Homemade Battery Packs

[iperov]

my Lifepo4-Polymer battery pack.
1-5 photos - 9ah
6 - 11ah

6.jpg (183.09 KiB) Viewed 1783 times

[DrkAngel]

I do have a few kWh of Sony cells.
Most impressive is that they still display 5 led, (on pack. power level, meter), after 6 months, from initial charge.
3.6V- 4.1V looks to be recommended "usable".

Sony%204320s.JPG (11 KiB) Viewed 6948 times

Smooth%20LiPo%20s.JPG (10.06 KiB) Viewed 6948 times

Compared to the "unbranded" cells, from same model pack.
3.7V ... maybe 3.6V, - 4.1V recommended "usable".Larger versions "attached" below -

[DrkAngel]

My recycled 4320 Dbl. recycled cells.
The "unbranded" cells have a wider, "beefier", discharge curve.
(Yes, you may be hearing "Where's the beef?", from me ... later.)
The Sony cells have a much more "even" curve, with a better "bottom end".


I have 2 kWh of the Sony cells tagged for my "44 Magnum" project.
The 2 kWh Sony packs appear to be new, never used, they came oem packaged, with nary a scratch or smudge.
8kWh of the "unbranded", set aside for my eMotorcycle, just got a genuine ETEK, as motovation.
The, reserved, 8 kWh unbranded, maintained 4 of 5 power level leds, still lit, 6 months after charging.
Also, the "unbranded" looks to have much better "limping" capability, from 3.7V and under.
Important, if you have no pedals!

[DrkAngel]

44 Magnum
I will test my 44.4V Lipo pack, initially as a 1kWh saddlebag configuration.
22.2V per side, straddling the top, triangle, bar.
"Saddle" will be center supported, and cut, allowing it to push forward with some cell protrusion in front of steering column.
Possibly, I will mount a headlight between this front protrusion, and turn indicators as outriggers ... camo.
Shifting the pack forward, in this manner, should allow adequate knee clearance, for pedaling.

Also, I intend this pack to be removable, and transferable.
So ... controller will be attached to saddlebag, in such a manner as to fit inside triangle, where all connections are placed.
When used as normal bike, standard, small type bag, should hide-protect wiring.

Such a setup would be ideal for a front hub conversion.
44 Magnum

Pack itself will be a 12S10P, using 120 "retasked", seemingly new, Sony LiPo cells.
(3.7V x 12) 44.4V x (2160mAh x 10) 21.6Ah = 959.04 kWh.

As verified by laptop & external charger, cells are designed to be charged to 4.1V.
I also verified this as advisable, using my mAh/100thV discharge test. - Sony 2160mAh
Providing a full charge 49.2V (4.1V) and discharging, to the optimal 43.2V. (3.6V)
48V controller has 40.5V LVC, should allow optimal discharge, even with heavy throttle voltage sag.

These cells are individually fused, a pack was tested with an initial 5C drain, that settled to a 2.5C+ drain, after several seconds, a fuse did blow.
Implying that spikes, near 80amps, can be handled and that a "drain", nearing 40amps, might be safely tolerated.
I will test this thoroughly, before pack assembly.
The only thing worse than bypassing 120 fuses, is having to disassemble a pack, then bypassing 120 fuses.
On the bright side, max surge draw should be less then 40amps and max sustained, near 20amps.
On the other hand, the "tasked" controller is a 48V 50A ... ?
Hmmm ....
Might go straight to a 43.2Ah pack ... ?

[dirkme]

What can I say, very informative and as eZip Trailz owner very helpful. Thanks a lot for putting that all together

[migueralliart]

On a side note anybody here had experience with 2.6Ah green sony US18650GR. I just got a batch of laptop batteries that are 5200 mah 10.8V 6 cell pack. My main concern with these cells is the discharge rate I have not tested them but pretty much all of them are 3.8V with only a few pairs damaged. Also I got LG red cells 2.6Ah from some of the packs. Anybody know about specs of these types of cells. The sony's seem newer and do not have the ENERGYTEC label on them (like the old designs)

[DrkAngel]

Just dug up a couple dozen old "ENERGYTEC" SONY cells.
Almost 3 years ago, I pulled these out of old packs and cut off the tabs, for use in flashlights n stuff.
Surprisingly, all cells, after sitting 3 years, still showed about 3.8V, with no corrosion where I ground off the spotweld residue.
Similar cells showed rust ... not stainless, magnet picks them up, must be some type alloy?

