Using Lithium Ion Safely in without BMS situation

[dnmun]

from your diagram, you have assumed that because the total voltage across all 4 of the cells is 16.4V then each cell will be limited to 4.1V. that assumption is wrong. the individual cell phone chargers do not have a way to stop the cells from being charged above the 4.1V level because there is nothing that can drain off the current flowing into it from the bulk charger.

if you had a balancing element, on each cell, that limited the voltage to 4.1V then you could manage to balance the pack very fast this way. but your balancing element would have to be capable of draining the amount of current being pushed by your bulk charger.

it would be more effective to turn off the bulk charger immediately when one of the individual chargers reaches the 4.1V endpoint. that would be the most effective control.

you could do that by having an opto isolator chain driven by the individual isolated chargers, and when one of the chargers signal endpoint, then you can take current for the opto isolators from the op amp inside then you could use that op amp output to turn off the bulk charger. you could even use the opto transistors to control the internal circuits of the charger so it would be done electronically and not by a relay type switch. that way the bulk charger could be active and when you swapped out the charging cell the bulk charger would reset and start charging again, until another of the cells in parallel would reach endpoint. then when the led went off and the bulk charger turned off, you could pull the cell out and put in the next one.

have you taken apart the cell phone chargers already? the opto transistor is along side the transformer, the four legs that cross that electrical isolation gap between the front end and the back end of the cell phone charger?

 

[etriker]

Ok. I have found these cell phone chargers called as Desktop chargers for the fact that one needs to take out the battery from the cell phone and fix the battery onto this charger in a clamp where it gets connected with the contacts of the battery. Some LEDs show it is charging by blinking. When the charge is complete the LEDs stop blinking and fully lit. I plugged in one cell and found out that it really works well but it takes the cell to full 4.2 and secondly it gives pulses of voltage going and up and down instead of stable voltage to the cell for charging. Moreover, it took an entire day for a single cell to get charged (approximately 11 hours). For a 5p it might take days to charge them. I opened the charger and found out that it is some chopper type charging unit with some micro chip installed also a transistor and some LEDs. I will post a video later on.

I just did a diagram (self explanatory) tell me would it work having only one side, either A or B charging which both the sides A & B connected all times?

I think I will keep the Desktop chargers as a part of battery with a 220 plug to charge the battery at the office which will also balance the pack, while quick series chargers (4 of them for all 4 series of 5p4s) for home charging. (Total of 5p16S).

My Hyperion charges using pulses of voltage to charge, not steady voltage.

I am thinking when charging a cell with no balance wires it pulses the cell then reads the voltage so it knows the voltage on the cell.

Otherwise the charger can't know the voltage on the cell without balance wires on the cell as long as current is flowing through the charging leads because of the voltage drop on the charging leads.

 

[USAEBIKECO]

Short distance rides under 5 miles you can get away without using a bms, but be careful and monitor the cells while charging.

 

[numberonebikeslover]

the individual cell phone chargers do not have a way to stop the cells from being charged above the 4.1V level because there is nothing that can drain off the current flowing into it from the bulk charger.

I mentioned earlier that only one side of charging system will work at one time, not both. The bulk charger has its own cutt off mechanism pertaining to an LM741 operational amplifier IC with a relay to cutt off charging at the right voltage at home, where I can pay full attention to the cells. While, the cellphone chargers that have a factory made cutting off system would be the part of the battery pack all the time connected with the cells to check for the voltage, while charging on the office desk.

you could pull the cell out and put in the next one.

For every 5p4s there is a separate bulk charger.

have you taken apart the cell phone chargers already? the opto transistor is along side the transformer, the four legs that cross that electrical isolation gap between the front end and the back end of the cell phone charger?

I am sorry to disappoint you but my electronics is not that good.

Thanks from the bottom of my heart for taking the precious time to put your feedback in my thread.
Yours Respectfully
Naeem

 

[numberonebikeslover]

Short distance rides under 5 miles you can get away without using a bms, but be careful and monitor the cells while charging.

That is what I have in mind. Bigger pack and smaller the distance.

 

[numberonebikeslover]

This is the 3s battery on a 2 amp bike's light bulb. The meter is connected to take the reading.

