Homemade Battery Packs

kje said:

I would never charge my batterypack with a lead acid charger.

Thanks for the inputs folks! I discovered my Imax B6 works with the 11-18V DC input.

After charging my batterypack without balancing, all 3 cells was at excatly same voltage! Thats nice. But how can that be when they where unbalanced before charging?

Click to expand...

i don't think you understand what balanced means. a battery pack is balanced when each of the cells will discharge the same amount of charge from fully charged state to fully discharged state. none of this gobbledeegook about balancing according the voltage at the end of charge means anything.

you will know if your battery is balanced if you discharge it fully to the discharged state where the BMS cuts it off and all the cell voltages are the same. not at full charge.

Yes I know a battery pack is balanced when each of the cells will discharge the same amount of charge from fully charged state to fully discharged state. If you bulk charge an unbalanced batterypack, will all cells be at the same voltage when fully charged? I guess not?

My computer powersupply gives 15A at 12.44V. Can I use this to charge my 3s60p batterypack? I guess it won`t be fully charged to 12.6V... For higer voltage can I use this DC DC converter which I already have? (max 6A)

if you charge lipo up to 4.2V then it is full charged. the capacity depends on the cell, but balanced is always in reference to a battery, not a cell. so all the cells in the battery pack have to have the same capacity for the pack to be 'balanced'.

so you have to measure the capacity of each and every cell you insert into the battery and then mix and match the high capacity with the low capacity until each channel has the sums of capacity for all the cans or pouches on that channel equal in total capacity.

if you never measure capacity of the individual cells you have no idea whether the capacity of that channel is even close to being balanced. it cannot be guessed at by some charging profile at the end of charging. it has to be measured by discharging from full charge to full discharge. nothing else matters, especially not the assumed self discharge rate off the charger. many of us have already proved that is a red herring.

kje said:

I would never charge my batterypack with a lead acid charger.

Thanks for the inputs folks! I discovered my Imax B6 works with the 11-18V DC input.

After charging my batterypack without balancing, all 3 cells was at excatly same voltage! Thats nice. But how can that be when they where unbalanced before charging?

Click to expand...

Read - Bulk Charging Review
I wrote it specifically to explain this, and your other related questions.

The best thing about bulk packs is that you do not have to capacity match-test every cell!
Only every bank!

Once again ... !
Begin with pack fully charged and equal voltage at each bank.
Discharge deeply, but not below 3.7V for any bank.
Mark weak and strong banks.
Recharge to full ... banks should be equal again - equal energy out >>> equal energy in = same voltage as at start. (at moderate rates)
Remove cell(s) from strong bank(s) and add to weak bank(s).
Banks should be more equal ... repeat as necessary.

When properly balanced:
Voltage between banks will be identical at full charge and at maximum target discharge!
Balance charger will not be required!
Bulk charger can speedily and reasonably safely charge your battery pack.

However!
If you failed to remove self-discharging cells ...
You will need to balance charge every single time ... immediately before any use!

Of course you should monitor your pack for broken connections, cell gone bad etc.
Just compare bank voltages, if any imbalance occurs ... hunt down the problem.

12.44V power supply will work nicely ... if!
If ... It survives a more than 15A discharge without cooking a or blowing some component.
Using a light gauge charging wire might help keep amps below 15A!

12.44V is much preferable to 12.60V for prolonging cell life.
Of course I recommended not exceeding 12.3V ... based on the cells you are using.
(Did you not notice that your iMax B6 charges Lion (Li-ion) to only 4.10V?)

Yes DrkAngel, that was a excellent post from you! I`ve learned so much from you and your skills. I should call you DrkGenius...

After next discharge at 11.2V I`ll compare the voltage of the three banks and move cell (cells) from stronger bank to the weaker bank. Then charge it up with my computer power supply at 12.44V using a light gauge charging wire.

Would you say 3.72V, 3.73V, and 3.75V was bad after my very first discharge?

I have bought the Low voltage Buzzer alarm. Should I program it to alarm at 3.7V under load with my 3s60p?

DrkAngel said:

kje said:

Thanks both of you. 11.2V under load or resting voltage?

Click to expand...

11.2V = "empty" voltage at rest.

