Homemade Battery Packs

Batteries, Chargers, and Battery Management Systems.
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DrkAngel
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Battery Builds

Post by DrkAngel » Dec 03, 2013 9:24 pm

A history of my battery builds.

24V 14Ah NiMh 20s2p New Cells - 2008
Image
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37V 10.4Ah - 10s4p - 2008 Too small! Added cells to build next ...
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37V 20.8Ah - 10s8p - 2008
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25.9V 31.2Ah - 7s12p - 2008
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25.9V 31.2Ah - 7s12p - 2011
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25.9V 22.8Ah New RC LiPo - proposed build - 7s4p - 2011
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37V 17.1Ah New RC LiPo - proposed build - 10s3p - 2011
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25.9 25.92Ah 7s12p - 2011
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37V 25.92Ah Pack (.96Kwh) - 10s12p - 2011
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Power tool rebuild - 4s2p (14.4V 5.2Ah) - 2011
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22.2V 41.6Ah - 6s16p - 2013
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29.6V 31.2Ah - 8s12p - 2013
29.6V 31.2Ah.JPG
29.6V 31.2Ah.JPG (106.92 KiB) Viewed 6191 times
22.2V 43.2Ah - 6s20p - 2013
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w/11.1V 43.2Ah - 3s20p module added
33.3V 43.2Ah - 9s20p - 2013
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33.3V 31.2Ah - 9s12p - Winter 2013-2014
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25.9V 25.92Ah - 7s12p - 2014 - passed 6500miles
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22.2V 30.24Ah - 6s14p - 2014
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With special care I was able to squeeze 4s2p 2160mAh Lipo into the Firestorm 14.4V
Required a V formation, splitting the retention tab spring location
(14.4V 1.2Ah NiCD upgraded to 14.8V 4320mAh) - Quantity 2

Image



Possibly my 1st conversion, 3s2p 2400mAh 18650 cells.
Used no balance connector but most recent test showed nice natural balance and very good capacity.
Not bad for a used daily 7+ year old build!
(12V 1.2Ah NiCD upgraded to 11.1V 4800mAh) - Quantity 2

Image



My 1stv LiPo RC upgrade
18650s were a bad fit and my Laptop Lipo were too long
Fortunately, I had acquired a quantity of 4s1p 2000mAh 10C Lipo, and was able to squeeze 1 in.
20A rated was perfect for the 5½" saw ... if used gently ...
(14.4V 1.4Ah? NiCD upgraded to 14.8V 2000mAh RC Lipo) - Quantity 2

Image

Postby DrkAngel » Thu Nov 12, 2015 4:14 pm

24V B&D Firestorm pack
Fit 6s2p 2160mAh laptop Lipo for 22.2V 4.32Ah
Excellent Hammer Drill, Sawzall
Fit 4 x 3s 2000mAh 10C LiPo for 22.2V 4.0Ah (required Swastika pattern)
Excellent for 7¼" saw etc.

Either were half the weight of the <50% capacity NiCd.

Note: 18V and 24V 7¼" saws seem identical. Same sound-pitch indicating same rpm from same 18.5V pack.
I modified 24V tools to accept 18V packs because 24V NiCd still worked.
Then modified many 18V to run from 24V pack @ 22.2V LiPo.
Did not modify 18V lights. Previously converted 18V Firestorm lights for optimal LED output at 18.5V (≤21V).
Found picture of test fitting 6s2p 2000mAh 10C Lipo into B&D Firestorm pack.

Image



DeWalt 18.5V RC Lipo

Postby DrkAngel » Tue Nov 17, 2015 9:10 pm
Pulled bad 18V 1.4Ah? NiCd and replaced with 18.5V 5s 2000mAh 10C RC LiPo

Image



Just 1 ...
Only 1 DeWalt 18V power tool.
A 5½" power saw.
Just got DeWalt Reciprocating Saw :D
Gotta find donor batteries for more rebuilds!


22.2V 34.56Ah >> 25.9V 34.56Ah - 6-7s16p 2016-17
Upgraded my 24V 20Ah SLA Homelite 20" mower last year.
Been running with upgraded 22.2V 34.56Ah (6s16p) Old used Laptop Lipo at possibly 25Ah+.

Image

Works OK but, since I run as a mulching mower, the extra rpm and torque seems advisable.
So, pushed over the main brick and was able to squeeze in another 1s16p.
Previous 6s were matched in capacity and IR, added bank was just insured to be of better!
Lesser would drag down whole pack - better allows full use.

