Homemade Battery Packs

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LiPo Resurrection?

DrkAngel said:
Thread Index


Now that the ...
Floureon 7S 5000mah 25.9V 40C Lipo Battery <$60 delivered from USA are all sold ...

"Recommended for rebuild of eZip 24V RMB battery packs.
Will fit up to 4 x 5Ah = 25.9V 20Ah vs oem 24V 10Ah (5-6Ah usable) SLA.
Every 24V controller I've ever tested works properly with 7s 25.9V battery, but a bit faster with some more torque ...



eZip RMB pack internal dimensions:
150mm x 65mm x 230mm"
Dead Cell Rejuvenated after setting for several months

Last Spring, had a balancing accident with 1 cell of a 7s 5000mAh Floureon LiPo.
Fully discharged #3 cell. It apparently did not swell (in center of "brick" and discharge was extremely gentle through 12V 3A heating element) <1 Amp @4.2V discharge would lessen till < ¹/₁₀₀A as nearing empty.
All attempt at gentle recharging failed, Ni-Cd charge setting at .1A, would not hold charge!
Months later ...
Rechecking my batteries and on a whim tested the voltage on the Floureon LiPo with the dead cell ... got a .43V, hmm.
Decided to try charging again and surprise, it was taking a charge, started with a "Ni-Cd .1A" setting till above 3.2V then charged LiPo .1A till 3.6V then bumped to .5A till 4.20V.
Ran a test discharge-recharge at 1A for a metered 5128mAh ! Yippee ...
Will monitor for self-discharge before labeling "resurrected".

So ... possibly, there might be hope for some "bad" LiPo! ... ?

Unknown-puzzled as to why it started taking charge again and seems to have full undiminished capacity! ... ?
 
More fun
Customer brought in some interesting batteries the other day.



Main Features:
● Quick charge current is 1100mA, quick discharge current 22000mA (22A), max discharge current 30000mA (30A)

Original owner tried soldering to cells but couldn't get a good stick. So sold new in boxes to me at great price.
Only 10, so not enough for any decent build, but I got cheap enough I can find some good use for.
I do have a few 26650 LED flashlights.
Could solder a few, 3s2p - 3s3p as 60-90A 12V car jumper.
Should solder at least a couple cells to demonstrate proper soldering methodology.
 
Will test Resurrected 7s 5000mAh Floureon LiPo tomorrow.
36V 600w front hub motor runs just fine at 25.9V.
I have 7s cell monitor meter and will be able to monitor all cells for any excessive sag.
1. Cell passes capacity test
2. Preliminary, looks OK on self Discharge
3. Tomorrow will determine if C-Rate meets oem, compared to the "good" cells
 
DrkAngel said:
Will test Resurrected 7s 5000mAh Floureon LiPo tomorrow.
36V 600w front hub motor runs just fine at 25.9V.
I have 7s cell monitor meter and will be able to monitor all cells for any excessive sag.
1. Cell passes capacity test
2. Preliminary, looks OK on self Discharge
3. Tomorrow will determine if C-Rate meets oem, compared to the "good" cells
Accidentally fully discharged cell seems to be fully rejuvenated!
Voltage sag and resultant voltage match the "good" undamaged cells nicely during and after a 60% discharge, used 3000mAh of 5000mAh. Final test will be self-discharge over a several-many day resting period.
I am metering with a Fluke meter with 1/1000V accuracy.
1st test at present 40% charge, if good will follow up with test at 100% (4.20V).

These 7s 5000mAh Floureon LiPo seem to have been a bargain purchase. 5 for $240 = $48 each. (370 per kWh) Price was $60 each, but due to mis-listing I got a free one.
Could build 2x 25.9V 10Ah eZip battery upgrades for $98 each, compare to oem 24V 9.6Ah LiFe offerings @ $540.
Alternatively, would make a nice 14s2p 51.8 10Ah battery for my 48V 1000w rear hub build, 48V rated at 28mph, 51.8 should push to 30mph. (1 spare)

Although they seem excellent quality, no self-discharge and equal capacity, I will add 7s BMSs for safety and longevity.
 
DrkAngel said:
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Electric Wheelbarrel Battery Upgrade - Update

Moved about 4 cubic yards of topsoil, about 30 x 150' round trips, half with ~200lb, half empty.
12.3V full to 11.6V, about 50% of 25.92Ah pack.
25.92Ah is oem new rated, actual probably still greater than 20Ah, even with moderated charge voltage.
Wheel barrel with "new" lipo battery, certainly, a very usable tool!
Getting Garden ready for Winter ...
Have 6 cubic yards of good topsoil and some cubic yards of seasoned Horse manure to rejuvenate beds with.
Just have to remind volunteers to recharge up at night.
Pantry Garden produced 1500lb+ of fresh vegetables for giveaway this year, up about 50% from last year.
Electric wheelbarrel made moving things so much easier.
Just got a good chipper-shredder--mulcher to recycle plant waste and coarse wood chips into better mulch - will cover beds for the Winter and turn into soil in the Spring.