Will have to test them up, don't even remember the mAh. (Somewhere between 1800-2400mAh?)

As always ... will post results ...

[DrkAngel]

iMax B6 - $19.95 w/shipping

Requires 11-18V power supply.

Fortunately, I have a pile of Ibm 16V 4.5A notebook chargers.
Unfortunately, I'm never satisfied ... started playing with one of the Server PS I had laying around.
Now ... I have to find a use for 55A of nice, clean, reliable, 12V ... ?

[DrkAngel]

If you are getting the iMax B6 balance charger, be aware that various reports, find full 5amp charging to be "iffy". Recommend 2-3amp charging initially. Personally, my B8, blew a Mosfet at 5amps, 12v input - 29.4v output. Mosfet replaced, will test with higher input voltage, lower output voltage etc. Will post results. - May 2011

Got a 12.47V, 40Amp, power supply ... had to test it ... decided to push my repaired iMax B8, back up to 5Amps @ 29.4V.
Amperage spooled up and settled at 5 Amps then died ... PS (server PS) showed red led. Reset allowed iMax power up, but dies after charge hits .2Amp.
Gotta open 'er up again ...

Guess I can't recommend past 3-3.5 Amps ... ?

[migueralliart]

iMax B6 - $19.95 w/shipping

Requires 11-18V power supply.

Fortunately, I have a pile of Ibm 16V 4.5A notebook chargers.
Unfortunately, I'm never satisfied ... started playing with one of the Server PS I had laying around.
Now ... I have to find a use for 55A of nice, clean, reliable, 12V ... ?

I have one of these nd an icharger 3010b. I love the size and options for the price of the imax. Mine has been very reliable and its more accurate than what people say on the bad reviews.

[DrkAngel]

iMax B6 - $19.95 w/shipping, arrived.
21 days shipping time.
Came with all cables and manual - no box.
Start-up, proudly proclaims SKYRC.

Ran a single bank, then a balance charge, seems to be working well ...

1 Problem! - button beep, sounds like a sick little bird ...

[mxer]

I have just ordered one of these with a built in 5a ac adapter for the price of a couple of Big Mac meals

http://www.ebay.co.uk/itm/220910513791? ... 1439.l2649

[DrkAngel]

I've been recommending a cheap non-balancing Li-ion charger.
7S 25.9V - charges to 29.4V.
It charges to, an average, ~4.2V, no adjustment.

Discharge testing of various Lithium "types", indicates that lower full charge voltages, might be advisable.
Rather than attempting any form of internal modification, I put a 3amp "blocking diode" inline, on the positive wire.
Worked nicely! Dropped the Voltage nicely .3V, supplying an average of ~4.16V per cell.
Added, is the benefit of, no danger of electrical "backwash", plugging the battery, into an unpowered charger.

Quality-voltage reduction of blocking\rectifier\bypass diode, varies widely, by manufacturer. ~.2V to 1V+.
I received a .3V drop, from a unknown brand diode, nice "fit" for my purpose.

Larger-large capacity, blocking diodes, require an electrically isolated heatsink!

[iperov]

24v 5ah x 2
in QQ sports mini frame bags

2.jpg (218.1 KiB) Viewed 1783 times

[DrkAngel]

24v 5ah x 2
in QQ sports mini frame bags

Nice! Neat little package.

[DrkAngel]

I built my (recycled 18650) 25.9V 31.2Ah Last Spring.
I thought it to be a good time to give it a capacity test, it has survived 100+ charge - discharge cycles.

EZip 31.2ah Liion (600 x 450).jpg (108.21 KiB) Viewed 3733 times

1st step was to do a balance charge, to 29.4V (4.2V per cell), I used my new iMax B8.
Then I discharged to 25.2V (3.6V per cell).