Image

Yeah, oops ...
6s battery had no fuse installed.
Had to rewire, so bridged with a 40A fuse + holder - "good build" now.
Cells are surrounded and set upon closed cell foam.
Prevents movement and protects from vibration and rough handling.
At probably less than 1C discharge, I am not worried about battery heat.

.
...
25.9V 26.4Ah #1 finished - 2017

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.

Image

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.
Image

.
...
25.9V 26.4Ah #2 finished - 2017

2nd pack ready
Not enough matched 7s2p premade strings. Used 4s2p plus 3x 1s2p pairs.
Made preliminary run and bank voltages were very similar, indicating cells of like condition ... age, batch etc.
Will double rails and retest before declaring acceptable.

Image

#1 pack appears immaculate!
Discharged to 3.566-3.567V, all banks within 1/1000th V.
Recharged to 4.166-4.168V, within 2/1000th V.
.
Attachments
37V 10Ah Li-ion.jpg
37V 10Ah Li-ion.jpg (100.94 KiB) Viewed 2044 times
Last edited by DrkAngel on Jan 10, 2018 6:51 pm, edited 15 times in total.
A little learning is a dangerous thing;
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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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2007blueprius
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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 04, 2013 12:08 am

you've been bussy, are all these recycled? those blue ones look new. I see that as far as 18650 you have a preference for the red ones.
got a couple of questions for you, this batch I just got, I have a handfull of 10.8 hp, 47 wh I think, another handfull of 11.1 sony 4400mah I think, I had a couple toshibas, seme spec as my pack, and a bunch of old ones 14.?v odd mah not sure what those are.
you usually try to match them v and ah right, same spec for the pack?
I took apart the 2 toshiba's, one was pink just like my old laptop bat, the other green, all below 3v ouch, eased them up charging now, and boy thay can take amps, there is definately something wrong with the pouches I was messing with last night they settled at about 3.4v btw.
my old laptop bateries, they are holding their voltage rather well at 4.15 I had them off the laptop for a while now, yet when under load/ laptop they sagg horibly, and it seemes rather even over the 3 sections , guess I'll be separating them next they are 4p blocks now, what do you recon I have here, it seems to me so far all cells are just as weak rather than one bad one in the pack, I wonder since I have 6 more maybe make an 18cell pack, they seem to operate but not a whole lot of umpf.
are those circuit boards some sort of bms? my pack is amasingly well balanced even if the cells apear to be worn out.
figure'd I'd tinker with my laptop pack for now as an experiment
now let me get this straight, I see a lot of original tabs on your 18650s, do you test your cells in pairs?, if you ever split a pair up, what is a giveaway one cell may be good one not?, is that common at all, or as a rule of thumb they either both work or both are bad?
my first harvest, 6 hp packs, 10.8v 47wh, looks can be deceiving, thou some of the packs looked like thay would be interchangeble, I got 4 different colors, and the ugliest, coroded, brittle of them all had the highest voltage, I lost patience a bit and scratched up a few, but all in all, I got 20 cells above 3v, 6 at 1.4v, 10 at 0v or very close, 0.2, 0.4, of which one pair is actually taking a charge, the others, act like open circuit, no amp draw or voltage drop at all, I even split those apart just out of curiosity and tested the 0.2v one and nada, I was also trying it at about 1.5 amp only.
this is fun

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Re: Homemade Battery Packs

Post by DrkAngel » Dec 04, 2013 10:24 am

DrkAngel wrote:Image
What?
No balance connectors? ... !!!

Yep!
After initial monitored cycles, I will be relying on bulk charging.
I took great care in testing and evaluating cells and have faith in them.
Besides long range, the pack is extra large to allow very modest charge and discharge voltages.
This should allow gigantic safety margins.

Charging to 4.05V and discharging to >3.75V will still give me the usable capacity of about 6 eZip battery packs.
And these reduced voltages will reputably prolong lifespan ~300%!
Which might equal 50-100+ eZip packs.
So 21lb doesn't sound so bad ... compared to 100lbs of SLA, or the total 500-1000+ lbs of harmless slabatts being laid waste in my wake, during the same period.
Cells were tested-evaluated-rated in their oem 6 pack configuration.

