Does the stitching of cells to make lithium battery pack matter at all? I'm building 24v battery pack for this electric scooter I found in the trash. I used 18650 batteries salvaged from used laptop battery packs. By using this hobby charger I depleated them, charged them - took notes to the draw / charge mah in my book, and tried to match up the best-of-the-best cells to make a battery pack. I see video's people salvaging these batteries and claim they get many miles from their electric bicycles from wiring these cells also salvaged from used laptop battery packs.
The first battery pack I tested was 6-cells in series about 24 volts. I got about 1/2 way down my very short street. I made an additional battery pack same wiring 6-cells, and wired the two packs in parallel to deliver the 24 volts with double the stamina. I could get down the street before the power fizzed out to nothing.
So I made a make/shift dyno wheel in the living room where I could test and kept swapping out cells that would get hot after the scooter seemed to die down after only 2+ minutes of 100% duty cycle. The battery cells aren't getting HOT, I would say a little warm. My speed controller and motor feel room temperature and don't show any OBVIOUS signs of being over worked.
So now my question is - will the actual lacing of these batteries make any difference? If more laced in parallel vs. series, could that make a huge difference or just a trival one? Should I be using large capacitors in some way to store/cache current carried from the batteries through the short 8" of 16 gauge wire to the motor?
I can't see any other option for me to try and test before I just consider this entire batch of cells unworthy for any type of distance motor use. I guess it has to do with the amount of current they can deliver immediately vs. lower current over a period of an hour.
DocStein99:
So now my question is - will the actual lacing of these batteries make any difference? If more laced in parallel vs. series, could that make a huge difference or just a trival one? Should I be using large capacitors in some way to store/cache current carried from the batteries through the short 8" of 16 gauge wire to the motor?
r.
With battery packs the cells should be matched in age and use.
When charging llithium cells a balance charger is needed.
With lead acid individual cell voltage is not to important although a cell can go duff rendering the whole battery useless.
If you do not know the charging curve you should NOT do this.
And having some batteries in series makes it more complicated.
Notebooks have a charging unit. No i am not talking about this black external power supply.
Lithium batteries are very powerful and very dangerous.
I have built many devices - power supplies, frequency counter, etc ... - however, I would never dare to build my own battery charger for lithium batteries.
samsung galaxy note 7
If a big company cannot do it, do you still want to try?
What is the voltage rating needed for the motor? That is what you need to stick with as far as series connections go. Next would be current, which is achieved by parallel packs. The more you have in parallel, the more current you have available, the faster it will accelerate, and the further it will go.
To put it another way---
I have 2 batteries in my truck, hooked in parallel. It's still only 12vdc, but packs about 1000 cranking amps. I also have 8 D-cell batteries in series, giving me 12Vdc. Do you think if I hooked it up to my truck it would even fire up my computer, fuelpump, glowplugs...... Absolutely not. Now if I were to put 500 of those in parallel, it might be a different story.
Just be cautious, as putting all those in parallel could prove disasterous should you have a short, but I guess it's easy enough to bail off a scooter and watch it burn.
Batteries obtained from discarded laptops are likely to be useless. Any battery has a limited number of cycles and these were almost certainly discarded because they were worn out.
A typical electric bike will take up to 250 watts - you need a lot more than 6 18650's to provide that for any length of time! Even a new top brand-name 18650 has not much over 2AH capacity. Beware false claims from eg ebay adverts ! That's all that can be crammed into that size.
And I concur with arduinoaleman - chargers for these are not trivial. Samsung obviously haven't learned all the tricks yet.
EDIT Or Boeing?
I worked with a load of ex-Apple guys some years ago - we were trying to build something like an iPhone ages before Apple brought theirs out. The project ran out of funds, so it never happened. Among other things I looked at their battery charging circuits - incredibly complex! I asked one of them why, and he replied that they'd had too many fires in the lab on tests with inadequate designs to take risks.
Danger.inc continued until Microsoft bought them and cocked it up.
I was just an RF consultant.
Remember that early iPhones had poor RF performance?
The Hiptop didn't, 'cos we were careful, and got it right. It was as good as the contemporary NOKIA ordinary phones. I did the measurements myself in an anechoic chamber.
My first battery pack was 6 18650 cells, all series to give 24 volts. I got about 45 seconds of run from scooter before it ran out of breathe.