 

[numberonebikeslover]

OK, I get it now. You want to be able to do it more than once, not just charge your own pack safely.

It is something like I want to make more packs like these because my other projects like Teadpole Trike and Electric Rickshaw is in the pipe line.

and I agree for the chemistry is far more dangerous than one can imagine. See the following video:
https://www.youtube.com/watch?v=SMy2_qNO2Y0

16 phone chargers, combined with 16 hvc boards should work well. Even where you are, I bet phone chargers are found in the trash.

Yes, following this I went to the market and found some which are called as Desktop cell phone battery chargers. You have to put your battery out of the cell phone and put it in to a mechanical clam like portion of this charger where it gets its connections from the charger and when you plug it in to the 220 plug it starts charging and cuts off automatically at certain HVC. I will put a picture of the same later on. The problem is that It takes almost 9 hours for a charger to take my cell from 3.7 to fully attain its charge in 9 hours. If i connect this to a 5p it might just take 2 - 3 days to charge them. But on the other side I think I would keep them for cell balancing and charge the whole thing in series to just roughly charge them to a certain HVC then to balance them through these small chargers.

Not simple, especially if you have to disconnect all your series connections. But that disconnecting could be handled by multiple plugs similar to what Icecube 57 makes. With such a harness, you could also paralell some of the 4v sections to use less lvc boards and chargers during the charge. So then you only need 8 lvc boards or 4 lvc boards, or perhaps, just one as you charge the whole assembly as one huge 1s battery. The set your cutoff to 4.1v for longer cycle life and increased safety.[/quote]

 

[The Mighty Volt]

There was a bombing this morning in Peshawar. Hope you are OK.

I have some spare bike parts, can I send them to you? Sprockets, free-wheels etc.

Do you have a relative maybe in London I can give them to?

Thanks and take care.

 

[numberonebikeslover]

I am sorry for I was at the office and so much busy with papers and files I did not pay attention although I am about 800 meters away in University of Peshawar.

About the spare parts; It would be too costly for you to send me spare parts which are easily available here in the market specially the sprockets, chains, freewheels and other stuff. What we don't have is the parts of electric bikes. like hub motors, controllers and all related stuff. But it is way to costly to send stuff through mail.

I don't have relatives but some research scholars of our University who might be studying there as one of my fellow faculty member of Institute of Education & Research (my old office) just completed his Ph.D. from Nottingham University about a year back.

Thanks for your offer and your concern.

Naeem

 

[arkmundi]

As an aside: There certainly are many ways to build and charge a battery pack of LiFePO4 cells without a BMS. Or to use yourself as the BMS, to manually monitor the pack and cells, during charge and discharge. Even balancing can be easily done manually. It is just time-consuming.

Regarding balancing, all the "cheap" BMSs simply make the cells all the same voltage, which does not necessarily mean charging them each to the same capacity, depending on the cells' internal condition, age, possible manufacturing flaws and variations, etc. So a BMS does not necessarily even give you the best capacity from a pack, unless it is designed to coulomb-count each cell's charge and discharge, as well as monitor it's LVC and HVC.

With a 12S A123 AMP20 pack, and ....
- Two CellLog 8S Battery Monitor 8001 (http://epbuddy.com)
- "Watt's Up" RC Watt Meter & Power Analyzer by Tenergy, through Amazon
- Smart Charger (6 A) for 38.4V ( 12 cells ) LiFePO4 Battery Pack (http://batteryspace.com)
- One Single cell chargers for LiFePO4 batteries (http://voltphreaks.com)
... I'm keeping my pack healthy with no difficulty whatsoever.

Procedure is:
1> know how far I can go on a single charge to stay out of the danger zone (<28.0 volts for the pack)
2> charge it with the smart charger afer a ride to full charge (~42 volts, taking about 30 minutes, at 6 amps)
3> check overall battery volts with the Watt's Up; If there is any difference from what I expect, assume a cell has sagged and proceed; otherwise, done
4> check voltage of each individual cell with the celllogs; expect 3.3 to 3.5 per; lower than 3.0 volts is cause to be proactive on that cell
5> at lower than 3.2 volts, manually balance that cell with the Voltphreaks single cell charger
6> if the cell continues to sag, replace it; I bought two additional AMP20 cells for that purpose; Agniusm's kit makes breaking down and rebuilding a pack a straight forward procedure.

