Homemade Battery Packs

[999zip999]

Good thread, Those were my questions also.

[DrkAngel]

What a great thread! I'm in the process of ordering my first hub kit from cellman and was just getting geared up to order the lipos as well... until I saw this thread! Just so happens I have about ten laptops at work which are getting thrown out with battery packs- I will have to rescue them. More will be coming through as well which is good!

Just a couple of quick questions- what chargers are being used to charge the packs and in what configuration? I'd be putting together a 48V 20/30ah pack if there are enough good cells. Is a bms a necessity for these packs?

With Li-ion, the "BMS" is often called a PCB or PCM.
With well matched cells, and a quality charger, a BMS is not "essential" ... BUT! ... for safety and longest life, it is highly recommended!

Personally, with my multiple packs, I put the PCB-charger, on a quick change adapter and use for charging only. I monitor pack voltage with a volt meter. This, additionally allows use of a cheaper, lower amp output, PCB.

Charger and PCB are both available on eBay, also all-battery.com, many other places. A google search for 48.1v should point you to a variety of choices.

An important bonus, especially with used cells, is the "balance"-"equilibrium" feature. This equalizes cell voltages, insuring highest capacity, lifespan and best performance. Usually costs a bit more, but I feel, definitely worth it!

[SamTexas]

..., do they just give them to you or what is the going rate,

They sold me the 56Wh Dell packs at $6/each. On average I got 5 good cells out of 6 or 46Wh or $0.13/Wh.

[Harold in CR]

Group buy, anyone ??

http://cgi.ebay.com/WHOLESALE-LOT-236X- ... 4cf65eb41c

[DrkAngel]

The EZips and IZips are limited by their 24v controller.

Since Li-ions can't match to 24v, I build 25.9v, it has proved compatible on several different models.

In conjunction with my "16T upgrade" *Zip speed is increased from 16mph, to 21+mph.
EZip - IZip 20mph Upgrade $20!

Anyhow, the limitation of 25.9v, does have a couple advantages.

1. iMax B8:
Charges, balances 1-8 cells, or banks of cells
programmable rates, time
PC link, through usb port (cable - software sold separately)
up to 7amp charging rate (10-18v input required - I use a used PC power supply 12v leads, 12v - 20 amps)
Also compatible with SLA, Lipo, Nimh, LiFe etc.
Available on eBay, better cost in US via google search iMax B8 $55-$80

2. 2 in1 Lipo Battery Voltage Tester Low Voltage Alarm New
This nifty little item plugs into the balance plug on your, up to, 8 cell battery pack
It provides you with pack voltage, then cycles through the individual voltages of each cell, or bank of cells
(nice, bright red leds)
Additionally, it has an adjustable low-voltage alarm. default is 3.3v, alarm is nice and loud
Tip: an Ethernet cable makes a nice extension, allowing mounting module on bars

[Red_Liner740]

Hi everyone...

Thanks so much for sharing your information...appreciate it!

now, just for fun i went on ebay and came across this.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... CcjJs%253D

price seemed very good so i jumped it, meh its only 22CAN with shipping.

Before i get too excited about it, what do u think of those pacs? compatible? would work good?

much appreciated.

Also, OP, would u entertain the idea of selling some of your made packs?

[DrkAngel]

Looks like a good deal.
Identical packs is preferable.
Cells should be sorted by capacity.
2600mah is typical of modern designs

Previous post with good info about hunting for cells:
"Also, cell count can be determined by doing an ebay search for the pack model number.
Other listings will post voltage and amperage. 11.1v is 3 cells in series, 14.8v is 4 cells in series x (2 x 2600mah cells = 5200mah)
10.8v or 11.1v 5200mah=6cells, 7800mah=9cells @2600mah
14.4v or 14.8v 5200mah=9cells, 7800mah=12cells @2600mah
(Li-ion are variously listed as 3.6v or 3.7v)"


4800 + 7200mah packs =2400mah cells
4400 + 6600mah packs =2200mah cells
etc."

