Repacking lithium tool batteries?

softdown

Watching youtube podcasts has led me to believe that lithium tool batteries (think DeWalt, Makita, Milwaukee etc) are packed with standard laptop type lithium batteries, they are designated 18650 and are significantly larger than a AA battery - guessing approx. 66% larger. 

I'm guessing that it is routine with some experience and the proper accessories. Probably a bit of a challenge the first time. 

Hoping to find a member to advise on what to expect. 

BB.

Generally, batteries are spot welded to the bus straps (soldering generates too much heat for too long of period). And they use a spot welder for this (some random spot welders on Amazon):

https://www.amazon.com/battery-spot-welder/s?k=battery+spot+welder

You can make your own spot welder too. One example is using a transformer from a scrap microwave:

https://www.instructables.com/id/Spot-Welder-from-a-microwave-oven-transformer-and-/

Would that work for spot welding a battery? No idea--Just an example of a DIY welder.

-Bill

BB.

Also, here is a link to a forum that deals a lot with DIY battery projects (a "flashlight" forum):

https://www.candlepowerforums.com/vb/forum.php

They have a good amount of information on Li Ion batteries too.

-Bill

softdown

Very useful information BB - thanks! Plus it seems one needs these nickel tabs that are pretty inexpensive: https://www.amazon.com/0-15x6x50mm-Soldering-Capacity-Lithium-Battery/dp/B07PQP55CM/ref=sr_1_24?dchild=1&keywords=battery+spot+welder&qid=1595957853&sr=8-24

Somewhat decent spot welders cost about $200 and don't have a lot of reviews - while getting about 4.0 stars. More mainstream welders can be had for about $50 less and offer much better ~ 4.5 star reviews. 

That's my preliminary take on it. I don't see much usage for a spot welder outside of battery assembly - so far. Guess I'll pass on this adventure for a bit. 

softdown

On the other hand - no serious prepper should be unprepared for a lack of replacement battery packs. I just wish we had a member who had luck replacing lithium 18650 tool batteries with an affordable spot welder. I might, and I might not,  try this one for ~
$24: https://www.amazon.com/KKmoon-Integrated-Welding-Automatic-Accessory/dp/B085GF7PM7/ref=sr_1_21?dchild=1&keywords=battery+spot+welder&qid=1595981676&sr=8-21

EDIT: Such pens are accessories for spot welding machines. The vendors, to date, tend to gloss over that important detail. Few have been sold so far. 

softdown

This one has a good chance of getting a $130 job done - I think: https://www.amazon.com/BoTaiDaHong-Battery-Welding-Machine-control/dp/B07RGTTTF4/ref=sr_1_2?dchild=1&keywords=JD-IIS+Pulse+Spot+Welder+Welding+Soldering+Machine+for+Battery+Packs+3kw+110V&qid=1595983380&sr=8-2

What does this mean? "Note:  Please match the air switch above 30A to prevent tripping."
Does it need a 30 amp power supply? That can't hardly be on a 120 volt tool.

Nothing wrong with 47 hobbies? Right? 

BB.

As far as I can tell--That is just the spot welding tool. You have to still purchase another power supply to supply the current for the "pen".

A "supply" like this (just guessing):

https://www.amazon.com/Mophorn-Battery-Soldering-Portable-Batteries/dp/B07MZP2BK6

Or  a "kit" like this:

https://www.amazon.com/737G-Soldador-Bater%C3%ADa-Bater%C3%ADas-Funciona/dp/B07M9JSQ7L

Not sure that any of these are really that "good"... Your mileage may vary.

There are lots of small spot welder videos/kits/methods of making a spot welder (even using Lipo batteries as a power source, etc.).

Just depends on how far down the rabbit hole you want to do...

-Bill

softdown

Yes - I figured out the above pens are accessories for machines. 
My next post has a complete machine that gives me a decent vibe. Here is the "power supply" for the pens I was looking at - the pens BB is referring to.  This is the back of the spot welder I am close to trying out. 

I could recover that much money from fixing a few power packs. 18650 batteries are quite affordable. Roughly $6 for pretty good ones as I recall. I probably have well over $1500 invested in lithium power packs for tools. They last 5-10 years - or so. 

mike95490

You got me on the air switch.  I see no connection for an air line, maybe they mean the foot pedal remote ?
 Does the electrode move down to the battery pack, or does the user grasp the pack and stuff it up to the electrodes and then mash the pedal?

softdown

Getting close to giving this a whirl. Ordered a batch of Samsung batteries already. 

Noting the machine in BB's link requires that batteries be within very close proximity to the machine. The machine I linked offers a lot more space. 

My next question: Everybody specifies a 10 year life span for 18650 lithium batteries. Now that Duracell D, C, and AA batteries come with  "10 year life spans" - it does seem like lithium would do much better. Then again, these are rechargeable lithium batteries. Ten years is not bad but my how the years do fly by!

mike95490

Will you be matching cells by internal resistance or tested capacity ?

softdown

Buying new Samsungs made in Korea, matching cells is not a currently anticipated issue. 

As always this endeavor is opening up to more possibilities. Seems that Battery Management Systems should be used on lithium batteries. A subject I know nothing little about.

It should be nice to replace lead batteries with lithium when size and weight are issues. Size and weight are potential prepper issues. 

softdown

Didn't we have a brave soul, or two, endeavor to make their own solar bank batteries out of 18650s? While most of us marveled at the combination of characteristics the endeavor required. 

I mean - Tesla does it. Called the Power Bank? I'd like to see the material used to connect the batteries. I believe each cell has a fuse? That BMS must be a $ight to behold.

softdown

Wish we had more experience on this. There is a huge problem with calling nickel plated strips - pure nickel. Plus one seem to have a choice between ~$10 worth of nickel plated strips/pure nickel and ~$80 worth. This endeavor got complicated pretty fast.