This is essentially Dogman's suggestion on this and other threads that the BMS free approach is viable, with the right data and chargers. Note I get data on the pack charge, the Watt's Up, the Celllogs and the single cell charge. This approach is neither difficult or time-consuming. Its certainly easier than attempting to debug a BMS when that approach goes wrong, which it does frequently (as suggested on this forum).

 

[CanadianWinters]

I want to make this battery from the parts that I can resource here easily because I want to create a model which could prove beneficial and could be reproduced in how many numbers I want. If I accept your kind gifts, it will take the challenge away from my project and I like challenges. Every one can buy the parts and make I want to make every part my self and then assemble the whole thing together. Though it may not be a high tech product which could compete against a product from an international company but it would work for me.
Moreover, as I mentioned earlier I would use a relay cutoff mechanism through LM741 Circuit that I designed my self and would works just fine for a series of 5P4s cells.
Keeping in mind the high density of LiIon cells, I guess that long before my pack is half empty my ride will be complete.

Hi Naeem,

many of us have suggested ways of using the li-ion laptop cells without bms and suggesting charging and monitoring systems, but most of us use things available in the market that you don't have or that will be to expensive to buy or ship in/to your country.

I was thinking you can use computer atx psu to charge the pack, finding a way to modify them to suit your purpose. They can supply enough amps to charge your battery in reasonable time.Are they cheap to buy in Pakistan?
You can also use laptop power supply but I don't know if you can source those for cheap.

Keep us updated with your project!

8)

 

[numberonebikeslover]

I was thinking you can use computer atx psu to charge the pack, finding a way to modify them to suit your purpose. They can supply enough amps to charge your battery in reasonable time.Are they cheap to buy in Pakistan?
You can also use laptop power supply but I don't know if you can source those for cheap.

That is awesome idea. I can find laptop power supply quite cheap then make a transformer for each charging unit the question is that can they charge 4s cells. Because in the battery of laptops the cells I have seen are 2p3s. About computer PSU yes I can source them easily but I don't know how much they would cost. Moreover, what is the output voltage of a computer PSU?

Keep us updated with your project!

That will give me a lot of pleasure to share my experiences. How can I stay away from my family in ES who has given me so much love support and even funds to go on with my work.

I thank all of you from the bottom of my heart.

 

[CanadianWinters]

That is awesome idea. I can find laptop power supply quite cheap then make a transformer for each charging unit the question is that can they charge 4s cells. Because in the battery of laptops the cells I have seen are 2p3s. About computer PSU yes I can source them easily but I don't know how much they would cost. Moreover, what is the output voltage of a computer PSU?

You have different output voltages & amps from a computer psu for example:



The voltage from a laptop supply is often 18.5 or 19 volts, depending on the brand, for example:



I was thinking you could use the internal board of the laptop battery as HVC, only problem is those boards have an internal eeprom and stop working (they don't charge the battery anymore) after a number of recharging cycles.

8)

 

[numberonebikeslover]

I was thinking you could use the internal board of the laptop battery as HVC, only problem is those boards have an internal eeprom and stop working (they don't charge the battery anymore) after a number of recharging cycles. 8)

That is true for one of the official laptop assigned to me in my old office. The battery wouldn't give me much backup. So I opened the battery to source the cells (as I had to buy a new one for office) I found the cells quite new by their charge and capacity then I realized that it is the board on battery that wouldn't let them to be used any more for the fact that they were done with the number of cycles they were meant for. Any way my other mechanism of LM741 will work just fine.
Thanks for useful information.

 

[numberonebikeslover]

Hello every body;

After discharging the battery 3s today with a 25 watt 12 volt motorcycle head light bulb I used the bulk charger to bring the state of charge quickly up in 30 minutes approximately till half or more then I connected them with each single cell as per the previous diagram I have shown in the following picture.

I have opened the desktop chargers (see the following pictures) and discarded all the rest except the main board having its LEDs to show its status (Cell connected, charging, charge full etc.)