[Red_Liner740]

Lets keep this thread going...

of all the laptop bats uve come across, have any ever came with all dead cells? on average how many cells are "good"?

[SamTexas]

of all the laptop bats uve come across, have any ever came with all dead cells? on average how many cells are "good"?

I have disassembled over 15 packs, the worst one had 2 good cells (out of 6), the best ones had all 6 good cells. Average ~4.5 good cells.

Laptop battery packs are labeled Li-Ion which is partially incomplete. The cells are Lithium-Cobalt, very high energy density, but not so high discharge rate. The cells are best used in lower power application. I built a 10-12s pack 10Ah for my 350W front geared hub. No problem so far.

[Red_Liner740]

^^ Thats encouraging...now i just have to find a local source that will let me have them for cheap or free...

wonder if the local dump/recycling depots would let you take them away...

[999zip999]

Bump.

[auraslip]

^^ Thats encouraging...now i just have to find a local source that will let me have them for cheap or free...

wonder if the local dump/recycling depots would let you take them away...

The local computer recycler said they get $3 a pound for battery packs, and they'd be willing to sell them for $4 a pound! Much cheaper than ebay.

[liveforphysics]

The cells are Lithium-Cobalt, very high energy density, but not so high discharge rate. The cells are best used in lower power application.

Lithium Cobalt makes both the highest (practical) energy density cells and highest power density cells (like the nano-tech's and other RC lipo for example.)

It is just the unique situation of laptop cells where the power density is so low, as the cell has no need for power density beyond 1C, and using thicker foils and more carbon to aid conduction in the slurry would just displace volume that could be occupied by active energy storage materials. In other-words, they are perfect for helping your laptop run as long as possible, quite unoptimized for EV duties (unless built into very very large packs).


Keep in mind, lappy cells, particularly old and sketchy ones can and do fail explosively if mis-treated.

[SamTexas]

The local computer recycler said they get $3 a pound for battery packs, and they'd be willing to sell them for $4 a pound! Much cheaper than ebay.

That's a very good price.

[DrkAngel]

The cells are Lithium-Cobalt, very high energy density, but not so high discharge rate. The cells are best used in lower power application.

Lithium Cobalt makes both the highest (practical) energy density cells and highest power density cells (like the nano-tech's and other RC lipo for example.) ...

In other-words, they are perfect for helping your laptop run as long as possible, quite unoptimized for EV duties (unless built into very very large packs).

Remember tho ... a 40ah Lithium Cobalt pack is about the same size and weight of a 20ah LiFePO4, and same weight as 8ah SLA.

Keep in mind, lappy cells, particularly old and sketchy ones can and do fail explosively if mis-treated.

"Lithium Cobalt" for notebooks, were specifically designed with lower input-output rates as a safety measure. All Li-ion are capable of dangerous reactions, if "mis-treated", as are LiFepo4, Lipo, SLA, Lead acid ... most any battery type, to some degree.

[Spicerack]

Started pulling apart and charging my first set of laptop battery packs.

Voltages have varied from 0v to around 3.5v so quite a range. One pack of 8 sony cells at 0v take a charge but discharge straight away so they're a bin job, but all the rest of them so far are charging up to 4.15v ok. I'll leave them for a day or two and see how badly they discharge.

I could certainly afford to buy lipo packs, but this is kinda fun! Recycling too- that's gotta be good, right? The batteries have come from the bin (from junk/faulty laptops) and a few off ebay so far. I also like the idea of going to a battery recycler- not too many around here tho.

Worked it out- I"ll need up to 170 or so cells to get my 48v pack up and running. Next challenge will be how to charge the lot!

[SamTexas]

"Lithium Cobalt" for notebooks, were specifically designed with lower input-output rates as a safety measure. All Li-ion are capable of dangerous reactions, if "mis-treated", as are LiFepo4, Lipo, SLA, Lead acid ... most any battery type, to some degree.

Very well said.