With battery at resting ("empty") voltage, run motor at normal.
Measure voltage ... This will give you "empty" voltage under load.

Click to expand...

I see it was 11.2V at rest. (11.2V : 3 = 3.7V pr bank)
But under load, at what voltage should I set my Buzzer alarm?

kje said:

I have bought the Low voltage Buzzer alarm. Should I program it to alarm at 3.7V under load with my 3s60p?

DrkAngel said:

kje said:

Thanks both of you. 11.2V under load or resting voltage?

Click to expand...

11.2V = "empty" voltage at rest.

With battery at resting ("empty") voltage, run motor at normal.
Measure voltage ... This will give you "empty" voltage under load.

Click to expand...

I see it was 11.2V at rest. (11.2V : 3 = 3.7V pr bank)
But under load, at what voltage should I set my Buzzer alarm?

Click to expand...

Answer is in your quote ... ???
You have to determine for yourself ... based on above method ...
and higher if you want enough left to get home.

kje said:

I have bought the Low voltage Buzzer alarm. Should I program it to alarm at 3.7V under load with my 3s60p?

DrkAngel said:

kje said:

Thanks both of you. 11.2V under load or resting voltage?

Click to expand...

11.2V = "empty" voltage at rest.

With battery at resting ("empty") voltage, run motor at normal.
Measure voltage ... This will give you "empty" voltage under load.

Click to expand...

I see it was 11.2V at rest. (11.2V : 3 = 3.7V pr bank)
But under load, at what voltage should I set my Buzzer alarm?

Click to expand...

You do a simple test. When the battery pack is at 11.3V at rest then take the voltage value at max throttle. And set buzzer to that amount.

Skalabala said:

You do a simple test. When the battery pack is at 11.3V at rest then take the voltage value at max throttle. And set buzzer to that amount.

Click to expand...

Good idea! But you mean at 11.2V?

Tragedy
Broke a LiPo ribbon cable - thin aluminum
One bank low, so I disassembled and traced the problem.
6pack, nearest the back-bottom, broke the pos power ribbon from one cell.
For convenience, I have the top banks setting on the connections.
I better supported the top bank by placing wooden spacers between the bottom banks and the Formica "shelf".
If it does not work for an extended period, I will ...
I will flip upper bank and run longer wiring. (Probably a good idea!)


Ribbon broke at poorly supported bank with brown heatshrink.

650+ miles
4th metered recharge 3.70V - 4.182V = 24.42Ah (Black iMax B8)

1st metered recharge 3.82V to 4.16V = 18Ah.(Blue iMax B8)
2nd metered recharge 3.695V - 4.170V = 24.264Ah (Blue iMax B8)
3nd metered recharge 3.666V - 4.185V = 27.647Ah (Black iMax B8)
4th metered recharge 3.70V - 4.182V = 24.42Ah (Black iMax B8)

I used a watt meter measuring the capacity of my batterypack while trolling with my boat-motor.


I measured 74ah when my batterypack was at 11.2V. I was hoping on 100ah.

I discovered some loose connections when I came home, so I soldered them. I also soldered a balance plug so I can easily check each cell, balance them, and use my buzzer alarm as well when using the batterypack.

I've been using these recycled LiPo cells in eBike packs, power tool packs etc. and decided that it would be handy to get more precise with capacity from remaining voltage.

Graphing program allows an area function ... allowing determining a percentage of area map.



I used 4.18V as 100% merely as an "ease of math" function.
I have been charging to 4.14V ... but may revise to 4.12V.
My preliminary determination of charging to only 4.02V seems unnecessary.

Unnecessary ... in that the extreme additional lifespan sacrifices a substantial capacity bulge that seems designed for and in want of being used.

As a "self justification" ... I estimate that my quick about town errands use less than 5Ah.
This means that if I charge immediately after each little "run" ... discharge-charge remains tightly within the 4.05-4.12V bulge.

Now ... Hypothetically ... cell damage-wear-deterioration is due to voltage range ...
additional .1V charge cutting cycle life in half ...
additional discharge depth damaging cycle life.