Due to the use of bulk charger to bring the charge level up to half or near to full helped these small chargers to balance all three by checking every cell individually for their state of charge and on reaching full they lit their LEDs full to denote that the charge is full.

Do put your precious feedback for any query feel free to bother me, I would be more than glad to answer.

Sincerely
Naeem

 

[numberonebikeslover]

Hello every one.

At last after searching every where I found a source where I can get a good bulk of Laptop cells for as low as Rs. 100/- (1.03 USD) a cell. Earlier the supplier was asking for Rs. 200/- a cell but this time I looked for his source and I went to the main source. It is a technician who repairs the laptop batteries and have so many discarded laptop cells. He promised me to test each cell for its voltage and guarantee it on the base of voltage. I had to pay him some advance for 120 cells of Rs. 3000/- only (remaining amount = 12000 - 3000 = 9000. It would be such a pleasure to put my hands on 120 cells and start the work.

In pursuit of my graduation I have to take an exam and for that I am busy with my studies these days. I will start my work on the battery soon after my exams.

Till then Ba-bye.

Naeem

 

[numberonebikeslover]

A smart idea to hookup 6 cells in parallel using copper sheet (the one used for making the Printed circuit boards) and rubber bands cut out of rubber tubing. I will post the statistics and details later. Right now I need to rush for office.

 

[numberonebikeslover]

I have got 60 cells (half the number) till now and being promised to be given the rest today.

I have checked all the cells and found different voltages and different brands of cells. I categorized the cells as per their voltage readings i.e. 4 and above, 3.9s, 3.8s, 3.7s, 3.6s and below the range of 3.6 which also included some reading 2 volts and below.

The plan is to charge all the cells for the first time using bulk charger and take them to certain safe point of charge.
Then charge it using the desktop chargers which are specially designed for the purpose which will ensure a good state of charge.
Then leave the cells to stay on desk for about 24 hours. After which the cells will be checked for voltage and a categorization of good, better, best cells would be made, alongwith identifying the bad cells as well.

According to my perception:
Good cells are those that stay near 4 volt (3.8 to 4.08 etc.)
Better cells are those that stay above 4 volt (4.09 to 4.15)
Best cells are the ones that reads (4.2 and above)
Bad ones are that below 3.5 volts

It is quite time taking and indeed two much work.

For bulk charging I am using a laptop charger (20 volt) having 4s configuration having 10ohms 5 watts resistance in series and not letting the charge go beyond 17 volt for 4.2 is the highest limit of voltage where a lithium ion could be charged. Technically speaking 4.2 x 4 = 16.8 but I take it to 17 which is about 4.25 volt per cell.

After taking apart the series I found out that some of the cells are not equally balanced and there are balancing issues. For example I took apart one series and found out that I have following voltage of cells:
3.75, 3.81, 3.83, 3.99. Before charging these cells were reading below 3 volt and I thought they were dead. Now I put them in the aforementioned categories as per their voltage.

This way I kept on charging the cells and kept shifting them in higher category cells. After finishing this phase I will charge them using desktop charger and ensure smart charging and leave these cells for about 2 days and see what the voltage reads.

State of charge and voltage reading are two different aspects; is that a right statement for lithium ion? If that is so then I would need to put each cell to the test and see which cell is what category. That is too much work again.

Any way thanks for being with me guys.
Yours truly,
Naeem

P.S. A web link about charging a Lithium Ion battery: http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

 

[numberonebikeslover]

Hello every body;

Connecting the Cells in series and charging them with a 20 volt supply putting a 10 ohms 5 watt resistance in series to lower down the amps to a safe level, as each cell is about 2 amps each. It is ideal to charge them at .5c or .2c. Moreover, paralleled cells tend to balance each other more readily then series connected. I have cells that it would take almost weeks to charge them to a balance. Therefore, I was in dire need of a supply that could give out at least 5 volts. Got an idea; why not use my transformer (a huge one, using bibon sizing 2.5 x 3, weighing about 30 kg) 220 volt in and out 24+24 volt. How? The transformer has gape between the core winding in the center and the side iron arm of E at both sides of the coil. I intend to wind few turns on it to the desired 5 volts. well to calculate the voltage per turn of wire around a coil in a transformer I have a formula:

voltage per turn = 8/total area of the coil. .........putting values we get
= 8/(2.5 x 3)
= 8/ (7.5)
= 8/7.5 = 1.0666666
It means that if i turn about 6 turns I will get around some where 5 volt. I had no magnet wire but had a aluminum wire used as magnet wire for the cost and weight reason in big transformers here. So I wound 6 turns and got about 5.2 volts almost ideal for Lithium charging.