Testing procedure (4320mAh recycled LiPo cells)

1. Charged in oem bulk charger (4.17V per cell) then,
removed from laptop plastic shell and
BMS removed.
2. Allowed to set for 1 month.
Any with noticeable bleed down or uneven voltage were set aside.
3. Cells were arraigned into 125V DC then discharged through 2 - 60w (120w) lightbulbs = 1000mAh discharge per hour from each 6 pack
Any with excessive or uneven voltage loss - set aside
4. After 2500mAh discharge (2hr 30min) all remaining packs sorted by residual voltage.
Best 30, of original 50, 6 packs selected and shuffled into 3 stacks of fairly precise equal capacity.
30 stacked with best on top and worst on bottom.
Shuffled as Left - Middle - Right - R - M - L - L - M - R - R - M - L - L - M - R - R - M - L - L - etc.
Stacks should be fairly precisely of equal capacity.

All packs seemed to be of very good capacity.
2500mAh discharge / 4320mAh oem rated = 58% discharged of original rated capacity with a 3.84 - 3.93 residual voltage.

Although I intend on limiting charge to 4.05V, I precisely equalized all cells at 4.16V.
As shown in graph, this is at the end of the last capacity bulge.

Image
"Equalization" should be ~5-8x more accurate than at the peak of the capacity bulge (4.125V).
I will monitor preliminary discharges and will be particularly interested in noting "equalization" at the next capacity dip (4.075V)

Near "empty" I should easily notice any flaw in my capacity matching method.
If one bank is "weaker" ...
I will 1st closely check for any bad solder connection, then
Add a cell(s) to any weak bank.

With modest discharge rate and limited charged voltage this pack should serve well for many years!
Last pack, with same type cells, served admirably for 2+ years and ~6000 miles.
25.9V 25.92Ah recycled LiPo pack has now exceeded 7300 miles but range is about 35% of when 1st built.
Surprisingly all cells seem to be deteriorating evenly, all banks, after initial patch, seem remarkably even in capacity.
A little learning is a dangerous thing;
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There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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2007blueprius
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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 04, 2013 1:30 pm

so you tested them as 2 packs, in other words .
you might have to dumb this down a bit, you are getting me confused at this point, somewhere in this thread you speak of single lithium chargers, now we are talking oem 6pack, that beeing said you may have ben working with some better packs than I. because I doubt most of mine would take an oem charge, so what I did is take them apart, sorted them all above 3v, paraleled them all and put them on my power supply, and boy do they like Amps, I had to turn it down because they were taking in 1c+, now I understand the CC/CV charging concept.
now when you say removed from laptop shell and bms, did you leave them in 3s2p configuration? I would have thought I would have to separate them into individual cells, to see which sags or not, in fact that is what I was going to do next.
now I like the 125v, 120w ideea, that must be like 12x6packs, even so, I would have thought it amounts to 1 amp per circuit, not each six pack, or pair of cells for that matter, but wait, voltage adds up in series, not current, right? curent adds up in paralel, I have to look this up been a while.
so 1 amp per 6 pack or might as well say 1 amp per 2pack block in the 12s series, 12x3s2p
other wise it all adds up, but like I said this is a bit different than what I read before and they must have been some good used packs because mine would not work, one I got 2 cells out of, one 6 cells but likely the bms was bad on that one, they all came from a computer shop and been tested and discarged because they would not take a charge.
at the moment I am using my own laptop pack as an experiment, since I have 6 more identical cells thou, I found them below 3v, I did charge them and paraleled all 18 of them over night they should all be about even by now.
as I described before, my own laptop pack is 3s4p, and all 3 blocks behave similarily and evenly bad, they take a charge, they maintain 4.15v, but they sag badly under load, now that is why I was asking if you broke the 2 packs apart, would 2 cells that spent their life in paralel act the same way, is that a safe assumption? is it likely all 12 cells are evenly bad, or one of each 4p block took a dump,
anyway guess there are more ways to skin a goat and whateve you are doing is working for you, just got me confused thats all

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Re: Homemade Battery Packs

Post by DrkAngel » Dec 04, 2013 1:44 pm

Just found the picture of my 125V DC "stack".
10 - 6 packs of 3s2p recycled Lipo, configured as 30s2p.
30 x 4.15V = 124.5V
2 - 60w (120w @ ~125V,) light bulbs equals 1000mA discharge rate
120V DC.JPG
120V DC.JPG (84.05 KiB) Viewed 6055 times
Ran this discharge test on 5 - (10 x 6) packs.
Used the best 30 on my build.
Saved the rest for 12V lanterns, etc.
2s 8.4V works nicely with 6V florescent lantern ... so far ...
Last edited by DrkAngel on Dec 06, 2013 1:05 pm, edited 1 time in total.
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2007blueprius
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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 04, 2013 4:54 pm

I was actually talking about the 18650s, what were these ones from?

