Homemade Battery Packs

Batteries, Chargers, and Battery Management Systems.
stealthhack   100 µW

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Re: Homemade Battery Packs

Post by stealthhack » Jul 18 2014 9:37am

DrkAngel wrote:Balance PRO discharges-balances at 150mAh.
34p x ~2000mAh = 68,000mAh
150mAh / 68,000mAh = 0.002 = .2% "balance" per hour

A single .1V high bank would take ~100 hours to balance ...
Worse! ... At near empty ... balancers would spend 100 hours bleeding down all the remaining 20 banks!
To be repeated with every cycle!

Much better to re-shuffle a few cells!!!
And how to re-shuffle a few cells without splitting the battery bank?
Some pictures of the battery bank:
DSC_0001.jpg
DSC_0002.jpg

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teslanv   100 MW

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Re: Homemade Battery Packs

Post by teslanv » Jul 18 2014 10:12am

stealthhack wrote:
DrkAngel wrote:Balance PRO discharges-balances at 150mAh.
34p x ~2000mAh = 68,000mAh
150mAh / 68,000mAh = 0.002 = .2% "balance" per hour

A single .1V high bank would take ~100 hours to balance ...
Worse! ... At near empty ... balancers would spend 100 hours bleeding down all the remaining 20 banks!
To be repeated with every cycle!

Much better to re-shuffle a few cells!!!
And how to re-shuffle a few cells without splitting the battery bank?
Some pictures of the battery bank:
DSC_0001.jpg
DSC_0002.jpg
HOLY SH1T!
I count 21X34 or 714 cells there!!!
Where do you mount a bank like that? It is for a Car?
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stealthhack   100 µW

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Re: Homemade Battery Packs

Post by stealthhack » Jul 18 2014 10:18am

teslanv wrote:HOLY SH1T!
I count 21X34 or 714 cells there!!!
Where do you mount a bank like that? It is for a Car?
Yes it is, but it needs proper BMS for longer life! :)
It's TESLA style! :D

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lxgoldsmith   10 W

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Re: Homemade Battery Packs

Post by lxgoldsmith » Jul 18 2014 10:20am

lol a lot of cells. Looks like it's for a go-kart. a car mod would take more amps than laptop cells could handle for long periods. 1c at a constant rate will generate heat for those cells, especially in the middle, where there's no airflow. what are you cooling them with?

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Re: Homemade Battery Packs

Post by stealthhack » Jul 18 2014 10:23am

lxgoldsmith wrote:lol a lot of cells. Looks like it's for a go-kart. a car mod would take more amps than laptop cells could handle. 1c at a constant rate will generate heat for those cells, especially in the middle, where there's no airflow. what are you cooling them with?
Tesla made 18650 cells with water cooling, so they can handle 300KW peak, from 8k 18650 cells!
Mine are just air-cooled 714 cells, so they will be controller limited to 1-2C charge/discharge, ffs your laptop eats about 80W under full load from 6 cells which is 2C minimum and they don't overheat! 8)

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Re: Homemade Battery Packs

Post by Skalabala » Jul 18 2014 10:48am

stealthhack, buddy be careful with what you are doing.
I see you have 3.6V mixed with 3.7V cells. So the max voltage should not go higher than 4.05V and lowest 3.75V otherwise you will be looking for trouble with old cells!
Did you do a sag test on each bank while putting a 1C load on the whole pack?

Read a bit more in this thread :) As you have a really BIG bomb there! :lol:
Image
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stealthhack   100 µW

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Re: Homemade Battery Packs

Post by stealthhack » Jul 18 2014 10:55am

Skalabala wrote:stealthhack, buddy be careful with what you are doing.
I see you have 3.6V mixed with 3.7V cells. So the max voltage should not go higher than 4.05V and lowest 3.75V otherwise you will be looking for trouble with old cells!
Did you do a sag test on each bank while putting a 1C load on the whole pack?

Read a bit more in this thread :) As you have a really BIG bomb there! :lol:
Still making the terminals(pos and neg) for the whole battery, but before assembling i tested them one by one for 1C load, and all do it perfectly, not to mention that most of them do 10-15A peak discharge(the good cells do 17-20A) without even hesitating!
So i'm pretty shure what i'm doing, the problem is that with time they will start to get out of balance, and i don't wan't that!
EDIT: and as i said in the first post the full to empty voltage will be 86.1(21x4.1V) - 77.7(21x3.7V) in the safe limits!
And about that sag, i do these bridges between packs on purpose so the energy to flow from the battery with less sag to that with more(energy ballance).

