Using Lithium Ion Safely in without BMS situation

[SamTexas]

You're welcome. Got your address. They will be sent tomorrow (by airmail of course.) I have sent these to some of friends in SouthEast Asia and it usually took about 3 weeks to arrive. Have no idea how long it will take to get to Pakistan. Be patient.

 

[kennybobby]

Having 60% of my cells at 4.09 state it was quite disappointing for knowing the fact that they are not worth.

Take one of those cells and connect a load to drain it at C/2 rate, then monitor the voltage, current and time it takes to reach the bottom--there may be quite a bit of useful life in there and you won't know unless you test them. You would do yourself a favor to test each cell, and you would do even better (having no BMS) to bottom balance all your cells after determining the actual capacity of the cells. If you bottom balance and then only charge up to the level that fills the "weakest" or lowest-capacity cell then you can safely operate without a BMS and may be able to get some useful mileage out of those cells.

Don't keep trying to charge them to hold the last little bit, overcharging is how they get permanently damaged and can explode. Old used cells are "worn out" meaning they have lower capacity than when they were new, and they will never hold nor attain the original capacity, but there may still be useful life left for your application.

You may already know all this, but how do you determine capacity? Depending upon the chemistry you will have spec voltages for charging and discharging. Set up a load to drain each cell at 1C or C/2, C/3, whatever you feel comfortable, and monitor and record the voltage, current and time it takes to reach the specified lower cutoff voltage. Current x time gives you capacity in amp-hours. Then CC charge the cell at C/3 or whatever rate at the CV cutoff voltage and monitor/record the same. You don't want the cells to ever get hot or puffy. A puffed out cell is definitely bad and not worth using.

Then drain them all again with monitoring/recording to determine capacity number again, then put them through a bottom balance procedure to prepare for charging as a pack. Each cell will have a different capacity and you can determine the "weakest" one, and only charge your pack until that one is about 95% full and not have to worry about fire or explosion in the situation of no BMS. The top and bottom 5% are fairly useless due to having the highest voltage sag and it's not worth the extra time trying to squeeze a few more in versus the fire risk of overcharging.

Good luck to you, i admire your ambition, spirit and will-power to make it happen!

 

[mushymelon]

I think your on the right track by removing the bad cells.

Capacity testing each cell is also recommended.

Don't bottom balance and mix good and bad cells.

If it won't hold good capacity discard or reuse them for something else.

Using many laptop batteries in series and parallel without a BMS is something I would consider unsafe.

If you start with matching cells with equal capacities, monitor voltages before during and after you can reduce the risks.

 

[numberonebikeslover]

It is a fact that I have cells of a number of different kinds having different brands and therefore qualities and performances and therefore some will have more capacity others have little.

About lead acid batteries, when we connect two different capacity batteries in parallel connection, we get a bigger capacity single battery right? I guess if I mix in a parallel pack different capacities in such a way that all packs have approximately the same capacity would work in my case.

Let me explain with examples:

Considering that we give the cells each a grade as per their voltage So;
4.20 and above as grade = A
4.19 as = B
4.18 as = C
4.17 as = D
4.16 as = E
4.15 as = F

Putting all these above grade each in one parallel pack of 6P would make a bigger battery in which cells will tend to balance each other and act as a bigger capacity.

The same goes for 4.10 and 4.09s, they also have some capacity but my question is, what happens when a cell in a parallel pack (6P) goes down earlier than the others? Does its internal resistance decrease when it discharges? If so, would it affect the performance of the other cells?

Thank you very much for your words of wisdom to make my project a success. I am greatly honoured.

Yours Respectfully
Naeem

 

[numberonebikeslover]

some shots of my pack and the stuff I used to make it (card boards out of packing materials, rubber bands cut out of bicycle and a bike's tire).

 

[numberonebikeslover]

Some Tests:
Took a cell that reads 4.07 volt and was staying there for few days. I had a 2 watt LED and couldn't find any other possible load. When connected to the said cell it took about .1 amps. following are the readings:

No load voltage reading of the cell = 4.07
Discharged @ .1 amp for 3 hours
On load reading after 3 hours = 3.81
No load reading after 3 hours = 3.87

It seems like this cell can hold some juice and my be useful. I would singly charge it and see if it can again hold the voltage.

 

[999zip999]

Doc has a thread on konions cells and how he use a spreed sheet to organzine a parelle set of cells before connecting in series. Plus if you like to check a cell in a string you need to disconnect the string at the neg. end and not mess with the pos. side. Are you soldering them togethere ? I will look for it.

Wow you have Zombie in a box.

 

[mushymelon]

Heres is a chart of Internal resistance in relationship to state of charge. (based on sony 18650 lico cells)

As you can see the resistance remains stable throughout discharge so this should not be a problem.



If you configure your batteries like lipo in series groups of 8 or less than you can use these to monitor your pack.





You would need one for each series group.

