Whole Laptop batteries transformed to ebike battery?

[KennyS]

You could look for a dead Bike battery where the Balance charger is ok
and just give it a load of fresh cells


found this here.
http://www.ebay.de/itm/14S-48V-Lith...hash=item33bff9a05d:m:mXJcv6WWEGQ-qOeNUcxNp9w

Thanks, I had seriously considered something along those lines to make at least the first build less confusing for me. I just had no idea exactly what to look for but the link you provided will help some in figuring that out..

 

[KennyS]

You need a special balance charger to charge the battery packs.

The balance charger in the Laptop is usually not in the battery pack.
The battery has probably a PCB build in but get the battery working with its electronics is most likely not possible.

5A charging current might be too high depending which cells you got.

for building a battery pack you have to measure the cells and match em up
for example you have 3x6 cells from three laptop packs with 11.1V
first with 1800mAh x2 second with 2000mAh x2 and the last with 2200mAh x2

to get the maximum performance each 3.7V unit of the battery pack needs the same capacity
so you got 18 batteries if you want to build a 33.3V battery with 9x2 cells you have to match each for 4000mAh
So first 3 are 2000x2 and the other 6 1800+2200, overall is 4000mAh

the mAh of the whole battery is equal to the lowest 3.7V unit
so if you just put the 3 laptop batteries in row you end up with 3600mAh

Thanks very much for taking the time to explain that...it was something I definitely needed clearing up.

 

[Lexel]

Those 2000mAh cells you recycled can take 4 Amps safely as constant discharge current

so if you put 4 parallel you end up with enough to run the bike motor with 500W With 12x4 cells
at max discharge you have 30V

another option would be using a 1200W buck step up driver to get a constant voltage to your motor, so you dont need to worry about the motor getting weak with dropping battery voltage
you could run this with 2 6 cell packs in series recharging with an Imax B6

 

[KennyS]

It is highly unlikely that you can reuse the laptop BMS - for various reasons. They are not designed for high-current apps such as ebikes. Nor are they designed to be assembled into larger packs. Further, they require special chargers that can speak the Smart Battery protocol.

Be aware that building large Li-ion battery packs (e.g. for ebikes) requires signficant expertise on Li-ion technology in order to design safe systems. Your questions seem to reveal that you have much to learn about such matters. Be very careful.

I put an 18650 into a cheap ebay powerbank backwards and the PB evidently didn't have the protection one might expect. It welded the pos to the neg (fortunately didn't hurt the power bank) and I couldn't even handle the battery to scrape the connection off, not to mention being afraid to handle it in that state. All I could do was put it in an empty tuna fish can and put it on the floor until it burned out. No explosion this time but I hear it's possible. Way back when I was kid, I had a good sized GTO car battery blow up in my face, and that is an excellent teacher. Aside from my cloths disintegrating no problem, but loud/ringing ears? Wow!

Of courses that had little to do with poor safety measures in building packs but educational nonetheless. I've watched several youtube videos, and some multiple times so, though I'm not fluent in this, I'm getting some general ideas of what to be careful of. Hey, it's electricity and I won't get into my close calls with that...but I do get that so much of it enclosed in such a small package does present it's own set of problems.

In the end though, obtaining significant expertise comes down to study first, then hands on doing it. So we get as ready, as we deem necessary, heed the warnings and then just jump in and try to be careful. As far as having a lot to learn, yes, I do...the reason I'm here.

 

[KennyS]

Those 2000mAh cells you recycled can take 4 Amps safely as constant discharge current

so if you put 4 parallel you end up with enough to run the bike motor with 500W With 12x4 cells
at max discharge you have 30V

another option would be using a 1200W buck step up driver to get a constant voltage to your motor, so you dont need to worry about the motor getting weak with dropping battery voltage
you could run this with 2 6 cell packs in series recharging with an Imax B6

Is what you are saying there what you advise or is it just to give me an idea on what's going on as it does? What exactly would you suggest I do for say a 22ah battery to run a 48v 1000w bike? Just some basics without taking up a lot of your time would be good. I presently have the 48 batteries I mention am am really happy with thus far, 8 more Samsung with consistent 2500mah but not sure if they are used or new, and 12 to 16 more that will range from 17mah to 2100 mah.

The step up is interesting, I hadn't thought of that. something like that would run the bike with consistent power, and then, it would just suddenly stop when out of juice?

Also, what you are saying there is it may be possible to use full packs for this? If so, if and when I decide to experiment with that, what you mention would be the way to go.... not too time consuming of a build and only involving a couple of packs just to see how it goes.