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DrkAngel   100 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Jul 19 2014 5:50am

stealthhack wrote:
DrkAngel wrote:Balance PRO discharges-balances at 150mAh.
34p x ~2000mAh = 68,000mAh
150mAh / 68,000mAh = 0.002 = .2% "balance" per hour

A single .1V high bank would take ~100 hours to balance ...
Worse! ... At near empty ... balancers would spend 100 hours bleeding down all the remaining 20 banks!
To be repeated with every cycle!

Much better to re-shuffle a few cells!!!
And how to re-shuffle a few cells without splitting the battery bank?
I see ...
Cutting Serial and Parallel tabs and wire tacking cells looks a bit daunting.

I would recommend, instead, a small auxiliary pack with wires to each bank.
Then assign the proper number of additional cells to each necessary bank.

Auxiliary pack could also contain-mount voltage monitors-balance modules.

Create a quick connect using ...
24pin ATX Extension - $4.99

Oh!
I like that your "pack" has each bank containing a fairly equal representation of each type of cell.
Each brand-model of cell has different capacity and IR characteristics ...
Keeping a proper mix helps maintain reasonably equal bank voltages during all rates and depths of discharge.
Last edited by DrkAngel on Dec 26 2014 9:51am, edited 1 time in total.
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stealthhack   100 µW

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Re: Homemade Battery Packs

Post by stealthhack » Jul 19 2014 10:00am

DrkAngel wrote:
stealthhack wrote:
DrkAngel wrote:Balance PRO discharges-balances at 150mAh.
34p x ~2000mAh = 68,000mAh
150mAh / 68,000mAh = 0.002 = .2% "balance" per hour

A single .1V high bank would take ~100 hours to balance ...
Worse! ... At near empty ... balancers would spend 100 hours bleeding down all the remaining 20 banks!
To be repeated with every cycle!

Much better to re-shuffle a few cells!!!
And how to re-shuffle a few cells without splitting the battery bank?
I see ...
Cutting Serial and Parallel tabs and wire tacking cells looks a bit daunting.

I would recommend, instead, a small auxiliary pack with wires to each bank.
Then assign the proper number of cells to each necessary bank.

Auxiliary pack could also contain-mount voltage monitors-balance modules.

Create a quick connect using ...
24pin ATX Extension - $4.99

Oh!
I like that your "pack" has each bank containing a fairly equal representation of each type of cell.
Each brand-model of cell has different capacity and IR characteristics ...
Keeping a proper mix helps maintain reasonably equal bank voltages during all rates and depths of discharge.
My first thought was to sort all type of batteries, then i will need 21 batteries of each type for a serial pack(for example Panasonic 2200Mah x21 cells or sony E5 type again 21 cells) i couldn't collect that quantity of cells for each pack, then i start to make packs with close enough fabric capacities.
I don't expect cells to drift voltages with big difference under 1-2C, which is what i need.

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DrkAngel   100 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Jul 31 2014 8:23am

Resource for identification and basic specs on many currently available cells.
18650's and more

Large data base of cell specs by independant tester.
See - 18650 Database - 2012

For older cells do a Google search for the cell label marking.
Typically 18650 with added characters eg. "18650GR" or "ICR18650-23A"
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Re: Homemade Battery Packs

Post by kje » Aug 16 2014 7:26am

I used this watt meter measuring the capacity of my 12V batterypack while trolling with my boat-motor, but I melted the wire and connection. The connection I used was Powerpoles 45. I draw about 50A continuos. I think maybe the leads on this watt meter is too small?
Wattmeter.JPG
Wattmeter.JPG (45.82 KiB) Viewed 3501 times

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Re: Homemade Battery Packs

Post by DrkAngel » Aug 16 2014 7:50am

"Rugged- handles 50A continuous and 100 A peak at 60V
14a ga., super fine stranded, high temperature, silicone rubber insulated wire"

Rated for 50A continuous = exceeding 50A for any prolonged time will produce damage - destruction.
14ga wire is UL rated for 15A ... for eBikes I recommend 30A limit.

So ... yeah ... wires, and likely more components, are too lightweight for exceeding 50A!

Also, Anderson powerpoles 45 are only rated for 45 Amps.
Wires and connectors will overheat at 50A+ ... wires mostly tho ...
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Re: Homemade Battery Packs

Post by kje » Aug 16 2014 7:52am

kje wrote:I used this watt meter measuring the capacity of my 12V batterypack while trolling with my boat-motor, but I melted the wire and connection. The connection I used was Powerpoles 45. I draw about 50A continuos. I think maybe the leads on this watt meter is too small?
Wattmeter.JPG
Would this one be better?
High-precision RC 150A Watt Meter and Power Analyzer w/ Backlight LCD

And what connection should I use for 50A continuos? Deans plug?

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DrkAngel   100 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Aug 16 2014 8:33am

Wires look beefier ...
Been running my digital magnifier over the wires in the pictures ... finally found "12AWG".
Definitely better than the 14AWG on old unit ... but ...
Still exceeds my recommended use.

