Hi Ron @zander,

   Thanks for finding the sizing which I missed. That's a fairly chunky box to put on the bottom of a drill handle, though perhaps it wouldn't be too bad on other units.

  By the way, my understanding, albeit I have never seen one to test, etc., is that the 'protection' in the top of some cells is simply an over-current trip/limit ... i.e. it is basically a FET + simple driver, that goes open circuit when a massive overcurrent is demanded, such as if a short circuit is applied. Maybe a helpful function, but a long way from a BMS.

I presume vape cells are not really 'high current', as they need to be cheap, etc. .. just misusing cheap cells by momentarily connecting them to a very low resistance heater load, with no current protection. I am certainly not going to be testing them, anyway!

Best wishes to all, Dave

@davee That's a bit on the smaller size; many home power tools now use 18V or 20V batteries. I am not positive about the chemistry, as that would greatly change the battery box volume. Since I am not building houses anymore, I gave away my construction-quality tools to a friend's son and purchased a very small driver. It is only 9V, but it is perfect for what I need now.

I do not know if the protected cells all have the same protection, but at least some have the full suite. I think they use the TP4056 in some cases.

Vape cells are the HIGHEST current, requiring a MINIMUM of 15A. Since a 18650 has a max discharge of 25A, vaping is the most extreme use.

Hi Ron @zander,

 Of course, 18-ish V is common for power tools, but I don't think they all have 4 X 'columns' of 5 X 18650s in parallel for each. Hence, the battery box can be much smaller and easier to handle, albeit with less run time, between charges and possibly lower power motor, commensurate with the battery.

The TP4056 is a small IC, requiring PCB, etc, which can indeed be included in a battery 'box', but the 'protected' cells I thought you were referring to is a tiny circuit inserted near the anode of each cell of that type. You are right in suggesting the TP4056 might be compared with a 'basic' BMS, but not the 'hidden in a cell' type of protection.

Obviously, the vape cells need to be able to supply a high current for a short time … that is quite different from supplying a continuous high current. My understanding is that many (not all) cells for vaping have been sold as one-use, even though they are inherently rechargeable, and I suspect will have been manufactured for cheapness. You might physically be able to persuade a vape cell to operate continuously at high current, but my feeling, but not knowledge, is that such use will probably result in them getting hot, and may well end badly. Hence, I was trying to point out that I do not regard them as satisfactory 'high current' contenders when choosing for a task such as this thread is discussing.

Best wishes, Dave

@davee I am not sure of your point. A modern day professional tool has generally 20V with much more power and run time. I doubt they are using the same chemistry as the eBay battery, possibly LiPo vs LiIon but that would surprise me due to the fire hazard but certainly helps the energy density.

The TP4056 is indeed under the + end of the battery and is a feww mm longer so does not fit in a non protected battery holder.

Vape cells are sold as one time use, and rechargeable.

The 18650 cell comes in many specs. My RV had 6 100AH batteries, each battery was a collection of Panasonic 18650 cells. When I calibrated my inverter to set the trip points, I drew 400A (I used 4/0 welding cable). For giggles last summer, I ran one of my AC units, can't remember if it was the 13,500BTU or 15,000BTU for a few hours. Yes the cables got warm but it was very hot outside, maybe 32C.

Literally 10's if not 100's of thousands of RVs all over North America are using these batteries and many are in the south. I know folks with 10 batteries, that's 1,000Ah or 12,000Wh. With 2,000 Watts of solar on the roof in the sunny summer they will run the AC all day, and even fire up a second AC during the peak 10 to 2 or 11 to 3 part of the day. 

@davee My apologies Dave, we switched horses and neither of us noticed. The construction grade tools that are 18V with Lithium Batteries, are 1.5AH! Since 5 are needed to yield 18V but that would give 3Ah they must use 3 with a buck converter to raise the voltage from 10.8 to 18 but then reduce the capacity to the quoted 1.5Ah. That eBay battery is a MONSTER if it is 18V at 12Ah or what we call 5S x 4P (5 x 3.6 is 18V and 4 x 3Ah is 12Ah)

Hey check this out -

https://www.ebay.com/itm/144979568547

Looks like I am not the only one thinking of using these batteries for other stuff.

Bill

@greendragon Looks handy, but that is not the battery you showed us earlier, that is maybe a 1.5 to 2 Ah battery, the one you posted was a 12Ah. MUCH bigger. Also I do not remember seeing that it was a Makita.

In addition, I am not aware that the batteries from one manufacturer will fit in the holders of another. That would rob them of ongoing revenue so that will not happen.

@greendragon I am not sure if you know, but Dennis (@inq) gets his batteries from old laptop batteries that he disassembles. I can't do that here; we have laws that prevent that. You can check your location for a cheap supply, but of course, there are significant safety issues.

Just to recap for everybody I was looking at this listing:

https://www.ebay.com/itm/166320027173

At the 18V 12AH Version (Choose for select box on ebay page)

The following is the title of the listing -

12Ah 6.0Ah Battery For Makita 18V Li-ion BL1860 BL1850 BL1830 Cordless Tool USA

Bill

Hi Ron @zander,

RE:The TP4056 is indeed under the + end of the battery and is a feww mm longer so does not fit in a non protected battery holder.

I haven't seen one to play with, but I think you might be mixing the devices up.