 

[Lexel]

To run a 1000W motor you need at least 6 healthy batteries parallel
or some high drain batteries as they are used normally

but its better you start with a 250W model as 1000W is too much to power with a DIY battery

 

[KennyS]

CPF is the wrong forum for this. try endless-sphere.com

gauss163 is right about the pack comm protocols. you don't really want to go there. that's why no one does what you're planning to do

i'm not going to go into the details but basically what you want to do is to crack open all those packs, perform a rigorous selection process to weed out the bad cells, then arrange the cells in a configuration of parallel groups that are wired together in series, in such a way that all your parallel groups are of the same capacity and internal resistance

but if you're lucky enough that ALL your cells have the same capacity and internal resistance then it becomes more straightforward

these were cells harvested from portable projector battery packs. all very healthy so it's just a matter of wiring them up in 17-series 6-parallel (17s6p config)

then you have to think about balancing and charging. i use this DC-DC boost module to "bulk" charge my packs:

you may also use a BMS battery management system but i'm not a fan of those things. i prefer to balance manually

do a ton of research before attempting any of this

That's helpful in summing up the process, and I'll probably go as simple as I can for now. On the groups being the same capacity...is that just a matter of taking whatever batteries are available, no matter their capacity, and just making sure they add up correctly to a nominal capacity? That way it doesn't really matter if some of my batteries are down there in capacity, they cas still be used as long as they are added in groups with batteries of excess capacity? That's probably obvious from what you say, but just making sure.

That looks like a big pack there, or is it pretty much an average size? Can you/anyone give just a very rough estimate on how far that would take a 1000w 48v ebike in miles with no hills, and no pedaling, 200lb rider? That would help me decide what size pack I actually need. I ask about no pedaling for the same reason I went with hybrid bikes....the beauty of this is normally one just pedals home if there is a problem..I can't pedal at all due to handicap, and the last thing I need is to get stranded so doing all I can to prevent that and why the no pedal range is important to me, especially if I should decide to go with electric only in the future, and maybe just carry an extra controller for backup.

 

[Lexel]

Depends on your speed, a 1000W can push you to 30 miles but drains the battery rapidly
if you drive 10 miles battery will last at least 5 times more distance

 

[Overclocker]

That's helpful in summing up the process, and I'll probably go as simple as I can for now. On the groups being the same capacity...is that just a matter of taking whatever batteries are available, no matter their capacity, and just making sure they add up correctly to a nominal capacity? That way it doesn't really matter if some of my batteries are down there in capacity, they cas still be used as long as they are added in groups with batteries of excess capacity? That's probably obvious from what you say, but just making sure.

That looks like a big pack there, or is it pretty much an average size? Can you/anyone give just a very rough estimate on how far that would take a 1000w 48v ebike in miles with no hills, and no pedaling, 200lb rider? That would help me decide what size pack I actually need. I ask about no pedaling for the same reason I went with hybrid bikes....the beauty of this is normally one just pedals home if there is a problem..I can't pedal at all due to handicap, and the last thing I need is to get stranded so doing all I can to prevent that and why the no pedal range is important to me, especially if I should decide to go with electric only in the future, and maybe just carry an extra controller for backup.

depends on your rejection thresholds. some people do with a low rejection rate and just arrange their packs creatively. if you ask me just reject all cells w/ voltage below the median. less problems in the long run

agree, go as simple as possible. that probably means building two 6s packs and charging them on a turnigy reaktor 250w. then connect them in series for 12s, which is a bit lower voltage than your typical 13s "48v" but it'll do for simplicity

have you figured out how to connect the cells?

don't forget to fuse

i get about 75kms on this bike on hilly terrain. i always pedal so i don't know the no-pedalling range. it has 96pcs of Samsung 26F which is 2600mah

 

[Phlogiston]

[...] On the groups being the same capacity...is that just a matter of taking whatever batteries are available, no matter their capacity, and just making sure they add up correctly to a nominal capacity? That way it doesn't really matter if some of my batteries are down there in capacity, they cas still be used as long as they are added in groups with batteries of excess capacity? [...]

Don't do that. It will get you into trouble.

As an example, if you put a cell having 1800 mAh of capacity in series with a cell having 2200 mAh of capacity, the 2200 mAh cell will reverse-charge the 1800 mAh cell towards the end of the discharge cycle.

Basically, you end up taking 1800 mAh out of each cell, at which point the 1800 mAh cell is empty, but the 2200 mAh cell still has 400 mAh left. If you keep drawing power, some of that 400 mAh will go into over-discharging and eventually reverse-charging the 1800 mAh cell.