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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 04, 2013 5:06 pm

Hillhater wrote:Do you have a spec sheet for those cells ?
Are they 3.3, 3.65, or some other "nominal" voltage ?

PS; .. I think you should take this back to your other thread..( and maybe mod the title)

I was looking for a spec sheet came across this http://www.youtube.com/watch?v=c0XS5ERhreA this is a bit of an explanation of the system, it's a joke really, I think 3.3v might be nominal for these cells, or so the rumor has it, I'll look for a datasheet, thou I can kindof tell by the way it takes a charge it's not right
http://www.enginer.us/products/lifep04_battery.php this is a link to the details on the batteries.
PS I could start a new thread I guess, but if you all don't mind I'd rather keep it here the whole purpose of this project is testing and repurposing whatever is salvageable out of an worn pack

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Re: Homemade Battery Packs

Post by DrkAngel » Dec 05, 2013 7:15 am

Index Updated - Dec 2013

I have designed this thread as something as a reference.
My provided posts and referenced threads are fairly comprehensive and complete.

So please read the thread before asking questions, I won't be re-posting the same information in the same thread.
I put a fair bit of work into building the index ... so please use it!

Please note:
Occasionally I do update my older posts-threads, but for "better" information rely on the more recent.
Last edited by DrkAngel on Dec 27, 2013 6:10 am, edited 2 times in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Homemade Battery Packs

Post by DrkAngel » Dec 10, 2013 7:49 pm

Usually I try to build packs from same brand-type-capacity cells.
Well, I charged and tested some of my leftover-oddball laptop packs.

A notable surprise were 2 - 10.8V 4000mAh w/3.6V 2000mAh Sanyo cells ...
They were nearly of full oem rated capacity and bulk charged evenly within a couple 100ths V at 4.10V.

Most impressive was that they displayed excellent IR, voltage sag during discharge with a 2800mA fan showed about 1/2 the voltage sag of the common 2600mAh cells I typically find.
Apparently, they designed these cells with a higher ratio of anode-cathode to electrolyte, for more substantial discharges! ... ?

Since I only had 12 cells, I just Lithiumized 2 - 12V Craftman NiCd battery packs for my old 75th Anniversary cordless drill.
Though long dead, when new they were 1.3Ah, now upgraded to 4.0Ah.

300% capacity with 1000%(?) the usable cycles.
Sadly?, even with daily use, they will probably outlive me.
Last edited by DrkAngel on Nov 15, 2015 10:39 am, edited 2 times in total.
A little learning is a dangerous thing;
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There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Nimbuzz
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Re: Homemade Battery Packs

Post by Nimbuzz » Dec 11, 2013 5:45 am

What the heck does "Lithimized" mean?!?

Am I the only one who doesn't know?!?

Is it kinda like lobotomized?
Al
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Re: Homemade Battery Packs

Post by DrkAngel » Dec 11, 2013 8:57 am

Nimbuzz wrote:What the heck does "Lithimized" mean?!?

Am I the only one who doesn't know?!?

Is it kinda like lobotomized?
Sorry! lost a "u".

Lithiumized - the process of replacing the oem power source with a lithium technology power source.

EG ...
1. Replaced Craftman power tool pack, Nicd sub-C batteries (12V 1300mAh) with lithium-ion Cobalt 18650 batteries (10.8V 4000mAh).
2. Replaced B&D power tool pack, Nicd sub-C batteries (14.4V 1200mAh) with lithium-ion Cobalt 18650 batteries (14.8V 5200mAh).
3. Upgraded eZip pack from 24V 10Ah SLA to 25.9V(& 29.6V & 33.3V) 31.2Ah Lithium Cobalt (18650 cells).
4. Upgraded eZip pack from 24V 10Ah SLA to 25.9V 25.92Ah Lithium Cobalt (Lipo cells).
5. Rebuilt 18V B&D power tool pack, Nicd sub-C batteries (18V 1200mAh) with lithium-ion (Cobalt) LiPo batteries (18.5V 4320mAh).
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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LeftieBiker
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Re: Homemade Battery Packs