To the best of my acquired understanding ...
The electrons are stored in a carbon-graphite lattice.
As electrons are added-subtracted , the lattice expands-contracts ... causing cracks and occasional collapse ... hence the gradual capacity deterioration.
Limiting voltage range to the voltage range of best capacity ... likely-hopefully would result in the least flexing = least deterioration for amount of usable capacity.
If amount of "flex" is due to voltage rather than capacity (As seem likely) then keeping use to within these energy rich regions should increase usable life better than lowering voltage!

And yes ... although this is presented as a hypothesis ...
I do anticipate rampant discord from the resident flat Earther(s) ...

DrkAngel said:

Tragedy
Broke a LiPo ribbon cable - thin aluminum
One bank low, so I disassembled and traced the problem.
6pack, nearest the back-bottom, broke the pos power ribbon from one cell.
For convenience, I have the top banks setting on the connections.
I better supported the top bank by placing wooden spacers between the bottom banks and the Formica "shelf".
If it does not work for an extended period, I will ...
I will flip upper bank and run longer wiring. (Probably a good idea!)

Ribbon broke at poorly supported bank with brown heatshrink.

650+ miles
4th metered recharge 3.70V - 4.182V = 24.42Ah (Black iMax B8)

1st metered recharge 3.82V to 4.16V = 18Ah.(Blue iMax B8)
2nd metered recharge 3.695V - 4.170V = 24.264Ah (Blue iMax B8)
3nd metered recharge 3.666V - 4.185V = 27.647Ah (Black iMax B8)
4th metered recharge 3.70V - 4.182V = 24.42Ah (Black iMax B8)

Click to expand...

Sadly my "repair" with added support etc. failed miserably!
2 banks showing additional damage, after a few cycles.
So, rather than another "repair" I pulled the 6 major banks and replaced with new 2010 cells.
Yes!
I did position to prevent further damage!



I have run a few cycles and then a deep discharge for capacity check.
Discharged to 25.66V.
All cells were equal within 2/1000th V at 3.666V!
This shows excellent matched capacity!
Beyond any reasonable expectation.
The quality control and durability built into these 4 year old cells is astounding!!!

Did a metered recharge using iMax B8 (Blue).
3.666 - 4.156V = 25.376Ah

#1 Laptop LiPo Build 2004-08 used cells
2011 - 24.0Ah (25.9 to 29.4V)
2012 - 20.8Ah (25.9 to 29.4V)
2013 - 15.8Ah (25.9 to 28.7V) 6500+ miles
2014 - 12Ah+ (25.9V to 29.2) 7000+ miles

#2 Laptop LiPo Build 2008 NOS cells
1st metered recharge 3.82V to 4.16V = 18Ah.(Blue iMax B8)
2nd metered recharge 3.695V - 4.170V = 24.264Ah (Blue iMax B8)
3nd metered recharge 3.666V - 4.185V = 27.647Ah (Black iMax B8)
4th metered recharge 3.70V - 4.182V = 24.42Ah (Black iMax B8)

#3 Laptop LiPo Build - Rebuilt 25.9V 25.92Ah 2010 Laptop LiPo (Dell)
1st metered recharge 3.666V to 4.156V = 25.376Ah.(Blue iMax B8)

22.2V 30.24Ah NOS Laptop Lipo ...
Yes, I will flip upper bank before I use again!

Replaced and repositioned LiPo cells in my latest 25.9V 25.92Ah eZip battery build.
Terminal, possibly fuse, damage to multiple banks.
All cells will be fuse removed and prepared for IR reduced-high output power tool use.
4 1s12p banks are perfectly equal in capacity and likely in IR.
1 1s12p bank has 1-2 damaged cells
1 1s12p bank has 2-4 damaged cells.

Enough good cells to rebuild:
5 5s2p 18.5V 4.32Ah cordless for 2 Craftmen 19.2V 1.4Ah and 3 B&D 18V 1.2Ah modules
and
2 14.8V 4.32Ah cordless for B&D

18.5V B&D runs weedeater continuously with no notable heat production.
Blower ... after clearing sidewalks, parking area and porch is slightly warm, possibly a 20ºF temp rise.
I smoothed bottom and firmly contacted cells to bottom as a makeshift heat dispersion "sink".

14.8V ran a sawzall for a fairly prolonged trimming session with no noticeable heat production.
I will gather up all similar used cells from previous projects and properly capacity and IR rate for matching and rebuilding packs for various florescent lantern,s portable radios, inverter packs etc.