That will do so much damage to the 1800 mAh cell that attempting to recharge it will cause it to fail. In the worst case, it will rupture and catch fire.

You might - note that I don't say "will" - get away with putting the 1800 mAh cell in parallel with the 2200 mAh cell, but I don't recommend that. Not only might you get strange effects during balance charging, you could easily put a weak cell in series with a stronger cell by accident as you build your battery pack, and then you're back to "rupture and catch fire".

Bear in mind that once one cell catches fire, you're looking at a chain reaction that ends with the entire battery pack on fire. That's a lot of energy and a truly impressive volume of extremely dangerous gases. Read this thread to see what I mean by "extremely dangerous".

In short, minimise your potential for human error and start with well-matched cells in the first place.

 

[Overclocker]

Don't do that. It will get you into trouble.

As an example, if you put a cell having 1800 mAh of capacity in series with a cell having 2200 mAh of capacity, the 2200 mAh cell will reverse-charge the 1800 mAh cell towards the end of the discharge cycle.

Basically, you end up taking 1800 mAh out of each cell, at which point the 1800 mAh cell is empty, but the 2200 mAh cell still has 400 mAh left. If you keep drawing power, some of that 400 mAh will go into over-discharging and eventually reverse-charging the 1800 mAh cell.

That will do so much damage to the 1800 mAh cell that attempting to recharge it will cause it to fail. In the worst case, it will rupture and catch fire.

You might - note that I don't say "will" - get away with putting the 1800 mAh cell in parallel with the 2200 mAh cell, but I don't recommend that. Not only might you get strange effects during balance charging, you could easily put a weak cell in series with a stronger cell by accident as you build your battery pack, and then you're back to "rupture and catch fire".

Bear in mind that once one cell catches fire, you're looking at a chain reaction that ends with the entire battery pack on fire. That's a lot of energy and a truly impressive volume of extremely dangerous gases. Read this thread to see what I mean by "extremely dangerous".

In short, minimise your potential for human error and start with well-matched cells in the first place.

you're not understanding the concept. but you're right about some of the safety aspects

these are groups of paralleled cells that are then connected in series. so as long as all parallel groups are more or less "equal" then the whole pack shouldn't get too out of balance. many people have done this successfully but as i've mentioned above i don't recommend it

 

[Phlogiston]

Fair enough; I was having trouble working out how the original poster intended to group the cells, which is why I commented on both serial and parallel cases. Always a pitfall of text-only communication!

Of course, the parallel groups are themselves subject to the serial over-discharging problem. You can certainly assemble mismatched cells into parallel groups having the same capacity, but the cells are likely to age and lose capacity at different rates due to their varying prior histories, which means that your parallel groups will eventually drift into having different capacities anyway.

At that point, the weakest parallel group will be over-discharged every time you put the battery bank through a full cycle, and you'll be back to the catastrophic failure scenario.

 

[Bright+]

Managing state of charge during discharge is very complex. Laptops sometimes have a power converter device that can disburse charge between individual serial segment.

 

[Bright+]

depends on your rejection thresholds. some people do with a low rejection rate and just arrange their packs creatively. if you ask me just reject all cells w/ voltage below the median. less problems in the long run

agree, go as simple as possible. that probably means building two 6s packs and charging them on a turnigy reaktor 250w. then connect them in series for 12s, which is a bit lower voltage than your typical 13s "48v" but it'll do for simplicity

have you figured out how to connect the cells?

don't forget to fuse

i get about 75kms on this bike on hilly terrain. i always pedal so i don't know the no-pedalling range. it has 96pcs of Samsung 26F which is 2600mah

I would be scared to mess with DIY battery setup that big for risk concerns. Even properly protected laptop cylindrical cells have had incidents. You've got to check your insurance policy to see if they would cover your home, car, or other people's property if you have a battery incident. There are some pretty nasty battery incident stories here.

 

[Overclocker]

96-cell isn't a lot... my next build is gonna be 204-cell

check this out:

 

[ChrisGarrett]

That's a badass pack right there!

I don't know if I'd want to sit on that thing, since there's a lot of energy right below 'the boys' and all.

Chris

 

[KennyS]

Ok, I tried to educate myself on the math so I could come back here and ask more lucrative questions/have some I idea of what's going on, but that didn't work out. lol. I've always been an idiot with math. I don't know if my mind just shuts down when I try due to refusal to get into learning or if I have some type of legit issue there, but ether way, that's the way it is. I never let that stop me form anything I want to do, so that said, If y'all don't mind leading me through this, I'd like to get moving on it. It'll be a slow process of asking, ordering parts, asking again, step by step, not blowing my mind with everything at once, and once it's done, it'll probably all come together for me, at least for the most part. At least that's the way it always worked in the past.