Will pull Lithium battery and store in my basement for the Winter.

See - Raised Bed Gardening - Cement Blocks!
 
DrkAngel said:
More fun
Customer brought in some interesting batteries the other day.

file.php


Main Features:
● Quick charge current is 1100mA, quick discharge current 22000mA (22A), max discharge current 30000mA (30A)

Original owner tried soldering to cells but couldn't get a good stick. So sold new in boxes to me at great price.
Only 10, so not enough for any decent build, but I got cheap enough I can find some good use for.
I do have a few 26650 LED flashlights.
Could solder a few, 3s2p - 3s3p as 60-90A 12V car jumper.
Should solder at least a couple cells to demonstrate proper soldering methodology.
Discharged-charged a sample cell.
After brief trial in flashlight, iMax B6 1A discharge to 3.0V metered 4278mAh
iMax 1A charge to 4.22V metered 4323mAh
It's so nice, and rare, to find a non-major manufacturer that produces honest capacity!
Have not tested heavy C-rate discharge but would still rate as excellent.
Pricier than I normally buy but got good enough deal that I am buying compatible chargers and flashlights.
 
Noticed my April 2014 25.9V 25.94Ah build had lost power with increased voltage sag. At 1st, thought it might be the cold weather but took it apart to be sure.

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The side bank (bottom in picture) is in 2 segments and the tinned copper braid connecting them had a deteriorated solder connection. re-soldered and did a manual balance and all looks fine now. Will do a monitored full cycle and report on present capacity.

At 5 years of reasonably constant use, this is one of my most successful reliable builds.
 
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Time for Winterizing batteries!

Electric wheelbarrel battery (11.1V 25.92Ah) to be removed, tested drained to 50% for storage (~3.85V per cell).
25A BMS added in Spring.
Will also replace charging port, weathered and sketchy at present.

EBike 25.9V 25.92Ah LiPo discharged to ~50% for Winter Storage.

Max Cell 33.3V 25.92Ah battery tested and discharged to 50% for storage

Cool Cell 33.3V 43.2V tested and tuned, will discharge to 50% for storage

24V lawn mower 25.9V 34.56Ah battery suffered failure on the 7th "s" I added when upgraded from 22.2V to 25.9V. Will test remaining banks discharge to 50% for storage. Will rebuild in Spring. May invest in 7s 45A BMS in Spring?

25.9V 26.4Ah Samsung 22p eBike battery tested and tuned for fair weather Winter use on my fendered Comfort Cruiser

2 - 36V 13.2Ah triple hoverboard battery builds tested for use on Snow Beast, 1 in insulated camera bag, 1 in eZip oem rack mount case.

Will adapt some 3s pocketable battery to power visor heater on snowmobile helmet, possibly red flasher on helmet rear also?

Also considering additional marker lighting, was using LED headlight (flashlight) and flashing taillight, almost got hit twice last night riding home after dark (~6pm)
Getting dark early with Winter coming and time change.
 
liitokala36.jpg

Has anyone tried making a case out of fiberglass cloth and epoxy resin? I would wrap over the PVC case with
fiberglass cloth and then saturate the cloth with epoxy resin. I want to add some attachment points like they
use in surfboards also. This is for my ebike. UV cure solarez would probably work much faster, but I already have the
epoxy.
 
DrkAngel,

Is 3,85 V storage voltage meant for LiPo only or also for Li-ion cells ?
If yes, do you have any reason to use such high voltage for winter storage ?
 
docware said:
DrkAngel,

Is 3,85 V storage voltage meant for LiPo only or also for Li-ion cells ?
If yes, do you have any reason to use such high voltage for winter storage ?
Oft recommended is storing at ≤ 50%
With some of my mapped cells 3.85V is closer to 20-25%
Newer cells this is near 50-60%
With the majority of my builds 3.85V is noticeable less than 50% but safely above 0%
Will have to moderate storage voltage for my Samsung 22p cell builds to ≤ 3.65V.

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Capacity Mapping (Optimal Charge-Discharge Voltages)
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Just a few facts.
3,85 V is about 60 % SOC for most of Li-ion cells. But probably, this is not so important. Here is something more interesting :

All Li-ion cells (LG, Panasonic, Sanyo,Samsung, Sony) are sent and stored for many months at 3,5 V .

Here, at well known video
https://www.youtube.com/watch?v=9qi03QawZEk#t=1h7m56s
at 1:07:55 is Jeff Dahn speaking about store of cells at cca 3,5 V for years.

