Using Lithium Ion Safely in without BMS situation

Big question;

Does internal resistance (IR) of LiCo cell increases with descending health?

I met one of the mechanic who is repairing laptop batteries. He is of the view that with descending health the internal resistance increases. He had a machine with two digital displays. One showing voltage while other showing IR. He says that the new cells have 40 ohms while the ones that we take out from discarded batteries have about 60 to 80 ohms. At 80 ohms they are worthless for laptops.

Finally found time and checked the battery. To my complete surprise the battery was way down (70 volt). checked the individual 6ps and found that two of them were showing zero voltage. Took them apart and found that one of the copper plat shorted the positive of plat with the body and destroyed all the 6 cells in a parallel. Oh God! after going through a lot of brain storming I think that soldering a good size fat wire would be more firm reliable.

Charged the individual cells to 4.2 and left them over night and found that I have lost 43 cells in the accident. That is quite a big loss for me. But I have not lost hope and have learned an expensive lesson. It is just that I got so busy with my office and were not able to even look at my bike. I love my e-bike work but to making a living is something that I can't get away with. So little time and so many things to do. Oh God help me.

Naeem
 
SamTexas said:
It's been a month since I sent you the laptop 18650 cells. You still haven't received them!?
It worries me also dear sam. Isn't there any way you could inquire from the company for the status of the goods. There must be a way to inquire about the package. Any ways, if it reaches my door I will inform you timely.

Thanks.
Naeem
 
That is a problem with those cells i think if you made a small gasket just for the pos. end before soldering or a wire with the insulation cut out for soldering ? You also need a big hot iron so as to have less time on pos. termanial. They can catch fire.
 
numberonebikeslover said:
It worries me also dear sam. Isn't there any way you could inquire from the company for the status of the goods. There must be a way to inquire about the package. Any ways, if it reaches my door I will inform you timely.

Thanks.
Naeem
Not a chance. Not one that I know of anyway. Once the package arrives in Pakistan (or any other south asian country), the US Postal Office no longer has control. OK, so it takes much longer than expected. Consider it "lost" if you don't see it in 2 weeks.
 
it is most probably being held up by the ISI wanting to inspect it since it came from the US. so customs has sent it to them to check before sending it to you i expect.

i really hope this does not make problems for you with the Quetta Shura.

we live in different world from yours so we take a lot for granted. but when i was young i had to worry about the FBI following me so i am more sensitive to the risk.
 
Some self explanatory pictures of which I will post the details later.
 

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999zip999 said:
numberonebikeslover
What the uckss of battery rainbows of cells you making. Junk from the garage is junk almost always. Most of the time. Second hand is second hand.
999zip999 said:
Sorry Bro but if you use
pklus or double plkus used cells there are just double plus used cells.
So get the biggest format and use them easily ect,
Are you becoming more and more of a jerk with every passing day? The knowledge he gains from working with "junk" in a few months exceeds the pitiful lifetime of yours. Why don't you go and promote OSN products which you know nothing about instead. Oh, and learn how to write too.
 
SamTexas are we all going to make batteries of used computer batteries cells of unknow used and go from there ? It's hard enough to guess on used cells as we all do like to save MONEY. So go buy from EIG or New A123 from Michigan or in the day ? How can you ?
 
Yes recycling used cells is the best way to understand cells if you know their life history or if not. It that's a lot of time finding the good form bad and still you have to monitor as not knowing when a cell could go south. Maybe even a fire ? All cells are not made the same.
 
numberonebikeslover said:
About setting the cutting off at 3.6; It might cut off when the motor starts or a little hill climb will temporary bring the battery to 3.6 then after when load is out it will rise back again. What do you think?
About HVC below 4.2: I noticed while charging one of the cells yesterday that when it reached 4.15 it started to generate a little amount of heat. I left it there then at 4.17 the heat increased but very little. So I guess cutting off at 4.1?
Putting a voltage monitor on every parallel unit means 16 units is very difficult and will take some energy to run all those.
Good Cells?
In my experiance, 3.6V rated cells charge well to 4.1V 3.7V rated to 4.2V. If at modest charge rate a cell gets warm, it is defective and should be trashed.
I found that any cell that bleeds down from desired voltage is defective and not worthy of use.
My preliminary test is to bulk charge a "lot" of cell to 4.20V for 3.7V cells, 4.10V for 3.6V cells, then separate.
Self discharge is my preliminary-primary condition indicator!
Any cell that self-discharges below expected build voltages is immediately "trashed".