This would let you monitor and do all the things a bms would do, but you would be doing it manually.

LVC, HVC, Discharging high groups, topping up low groups ect.

You would also need to reduce the amount of power you draw during testing until your more confident you have good cells.

Its good you have a source for cells because you may need extras to get a heathy pack from a lot of used cells.

After a bunch of short cycles and balance sessions. You may need to pull apart the suspect groups and test the individual cells then replace the bad ones. This is when its best to capacity test the cells, checking internal resistance would be good too. Keep a log book and record everything for reference try to use the same methods for testing every time so you get good data.

I have ordered extra lipo monitors I should have three extra. I can send them too you when they arrive if you like. I will pay for everything no prob. Let me know if your interested.

 

[mushymelon]

New and improved Zombie sour chews.

Awesomeness

 

[numberonebikeslover]

Plus if you like to check a cell in a string you need to disconnect the string at the neg. end and not mess with the pos. side. Are you soldering them togethere ? I will look for it.
Wow you have Zombie in a box.

I have this intelligent use of household stuff available. I hook up the cells using rubber bands to a copper stick / strip at both sides which is cut off of a PCB board sheet (see the pics on previous pages). Also used the card board covering the cells at both sides. I can easily dis-mental the whole pack by slipping off the rubber bands. I have arranged a pack of 6p then used a bigger rubber bands (3) to hold 5 such packs together as shown in the above picture. This way a whole pack of 30 cells would act as a unit in which the situation is 6p5s.

About Zombies. LOL; I asked the shopkeeper adjacent to my house for some packing card boards. He gave me this chewing gum pack known as Zombies chewing gum. Did not notice till you mentioned it.

 

[numberonebikeslover]

I have ordered extra lipo monitors I should have three extra. I can send them too you when they arrive if you like. I will pay for everything no prob. Let me know if your interested.

That is very kind of you. I would love to have something like this. Things like these really are unknown in this part of the world. I would pm you my address.

Thanks mushymelon.
Yours Respectfully
Naeem

 

[999zip999]

He could use some balance leads with those. Musymelon where do you live ?
Becareful with the pos. end as the copper strips could short on the neg. case and ?

 

[numberonebikeslover]

Becareful with the pos. end as the copper strips could short on the neg. case and ?

To ensure that there is no short between positive and negative at the positive terminal I Put on some solder so it just raised a bit to touch the copper strip and to ensure that the strip does not touch the rest of the body of the cell. Moreover, I rapped around some scotch tape near the positive side of the cell also.

 

[mushymelon]

He could use some balance leads with those. Musymelon where do you live ?
Becareful with the pos. end as the copper strips could short on the neg. case and ?

I live in Ontario, Canada

I will send along some 6s extension cables as well.

 

[numberonebikeslover]

Hello every body;

I had a road accident on my e-bike. Some times very minor things give rise to an accident. Thanks God I am OK with some scratches and bruises otherwise I am easily walking on my two feet.

What happened was that My front wheel got locked while I was cruising with the speed of 40 km/hr. The bike slammed me like a wwf wrestler and I fell on my face. The front mudguard snapped off and locked the front wheel. The scary part was that I was thrown in front of traffic on the other side of the road. The vehicles had to hit the breaks hard and I had a real narrow escape. I was so confused. I thought may be a vehicle hit me from behind. It was a lot later when I come to know that It was my front wheel that got locked.

About the battery; It woks amazingly well and I am a very happy man today. Most surprisingly the battery was not hurt at all. It was very sturdy and firm therefore it did not even moved a bit.

Right now I feel pain in my body and I need to take rest.

bye for now. Thank God I lived to tell the story.

Yours Sincerely
Naeem

 

[numberonebikeslover]

Hello everybody;

After the accident I noticed that my front fork is bent inward and it seems like I would need to replace it. As it is homemade and there is no replacement available in the market I think I have to re-do every thing. If it is not that much damaged, may be slight bending back to its normal position would resolve the issue but I have to carefully look for the points of stress on the mettle.

After fitting my Lithium Ion Battery it was my first ride. My bike became so light that it feels like a toy now. The acceleration is amazing due to light weight. Now I really understand how it feels to have a lithium pack.

Now is the time for fitting protection systems and HVC LVC cut off systems.

My next challenge would be to make a BLDC Motor out of Car alternator.

Wish me luck guys.

Yours Sincerely
Naeem

 

[floatingdog]

I'm glad you were not hurt seriously. Going down at 40km under the best of circumstances is usually not a pretty picture. High siding (going over the front) is the least fun way to go down. You must be quite the acrobat.

 

[999zip999]

Naeem where you wearing a helmet ? Not for you but for you wife.
Glad you now feel the power of lithuim. You will find that this battery has a personality and you will find weak and strong parelle cells. it's only as strong as your weakest cell and you don't need to find the bottom limit of your battery. it will last much longer.
Good to hear you are o.k. good luck the pain will past.