Alternate description states "Handles up to 150 amps intermittently and 75 amps continuous duty."

Might do you OK ... ?

Next better is likely a hefty step up in price or requires external shunt and loses functions.
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DrkAngel   100 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Aug 16 2014 3:54pm

kje wrote:
kje wrote: And what connection should I use for 50A continuos? Deans plug?
Deans (T Plugs) are reputed to be 100A capable.
Anderson powerpole 75 are available also ... if you like them.
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DrkAngel   100 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Aug 29 2014 9:13am

DrkAngel wrote:Gitten-er-done!

After draining my 33.3V 26Ah (9s10p) to 33.2V, ~3.7V per bank, I marked resultant voltages and added complementary 2s to each bank as deemed advisable.
Lowest bank got the best cells - best got the worst.
Lowest bank (3.65V) got 4500mAh, highest (3.71V) got 4100mAh, the remainder apportioned in between.
Since I will discharge to not below 3.8V, where cells were within 2/100th of each other and "good" ... now they are just "more good".

At 3.8V - 4.05V capacity is still >20Ah ...
I will measure Ah capacity after next deep discharge ... though I typically recharge immediately after any use and weather is too cold for any extended rides, so, full capacity test might wait till near Spring.

Image

Last 2 "p" were pulled from a different batch that had oddball tabs ... sorry, wanted it to look prettier!

I will monitor 1st few discharges ... mainly to check for bad-poor solder connections.
After that I will rely on bulk charging with the occasional balance check.

Edit - I did add 4 - 9mm, 1/2 cell height, blanks as support for the alternate banks.
And re-covered all cells with a wrap of boxing tape.
Both ends of cells were covered with closed cell polystyrene, (foam sheet, as is used for durable padding), to secure-stabilize cells tightly in pack.
33.3V 31.2Ah = 1 kWh pack got another test drive.
Controller failed in my 2013 Trailz LS.
Dropped in a very cheap 24V 500w controller, checked = 50V caps!
Ran great at 25.9V so ... pulled out my Snow Beasts 33.3V pack and plugged 'er in.
Wow ... eZip w/13T mod pushed right up to 25 mph ... without pedal assist!

Too fast to pedal, 44T >> 14T hits 90rpm pedal speed at about 19mph.
Was able to hit 28 mph with frantic 55 year old legs ... Likely could maintain 30 mph with higher gears.

But the 2013 is my comfort Cruiser, so will drop cheapo controller into some older model and regear it for higher speed commuting.
Will likely exceed recommended throughput, so I will trim the mounting tabs, on the controller and add heatsink compound to base.
Placed firmly against inside of eZip aluminum rack box, should use the entire rack as a large heatsink!


More info - $12.59 24-36V brush controller
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DrkAngel   100 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Sep 10 2014 8:24am

Been running cheapo 24V controller for several hundred miles with a mix of 25.9 and 33.3V batteries.
Running nice!
Seems to have "sharper" take off with hard throttle ... initial surge.
2 additional eZips slated for controller upgrade ... waiting on delivery ..

Yes, I will build 2 additional 33.3V battery packs.

LiPo:
Laptop recycled - 8p 2160mAh = 17.28Ah
+ RC LiPo - 2p 2000mAh = 4Ah
= 33.3V 21.28Ah
Intended for eBike, re-geared for 20mph top speed.
Will pull 1C plus from stop, but only briefly.
Local hills should demand less than 1C, at specified gearing
RC added to supplement 1C+ surge requirements

Li-ion 18650's:
9s12p 2600mAh NOS Sanyo cells 33.3V x 31.2Ah = 1039wh = 1.039 kWh
For trips ≤20mph and for "geared up" eZip for assist toward 30mph!

Side note:
broke a spoke on 2013 eZip, maybe 33.3V extra torque and better surge from new controller?
I will rebuild 4 wheels for eZip.
Been waiting for mass production opportunity.
2 OEM wheels with 13ga SS spokes and washers.
2 aftermarket alloy hubs, better rims and 14ga SS spokes - got 2 WheelMaster alloy w/SS spokes on clearance, relace onto new hubs.
Will document ...
See - Broken Spokes - eZip - Solutions!
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There, shallow draughts intoxicate the brain,
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I enjoy enlightening ... and enlivening the spirit of the innovators.

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DrkAngel   100 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Nov 01 2014 10:14am

DrkAngel wrote: Yes, I will build 2 additional 33.3V battery packs.