Post by LeftieBiker » Dec 18, 2013 12:22 am

A little OT, but it's so cold I can't even work in the garage with a heater running, so I'm speculating and daydreaming instead... Is there a way to selectively connect (with a switch) a 12V pack with a 24V pack, on an EZIP, to make an optional 36V circuit? I was thinking that if I reconnected the two 12V batteries in a Currie case in parallel, I'd have 12V at 20AH (on paper, actually about 14AH) SLA, which I could carry opposite my 24V Ping lithium pack. Even better would be if somebody were to assemble for me a 12V 20AH pack out of 'second team' lithium cells, so the discharge rates were better matched...Could this work if connected down-circuit from the 24 volt controller, or would the 36 volts feed back into the controller and burn it out?

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Re: Homemade Battery Packs

Post by DrkAngel » Dec 26, 2013 10:12 pm

33.3V 43.2Ah Lipo build performs nicely!
Below freezing today with snow on the streets, so I pumped up my snow beast and took a spin.
I forgot how loud the motor was on my 2008 eZip Mountain Trailz, sounds about like a siren spinning up.
Anyhow, even with only 33.3V, acceleration and torque were impressive, much better than with my old 36V 21Ah ... in the cold ...

Image
At 21lb, I didn't want to mount it on top of the rack ... too top heavy.
So I built a little shelf and mounted it on the "starboard side".
But 43Ah is big-too heavy for my short Winter trips, so ...

Looks like I can squeeze 17.28 Ah of recycled Lipo and 4Ah RC Lipo into an eZip pack and maintain my 33.3V.
After much previous speculation, this will be my first trial "hybrid" build.

Oh, even with the oem gearing, 33.3V pushes my old eZip and its 2 studded tires along at 21.7mph(25ºF - cold bike but warm battery).
Best motor output should be in the 10-12mph area.
Last edited by DrkAngel on Dec 29, 2013 10:22 am, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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9s12p (33.3V 31.2Ah) eZip Rebuild = 1kWh!

Post by DrkAngel » Dec 29, 2013 9:36 am

Well, I keep claiming that I have squeezed the maximum number of 18650s into the oem eZip pack.
7s12p .. 8s12p ...
Finally ... this might be true.

Next build was going to be a "hybrid" 18650 & flat Lipo project ...
but I got tired of all the old Sanyo 18650s laying around.
So I gathered them all up and selected all that measured a retained voltage higher than 4.10V.
(After being equally charged to 4.20V+ 8+ month ago)

9s12p (33.3V 31.2Ah) eZip Rebuild = 1kWh!!!
By staggering the cells I am able to fit the cells in 9 wide.
Case will stack 12 1/2 cells high if I remove center screw and use only a 3/16" Masonite bottom support-protection "shelf".
I chose the 90 best retained voltage cells and stacked so as to have "equal" capacity per stack.
Now, 9 x 12 is more than 90 cells ... and sorting solely by retained voltage is a poor measure of capacity! ... ?
But ...

Bulk Building
I rated and sorted "build" cells solely by "bleed down" - "retained voltage", and will assemble and test as a 9s10p pack.
After initial discharge-recharge cycles, I will "equalize" pack using precisely capacity rated Sanyo cells pulled from my last batch of recycled Lenovo packs.
By adding them as the final 9s2p.
Pack will be used on my Snow Beast and as a testbed for a future build using "new" (NOS) cells.
I have 2 eZips that run nicely on 33.3V batteries.
These Sanyo cells are 3.6V and after learning my lesson by damaging with 4.20V charging, I will be charging at 4.0-4.05V, for increased life.
33V 18650_1.JPG
33V 18650_1.JPG (104.69 KiB) Viewed 4837 times
I will add 1/2 cell height (9mm) "blanks" as additional support for the alternate "banks".
33V 18650_2.JPG
33V 18650_2.JPG (90.09 KiB) Viewed 4837 times
Leftovers?
Well ... this leaves a couple hundred "lesser" condition-capacity old Sanyo 18650 cells laying around.
Leftovers and re-recycled from 6 years of multiple builds.