So I am a computer repair tech and we have a box of recycled batteries. I just checked the box and ended up with a huge stash. They are 13 and 15 inch macbook pro non unibody and unibody batteries. Some have swollen and some are just "used" Are these worth hanging onto?

I am in Poughkeepsie NY if anyone is interested in working with me. I will split the batteries with you and we can each make a pack.



Here is one of the 15 inch packs non unibody opened up.

If there are enough good cells of the same size/capacity then I'd use them. I've got a 12ishV pack for general use made from a macbook battery and it's been going strong for 3 years now.

If I had enough I'd make an ebike battery out of them- they seem to be pretty decent but I guess I'd like to know the C rating first.

22.2V 30.24Ah pack performing ... OK ...
Sadly, the loss of low end torque and top end speed is frustrating ... to me.

Possibly, the eZip 24V controller partially limits current as LVC is neared?
Anyhow, I "need" to reposition upper bank, flip to protect connectors so, while rewiring, I will also reassign side cells as a 7th bank.
Creating a 2nd "new" 25.9V 25.92Ah pack.



I will either use on a lower geared eZip or learn ... throttle restraint!
I have 2 eZips in need of new controllers.
I will test acquired controllers, looking for 24V - 36V+ multi-compatibility.
At the least I will build another 33.3V capable w/22T freewheel mod ... looking for 20mph "legal" with greatly increased torque and acceleration.
If multi-voltage capable ... 25.9V w/22T mod will be perfect at 14mph limit for certain hefty oldenfoegy.

micro23 said:

Here is one of the 15 inch packs non unibody opened up.

Click to expand...

I've never seen a lipo so swolen. don't use that cell.

Hi guys, i'm new here and i want to ask something.
Recently i've built Li-ion 3,6 and 3,7V battery pack for EV project. The battery is 21S34P(wich have bridges between every 1S of the all 34P cells).
My balancer will be 4 of these modules:

My asking is: did these balancers will do the job of balancing the whole battery while charging/discharging the pack on the move.
The maximum charged voltage is 86.1V, and fully discharged voltage is 77.7V for the pack.
Pictures soon.

most, if not all, balance circuits discharge the cells with a higher voltage to equalize. It gives every cell the voltage of the lowest cell, which is good if you're not planning on paying attention to each cell's voltage, but maintenance requires a periodical check to see that it's doing it's job.

stealthhack said:

Hi guys, i'm new here and i want to ask something.
Recently i've built Li-ion 3,6 and 3,7V battery pack for EV project. The battery is 21S34P(wich have bridges between every 1S of the all 34P cells).
My balancer will be 4 of these modules:

My asking is: did these balancers will do the job of balancing the whole battery while charging/discharging the pack on the move.
The maximum charged voltage is 86.1V, and fully discharged voltage is 77.7V for the pack.
Pictures soon.

Click to expand...

With the size of your pack, those "balancers" will have no noticeable effect!
Balance-discharge current is a mere microscopic percentage of the pack.

Worse ...
if the banks are not equal in capacity, the item will drain certain banks at full but different banks as cells are discharging.

Highly recommend that you not use!
Much better, in every way, to rebuild or "tune" pack by equalizing the capacity of each bank of cells.

DrkAngel said:

Once again ... !
Begin with pack fully charged and equal voltage at each bank.
Discharge deeply, but not below 3.7V for any bank.
Mark weak and strong banks.
Recharge to full ... banks should be equal again - equal energy out >>> equal energy in = same voltage as at start. (at moderate rates)
Remove cell(s) from strong bank(s) and add to weak bank(s).
Banks should be more equal ... repeat as necessary.

When properly balanced:
Voltage between banks will be identical at full charge and at maximum target discharge!
Balance charger will not be required!
Bulk charger can speedily and reasonably safely charge your battery pack.

However!
If you failed to remove self-discharging cells ...
You will need to balance charge every single time ... immediately before any use!

Of course you should monitor your pack for broken connections, cell gone bad etc.
Just compare bank voltages, if any imbalance occurs ... hunt down the problem.

Click to expand...

See - Bulk Charging Review!