Have a look at https://www.best-microcontroller-projects.com/tp4056.html.

TP4056 is basically a charging control chip, limiting charging current to a value of up to 1A, the value being set by choice of a resistor. ... This article shows the typical circuit board involved, complete with a pair of LEDs, and the schematic shows the only current flow that goes through it, is from the charger.

The cell protection from over-discharge uses a DW01A chip plus a pair of separate MOSFETs, also on the board.

Something like this could be integrated into some sort battery module, reminiscent of the drill power packs, but smaller, containing with just one cell. I don't see it being applicable to sitting under the anode cap of an 18650, even it is about 67-ish mm high.

-------

Equally, I haven't checked out the '20V' marked power packs that some power tools mention. It might be based on 6 cells of slightly different Li-ion chemistry, giving about 3.3V a cell, but the cynic in me is wondering if the marketing crowd are trying to make their tool look better, by considering the voltage when charging. Of course, this is just speculation, not a claim.

----------

So far as I can gather, there isn't much of an increase in energy density (specified in Ahr or Whr) with LiPo ... however, the LiPO batteries, but the maximum current/power output (specified in A or W) can be greater due to the reduced internal resistance of the modified structure.

----

I am aware that Li-ion batteries are widely used, and a few standard sizes, especially 18650, are often packaged up to form larger battery packs, including some variants as plug-in replacements for lead-acid accumulators which include BMS circuits.

---- 

re: 18V with Lithium Batteries, are 1.5AH

,,,

Since 5 are needed to yield 18V but that would give 3Ah they must use 3 with a buck converter to raise the voltage from 10.8 to 18 

Your suggestion is feasible, and once again I haven't disassembled one, but my first guess is they would still have 5 cells, possibly about half-height .. a sort of 18350 perhaps? Certainly the nickel cadmium and nickel metal hydrides cells were produced in a variety of sizes, and I see no reason not to do the same with Li-ion

Best wishes, Dave

@greendragon Be cautious. I noticed something earlier, I don;t see the word Makita anywhere in your eBay ad other than the ad copy. I took some screen shots, I don;t know if you will be able to see it, but as a photo editor, Ican see the blur that was used to photoshop the word Makita out of one picture. I then found that tool on the Makita site so you can see the difference. Also you can see the batteries are clearly labelled Makita. I guess as long as you can return them then go ahead, but first check if you are allowed to ship Lithium products, and if eBay allows returns on batteries (I wouldn't, too easy to swap an old for new)

@davee I mnay have got the part # wrong, but the 'protected' cells have both charge and discharge protection. This is from a very reputable website.

Lithium-based cells, however, don’t allow overcharging or over-depletion well and need protection from these conditions to achieve maximum life. These 18650 li-ion cells are protected against both of those problems by internal circuitry and also add short circuit protection for safer operation.

I just noticed this, I have not seen one yet but it is a different chemistry, shorter slightly narrower as well. 3.7V 780mAh cap. These may be in those high drain power tools.

Posted by: @greendragon

↑

Just to recap for everybody I was looking at this listing:

https://www.ebay.com/itm/166320027173

At the 18V 12AH Version (Choose for select box on ebay page)

The following is the title of the listing -

12Ah 6.0Ah Battery For Makita 18V Li-ion BL1860 BL1850 BL1830 Cordless Tool USA

Bill

Interesting!!!  I've bookmarked this for future study.  Thanks.  If I'm doing calculations right, this is something like a 5S3P battery of 18650 cells and you certainly can't get 15 for $19.

Bill, I don't know if you've read some of our forum's threads on LiIon batteries... the pros, cons, risks, etc.  Ron is instrumental in many of them.  There are a LOT of snake oil batteries out there... claiming 6000mAh out of a single 18650 which is complete and utter BS.  As Ron mentioned, I've had great success in scavenging 18650 cells from name brand laptops.  The Dell's and HP's cells are usually top quality Japanese cells.  They can't afford lighting up a laptop and getting sued... Deep Pockets.  I am meticulous in charging and discharging within their rated limits and have never had any trouble.  

I looked over the ad, but I don't see the dimensions... if that can hold 15 18650's.  Is the true Makita rated the same at the same size?  That would be re-assuring.

I just realized I missed this thread.  Don't know why, I'd have found it interesting... need to catch up.  I looked over you OP and it sounds intriguing.

I can give you a data point for if its enough Whr's.  You can certainly have enough motive power with 18V on right Nema-17's.  I'm using 4S or about 30 Whr.  My bot's a feather weight compared to what you're proposing, but I can easily get a couple hours on a charge barreling around.  Be aware that steppers pretty much use the same power whether they're still or not.  From what I've found, they actually use less power at full speed than sitting idle or tooling around slowly.  Depending on stepper drivers, you can disable them if you are still.  I take advantage of that as I expect to pause at locations and it greatly extends the run time.  If you use the TMC drivers and know how to program them, they can sense how much current it takes to hold or accelerate and vary that, thus extending range.

@zander I can see the blur that was used to photoshop the word Makita out of one picture.

Ok I know the answer to this one! Dumb as it sound if you post a picture of a Makita product with the Makita logo on eBay Makita can, and will sue you for trademark infringement.

Bill

@INQ Please note that the battery I am looking at is $45.00 (USA).