LiPo:
Laptop recycled - 8p 2160mAh = 17.28Ah
+ RC LiPo - 2p 2000mAh = 4Ah
= 33.3V 21.28Ah
Intended for eBike, re-geared for 20mph top speed.
Will pull 1C plus from stop, but only briefly.
Local hills should demand less than 1C, at specified gearing
RC added to supplement 1C+ surge requirements

Li-ion 18650's:
9s12p 2600mAh NOS Sanyo cells 33.3V x 31.2Ah = 1039wh = 1.039 kWh
For trips ≤20mph and for "geared up" eZip for assist toward 30mph!
Presently in the process of testing cells for 33.3V 18650 build.
Looks like 6 Sanyo and 3 Sony 3s4p packs will be shuffled into 9 banks of 8 Sanyo and 4 Sony.
Dependent on test results of course ...
I am testing 6 Sanyo packs and 6 Sony packs, in case there is a pack of less than optimal condition.
I intend on using the leftovers to re-cell Ryobi power tool Lithium battery packs.
Yeah ... I know! They will not have the surge capability of the oem cells.
But, they will have substantial greater capacity for lower drain devices - lights, fans, radios, jigsaw, light duty drill etc.

Might have time to open up and test NOS Lipo for Lipo-RC Lipo hybrid pack ,,,
Better test up all the 3s1p 2000mAh RC Lipo. Need 6 for hybrid pack and would like 4 for 6s2p 22.2V for B&D NiCd upgrade power tool pack.
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Re: Homemade Battery Packs

Post by LeftieBiker » Nov 02 2014 6:52pm

If you ever get enough extra almost-perfect cells to build a ~29 volt pack, I'd like to have one of those to use with the OEM controller. I don't have the equipment to charge cells alone or in pairs, and I'm swamped with home wiring projects. I have a spare EZIP slope tube bike, in nice shape except the motor, that I'd be willing to swap for a pack and a charger that could do 29 volts..

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DrkAngel   100 GW

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Re: Homemade Battery Packs

Post by DrkAngel » Nov 03 2014 7:15am

eZips controller handles 7s 25.9V (29.4V fully charged) in every tested model.
7s12p fits in the oem pack.
New 2600mAh cells can provide 25.9V x 31.2Ah = 808Wh.
Compare to OEM SLA (usable) 24V x 10Ah = 240/2 = 120Wh
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Re: Homemade Battery Packs

Post by drmacgyver » Nov 03 2014 1:06pm

Hi all,

I'm looking to build a 6s10ah 18650 battery pack for my skateboard. I haven't found a 10ah battery but I have found 5ah, so if I'm understanding correctly, I will need 12x 5ah = two 6s5ah packs connected in parallel. If this is correct, can someone please point me to a diagram/tutorial that will show me how to connect in both series and parallel, including how to connect the balance leads?

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Re: Homemade Battery Packs

Post by DrkAngel » Nov 03 2014 1:53pm

drmacgyver wrote:Hi all,

I'm looking to build a 6s10ah 18650 battery pack for my skateboard. I haven't found a 10ah battery but I have found 5ah, so if I'm understanding correctly, I will need 12x 5ah = two 6s5ah packs connected in parallel. If this is correct, can someone please point me to a diagram/tutorial that will show me how to connect in both series and parallel, including how to connect the balance leads?
Well 1st ... !
A 5Ah 18650 is likely Bogus!

3A+ 3000mAh+ cells would be listed as genuine Panasonic or Samsung ... or ... some other major manufacturer.

2.6Ah 18650s are very common.
6s4p = 22.2V 10.4Ah
Last edited by DrkAngel on Nov 03 2014 6:23pm, edited 1 time in total.
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Re: Homemade Battery Packs

Post by drmacgyver » Nov 03 2014 2:06pm

I've been searching ebay and I've started to figure a 5ah battery is a myth. I found one, but then in the fine print it says "actual capacity 1800mah" - wtf? Anyways, just based off the price alone I'm guessing this is fake: http://www.ebay.com/itm/12-Pcs-18650-2- ... 51c10d42e4

I'm finding lots of 2600mah like you said, so 6s4p it is!

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Re: Homemade Battery Packs

Post by teslanv » Nov 03 2014 3:16pm

Yes, as far as 18650 cells go, 3400 mAh is the largest you will find that is "authentic", and which is a High-capacity/Low C" rate Panasonic cell. The Ultrafire and other generic name cells, I would not believe any advertised capacity greater than around 2500 mAh.
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Re: Homemade Battery Packs

Post by drmacgyver » Nov 03 2014 3:36pm

Thanks for the feedback guys! Regarding the build, I don't have access to a spot welder but I have a soldering iron. Am I SOL, or with some flux can I do it? Also are there any good tutorials/diagrams that you know of off hand for our purpose? I found this, which seems comprehensive: http://www.youtube.com/watch?v=R4aW_i-EAoc
Can anyone confirm if this is a good guide? If yes, the only info I'm missing is how to connect balance wires.

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