So, a "true" bulk build!
I have a couple "antique" 200w inverter packs.
2 - 18Ah SLA outputting 200w continuous through a GFCI 110V AC outlet.
Well I'll pull the 12V 36Ah Lead Acid and pile in all the 18650 cells that will fit.
3s66p might fit = 171Ah
(Check bank voltages after 1st discharge, add cells to any low bank - re-cycle - repeat.)
But, probably be lucky to get 72Ah actual capacity out of these ... rejects.
Still, that is 200% the oem capacity at 1/2 the weight.
Most importantly!
I have those old cells safely stored and not laying around.
And, of course, a nice supply of emergency-portable power.
It also has a 12V "cigarette lighter" outlet for a more powerful inverter or 12V.


Will add pictures ...
Last edited by DrkAngel on Jan 06, 2014 10:00 am, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - November 2015

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Re: 9s12p (33.3V 31.2Ah) eZip Rebuild = 1kWh!

Post by DrkAngel » Jan 01, 2014 8:52 am

DrkAngel wrote: 9s12p (33.3V 31.2Ah) eZip Rebuild = 1kWh!!!
By staggering the cells I am able to fit the cells in 9 wide.
Case will stack 12 1/2 cells high if I remove center screw and use only a 3/16" Masonite bottom support-protection "shelf".
I chose the 90 best retained voltage cells and stacked so as to have "equal" capacity per stack.
Now, 9 x 12 is more than 90 cells ... and sorting solely by retained voltage is a poor measure of capacity! ... ?
But ...

Bulk Building
I rated and sorted "build" cells solely by "bleed down" - "retained voltage", and will assemble and test as a 9s10p pack.
After initial discharge-recharge cycles, I will "equalize" pack using precisely capacity rated Sanyo cells pulled from my last batch of recycled Lenovo packs.
By adding them as the final 9s2p.
Pack will be used on my Snow Beast and as a testbed for a future build using "new" (NOS) cells.
I have 2 eZips that run nicely on 33.3V batteries.
These Sanyo cells are 3.6V and after learning my lesson by damaging with 4.20V charging, I will be charging at 4.0-4.05V, for increased life.

Image
I will add 1/2 cell height (9mm) "blanks" as additional support for the alternate "banks".
Just ran a partial discharge and opened pack to test bank voltages - within 2/100V.
Oh no! ... I noticed another option.

37V 26Ah 18650 in eZip OEM Pack
Previously, I was able to build only 10s8p (8 wide 10 tall) 18650 packs in the eZip packs (37V 20.8Ah) ... no room for 10 more paired cells.
Well, with the 9 wide 10 tall staggered cells there is room for 9 more cell pairs ...
Instead of adding 9s2p for 33.3V 31.2Ah it is easy to add 1s10p for 37V 26Ah.
Only .962kWh ... but still nice for those wanting 37V.
Last edited by DrkAngel on Jan 11, 2014 9:45 am, edited 3 times in total.
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NaturalPath
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Re: Homemade Battery Packs

Post by NaturalPath » Jan 01, 2014 12:55 pm

Hello DrkAngel;

I am about to undertake the building of a laptop cell battery pack to replace the existing SLA's in a used ebike that I recently acquired https://endless-sphere.com/forums/viewto ... =3&t=54489 First, I want to thank you for making all this information available, because money is certainly an issue in my world, and your methods seem to be the best way for me to build a battery that will give me maximum range, with minimum cash input.

I've read all the information you have posted at least once, but I will certainly have to go over them again in order to fully absorb and understand the process. I do have 15 Lenovo battery packs on the way, which I'm assuming will all have cells from the same manufacturer, although they may be different capacities. I know that I'll have to test and sort them first, but I have a question that will have to be determined fairly early in the process. The space I have available for the battery pack is long and narrow, about 4"x 4"x 19". This should allow me enough space to put 5 cells across, giving me 18V per row. Would it be a better idea to build two 18V packs, and series them together for the 36V I need, or would building one long 36V block be the best way to go? For one thing, the charger may be cheaper for the 18V battery, although I would have to charge each 18V bank separately, and this might complicate things enough so that making the battery one long 36V would be more cost efficient.

I'm looking at building a 30ah to 40ah battery, depending on the capacity of the cells I have. My primary focus is on range, so I won't be modifying anything else on the bike, if I don't have to. Thanks for any input you might be able to give.