I rated 3.6V as optimal minimum usable voltage, based on the discharge test, graphed below.
Cell variance at max discharge was within 2-3 100ths volt of 3.6V, excellent, IMO, for used cells.


(Different cell types have different discharge profiles!)


So test voltages were:
4.2V - full
3.6V - empty

The pack is a 7S12P, 3.7V 2600mah per cell.
With a 31.2Ah rating.
My iMax B8 balance re-charge, metered a 30.87Ah input.
Charging rate was 3A = .1C, for maximum efficiency.
Giving a 98.9% , of rated, capacity!
Not bad for old recycled cells!!!

Typically I do not charge this "fully" or discharge this deeply.
4.16V - full
3.7V - empty
are the voltages I use during "bulk" charging, and typical "lowest discharge voltage".
I, variously, use a modified Meanwell clone (7.3A) and a 29.4V (2A) Li-ion charger (trimmed with a blocking diode.)

I attribute the quality and survivability of this pack to the extra care I took in testing and matching cells!

I am presently performing the same testing procedure on the recycled Lipo build of similar age and more severe usage, (150+ cycles & and Winter usage)

[chilledoutuk]

I attribute the quality and survivability of this pack to the extra care I took in testing and matching cells!

That helps but honestly the quality of 18650 cells from the big manufacturers is what makes them so reliable.

out of interest what measures did you use to prevent the nickle strips cutting through the thin shrink on the pack you just showed and shorting cells?

[DrkAngel]

I attribute the quality and survivability of this pack to the extra care I took in testing and matching cells!

That helps but honestly the quality of 18650 cells from the big manufacturers is what makes them so reliable.

out of interest what measures did you use to prevent the nickle strips cutting through the thin shrink on the pack you just showed and shorting cells?

All the "nickle strips" are spot welded oem.
I added the angled tinned copper braid.
These cells have a blue plastic disc that covers the negative edge of the positive end, under the shrinkwrap.

The only place that I felt warranted extra protection, was on the positive edge, (upper, in picture), the tabs are folded over.
If you look carefully, you should be able to see the black duct tape, between the "strips" and the corners of the cells.

[DrkAngel]

I just capacity tested my 1 year old 25.9V 25.92Ah, homemade recycled Lipo pack.
(150+ cycles & and Winter usage)

Laptop Lipo.JPG (76.05 KiB) Viewed 3648 times

1st step was to do a balance charge, to 29.4V (4.2V per cell), I used my new iMax B8.
Then I discharged to ~25.9V (3.7V per cell).

I rated 3.7V as optimal minimum usable voltage, based on the discharge test, graphed below.
Cell variance at max discharge was within ~2 100ths volt of 3.7V, excellent, IMO, for used cells.
(1 bank "patched" by adding 1 - 18650 cell)

(Different cell types have different discharge profiles!)

Smoothed LiPo.jpg (22.9 KiB) Viewed 3648 times

So test voltages were:
4.2V - full
3.7V - empty

The pack is a 7S12P, 3.7V 2160mah per cell.
With a 25.92Ah rating.
My iMax B8 balance re-charge, metered a 20.8Ah input.
Charging rate was 3A = .125-.15C, for maximum efficiency.
Giving a 80.2% , of rated, capacity!
Acceptable for old recycled cells! ... ?
(Maximum capacity input measured 24Ah, deeper discharge, (last year))

Please note!
This pack was built from the reject Lipo packs.
These recycled cells were pulled from the laptop packs that failed to recharge in the oem charger.
I still have 8kWh's of these packs that do charge properly - designated eMotorcycle "fodder".

Typically I do not charge this "fully" or discharge this deeply.
4.16V - full
3.75V - empty
are the voltages I use during "bulk" charging, and typical "lowest discharge voltage".
I, variously, use a modified Meanwell clone (1V-56V adjustable 7.3A) and a 29.4V (2A) Li-ion charger (trimmed with a blocking diode.)

