sold on eBay, so it would seem it would be a pretty inexpensive upgrade if you're currently stuck with some unprotected batteries.
Edit: Just came across these on DX. Any experience with these here?
I realize that this is probably not the best way to acquire protected batteries, but I do have some that are unprotected and was curious if it has been done around here. I searched the forum but couldn't find anything related.
I have thought about that myself but it wouldn't be worthwhile unless you used decent quality protection circuits. Also people aren't fond of using soldering irons and lithium batteries.
I read the comments and watched that video, and it seemed to be a decent protection circuit to me! Looks like it cuts off at 2.75 on the low side (another comment said that it cut off at 2.37 V at 4a then recovers to 3.2V).
Looks like th high side cuts off at 4.25V. So to me it seems like a good circuit, and would prevent disaster. I must be missing something though, what's the downside with this?
And I did see some warnings of soldering on these batteries, and I think that mIght keep me from trying this at all. So I guess I'm just curious about protection circuits in general and what kind of qualities to look for in a good one.
The only thing put be back was the soldering process as heating the battery could shorten its life. I don’t know if I could make this cooler by using paste solder or not. You’ll need some kapton tape to insulate the tin across the battery, PVC shrinks sold on EBay or if you’re lucky you can find locally, a plastic spacer to lay the PCB on to, and not necessarily a tab for the positive side. I made a calculation and decided to buy protected batteries instead.
I've already purchased some TF Flames, but I have two other unprotected 18650's that I probably won't use much after getting the flames. Just figured this would be a interesting project to make better use of them.
What about using them on laptop/salvage batteries? I pilfer good batteries and they have useable tabs. By soldering on the tab, no heat to battery. Who has a good source for positive nipples?'…here comes trouble!
Maybe just a heat resistant tape and the circuits from Dx can do. I could only get PVC shrinks from eBay and those were bringing the main cost. The price for circuits drop quick if you buy above 5.
I really want to try doing this. Any recommendations with the soldering process? I have flux paste I can put on the battery first. I would imagine that having the strip tinned first would make it a quick touch and go, with minimal heating of the battery. I think I'm going to order a couple of the boards from DX, and some PVC shrink wrap from eBay. I'll start looking for some of that kapton tape too. I'm guessing it will be about a month before I get the supplies, so I'll update then.
I found these shrinks on ebay for $4.99 shipped. Found some kapton tape here on ebay for $2.18 shipped. So for about $10 I can put some protection on these batteries. Let me know how it goes for you, pictures are always good!
The protection circuit is used for more than lo-voltage cutoff - it also cuts current in the event of a dead-short.
The working current limit is also a PCB variable not mentioned here. There is little use for a PCB that allows no more than a 1.5A current draw, for example, with an XM-L.
Having been self employed for years, I can't forget paying the bills.
I think we have to remember the manufacturer is in this for a profit. There seems to be fewer buyers than builders need to make it worthwhile to bring these "logical" products to market.
When was the last time you went to your job and worked for free?