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DrkAngel
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Re: Homemade Battery Packs

Post by DrkAngel » Jan 03, 2014 1:25 pm

NaturalPath wrote:Hello DrkAngel;
The space I have available for the battery pack is long and narrow, about 4"x 4"x 19". This should allow me enough space to put 5 cells across, giving me 18V per row. Would it be a better idea to build two 18V packs, and series them together for the 36V I need, or would building one long 36V block be the best way to go?
4"x 4"x 19" will give you 5 wide 26 deep. 2 segments of 5s12p ... 37V 31.2Ah ... if 2600mAh cells.
Which should give you 4x, maybe 5x, the range of the oem SLA batteries.

I would charge as 10s 37V, 37V-2A Li-ion charger is $18.49.
Or get a larger adjustable PS as a bulk charger and charge faster, (<.5C recommended), or to trim voltage for longer life.

Balance charging 5s at a time, (iMax B6?), might seem advisable for initial charges, but it gets old fast.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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NaturalPath
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Re: Homemade Battery Packs

Post by NaturalPath » Jan 03, 2014 1:44 pm

Thanks very much DrkAngel. I'm sure there will be a learning curve doing this, but I'm willing to learn, and the cost fits my budget. Again, I very much appreciate all the info you've posted on this subject, it would have been much more difficult without that.

Unfortunately, the cost for shipping that Tenergy charger to my location in Canada is $100. and I haven't been able to find it anywhere else. I'll keep looking.

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spinningmagnets
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Re: Homemade Battery Packs

Post by spinningmagnets » Jan 04, 2014 4:22 pm

Found on Russian website:

Image

NaturalPath
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Re: Homemade Battery Packs

Post by NaturalPath » Jan 10, 2014 3:17 pm

DrkAngel wrote:
NaturalPath wrote:Hello DrkAngel;
Balance charging 5s at a time, (iMax B6?), might seem advisable for initial charges, but it gets old fast.
Okay, I understand.
Last edited by NaturalPath on Jan 11, 2014 10:01 am, edited 1 time in total.

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kje
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Re: Homemade Battery Packs

Post by kje » Jan 10, 2014 3:34 pm

DrkAngel wrote:
kje wrote: Bonus! Capacity testing, for large packs is not "necessary".
Bleed down test recommended, this eliminates almost all bad-poor cells!
Build pack in 3 equal banks.
Discharge ... till one bank dips below ~3.7V.
All 3 banks should be of various voltages, mark as H M L (High Medium Low).
Recharge to equal voltages.
Remove cell (cells) from H bank and add to L bank, or add cell to M and more cells to L bank.
Repeated monitored cycles will allow you to create nicely balanced capacity pack.
Is it possible to have different number of cells in the 3 banks?


If i connect balancing leads to my 186500 battery pack and use the Imax to balance each time I charge the pack, there is no need for a PCM?

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Re: Homemade Battery Packs

Post by DrkAngel » Jan 11, 2014 7:15 am

kje wrote:
DrkAngel wrote: Bonus! Capacity testing, for large packs is not "necessary".
Bleed down test recommended, this eliminates almost all bad-poor cells!
Build pack in 3 equal banks.
Discharge ... till one bank dips below ~3.7V.
All 3 banks should be of various voltages, mark as H M L (High Medium Low).
Recharge to equal voltages.
Remove cell (cells) from H bank and add to L bank, or add cell to M and more cells to L bank.
Repeated monitored cycles will allow you to create nicely balanced capacity pack.
Is it possible to have different number of cells in the 3 banks?
Equal capacity per bank is more desirable than equal number of cells. I intend on building a 11.1V (12.3V charged) "bulk" pack for an inverter pack. After bulk charging all cells to 4.10V then separating, I will eliminate any with a noticeable "bleed down" (self-discharge).

Then I will test each pair of cells for a comparative IR (Internal Resistance) by applying a specific drain and noting voltage sag. This is a rough "yardstick measure" of capacity-condition. (Severe sag indicates one cell of pair bad and will eliminate from build, will separate pair and keep good cell for flashlight etc.) Cells will be sorted, best IR to worst, then shuffled into 3 relatively equal banks by 1 -2 - 3 - 3 - 2 - 1 - 1 - 2 - 3 etc. After 1st discharge any low voltage bank will have cell-cells added, then process repeated till banks are accurately "equalized" at full and empty voltages.
kje wrote:If i connect balancing leads to my 186500 battery pack and use the Imax to balance each time I charge the pack, there is no need for a PCM?
A "PCM"-PCB-BCM ,supposedly, guards against any bank charging to too high a voltage or discharging to too low a voltage and some equalize voltage at full charge. An iMax prevents overcharging and does equalize banks at full charge but offers no help for too deep discharge of any bank. Low voltage alarms are cheap safety "insurance". More important IMIO is to build-insure banks to be of equal capacity! With a basic "bulk charger" the pack will naturally re-attain equalized full and empty voltages. Of course you should still monitor charged and discharged bank voltages. These voltage monitor alarms are cheap and fairly, not "good"ly, accurate so you might want to get multiple and test for acceptable accuracy.