Voltages have varied from 0v to around 3.5v so quite a range. One pack of 8 sony cells at 0v take a charge but discharge straight away so they're a bin job,...

I too tried to salvage low voltage cells at first without much success. Now I discard everything below 2.0V.

[auraslip]

Remember tho ... a 40ah Lithium Cobalt pack is about the same size and weight of a 20ah LiFePO4, and same weight as 8ah SLA.

18650 - li-ion cobalt 50.4 volts 40 Ah 28.7 lbs $448.00 2016 Whs
Headway 10ah 51.2 volts 40 Ah 42.3 lbs $1,024.00 2048 Whs
A123 20ah 51.2 volts 40 Ah 33.8 lbs $1,600.00 2048 Whs
ZIPPY 5Ah 6S1P 30C 49.2 volts 40 Ah 27.6 lbs $900.96 1967 Whs

This is from a battery pack building spreadsheet I'm working on. Feel free to correct it if the cell weights are wrong. I can't remember where I got the weight information for the li-ion 18650.

[DrkAngel]

Started pulling apart and charging my first set of laptop battery packs.
...
Worked it out- I"ll need up to 170 or so cells to get my 48v pack up and running. Next challenge will be how to charge the lot!

Li-ion 48.1v chargers, and PCB are available. Charger & PCB, about $100. A balancing PCB ... Highly Recommended!
Search for 48.1v, eBay, Google, yahoo, etc. Balanced charging recommended, but personally I discharge without PCB, allows a lower capability - cheaper, PCB. Just monitor pack - cell voltages, during initial trials and replace any "weak" cells. I recommend a volt meter, mounted within view. Do not discharge cells below 3.5v(static voltage) or below 3v(under load-throttle)

As a fuel gauge, a volt meter is excellent, LI-ion voltage is very predictable with <4.2v as "full" and >3.5v as "empty".

If compatible, 44.4v can be charged in 2 sections, with a iMax B6 5amp balancing charger (about $30 but requires 12v input).
A cheap, multicompatible, option, before investing in more expensive charging, hardware.

48.1v with 1 iMax B8 and 1 iMax B6. Warning! Unless confirmed Isolated power supplies. 2 chargers should not be used on single pack. Either separate, or charge 1 section at a time.

I found that "T Plug" connectors work excellently for modular construction.

100 amp capable, easy connect. Variously called: Deans connector, Deans compatible, or T Plug

T Plug.JPG (25.13 KiB) Viewed 5715 times

T Plug search, on eBay

2 - 22.2 v modules easily separated.
T Plug on any external wire prevents probable damaged from snagged, or pulled wires.

Oh! When building battery "packs" make sure you install an inline fuse, a low cost item that can save a whoole lot of heartache!

[DT98]

DrkAngel, Super writeup! Thank you for the info.

I have never done anything like this before but I think I can do it if you don't mind a lot of questions later on.

I asked at work today and jackpot...I got 42 laptop battery packs. 95% Lenovo name on them.

9 packs are labeled 10.8v 7.14AH. I measured the voltage without opening the pack and the low was 11.42, high was 12.49.
10 packs are labeled 10.8v 5.2AH. Low voltage was 10.96, high was 12.45. One pack was 7.17v.
3 packs are labeled 10.8v 7.2AH. They measured 11.5, 11.6 and 12.22.
2 packs are labeled 10.8v, 4.8AH. They measured 12.0 and 12.4v.
18 packs I will have to open to measure the pack voltage...couldn't get a reading or my probes were not making contact.

I just ordered six of the chargers on ebay. Thanks for the link.

It looks like the next thing I need to do is to start opening the packs and separating the individual batteries. Should I leave them in pairs or break into singles? In your picture it looked like some of the batteries were still in pairs unless you did some really cool soldering.

After the chargers arrive I will start charging and testing thanks to your write up.

The only issue I'm trying to figure out right now is how to load test the cells...

Thanks! Excellent thread!!