In the Lithium Ion Rechargeable Batteries Technical Handbook (SONY) there are some graphs for long term storage tests. Storage at 3,2 V have smaller capacity loss than storage at 3,8 or 3,9 V.

https://cdn.sparkfun.com/datasheets/Prototyping/Lithium%20Ion%20Battery%20MSDS.pdf


Storage characteristic 20 C.jpg


All these facts invoke qestions :
Do all of you really still use archaic 3,8 (3,85) V for winter storage ?
Is there any reason why not to use 3,5 V for Li-ion cell long term storage ?
….or less for those brave enough … :)

Of course, I am assuming BMS current in the standard range 10 – 30 microamps. And normal Li-ion cells with low self discharge. Definitely not any old recycled cells from laptop.
Also assuming that any device like battery gauge is really switched off. Just Li-ion cells and BMS.
And if you are not sure, you should check battery voltage each 3 - 4 weeks, let´s say.
 
Al cells vary at optimal usable voltage!
Some cells are effectively empty at, as high as, 3.75V.

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Storing at below "empty" is liable to be damaging (and dangerous)!
I like to ensure a "safe" storage voltage, which is dependent on cell formulation.

It is important to investigate your battery's "usable voltage" before deciding on a storage voltage!!!
 
Well,
back to the merits of my question. In the light of the facts I mentioned, do you still consider 3,85 V suitable voltage for winter storage of non recycled Li-ion cells ?
 
docware said:
Well,
back to the merits of my question. In the light of the facts I mentioned, do you still consider 3,85 V suitable voltage for winter storage of non recycled Li-ion cells ?
DrkAngel said:
Al cells vary at optimal usable voltage!
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#1 Too deep discharge destroys batteries!
IMO optimal storage would be @ 20-50% capacity (voltage varies by formulation!!!)
I would never store at "0%"!
The danger of 2-5% capacity loss per year palls at the risk of destroying your battery due to further self-discharge, discharge through BMS, etc.

Possibly at the same, or even greater, consideration is storage temperature.
Optimal storage temperature is usually listed as near 40ºF.
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I hope we are speaking about cells from trustful manufacturers like LG, Panasonic, Sanyo, Samsung, Sony, with low self-discharge rate. Definitely not fake cells.

From my measurement of 18650 cells from all above mentioned manufacturers, there is at least 20 % of capacity bellow 3,5 V even at 3 A discharge.

Lygte measurements display more than 20 %.



View attachment 1







Let´s take a new battery with really small capacity 11 Ah. After few years of usage the capacity is only 70 % thus 7,7 Ah. If I put this battery to sleep at 3,5 V, it has at least 20 % of capacity, thus 1,54 Ah. 20 microamps BMS takes off 0,072 Ah during 5 months of storage. Two orders bellow the capacity for winter storage.

I have never mentioned storage at 0 % capacity.

Of course, optimal storage temperature is presumption also.
 
You must 1st realize the difference between static voltage (after discharge) and sag voltage (during discharge)!
If you notice ... when used, I draw data from minimal discharge rates (0.2A < 0.1C)

Samsung%20ICR18650-28A%202800mAh%20(Purple)%204.3V-Capacity.png


Note difference between red line and yellow line!
Discharging "Voltage" sags drastically from actual cell voltage.
When discharge removed red (voltage) line will rise slightly ...
When discharge removed yellow (voltage) line will rise greatly, to above red line.
 
Well, it´s my mistake that I take into account only cells like Samsung 30Q, Sanyo GA, SONY VTC6, LG MJ, ….. Cells that are on the market few years and that have suitable capacity and power for ebikes.

I completely missed (for me) exotic cells like Samsung ICR18650-28A which are not adequate for ebikes. Max discharge current for Samsung ICR18650-28A is 5,6 A. Simply I consider only suitable, modern cells.


Samsung ICR18650-28A.jpg

Samsung 30Q 0,2A 3A.jpg

Sanyo GA 0,2A  3A.jpg



So you are right, owners of such exotic cells should use winter storage voltage 3,7 V.

I agree, we have to measure voltage at least few hours, better 24 hours after discharging or charging, after the voltage change is stabilized enough.
 
Index

DrkAngel said:
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25.9V 26.4Ah #1 finished

7s12p Samsung cells are capable of 120A continuous 240A surge but controllers are <30A and installed 40A fuse (trying new 58V fuses & holder)
Just finished 1, had to test drive it ... rain stopped for awhile.
No BMS installed! Turned out were only 20A continuous.
Mostly worried about parasitic draw when customers let set for the Winter.

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10s2p Bricks disassembled into 8s2p + 2s2p and I was oh so tempted to build as 8s12p ... but needed for 24V bikes and I already have the 7s chargers.
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25.9V 26.4Ah #2 nearly complete
Just need to run the parallels and power rails and install fuse.
Entering it's 2nd year, and Winter, these Samsung cells are performing excellently.
Most markedly, #1 build maintains equality within 2/100ths V at near empty discharge.
A testament to genuine Samsung icr18650-22p!

Tested at 14ºF and still outputs good Voltage-amperage.
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