I have paralleled 29 cells and put them on charge. It took about 24 hours to make them reach 4.23 volts. I took the pictures and here I am putting all in ES. Such a nice feeling after a success.

Please note following things: The cells I gather for this series had almost same kind of voltage. Moreover, I have also made sets of cells having same voltage before charge and decided to put them parallel with their kinds in order for accuracy.

After charging them to 4.25 I will take out the cells and store them off charge for about a day and then notice their voltage status. If they stay beyond 3.8 they are useable.

There is one more thing worth mentioning: The positive terminal wouldn't touch the copper plate in some cells which is bad in my situation therefore I put a small drop of solder on the terminal, making a small raised area which will make sure that it may touch the plate.

Ok guys bye for now.

Yours Sincerely
Naeem

 

[numberonebikeslover]

Hello every body; (Assalam-O-Alaykum, meaning May Allah shower His blessings upon You);

I have took some readings of my cells which were charged a week back were of following categories as per their voltage.

4.2 and above.
4.1s
4.0x
3.9x

It may be the case that some of the cells below 4.2 were not charged well enough, therefore, I’m intending to put them to charge in parallel (of same voltage readings).

A question for senior members:
I am charging with the aforementioned transformer, putting about 18 to 24 cells in parallel. A meter takes the reading. The charge raises to 4.2 then I stop, the charge again goes down to 4.08 to 4.01.
Can I charge them safely beyond 4.2 so that when I stop charging it would read 4.2x?

Thanks for taking time to read my thread. May Allah bless you all.

Sincerely, Naeem

 

[SamTexas]

Laptop batteries should be charged at 0.5C or less using a CC/CV charger. I've never used anything higher than 0.3C. The highest voltage is 4.20V. A CC/CV charger lowers the current to almost nothing when the batteries voltage reaches 4.20V and keeps it there for a pre-determined time or until the current drops to a pre-determined threshold. Once charging is complete, the batteries should be separated from the charger (to prevent current from flowing back into the charger). A good, healthy battery will hold the final voltage (4.18 to 4.20 depending on the charger) for at least 12 hours. Any cell that drops 2% or more after 12 hours is bad.

Example: Cell voltage = 4.18V one minute after removing from the charger. Cell voltage after 12 hrs = 4.09V. Bad cell.

A good, healthy cell voltage would never drop more than 1% after 48 hrs (4.14V from 4.18V).

You might want to read the first 3 posts in the "Info on Laptop 18650 LiCo Cells" thread.

No you should not charge at a higher voltage than 4.20V. All manufacturers set 4.20 -/+ 0.05V as the absolute upper limit. That said, I have used higher voltage charger (4.56V terminal) to charge my cells, 4.35V under charging load and 4.20V after charging load is removed. No immediate negative effects, but who knows what happens to the longevity of the cell.

 

[Dlogic]

For my custom built 6S*4P 18 cell Turnigy Nano Tech 8000 mAh cell lipo pack i use 3 i-chargers in parallel. A 42 pin plug is used to establish all balance leads and battery + and - connections at once. Then all i do is push 3 start buttons on the i-chargers and the 3 big packs, made up of 4 individual packs each, get a safe balance charge.

For riding another plug is inserted that makes the serial connections amongst the 3 packs giving me the desired 72 volts at 32 Ah. It does take long to figure it all out and solder the plugs. After that though it´s just a matter of plugging in and charging up. With this setup there´s no need for a BMS as i´ve integrated 3 battery medics into the cnc machined dashboard, giving me a precise readout of every single cells voltage.

