Here is a good used source for 18650 batteries

[eccerr0r]

Well, was trying to use that laptop battery pack as is, and it refused to give me any power. So I had to open it. Got 4 purple shrink wrapped noname INR18650E and they were *DEAD* or at least they were around 2VPC. They were marked 3.7V 9.62WhPC = 2.6Ah. No shorted cells. So, playing with fire, I tried using a power supply to charge them without protection. Seem to slowly take charge... though unsure about the quality of the cells, they seem somewhat balanced.
The pack seemed to exhibit about 0.5Ω ESR by cursory estimation at this SoC, alas, 125mΩ/cell which is kind of crappy. However they are still kind of really undercharged. Will have to check again after charging 1A for 15 mins or so which would be 0.25Ah... which really isn't much energy, but would be interesting to see their behavior at 10% charge...

--

At ~ 20% SoC the ESR has dropped to 85mΩ/cell. This is a bit better...

[Saihah Fakhriyah]

appreciated

[sam_sam_sam]

Originally Posted by eccerr0r

So, playing with fire, I tried using a power supply to charge them without protection. Seem to slowly take charge... though unsure about the quality of the cells, they seem somewhat balanced.

There is nothing wrong with charging them with a power supply that you can adjust the current and set your voltage at what you want the cutoff voltage to be

I would caution you on one aspect of doing it this way you need to monitor the temperature of the battery cell or cells now if you do not want to babysit them while you have them on charge ( any voltage below 2.5 volts that you plan reviewing to see if they are good I personally would do any more than 100 milliamperes or less with batteries that you are not sure of )

Then buy a thermostat controller and set for 100*F to turn off power to the battery on charge

This is why I have a SkyRc IMAX b6 battery tester for battery packs or single battery cells that I am not sure of because this charger has the temperature sensor cutoff that actually works the way it should

[eccerr0r]

Was using the "touch" temperature sensor. If it was anything like the other bad cells I've ran across (two prismatic "cell phone" cells) they were simply shorted cells which got hot as I charged them. Needless to say it was a waste of energy to try to charge them.

One thing that was "nice" that I could salvage is that the pack had a discrete thermistor in it. Was kind of surprised, though it sort of made sense because the cells were not right next to the protection board.

Indeed I was using my homemade CCCV bench supply. I initially started at 100mA until they hit 2.5V/cell which they did promptly. After hitting 2.5V/cell I started with 500mA until they hit 3V/cell, and then hit them with 1A for 15, and then another 15 minutes.

Not sure what the correct current limit for these cells should be. Thinking 1A should be safe, it's still less than 0.5C.

Now. Whether or not I should parallel them with the weak/bad cells I was using... turn that existing bad 4S2P into a 4S3P so I can share that underutilized protection circuit. These "new" cells are much better condition than the abused/older cells.

And ... I need moooorrreee... moooooreee cells... 38.5Wh is a drop in the bucket for the kWh I want to get. Alas still no capability to capacity test yet. Now this 38.5Wh was a lot cheaper per Wh than those other (2 pcs * 24V 6Ah=288Wh) packs I was thinking about getting. Those are much more expensive and thus risky to buy untested.

[sam_sam_sam]

Update on the use of this battery pack

https://batteryhookup.com/products/2...-6-4a-299-99wh

I have modify one of the half battery pack that I split into two separate battery packs one of them is seven cells the other one is a six cells

The six cells battery pack is the one that I modify I am turning it into a 3S8P instead of 6S4P
which is fairly easy to do but you have to be very careful removing the tabbing from the batteries that you are separating I just have to make a slot in the plastic battery enclosure for the extra battery terminal and wire into the the battery pack that I want to create

I also bought the metal enclosure for this battery pack that I plain on putting the battery charger board in this enclosure

I will post some pictures of it when I have finished the project

I have not decided what I going to do with the other half of this battery pack that is 7S4P
I might remove all the tabbing and reconfigure how this battery pack is setup
I might make it 5S5P and have three open battery slots that would not be used I just need to decide how I am going to use these batteries

[sam_sam_sam]

Well I had some time to work on the issue of battery charger for the air compressor that I bought I found a 21 volt switching power supply from EBay and found that at least this switching power supply charging the batteries with out over heating in a short time

Here is some results after 20 minutes of being on the center of switching power supply transformer has only gotten to 100*F and the top of switching power supply transformer is only 98*F which is hole lot better than the original switching power supply transformer was

https://www.harborfreight.com/20v-li...ger-63529.html

https://www.harborfreight.com/20v-li...ger-57006.html

If this works and does not get extremely hot then I will probably buy a few more of these switching power supply’s that are supposedly 3 amps

