Here is a good used source for 18650 batteries

[eccerr0r]

Re: Here is a good used source for 18650 batteries

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]

Re: Here is a good used source for 18650 batteries

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

[Saihah Fakhriyah]

Re: Here is a good used source for 18650 batteries

appreciated

[eccerr0r]

Re: Here is a good used source for 18650 batteries

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...

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

I was trying to balance them outside of the BMS balancing... with the other two that are weaker but ended up killing them instead....uuggh.

They are panasonic IIRC.

Unfortunately I have seen this also but this seems to happen to certain series of them but not all them

[eccerr0r]

Re: Here is a good used source for 18650 batteries

I was trying to balance them outside of the BMS balancing... with the other two that are weaker but ended up killing them instead....uuggh.

They are panasonic IIRC.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

Oh they charge fine, got them back up to 4.2V and they don't warm up...just doesn't hold as much energy as they used to.

BTW I overdischarged them to like 1V or so. Not down to 0 but well below the 2.5V typical low voltage. They were running 2S with a fairly substantial load, and were still producing electricity when I stopped it, but they have not behaved the same since.

This is weird what brand are these batteries

You are not using a BMS protection board

I will test batteries with out a BMS protection but not use them with out one

[eccerr0r]

Re: Here is a good used source for 18650 batteries

Oh they charge fine, got them back up to 4.2V and they don't warm up...just doesn't hold as much energy as they used to.

BTW I overdischarged them to like 1V or so. Not down to 0 but well below the 2.5V typical low voltage. They were running 2S with a fairly substantial load, and were still producing electricity when I stopped it, but they have not behaved the same since.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

I destroyed by overdischarging by accident.

Maybe not try this before you throw them out

Put them on a very slow charge over night and see if they will come back ( like 100 milliamperes or less and just keep an eye on them )

I have also done this in the past and sometimes they will come back but one cell at a time not a bunch of them together

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

I going to buy a couple of more of them and pair them up so that I the same exact number of cells for each side

Although the 7 cells one is a little odd 29.5 volt battery pack right now I do have anything that I use it on with out putting some kind-a of regular on it

I have a use for a 8 cell battery packs but not 7 cells
I have uses for a 6 cell battery packs but not 7 cells

Oh by the way I will not be charging it that way anymore I thought they were the same on both sides but they are not

It might have but I think it would be worse if you continuously over charging it which do not plan on doing

[eccerr0r]

Re: Here is a good used source for 18650 batteries

at least it didn't immolate...

Charging that high probably cuts some cycle life...

What will you do with the 6S vs the 7S halves?

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

It is really a 13s I was confused about this at first but if you take a volt meter you figure out that it one pack has 6 cells and the other one has 7 cells

I slightly over charged the the 6 cell side to 4.66 volts this is reason I such high milliamperes hours rating and the funny thing is that it did not over heat which was a good thing ( but it is a good thing that I was only charging it at one amp so each cell was only getting about 250 milliamperes it did get a little warm but nothing terrible to be concerned about )

The other side I did not fully charge I will have to redo it to get a more accurate milliamperes hours rating of this battery pack

Actually I need to retest the first battery pack again for a real milliamperes hour reading

[eccerr0r]

Re: Here is a good used source for 18650 batteries

It was the local store, alas there was only one.
I need to dispose of the cells I destroyed by overdischarging by accident. Probably holding around 500mAh now

How do you split a 13S pack in half?

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

Here is a super nice battery pack it tested way better than it is saying in the description

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

I tested half of the battery pack because I split it in half which is very easily done just take the buss bar off and remove a few screws and now you two 28.6 volt battery packs when fully charged and 21 volt when discharged

Now I going to test the other half of this complete battery pack before I split in half

1.5X4=6 amps hours what the battery specifications are I got 8182 milliamperes hours

I just got to find a low watt pure sign wave inverter and the solar controller that someone talked about in a post I recently read

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

I have started testing the batteries in this battery pack and I am not real impressed with the results so far

The rating for these battery are supposedly over 8 amp hours however it falling just short of 8 hours more like 7.2 amp hour not real bad but would be better if it were over 8 amp hours

But now let's see if the majority of them test close to each other if they do this would be great

https://batteryhookup.com/products/2...41044571062434

The description of this battery pack its says that it is 7s3p and 21 batteries but 7s 2p and there 28 batteries instead of 21 batteries so I suspect that the watt hours are not correct either

The description turns out to be correct very strange the way this battery pack was put together

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

Hmm... picked up a 4S 40Wh laptop battery for $1... Unknown condition, theoretically fresh off boat... Wonder how bad this pack is...

From EBay or some where else or from that surplus place that you mentioned earlier

[eccerr0r]

Re: Here is a good used source for 18650 batteries

Hmm... picked up a 4S 40Wh laptop battery for $1... Unknown condition, theoretically fresh off boat... Wonder how bad this pack is...

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

I have started testing the batteries in this battery pack and I am not real impressed with the results so far

The rating for these battery are supposedly over 8 amp hours however it falling just short of 8 hours more like 7.2 amp hour not real bad but would be better if it were over 8 amp hours

But now let’s see if the majority of them test close to each other if they do this would be great

https://batteryhookup.com/products/2...41044571062434

The description of this battery pack its says that it is 7s3p and 21 batteries but 7s 2p and there 28 batteries instead of 21 batteries so I suspect that the watt hours are not correct either

[eccerr0r]

Re: Here is a good used source for 18650 batteries

yes craptacular life. Should just get LiFePO4 cells and do away with the LiCo/LiMn cells...

Yep need to stop it from charging when done, though technically speaking they have protection boards that work for drones that pull large fractions of a horsepower. Starter motors are only like 4 horsepower max... and could work with more of the same circuit in parallel.

[sam_sam_sam]

Re: Here is a good used source for 18650 batteries

I'll have to see how much batteries I really want... and since these are perishable I really don't want to overbuy.

What I can tell you is if they are brand name batteries they last at lease 3 to 5 years that much I can tell you
You just got to check them every so often to make sure that they have not gone below a certain voltage which I have not been very responsive to so I have had some go bad because of my own laziness

But I would agree you about over buying them but I am going to build low voltage power high amp hour battery for my tablets I just have to finish testing a lot of batteries but the first project that I need to finish is the battery pack for the battery operated air compressor that I need to finish testing the batteries and I hope that I have enough of the same milliamperes hours rating that are close enough to each other and then make a 12 volt jumper battery pack out of some of them that use a PWM controller to being with then switch to a boost converter control the amperage to the vehicle battery until the vehicle battery can start the vehicle or least is the plan ( which I have to test this concept to see if it is doable )

I have seen some people on YouTube that have used this type of battery to start a car with the only issue is over charging the batteries that is the only reason I have not tried this yet but I have even thought of using 4 battery cells instead of 3 batteries but then you have an issue of the batteries not getting fully charged so I am not sure what the solution to this problem is