[liveforphysics]

DrkAngel, Super writeup! Thank you for the info.

I have never done anything like this before but I think I can do it if you don't mind a lot of questions later on.

I asked at work today and jackpot...I got 42 laptop battery packs. 95% Lenovo name on them.

9 packs are labeled 10.8v 7.14AH. I measured the voltage without opening the pack and the low was 11.42, high was 12.49.
10 packs are labeled 10.8v 5.2AH. Low voltage was 10.96, high was 12.45. One pack was 7.17v.
3 packs are labeled 10.8v 7.2AH. They measured 11.5, 11.6 and 12.22.
2 packs are labeled 10.8v, 4.8AH. They measured 12.0 and 12.4v.
18 packs I will have to open to measure the pack voltage...couldn't get a reading or my probes were not making contact.

I just ordered six of the chargers on ebay. Thanks for the link.

It looks like the next thing I need to do is to start opening the packs and separating the individual batteries. Should I leave them in pairs or break into singles? In your picture it looked like some of the batteries were still in pairs unless you did some really cool soldering.

After the chargers arrive I will start charging and testing thanks to your write up.

The only issue I'm trying to figure out right now is how to load test the cells...

Thanks! Excellent thread!!

I don't care what you guys want to do, and I'm all for enjoying fires and explosions and things, but somebody should at least be made aware of the risks.


This is such such such a bad idea...

Mis-matched used cells in groups, people trying to revive over-discharged cells (which can result in fire/explosion on its own), and proposals of putting cells of various and unknown capacities in series with a cell chemistry that explodes when reversed and/or overcharged.

[DrkAngel]

DrkAngel, Super writeup! Thank you for the info.

I just ordered six of the chargers on ebay. Thanks for the link.

It looks like the next thing I need to do is to start opening the packs and separating the individual batteries. Should I leave them in pairs or break into singles? In your picture it looked like some of the batteries were still in pairs unless you did some really cool soldering.

After the chargers arrive I will start charging and testing thanks to your write up.

The only issue I'm trying to figure out right now is how to load test the cells...

Thanks! Excellent thread!!

Leave cells in pairs! one in the charger, charges both.

As for discharging:
6v headlight?
place 3 cells, or 3 dbl cells in series? Use 12v headlight, motor etc. Test 3 cells at once?

A supply of jumper wires is handy.
.

[DT98]

Yes, 6v headlight, good idea. It will be almost a month before I could even start to test. I will be watching this thread...

And I agree with the other post...don't be stoopid...
I prefer to be very careful and ask LOTS of questions and at minimum, over-engineer.
I studied EE in college albeit back in the mid '70's...when in doubt I will ask and observe caution at all times.

[auraslip]

I tend to agree with LFP.
Re-thinking this with safety in mind - it'd be hard to get enough matching cells from the same factory to build a decent battery. It'd be even harder to get cells matched in life cycles.

This will be a fun summer project for me once school gets out and I have time to kill. I've always wanted to make an ebike that is more bicycle than motor.
On the other hand, I would in no way think it'd be acceptable to give this bike to my girlfriend or sell it on craigslist!

Unless their was a way to monitor every cell in the pack, fuse it, and physically isolate it so it won't melt and short to other cells in the pack.
Lyen had a lifepo4 cyndrilical pack go up, and lifepo4 is supposed to be safe!
Their are some accounts on here of li-ion lico cells going into thermal runaway and exploding from soldering alone.

If that doesn't sound cool, then you don't belong on this forum!

[Spicerack]

I think some of us got burnt playing with fire as kids and now we're doing it all over again!

I monitor the temp of each cell as they charge and also try to keep the current in check as well. You can tell the bad cells straight away by the rapid temp rise (infra red contactless temp guns are good for this). Most cells go from ambient 25 celcius to low 30's at 2 amps charge rate but the bad ones go very quickly up to 50+. The worst one went to 80 in less than a minute. I have no doubt that it would have gone critical mass if I continued trying to charge it.

So yes, take all care people!