One note the battery packs that I am charging are mostly charged but this did not matter with the original switching transformer it still would over heat after a short period of time being on charging the battery pack

[sam_sam_sam]

Originally Posted by sam_sam_sam

Update on the use of this battery pack

https://batteryhookup.com/products/2...-6-4a-299-99wh

I have modify one of the half battery pack that I split into two separate battery packs one of them is seven cells the other one is a six cells

The six cells battery pack is the one that I modify I am turning it into a 3S8P instead of 6S4P
which is fairly easy to do but you have to be very careful removing the tabbing from the batteries that you are separating I just have to make a slot in the plastic battery enclosure for the extra battery terminal and wire into the the battery pack that I want to create

I also bought two more of these battery packs that I will reconfigure for the air compressor that I bought a while back I was going to use some other batteries but when I have done some testing the batteries have a self discharge rate that I am not completely satisfied with and going to use those batteries for something else that I can have them on a low cc/cv setup probably a solar cell panels that I have for lighting my shed/and power sign wave inverter instead of using the power grid at least that is the plan for now

I also bought the metal enclosure for this battery pack that I plain on putting the battery charger board in this enclosure

I will post some pictures of it when I have finished the project

I have not decided what I going to do with the other half of this battery pack that is 7S4P
I might remove all the tabbing and reconfigure how this battery pack is setup
I might make it 5S5P and have three open battery slots that would not be used I just need to decide how I am going to use these batteries

I have decided that I will be removing all the tabbing and reconfigure the battery pack for different batteries and for a 5S5P but have not figured out how I am going to lay out the battery cells in the battery cell holder that make the most sense

[eccerr0r]

hmm ended up taking the gamble on the 24V 6Ah packs...
hope this wasn't a huge mistake...

[sam_sam_sam]

I do not think that they will be a mistake because I just bought two more of them my self and I just got done with modification on one half of the battery pack I just can not completely decide on just how I want to do the other side of the battery pack that has 7S4P because I want to make a 32 amp hour battery pack for powering a boost converter for a project

I have only had a few batteries that have not been good at all and have gotten a refund for most of the money except for the shipping because I want to keep the enclosures for the batteries

But do not make the same mistake as I did and over charge one side because the configuration is a little weird take the face plates and count the battery cells on the half that you are working on so you which side has 6P and which one has the 7P

The tabbing is very easy to take off however the cells are very close to each other so be very careful when removing the tabbing

[eccerr0r]

Err... I took the gamble and bought those local packs when it went on discount.

6S - voltage was about 23.8V OCV, I tried to put a 2A load on them, drooped about a volt or so... which is actually not great, but it may still work fine. Ugh. Oh well, shipping one way would have killed the deal.

Now I wonder if I should stick one or both of them in the electric kick scooter and how far would it go. Original battery pack that failed in them were the common 12V 7Ah (20h) packs, wonder how well these Li-ion packs would work, and whether to incorporate one... or two of them...

[sam_sam_sam]

The results that you have might be better than you think for these batteries because these batteries are tools rated batteries and the voltage drops a little bit more than normal battery type

I just found out that my bench power supply volt meter is about 0.200 volts lower than it should be and slightly over charged this battery pack again so need to go by the voltage reading from the battery tester because it voltage reading is more accurate than the bench power supply

One other note about when you discharge at a higher rate the amp hours are a little bit lower than you expected it to be ( for example at one amp load you will get the results that the manufacturer has rated for this battery type [ 2.6 amp hours tested at one amp load you will probably 2.6 amp hours but at two amp load it might drop down to 2.2 amp hours or slightly lower than this

I found this a little strange the first time I ran these different loads on these battery tester but I realized that it because when it reaches the drop out voltage it stops the load testing but the battery recovery’s some and you can restart it and it will give you a little bit more amp hours and closer to the rating that you would get from a lower amp load

[eccerr0r]

I still need to set up a way to charge them

At least they have protection. Now I wish I have a calibrated meter, all my DMMs are out of calibration.

And yes indeed, the higher you draw, the lower the ampere hours. Always was familiar with this with lead acid batteries, though Li-ion is not as pronounced at least when they're in good condition. I think lithium ion won't kill you too bad but lead acid will die faster if you milk the last bit out like this...

I still think 83mΩ/cell is awful for a pack like this... should be lower I think. At 6Ah drawing at 1C would droop a half a volt, so that 4.2V would instantly be at 3.7V. Then I suppose the low voltage cutout would need to be less than 3V?