I added another pack of batteries, same thing - 6 cells to give 24 volts. Both battery packs are in PARALLEL with each other - output voltage is the same 24-25volts fully charged.
The CURRENT used is between 3.5 amps and peaks out about 5.83 amps, maybe 6 amps at the very most. When it runs out of breath, it goes from around 24 volts down to 9, which isn't enough power to spin the motor with zero load.
I am using an iMax lipo charger to charge the cells, and have the JST connector wired to balance.
(2) packs, (6) cells in each pack. 2 packs wired parallel to parellel into speed controller = 24-25volts. I get about a minute+ before the whole scooter runs out of breath. If I take a break, I can run the scooter again for 1 minute. I get 1 minute bursts before it gets tired. The batteries do not appear to lose much current at all, 300 mah after about 10 tests or so.
I'm aware of fake eBay 18650 batteries, I bought a few to test for use with my flashlights and I get like 560 mah out of some, maybe 680, I got like 980 out of one of them, was probably the strongest. No big loss for a few bucks just to try, but I will not spend good money on new 18650's. If I were to buy something else to try, seems like these FLAT lipo batteries I think they use in the quadcopters look strong, but I'll never know until I can get one to test - a 8000 mah 3.7v cell is like around $15.00 each.
I am actually more interested in teaching myself about these batteries and getting experience, then just to build a scooter or a bike. If i buy new batteries, my next move would be trying those packs from hobby r/c cars, since it seems they are designed to power motors instead of supply current for long periods of electronics use.
It seems like i am pulling too much current then the batteries can immediately supply, since they arent discharging dead, is just they want a break before doing more work. I am beginning to believe the people making youtube videos about how great their recycled laptop packs are - are the same people on ebay trying to sell used dead laptop batteries.
Is this a rating on the batteries - like cold cranking amps?
DocStein99:
I am actually more interested in teaching myself about these batteries and getting experience, then just to build a scooter or a bike. If i buy new batteries, my next move would be trying those packs from hobby r/c cars, since it
I am an aero modeller.
LIPO batteries are very common for all RC modellers.
The likes of scooters use a different battery chemistry as do power tools.
These batteries are larger physically but generally safer.
They should be balanced charged but in the case of power tools are often not.
The likes of DE Walt and Makita do this and is the reason professional tradesmen use them as they give much better battery life.
Google on Battery university for information on battery types.
I believe that laptops and phones use LIPO batteries but for modelling purposes the packs are large and i do not store or charge them indoors.
Ive got a 250 Watt electric bike , and its battery pack has 40 panasonic NCR18650Bs with 4 cells in parallel, connected in a series string of 10 .
Cells from laptops are usually only 2.4 AH each when new , and will be in various states of depletion after use.
You need a lot more than 6 cells.
I kept scanning for ideas, like using powerdrill / dewalt batteries. They are also expensive. And nobody throws out or sells - good used battery packs.
srnet:
Things that can explode and cause serious injury are normally considered dangerous.
Yeah but using terms like "very powerful and very dangerous" sounds more like an exaggeration.
I know how much damage icr cells can make, I have destroyed icr cells by burning them in fires, short circuiting them and by throwing blunt objects at it. So on a scale of 1-10 of everyday dangerous items I would say an icr cell is more like 2 or 3.
There are other items which are more powerful and more dangerous, like a lpg tank which could almost instantaneously wreck my entire house along with me in it if it explodes. I also have a petrol powered electric generator which could explode and cause serious burn and has the risk of carbon monoxide poisoning. That doesn't stop me from using it anyway, just take the proper precautions and safety measure and you're good to go.
Ok thanks for the safety concern. I will try and remember that when I bring up to the owner of the business where I rent machine time, and protect my used laptop batteries in a nice place, while I machine sidewinder missile valves in magnesium on the CNC lathe for a government contract.
Noobian:
Yeah but using terms like "very powerful and very dangerous" sounds more like an exaggeration.
I have a spare petrol can which i would not consider storing inside my house.
Simple sensible precautions are enough.
With large lipo batteries used in modelling , they tend to be unprotected and susceptible to puncture damage.
Sensible use will prevent most problems.
Biggest problem here though is that some modellers live in tower blocks, safe storage of large lipo batteries then becomes a problem.
mauried:
Ive got a 250 Watt electric bike , and its battery pack has 40 panasonic NCR18650Bs with 4 cells in parallel, connected in a series string of 10 .
(still not as powerful and dangerous as petrol, not even close)