Prior to assembly all cells in those packs where charged one by one with a single cell charger. This is important as the i-chargers will have a hard time if the packs are to much out of balance. Not with one pack, but since there´s 4 in parallel i thought that it might take too long for the resistor banks in those chargers to balance them.

Bulk charging is another option, but i don´t mind a bit more work to obtain safety. There´s just to many horror stories out there when referring to lipo.

So far my packs stay in perfect balance. At a charge current of 18 A, it takes just 2 hours for the juice to return.

The charger disconnected.

The charger connected.

To prevent the medics from draining the packs, a 24 pole switch was installed. With a single turn all balance connections to the medics are cut. This switch also acts as my ignition for the motor controller.

 

[numberonebikeslover]

Laptop batteries should be charged at 0.5C or less using a CC/CV charger. I've never used anything higher than 0.3C.

First of all; thanks a lot for such a comprehensive response to my question. I am honoured and at a loss of words.
For the aforementioned charger setup I do not possess a charger like that but I did following.
36 parallel cells connected to two chargers; one giving out higher current rate (not more than .3C) while other very low current (.01C) When the voltage reaches the mark 4.20 I shut off the higher current charger. the voltage dropped to 4.09 volt. Left it over night like that with the low current charger. In the morning the reading was 4.1 so, left it on charge and instructed my wife to monitor for 4.20 volt. When I came back still it was 4.15. So I gave it high current charging with intervals of 3 to 4 minutes and did not leave my sight out of the reading. when it reached 4.25 I shut off the higher current charger. And by doing so again and again it reads 4.20 with low current charger connected. CC/CV charger do not exist here.

A good, healthy battery will hold the final voltage (4.18 to 4.20 depending on the charger) for at least 12 hours. Any cell that drops 2% or more after 12 hours is bad.

How good is a 4.09 volt cells because 60% of my cells are in this category. It may be the reason that they are not fully charged. May if i charge them at a very current rate would it solve the problem?

You might want to read the first 3 posts in the "Info on Laptop 18650 LiCo Cells" thread.

I am really grateful for directing me to the post because it is so comprehensive and it explains the practical experiences with examples. Thanks

No you should not charge at a higher voltage than 4.20V.

Meaning that the charger when connected to the meter before connecting to the cells should read 4.20 right? There is this problem of electrical fluctuation in our region of the world so the voltage is never steady. it fluctuates between 235 volt to 175 volts which definately affects the output of a transformer a great deal.

Yours Sincerely
Naeem

 

[SamTexas]

First of all; thanks a lot for such a comprehensive response to my question...

How good is a 4.09 volt cells because 60% of my cells are in this category. It may be the reason that they are not fully charged. May if i charge them at a very current rate would it solve the problem?

You're welcome.
I assume the cell can not hold any voltage above 4.09V. If that's the case, it's bad. Not acceptable, not fair, just bad or badly degraded. Cells like that are not worth keeping.

No you should not charge at a higher voltage than 4.20V.

Meaning that the charger when connected to the meter before connecting to the cells should read 4.20 right?

As far as the cell is concerned, the only voltage that matters is the one measured at its + and - posts (terminal). The voltage at the charger's ends is higher, so is the voltage somewhere between the charger and the battery.

You need a perfect cell to use as a reference for both capacity and behavior. PM me your address and I will send you a few brand new cells from Panasonic, Sony and Sanyo. Not cost to you at all.

 

[numberonebikeslover]

Having 60% of my cells at 4.09 state it was quite disappointing for knowing the fact that they are not worth. But I gave it a try any way and charged them at a slower rate and gave it about 24 hours to reach 4.27 volt on charging load. Then left them disconnected from the charger and took them apart to rest for 24 hours. It was observed that 98% of the cells reached the required 4.20 mark and stayed there for more than 24 hours. I kept doing so till I found 95% of my cells at this useful condition while others went down at different lower voltages like 4.0x, 4.1x, 3.9x, 3.8x and below 3 volts were all bad. I am at a short of 12 cells now and I am sure that my supplier will agree to replace some of them. If not then I would need to buy some from him with the surety of good cells.

Thanks a lot SamTaxes I really appreciate your offer. I have PM you about the address.

Yours Sincerely
Naeem