Now what should I do with these cells packs first...see how far these packs would take me on a e-scooter... if I knew how to ride one, in the snow...

If I'm not going to take them apart to reconfigure them to 3S and lose the protection circuitry with built in LED fuel gauge...probably should hack up a 3D model that can latch onto these packs. And probably hack up a charger. 25.2V is the magic number?

[sam_sam_sam]

Originally Posted by eccerr0r

If I'm not going to take them apart to reconfigure them to 3S and lose the protection circuitry with built in LED fuel gauge...probably should hack up a 3D model that can latch onto these packs. And probably hack up a charger. 25.2V is the magic number?

You could one of two things on you could get a buck converter and adjust it to 24 volts and use all the batteries from 48 volts or the battery pack that has the 7S configuration take the tabbing loose and make two 24 volt battery packs and just use the four battery that are left to be used as usb battery power bank for your phone or MP3 player or any other device you could think of these are just some ideas that came to mind

Well I have retested the battery pack that I split into two battery packs and split the 6S4P and made a 3S8P instead 15.25 amp hour at 10.50 volt roll off at 4 amp load very good results from these batteries

[sam_sam_sam]

Here are some pictures of the 7S4P modified to 3S8P fairy easily to do but a little bit time consuming to get it this way

[eccerr0r]

hmm need to find a way to safely drain 10+ amps at 24V...
probably should hook up to the scooter after all. That's a 250W motor which is just about right...

[sam_sam_sam]

Originally Posted by eccerr0r

hmm need to find a way to safely drain 10+ amps at 24V...
probably should hook up to the scooter after all. That's a 250W motor which is just about right...

You could use a incandescent light bulb bank as a load I use to it this way before I bought a battery testing machine but you had to calculate the amp hours and you have to stop the test when your battery voltage cutoff was reached

You might be interested in this item

https://www.mpja.com/specialsview.asp?r=ref&s=7

Watch the video to see all the features this device has

This device would be good for testing individual battery cells and you would not need to calculate running time or amp hours

[eccerr0r]

Ugh...hmm. Not sure how to charge these now either, my highest voltage wall wart is 29V which is sufficient, though at 1.5A. Would be 4h to charge one pack(!). Have to see if I can hack up something else, perhaps something I can draw off of ~60V and charge both at the same time perhaps, but need to prevent overcharge while still able to charge the other pack that's in series...

Ah the brick is was indeed 2A limit actually and was designed to be a battery charger, so it actually folds back if the pack is shorted or draws too much current, so have some safety here. Still need to limit to 25.2V, may have to hack up a small DC-DC converter to do this. Still 3 hours to charge at this rate not counting the drop off when the charge nears completion.

[eccerr0r]

OH KAY...
This 29.4V PSU, I need 25.2V for 6S
Well, lookey lookey, 29.4V is actually for 7S, go figure! Hah. Oh well. No 7S here - no prot board anyway.

Now I could add or even build an external step down from 29.4V to 25.2V... but what's the fun in that?

So, hack the regulator it is. Looks like I need to solder a 236K or a 267K resistor in now... sigh. No pots, 1% resistors only, looks like I have to manually bin.

Or if I remove the glued down existing resistors I need something like 42.1K... but past experience with glue did not leave a good taste.

Hmm. how to get this accuracy of resistors with my junk pile...

---

HO HO!

Well these are from my gold band, i.e. 5% resistors. Found a 47K resistor that was -0.6% off and a 220K resistor that was +0.13% off. Add them together and I get a resistor that's got 0.04% error to the 267K needed resistance! Close enough! Now I hope the math is correct, time to solder in and my 29.4V charger should now be 25.2V charger...

[eccerr0r]

And done. Not perfect but... after installing the two resistors my 29.4V battery charger is now 25.17 volts and will now charge my 6S packs safely. A quick test says 1.35A charge which isn't exactly the 2A limit but it's "OK" though this would mean, if it was only 1.35 when fully discharged, would take more than 4 hours to complete...

Still would like to be able to charge closer to 1C but good enough for now.

Now off to the discharge side of things...

[eccerr0r]

Tried to connect the two packs in series for 48V and fed it to a 1500W @ 120VAC RMS heat gun. It drew around 4A for about 175W and yes it spit out quite hot air. That is about the limit at 48VDC into a 120VAC device. As for capacity, not sure how long it can maintain this power... and now need to find something that can draw even more power...