Low Voltage Alarms?
Voltage monitors with low voltage alarms are dirt cheap, and monitor 8s - about $3 each.
Low voltage alarm is adjustable.
A static "empty" of 18650 LiCo cells is near 3.6V, under a modest load that might equal 3.4V.
A heavy load might set off alarm but alarm would quiet when load returns to normal.
"Empty" would be when alarm sound under "normal" load.
Determine your cells empty level , 3.6V? With cells at this voltage apply "normal" load, resulting Voltage should be your low voltage alarm setting.

Check - eBike Toolbox Bargains! $ 8s voltage monitors-alarms are $2.79, much more !
 
DrkAngel said:
Good Cells?
In my experiance, 3.6V rated cells charge well to 4.1V 3.7V rated to 4.2V. If at modest charge rate a cell gets warm, it is defective and should be trashed.
I found that any cell that bleeds down from desired voltage is defective and not worthy of use.
My preliminary test is to bulk charge a "lot" of cell to 4.20V for 3.7V cells, 4.10V for 3.6V cells, then separate.
Self discharge is my preliminary-primary condition indicator!
Any cell that self-discharges below expected build voltages is immediately "trashed".

Low Voltage Alarms?
Voltage monitors with low voltage alarms are dirt cheap, and monitor 8s - about $3 each.
Low voltage alarm is adjustable.
A static "empty" of 18650 LiCo cells is near 3.6V, under a modest load that might equal 3.4V.
A heavy load might set off alarm but alarm would quiet when load returns to normal.
"Empty" would be when alarm sound under "normal" load.
Determine your cells empty level , 3.6V? With cells at this voltage apply "normal" load, resulting Voltage should be your low voltage alarm setting.

Check - eBike Toolbox Bargains! $ 8s voltage monitors-alarms are $2.79, much more !

1-8S Lipo Battery Low Voltage Tester Buzzer Alarm $2.79
Programmable, individual bank LVA- Low Voltage Alarm
Displays pack voltage then individual bank voltages
Use multiple for larger packs. 2 for upto 16s, 3 for 24s etc.
I ran to front bars using 8 wire Ethernet cable (7s 25.9V Li-ion)
Use as voltage meter only, hook to wires going to 24V leds on throttle. (36V max)


These VMAs (Voltage Monitors-Alarms) can be built into pack or extended to bar for easy view.
I use an 8 wire ethernet cable for my 7s 25.9V builds.
16s could use 2 ethernet cables plus a 2 wire (speaker wire?) with switches to the neg terminals of the VMAs.
Continuous use is not recommended as there is a slight drain on banks 1 & 2, after many cycles there might be a noticeable voltage reduction in these 2 banks ,,, cured by occasional balance charge.
A switch on the neg wire at 1s will shut off the unit, when not in use, or merely unplug it.

You will be capable of monitoring:
full charge of pack
full charge of each bank
empty voltage of pack
empty voltage of each bank
Voltage of pack and each bank while under various loads

If "balanced" at peak charge, monitor bank voltage at deep discharge!

One bank at a lower voltage indicates some weaker, or a bad cell.
You can separate and retest or ... mark weak bank and add another cell-cells to it after recharge, equalizing banks by capacity!
This is an ideal method for large packs or when capacity testing of every cell is not performed.