BB.

There are "bare" 18650 cells, and protected 18650 cells (each cell has an over/under voltage and sometimes over current protection disc on one end of the cell).

You should look at the battery box and figure out if the original cells were protected or not (the pack can have extra connections to monitor each battery for over/under voltage and "commercial" battery packs probably do not used "protected batteries"). And if they are LiFePO4 3.7 volt or other chemistry battery.

Battery Manufactures generally do not sell "bare cells" to hobbyists. Worried about cells being stressed/damaged/catching fire/etc. if not correctly used.

Placing two or more cells in series, and unprotected, you do run the risk of "unmatched cells" behaving badly during charging/use. Many (some/most/all?) power tool batteries should have separate connection points for each battery in the series string so that the charger can monitor/equalize the batteries.

Charging the batteries to the same starting voltage (if needed) should be done too.

Here is a simple video showing what is in a 12 volt Dewalt LiFePO4 battery.

https://www.youtube.com/watch?v=CZVr2B4GMvM

Just so that you can see what is in a "typical" battery pack. Note--The person making the video did solder the batteries instead of spot welding the battery connections--Not good (overheats the ends of the batteries, one end usually has an over pressure vent which can be damaged by excessive heat from soldering).

-Bill

mike95490

Some cells have "protection"  it's a tiny BMS built into a dime sized wafer at the end of the battery, to prevent overdischarge.  Overdischarge is the really dangerous thing, it sets the cell up to grow dendrites at some random point in the future, and the dendrites short out the cell and you get a firebomb in the middle of your battery bank, which triggers the rest !!

https://batteryuniversity.com/index.php/learn/article/bu_304b_making_lithium_ion_safe

BB.

Here is a nice web page that lists many of the "protections" that can be "fitted" to a Li Ion 18650 Cell:

https://batterybro.com/blogs/18650-wholesale-battery-reviews/18306003-battery-safety-101-anatomy-ptc-vs-pcb-vs-cid

Hate to harp on this--But if you do rebuild your own Li Ion packs... I highly suggest that you recharge them outdoors/sheltered location on a fire proof surface (at least the first few times).

Not that YOU will have a fire--But if a Li Ion battery does catch fire/spill its guts out/etc., you don't want that to happen in your home or work shop (sometimes, a very hot fire and/or some very hazardous chemicals can be created/expelled from a failing Li Ion cell and create a very expensive/difficult to clean mess.

LiFePO4 is one of the safer Lithium chemistries (the 3.7 volt type you purchased??). But I don't suggest taking any chances.

-Bill

softdown

Seems the key to safely employing lithium ion batteries is the BMS systems. Nice thing about repacking is the ability to reuse the manufacturers BMS system. 

Changing the subject now. Doing more than two in parallel is generally discouraged due to safety. Think I have seen up to 11 in parallel. I need to study Li Ion BMS systems a lot more. Seem to mostly concern over charge and under charge conditions. 

mike95490

generally nowdays, actual battery failures are rare, unless the BMS fails.   Most failures seem to be related to over/under charge or car crash damage

And what's the wisdom of a $5K battery with a cheesy $30 "BMS" ??

softdown

mike95490 said:

generally nowdays, actual battery failures are rare, unless the BMS fails.   Most failures seem to be related to over/under charge or car crash damage

And what's the wisdom of a $5K battery with a cheesy $30 "BMS" ??

That is definitely not what I am reading. In fact I have encountered nothing that indicates that lithium batteries are now rarely failing. You are referring to automotive traction batteries which I is a bit of a leap. Though I am starting to study 12 volt lithium storage batteries. 

Lithium advantages:
Long life
Efficient charge and discharge
Deep discharge is safe
Light and small

Disadvantages:
Toxic fumes if they catch fire
Destroyed if charged when frozen
Perform poorly when cold
Expensive
Need BMS 
Not friendly to recycling 
Sellers still ask high prices for lithium battery packs that are for "parts only". Takes an optimistic buyer. 

softdown

mike95490 said:

generally nowdays, actual battery failures are rare, unless the BMS fails.   Most failures seem to be related to over/under charge or car crash damage

And what's the wisdom of a $5K battery with a cheesy $30 "BMS" ??

Yesterday I encountered a string of podcasts about lithium BMSystems. Apparently you are right and I stand corrected. 

Here is a $4.49 BMS preceeded by 37 pages of even cheaper BMS boards. It doesn't look bad either: https://www.ebay.com/itm/25A-Li-ion-Lithium-Battery-BMS-18650-Charger-Protection-Board-12V-Cell/114292277400?hash=item1a9c59c098:g:dK8AAOSwaSpfBBD7

Super cheap BMS boards are quite likely to fail. But it seems like a savvy user could easily replace the board - knowing that is the likely issue.

If we could get quality BMS boards for sub $50 I would be inclined to make my own 12 volt batteries. But the issue of being compatible with serial connections is a huge one.

Much of the attraction of off grid solar is the independence from the grid. The same attraction likes with making ones own batteries. But one has to really know what they are doing. Even many of the manufacturers make stupid errors which are easily avoidable. 

What does it take to make lithium battery packs compatible with serial connections?  Battle Born is one of a select few that seems to know what they are doing. 

Renogy, for example, is a large force in solar. Yet their lithium battery packs say this:  These batteries can not be wired in series they can only operate at 12 volts. Odd. 

Changing the subject a  bit but I don't see why someone would pay somewhat similar money when Battle Born offers a 10 year warranty and serial connections. 12 volt solar systems are toys in my opinion - OK for RVing and part time cabin use etc. 

mcgivor

mike95490 said:

Will you be matching cells by internal resistance or tested capacity ?

An air switch is a circuit breaker