So lets go with safety within reason, give a little where we can, and go fairly small for now, if that sounds good? Judging from the pack I asked about and it getting around 40 MPC from a 90 some odd count battery pack, I should get somewhere around 25 to 30 miles or so from a 60 count battery pack, and later I can always build a second to go with it. That'll get me well on my way, and do most of what I need to do.

I've looked into the cooling aspect of going with those black honeycomb brackets, the fact if I ever have to take it apart that would make it easier and they just seems to make the whole thing a lot neater as well. I don't mind the extra space it'll take, so I'd like to go with those. I think the fixed brackets are probably a better idea than the X1, X2, X3 and so on that you clip together. I just found 2X60 (1 top/1 bottom) on ebay for 10 bucks and I want to go ahead and order that. Any problem with any of that?

I'm thinking for the first pack, instead of investing in a spot welder, I'll go with solder, the strips and whatever fuses you recommend. I won't concern myself with how everything is to be situated for the moment, I'll just get the parts and cross the technical bridges as we come to them or as necessary.

Sound ok so far? And I should add, I'm not obligating anyone to anything, but as long as I ask and you are answering I'll roll with it.


Some questions for lets call it step one...getting all batteries together, in the brackets, stripped, fused and soldered. And that's is assuming what I want to do thus far is ok and in the right order:

I have a 937D Soldering station, will that be sufficient for this? (I'll fire it up and see what max temp is if you need me to.

Do the brackets I want to use sound ok?

What kind of and roughly how much solder to order?

The metal strips? What type metal? Just order strips or some type of reconfigured set up? Roughly what size and how many?

Fuses? ebay ok? what type? how many?


That should do for the moment, and if there is anything you don't like about where I am so far just say so. On the batteries, I ordered another single battery to see if it would be worth ordering several more but they ended up all 1800 mah each so, I guess those are out? I've seen people using high and lower capacities together but if y'all say not a good idea then I'll go with your decision on that.

Important question so I can get the few batteries that I am short of. What do we consider too much variance on capacity? Say the base mah is 2100 per battery, what is the plus or minus on that?

If some of this was already answered, please bear with me, lots of info here to get lost in.

 

[ChrisGarrett]

I really don't know how prudent it would be for one to try and learn how to build a safe and effective moster battery pack, containing lots of energy with potentially grave bodily injury at stake, on an internet forum, but that's just me?

I think that you should be reading a bunch of books on the subject and working in a shop as an apprentice.

You're not building a plastic model airplane.

Chris

 

[KennyS]

I really don't know how prudent it would be for one to try and learn how to build a safe and effective moster battery pack, containing lots of energy with potentially grave bodily injury at stake, on an internet forum, but that's just me?

I think that you should be reading a bunch of books on the subject and working in a shop as an apprentice.

You're not building a plastic model airplane.

Chris

I appreciate the concern, but I'm a big boy. 62 and have had a good chunk of life to learn from. Work as an apprentice just so I can build a battery pack?

If it helps any, and not to brag, just facts, I built my little house single handed, all but the carpet flooring and a small portion of the roof. I was just to weary to bother or I'd a done the flooring/carpet too and I welcomed the offer for a few hours help on the roof. Wired it, plumed it, everything, no other help on labor but what I mentioned, only from a friend who was a builder whom I could ask questions of if I needed too. I never worked in construction or as an electricians apprentice, so no experience at all. But the state allows it, as they know it's not rocket science, even though there is potential for danger. The house passed every inspection and on the first try. No issues with the house 16 yrs later. Oh, and I have the fairly severe residuals of the Polio virus in one leg to boot so, that has been a great teacher as well. No matter what if one man can do it, so can another, even with the odds a bit against us. Those are all things I'd rather not have brought up, but FWIW, those are my credentials.

I've found experience to be the best teacher by far, and this doesn't worry me in the least, as long as I take it slowly. And I'd much rather have this than a book that can't talk back...do people still use books? As far as it being an internet board, where better? Plenty of good experience here I could never run across out here.

But in the end, it's up to you all.

 

[Overclocker]

if you can build a house then you could certainly build a battery pack. it's not rocket science either

here's the first pack i built. soldered since i didn't have a spot welder back then:

here's my latest one:

everything you need to know is on the interwebs. lots of build threads on endless-sphere