Further note on the VMAs - buy multiple, they are cheap and there is some variance in accuracy.
Test accuracy when new and after reasonable use.
100th V volt meter recommended!
 
DrkAngel said:
Good Cells?
In my experiance, 3.6V rated cells charge well to 4.1V 3.7V rated to 4.2V. If at modest charge rate a cell gets warm, it is defective and should be trashed.
I found that any cell that bleeds down from desired voltage is defective and not worthy of use.
My preliminary test is to bulk charge a "lot" of cell to 4.20V for 3.7V cells, 4.10V for 3.6V cells, then separate.
Self discharge is my preliminary-primary condition indicator!
Any cell that self-discharges below expected build voltages is immediately "trashed".

Self-Discharge Test - Step One!
Present test on 3.7V - cells were charged to 4.25V, then
allowed to sit, potentially self-discharging for 1 month!
(These cell were previously determined to hold good capacity at 4.20V+) - see image below
Cells are now being sorted by retained voltage.
4.25V = A++
4.24V = A+
4.23V = A
4.22V = B
4.21V = C
4.20V = C-
Below 4.20V but above 4.15V for separate build.
Below 4.15V but above 4.10V tasked for bulk project ...?
Below 4.10V ... binned or experimentation?

Although testing is for being 4.2V capable, these cells will be charged to 4.15V or less, as a means of prolonging usable lifespan. DOD depth of discharge looks optimal at 3.65V.
Red line is results of capacity - mah/100th V test
Every brand, model, possibly batch, tests differently! I will post easier diagnostic method using 5V Meanwell with Ah meter and 100th V capable meter
Yellow line is results of same test on a specific type recycled Lipo.

file.php
 
So much stuck in office some work and pics below:
 

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DrkAngel said:
DrkAngel said:
Good Cells?
In my experience, 3.6V rated cells charge well to 4.1V 3.7V rated to 4.2V. If at modest charge rate a cell gets warm, it is defective and should be trashed.
I found that any cell that bleeds down from desired voltage is defective and not worthy of use.
My preliminary test is to bulk charge a "lot" of cell to 4.20V for 3.7V cells, 4.10V for 3.6V cells, then separate.
Self discharge is my preliminary-primary condition indicator!
Any cell that self-discharges below expected build voltages is immediately "trashed".

Self-Discharge Test - Step One!
Present test on 3.7V - cells were charged to 4.25V, then
allowed to sit, potentially self-discharging for 1 month!
(These cell were previously determined to hold good capacity at 4.20V+) - see image below
Cells are now being sorted by retained voltage.
4.25V = A++
4.24V = A+
4.23V = A
4.22V = B
4.21V = C
4.20V = C-
Below 4.20V but above 4.15V for separate build.
Below 4.15V but above 4.10V tasked for bulk project ...?
Below 4.10V ... binned or experimentation?

Although testing is for being 4.2V capable, these cells will be charged to 4.15V or less, as a means of prolonging usable lifespan. DOD depth of discharge looks optimal at 3.65V.
Red line is results of capacity - mah/100th V test (5200mAh - paired cells)
Every brand, model, possibly batch, tests differently! I will post easier diagnostic method using 5V Meanwell with Ah meter and 100th V capable meter
Yellow line is results of same test on a specific type recycled Lipo. (4320mAh - paired cells)

file.php

Pack Assembly - Step 2
After setting, for about 1 month, I sorted cells by retained voltage.
4.25V preliminary charge.
(These cells were re-re-cycled from my 2008 builds, plus a few "left-overs")

Results
4.23V+ = 52 cells
4.22V = 80 cells
4.21V = 52 cells
4.20V = 44 cells
4.15-4.19V = ~120 cells
4.10 -4.14 = ~20
sub 4.10 = 12 cells
(All cells are tandem.)