DrkAngel said:

stealthhack said:

Hi guys, i'm new here and i want to ask something.
Recently i've built Li-ion 3,6 and 3,7V battery pack for EV project. The battery is 21S34P(wich have bridges between every 1S of the all 34P cells).
My balancer will be 4 of these modules:

My asking is: did these balancers will do the job of balancing the whole battery while charging/discharging the pack on the move.
The maximum charged voltage is 86.1V, and fully discharged voltage is 77.7V for the pack.
Pictures soon.

Click to expand...

With the size of your pack, those "balancers" will have no noticeable effect!
Balance-discharge current is a mere microscopic percentage of the pack.

Worse ...
if the banks are not equal in capacity, the item will drain certain banks at full but different banks as cells are discharging.

Highly recommend that you not use!
Much better, in every way, to rebuild or "tune" pack by equalizing the capacity of each bank of cells.

DrkAngel said:

Once again ... !
Begin with pack fully charged and equal voltage at each bank.
Discharge deeply, but not below 3.7V for any bank.
Mark weak and strong banks.
Recharge to full ... banks should be equal again - equal energy out >>> equal energy in = same voltage as at start. (at moderate rates)
Remove cell(s) from strong bank(s) and add to weak bank(s).
Banks should be more equal ... repeat as necessary.

When properly balanced:
Voltage between banks will be identical at full charge and at maximum target discharge!
Balance charger will not be required!
Bulk charger can speedily and reasonably safely charge your battery pack.

However!
If you failed to remove self-discharging cells ...
You will need to balance charge every single time ... immediately before any use!

Of course you should monitor your pack for broken connections, cell gone bad etc.
Just compare bank voltages, if any imbalance occurs ... hunt down the problem.

Click to expand...

See - Bulk Charging Review!

Click to expand...

The battery bank is already assembled, all cells tested for bleeding voltage before assembling so the lowest capacity of some cells is about 1.6Ah(fabric capacity), highest is about 2.6Ah the max discharge rate for the entire pack will be no more than 1C(68Ah) Cont. and 2C(136Ah) controlled, and up to 2C at charging.
After all we're speaking at about 714 cells, every one tested, and assembled with capacitor welder.

that's a lot of cells. How many bms are you using?

stealthhack said:

The battery bank is already assembled, all cells tested for bleeding voltage before assembling so the lowest capacity of some cells is about 1.6Ah(fabric capacity), highest is about 2.6Ah the max discharge rate for the entire pack will be no more than 1C(68Ah) Cont. and 2C(136Ah) controlled, and up to 2C at charging.
After all we're speaking at about 714 cells, every one tested, and assembled with capacitor welder.

Click to expand...

Laptop cells(?) are not designed to be charged at 2C!
<.5C recommended! (Certain manufacturers limit at .8C)
Watch for heat ... heat is damage, to Li-ion cells.

Just add cell-cells to weaker banks ... or cut cells from stronger banks.
Equal capacity is much more important than a tidy appearance.
(Cut cell-cells, out of circuit and wire to bank needing more capacity? Leave in your nice tidy package-location.)
Otherwise you will constantly be balancing all banks, some at full and others the rest of the time.
And this will cause the weaker banks to deteriorate more quickly ... getting worse constantly and at an accelerating rate.

Equal capacity between banks will negate the need for any balancing devices and provide an even-equal capacity deterioration as use continues.
Of course you should still monitor bank voltages!

stealthhack said:

DrkAngel said:

stealthhack said:

Hi guys, i'm new here and i want to ask something.
Recently i've built Li-ion 3,6 and 3,7V battery pack for EV project. The battery is 21S34P(wich have bridges between every 1S of the all 34P cells).
My balancer will be 4 of these modules:

My asking is: did these balancers will do the job of balancing the whole battery while charging/discharging the pack on the move.
The maximum charged voltage is 86.1V, and fully discharged voltage is 77.7V for the pack.
Pictures soon.

Click to expand...

With the size of your pack, those "balancers" will have no noticeable effect!
Balance-discharge current is a mere microscopic percentage of the pack.

Worse ...
if the banks are not equal in capacity, the item will drain certain banks at full but different banks as cells are discharging.

Highly recommend that you not use!
Much better, in every way, to rebuild or "tune" pack by equalizing the capacity of each bank of cells.

Click to expand...

Click to expand...

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!!!