[SamTexas]

The pack is a 7S12P, 3.7V 2160mah per cell.
With a 25.92Ah rating.
My iMax B8 balance re-charge, metered a 20.8Ah input.
Charging rate was 3A = .125-.15C, for maximum efficiency.
Giving a 80.2% , of rated, capacity!

DrkAngel: I'm confused. Sounds like your capacity is measured by the amount of energy going INTO the battery during charging. Is that correct? If so, why do it that way?

[Ypedal]

this entire thread is a trainwreck........ it reeks of " safe " ..

[DrkAngel]

The pack is a 7S12P, 3.7V 2160mah per cell.
With a 25.92Ah rating.
My iMax B8 balance re-charge, metered a 20.8Ah input.
Charging rate was 3A = .125-.15C, for maximum efficiency.
Giving a 80.2% , of rated, capacity!

DrkAngel: I'm confused. Sounds like your capacity is measured by the amount of energy going INTO the battery during charging. Is that correct? If so, why do it that way?

Lithium Cobalt charging, at moderate rate, is 98-99% efficient, a good measure of capacity.
A typical discharge, at varying discharge rates gives varied percentages of efficiency.
An iMax, 1 amp, regulated, metered discharge might be more accurate but ~30 hours ... seems excessive?

SLA, Nicd, Nimh charging might rate at 50-70% efficient, but lithiums, particularly Lithium Cobalt, at moderate charge rates, attain near 100% efficiency-accuracy!

As specifically noted, charging rates were between .1C for 18650's and .125C, of rated, for the Lipo, so as to attain maximum efficiency.

[SamTexas]

Lithium Cobalt charging, at moderate rate, is 98-99% efficient, a good measure of capacity.
...
, but lithiums, particularly Lithium Cobalt, at moderate charge rates, attain near 100% efficiency!

Those percentages sound impressive. But have you verified their accuracy?

A typical discharge, at varying discharge rates gives varied percentages of efficiency.

The Peukert effect is minimal on Lithium, especially at much lower discharge rate (less than 0.33C in your case I believe). But that's beside the point. Why not just use the Cycle Analyst for capacity measurement? After all, that's the only meaningful capacity as far as riding an ebike is concerned. No?

[DrkAngel]

Lithium Cobalt charging, at moderate rate, is 98-99% efficient, a good measure of capacity.
...
, but lithiums, particularly Lithium Cobalt, at moderate charge rates, attain near 100% efficiency!

Those percentages sound impressive. But have you verified their accuracy?

Not personally.
Based on remembered ratings.
BatteryUniversity.com - I think.
Just did search - "Lithium-ion polymer battery - Wikipedia, the free encyclopedia
en.wikipedia.org/wiki/Lithium-ion_polymer_battery
•
Found on: Google, Yahoo! Search, Bing
"Li-Po" and "LiPo" redirect here. ... Charge/discharge efficiency, 99.8% ... LiPo batteries are usually composed of several identical secondary cells in parallel to ..."

A typical discharge, at varying discharge rates gives varied percentages of efficiency.

The Peukert effect is minimal on Lithium, especially at much lower discharge rate (less than 0.33C in your case I believe). But that's beside the point. Why not just use the Cycle Analyst for capacity measurement? After all, that's the only meaningful capacity as far as riding an ebike is concerned. No?

Don't have one (Cycle Analyst).
Your ... typical usable capacity could be easily determined, but output, compared to oem rated, would have to be measured at a regulated, moderate drain.

My purpose was to compare present capacity vs oem rated.

Lipo might have rated better if I discharged below 3.7V, but I rated that as minimum usable, leaving plenty of safety for unbalanced banks of cells and to help maximize usable cycles.

[SamTexas]

Don't have one (Cycle Analyst).

CA is just an example. Any watt meter would do the job just as well.

Your ... typical usable capacity could be easily determined, but output, compared to oem rated, would have to be measured at a regulated, moderate drain.

That's my whole point. I don't care about the OEM rated capacity (after all, these are recycled cells). I only care about the actual usable capacity of the pack when I assembled it, and its actual usable capacity now (after xyz cycles). But that's just me.