I felt it to be per-ordained that I should build my prototype 22.2V pack using the 96 cells available from the 4.20V and 4.21V piles.
6s 16P x 2600mAh cells = 41.6Ah.
And ... they fit snugly in the oem eZip RMB battery case!
Pack was constructed in 2 - 6s 8p modules.
Center screw post could be retained, but I previously removed it.
So I spaced the 2 modules with 1/4" paneling.

Cells were connected using the oem tabs, on the tandemed pairs.
I used 22ga tinned copper braid as balance connection wires.
The "power rails" were built using 10+ga tinned copper braid, ~40-50A capable.
10ga insulated copper wire used to connect the rails to the terminals.
Charging port 22ga wires replaced with 14ga insulated.
(25.9V 10A charger replaced with 22.2V 12A charger - MeanWell Mods)

It should be noted that I performed no capacity test on the implemented cells.
I am testing a theory that retainable voltage is a good indication of condition capacity.

Also, although I added balance wires, I have not, yet, added a balance plug.
I am planning on using a ethernet plug to attach to ethernet cable to balance charger or VMA (Voltage Monitor Alarm).
Should work nicely with 6s and 7s builds.
Ethernet plug could be safely covered with tape, when not in use?
 
Quote.

It should be noted that I performed no capacity test on the implemented cells.
I am testing a theory that retainable voltage is a good indication of condition capacity.

You would have to do a capacity test to to confirm the theory ?

Retainable voltage will relate to capacity but you need to relate it to capacity for the brand and size you are testing.

This requires you to test several cells for retainable voltage and then for capacity.

Once you know then you can watch the voltages on a brand and size of cell and get a good guess what the capacity will be.

Still won't know until you capacity test them.

For large packs with a large number of cells in parallel the cell matching may average out better without close capacity matching the cells but for smaller laptop cell ebike extender packs cell matching is more important ?
 
etriker said:
Quote.
DrkAngel said:
It should be noted that I performed no capacity test on the implemented cells.
I am testing a theory that retainable voltage is a good indication of condition capacity.

You would have to do a capacity test to to comfirm the theory ?

Retainable voltage will relate to capacity but you need to relate it to capacity for the brand and size you are testing.

This requires you to test several cell for retainable voltage and then for capacity.

Once you know then you can watch the voltages on a brand and size of cell and get a good guess what the capacity will be.

Still won't know until you capacity test them.

For large packs with a large number of cells in parallel the cell matching may average out better without close capacity matching the cells but for smaller laptop cell ebike extender packs cell matching is more important ?

"Capacity test" will be determined by checking voltage after 1st discharge.
Testing voltage of each bank at discharge ...
If all banks of reasonably equal voltage then all cells of equally retained voltage are, reasonably, of equal capacity-condition.
Of course, 8 cells in parallel ... "buffers" this assertion, but there are still 12 separate banks of cells, (balance wires not connected), if all reasonably equal then theory seems reasonable.

A "truer" test would have been not to install the balance wires.
Any "lesser" capacity cell would clearly demonstrate a lower voltage at depth of discharge.
If there is any noticeable variance, I will remove balance wires for more precise testing.

Will test DOD (Depth of Discharge) in steps.
 
I have many charts where I tested this and you can relate resting voltage and capacity.

The reason I do capacity checks on every cell is because I can, while the cells are all loose. :)

Write the numbers on numbered cells and in a chart in a book with dates they were tested and all.

I am studying the way they live and die. :)
 
I have seen A123 m1 cells that were below 1v and would charge up and put out over 2ah in a discharge test and discharge back to below 1v left sitting for a few days.

The retain voltage test is first for sure. You sure don't want a leaker in the pack.

When you do enough capacity tests on laptop cells you see how a good cell handles discharge right in the first min or so of discharge. If it handles the first min well the test goes on.

A bad cell can also be spotted in about a min or less of discharge. The test is stopped and the cell tossed.

You can hook the B6 to a display and see it happen and save the results with one of these and an old computer. :)


http://www.hobbyking.com/hobbyking/store/__7348__iMAX_Software_Kit_.html
 
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