 

[numberonebikeslover]

I indeed had a narrow escape yesterday night.

Here is a video of mine explaining about my battery: https://vimeo.com/58760972

For protection of the battery pack it is very easy for me to use a relay which is operated by a LA 741 which reads the pack for low voltage. Moreover, I would be using three of such LA741s. Two would read 6p7s portion of entire pack respectively while the third one will read the remaining 6p6s portion of the pack for low voltage. If any one of the three portion senses low voltage, it would shut off the entire pack. It would not start until the higher voltage are gained by letting the pack rest for may be 5 minutes or connected to the charger. I am sure it will work just fine.

One of the member has promised to send me three Lipo monitors in near future which will make the entire setup very secure.

Not only this, I also intend to include a break switch which is mechanically re-settable. It will cut off battery insteantly incase of a short circuit or suppose the motor gets stuck too bad due to any mechanical problem.

Thanks for your valuable comments.

Looking forward for feedback and guidance.

Naeem

 

[numberonebikeslover]

Naeem where you wearing a helmet ? Not for you but for you wife.
Glad you now feel the power of lithuim. You will find that this battery has a personality and you will find weak and strong parelle cells. it's only as strong as your weakest cell and you don't need to find the bottom limit of your battery. it will last much longer.
Good to hear you are o.k. good luck the pain will past.

I was in such a hurry that I did not take the time to wear a helmet. I was thinking about coming back in minutes to check the pack for voltage. My father being a very religious man with so much knowledge of literature of many subjects has done his masters in 7 different subjects and literatures has also have the knowledge of Quran (the Holy book of Muslims) He has told me some verses if recited before riding any thing keeps one safe from any accident. It is believed that angels help such person while going through an accident. I have encountered many such accidents in which I lived to tell the story. You people might not know but I used to be a sports biker in my teenage and have taken part in several illegal street racing. I have hurt my body several times but since the time I started reciting some of the verses my father told me I never had such accident which could hurt me badly.

About weakest cell, yes it is indeed true that the battery is as strong as its weakest cell. I intend to check the individual Packs (6p) for their voltage after some serious ride like about 5 - 10 kms. In case of noticing any pack way down than the others I will take it out and check for individual bad cells and replace them. It would be tiresome but it would finalize my pack to better performance and then the time will come when I will finally enjoy it.

Yes indeed I do not need to find the bottom discharge of my battery and I know it will last for so many kms, therefore, I intend to keep on very slow charge (.01C) most of the times with having an HVC cutt off system in place. I will also monitor the battery in times for any HVC might fail to work. Charging at so little current will also balance the cells efficiently.

Thank you very much for your love, support and guidance.

Yours Respectfully
Naeem.

 

[mushymelon]

Hi Naeem

I'm glad you where not seriously injured in your accident, close call.
I have sent your battery alarms along with some 6s extension cables.
Unfortunately these monitors are not as accurate as I hoped but still useful for Low voltage warning.
Good luck with your batteries!

Mushymelon

 

[numberonebikeslover]

Hi Naeem

I'm glad you where not seriously injured in your accident, close call.
I have sent your battery alarms along with some 6s extension cables.
Unfortunately these monitors are not as accurate as I hoped but still useful for Low voltage warning.
Good luck with your batteries!
Mushymelon

Thanks a lot my dear friend for your concern and thanks for sending the monitors. I really appreciate what you are doing for me.

I have been transferred from the Office of the Vice Chancellor, University of Peshawar, back to my previous position in the Institute of Education & Research, University of Peshawar as Personal Assistant to the Director (my old position) with the same promoted grades and facilities. It was due the kindness of my Director who couldn't stop missing me for my efficiency and dedication. He requested the VC for my services which was granted. Back in my old office with a lots and lots of work and thats why I am not showing up. Still trying to find time to test the battery but other things are keeping me from it. Hoping to get back to you with some test results of the battery.

With great respect and warm regards.
Naeem

 

[999zip999]

The Vice chancellor my ask for you back after his work backs up. Do have a choice ?

 

[numberonebikeslover]

The Vice chancellor my ask for you back after his work backs up. Do have a choice ?

Actually it was a little tricky. My Vice Chancellor (Prof. Dr. Qibla Ayaz) was an acting Vice Chancellor at that moment. When I got promoted, he chose me to be in his office. After when it was his last day. I requested him to transfer me back to my old department. This was also supported by my Director in Institute of Education & Research (IER). Although there is a lot of work in IER but with this feeling that my efforts are making a large difference in the society it gives me great satisfaction and pleasure. It is rightly said that "Teacher can change the fate of a nation" and that "Teacher is the agent of change in the society". IER is producing and training Primary and Middle school teachers and I am facilitating it gives me great honour and pleasure.
Thanks for asking zip

 

[999zip999]

Naeem Do you have kill switch, just in case on the handle bars ? Also more parelle cells the better in a battery of used cells.
Good to hear about your work. Thank you.