But an iMax B6 is an OK charger to start with and a good tool to always have.
Last edited by DrkAngel on Jan 12, 2014 12:21 pm, edited 1 time in total.
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Re: Homemade Battery Packs

Post by kje » Jan 11, 2014 10:40 am

DrkAngel wrote: Equal capacity per bank is more desirable than equal number of cells.
Ok, so it`s no danger ending up with e.g. Bank1: 50 cells, Bank2: 60 cells, Bank3: 70 cells, if all banks has equal capacity?
DrkAngel wrote: I intend on building a 11.1V (12.3V charged) "bulk" pack for an inverter pack. After bulk charging all cells to 4.10V then separating, I will eliminate any with a noticeable "bleed down" (self-discharge).
After opened old laptop batteries I`ve charged each pair to 4.20V. When you are bulk charging you charge all cells at once?
DrkAngel wrote: A "PCM"-PCB-BCM ,supposedly, guards against any bank charging to too high a voltage or discharging to too low a voltage and some equalize voltage at full charge. An iMax prevents overcharging and does equalize banks at full charge but offers no help for too deep discharge of any bank. Low voltage alarms are cheap safety "insurance". More important IMIO is to build-insure banks to be of equal capacity! With a basic "bulk charger" the pack will naturally attain equalized full and empty voltages. Of course you should still monitor charged and discharged bank voltages. These voltage monitor alarms are cheap and fairly, not "good"ly, accurate so you might want to get multiple and test for acceptable accuracy.
Actually I have bought that voltage monitor alarm. :) So if I use that and monitor the battery pack after each boat-trip and balance charge it with the Imax charger, I should be safe?

Thank you!

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DrkAngel
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Re: Homemade Battery Packs

Post by DrkAngel » Jan 11, 2014 11:39 am

kje wrote:
Ok, so it`s no danger ending up with e.g. Bank1: 50 cells, Bank2: 60 cells, Bank3: 70 cells, if all banks has equal capacity?
Equal capacity banks deteriorate equally (in my experience).
A bank discharging deeper will deteriorate faster ... getting worse every cycle.
So, YES! More cells in different banks is OK!
Tho ... 20% different would prompt me to retest and resort my cells.
kje wrote: After opened old laptop batteries Ive charged each pair to 4.20V. When you are bulk charging you charge all cells at once?
See - 40 cell 4.20V charging
2nd picture is charging 38 cells per bank with wire rails soldered to oem pack wires.
kje wrote: Actually I have bought that voltage monitor alarm. :) So if I use that and monitor the battery pack after each boat-trip and balance charge it with the Imax charger, I should be safe?
Sounds like a reasonable-safe method.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - November 2015

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kje
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Re: Homemade Battery Packs

Post by kje » Jan 11, 2014 11:48 pm

Thank you!
DrkAngel wrote: Step 2
Apply 4.2V charge to cells (These particular type cells have been predetermined to retain good capacity at 4.20V.)
Monitor for any cell producing heat, if found , cut out of circuit.
Isn`t it dangerous to bulk charge all the cells simultaneously without balancing?
DrkAngel wrote: Self-Discharge Test - Step One! Dupe from a thread on BMS, but really belongs here ... too!
Present test on 3.7V - cells were charged to 4.25V, then
allowed to sit, potentially self-discharging for 1 month!(Oops! ... 2 months!)
(These cell were previously determined to hold good capacity at 4.20V+) - see image below
Cells are now being sorted by retained voltage.
4.25V = A++
4.24V = A+
4.23V = A
4.22V = B
4.21V = C
4.20V = C-
Below 4.20V but above 4.15V for separate build.
Below 4.15V but above 4.10V tasked for bulk project ...?
Below 4.10V ... binned or experimentation?
Why do you charge them to 4.25V and not 4.20V?

What copper wire and dimension will work for a battery pack like this?

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