Homemade Battery Packs

Batteries, Chargers, and Battery Management Systems.
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DrkAngel
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Re: Homemade Battery Packs

Post by DrkAngel » Nov 04, 2013 4:58 am

Toorbough ULL-Zeveigh wrote:
DrkAngel wrote:some dated 2004 still measured at better than 90% of oem rated capacity!
define 'some'!
DrkAngel wrote:Previous 2 year usable life might extend into 5-6 years and previous 6000 mile total might exceed 12-15 thousand miles.
increase cycle life, yes!
calendar life, no!
Battery performance deteriorates over time whether the battery is used or not. This is known as "calendar fade". Performance allso deteriorates with usage and this is known as "cycle fade"
http://www.mpoweruk.com/life.htm
After one year on the shelf, a LiFePO4 cell typically has approximately the same energy density as a LiCoO2 Li-ion cell, because of LFP's slower decline of energy density. Thereafter, LiFePO4 likely has a higher density.
http://en.wikipedia.org/wiki/Lithium_ir ... te_battery
I would have to dispute.

1. 2004 & 2006 Lipo Lithium cobalt 4320mAh 6 packs measured at 3900mAh+ (used 7 & 9 year old packs were precisely capacity tested as test modules)

2. Used ~6 year old 10.8V 5200mAh Lenovo packs.
"Just ran a 18s capacity test.
Took about 4 hours with preliminary cell voltage monitoring - every 1/2 hour.
In the 3rd hour I began testing at 10 min intervals, then sooner.
The 36 2600mAh cells were left in 3s2p 6packs.
5200mAh oem rated
1 - 3300mAh+
5 - 3700mAh+
2 - 3800mAh+
2 - 4100mAh+
2- 4200mAh+
2 - 4300mAh+
4 - 4500mAh+
18 pairs thoroughly tested and accurately rated for capacity in 4 hours with minimal attention till the last hour."

3. NOS HP 10.8V 10,400mAh packs ~5 years old
6 - Sanyo cells - all discharged tested between 9000 - 10,000mah+
6- Samsung cells - all discharged tested between 8000 - 10,000mah

LiCoO2 has approximately 200% the energy density of LiFePO4.
According to your reasoning the LiCoO2 loses 50% capacity in one year! ... ?
So ...

..... OEM(new) ... 50%\year ....... Actual
1. 4320mAh ....... 9x = 8mAh ..... 4000mAh+
2. 5200mAh ....... 6x = 80mAh .... 4500mAh+
3. 10,400mAh ..... 5x = 325mAh ... 10,000mAh+

Something is very wrong with your "reasoning(?)"!
If LiCo lose 50% capacity, setting for 1 year ...
then:
1. LiPo has 500x your estimated capacity
2. used Lenoveo has 56x your estimated capacity
3. NOS HP has 30x your estimated capacity

At the very minimum they should have lost 50% of their capacity, in the first year!
But even the 9 year old cells lost less than 10%.

I think you had better re-evaluate the reliability-veracity of your sources!

Partially retired Lipo pack (25.9V 25.92Ah Lico pack. 6500 miles - so far...)
Capacity loss was less than 50%, with ~daily use (300+ discharge-charge cycle) for a full year - 3000++ miles.
Last edited by DrkAngel on Nov 05, 2013 9:36 am, edited 1 time in total.
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3.6V vs 3.7V Lithium Cobalt cells

Post by DrkAngel » Nov 04, 2013 9:39 am

3.6V vs 3.7V Lithium Cobalt cells
Apparently there is a difference!

After exhaustive-exasperating research, although there seems to be a lack of definitive sources, the consensus seems to be that:
3.6V cells are designed to be charged to 4.1V
and
3.7V cells are designed to be charged to 4.2V ... !

This might explain why my 18650 Sanyo cells deteriorated so quickly when being routinely charged to 4.20V.
They were oem pack labeled 10.8V = 3.6V.
Charging 4.1V cells to 4.2V would cut usable cycles in half!

3.7 - 4.2V would be labeled 11.1V or possibly 14.4V.

Just checked my LiPo cells, that survived 4.20V charging, admirably, and yes, they are labeled 3.7V - 11.1V.

I don't understand how such a basic difference was allowed to continue unexplained so prevalently.

If anyone has found authoritative documentation on this subject, could they please reference it?
Post a link.
Last edited by DrkAngel on Nov 10, 2013 10:20 am, edited 3 times in total.
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Re: Homemade Battery Packs

Post by DrkAngel » Nov 04, 2013 10:13 am

3.7V capacity "map".
Although not from 18650 cells this chart documents capacity, cycle life etc. for Lithium Cobalt 3.7V - 4.2V cells

Source - http://www.powerstream.com/lithuim-ion- ... oltage.htm
Image

Not surprisingly, this concurs fairly well with my tests.
Limiting charge from 4.20V to 4.05V decreases capacity 17% while increasing cycle life to 280%
Substantial capacity begins above 3.7V.
3.3V - 3.5V = 3% capacity
3.5V - 3.6V = 2.2% capacity
3.6V - 3.7V = 3.6% capacity
3.7V - 3.8V = 28.2% capacity
3.8V - 3.9V = 26% capacity
3.9V - 4.0V = 12% capacity
4.0V - 4.1V = 17% capacity
4.1V - 4.2V = 11% capacity

Charging to 4.3V cuts cycle life in half for 6% capacity increase.

Image
Attachments
Capacity Map1.jpg
Capacity Map1.jpg (53.4 KiB) Viewed 277 times
Capacity Map2.jpg
Capacity Map2.jpg (82.87 KiB) Viewed 4506 times
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Re: Homemade Battery Packs

Post by DrkAngel » Nov 10, 2013 9:04 am

DrkAngel wrote:3.7V capacity "map".
Although not from 18650 cells this chart documents capacity, cycle life etc. for Lithium Cobalt 3.7V - 4.2V cells

Source - http://www.powerstream.com/lithuim-ion- ... oltage.htm
Image

Not surprisingly, this concurs fairly well with my tests.
Limiting charge from 4.20V to 4.05V decreases capacity 17% while increasing cycle life to 280%
Substantial capacity begins above 3.7V.
3.3V - 3.5V = 3% capacity
3.5V - 3.6V = 2.2% capacity
3.6V - 3.7V = 3.6% capacity
3.7V - 3.8V = 28.2% capacity
3.8V - 3.9V = 26% capacity
3.9V - 4.0V = 12% capacity
4.0V - 4.1V = 17% capacity
4.1V - 4.2V = 11% capacity
According to these tests ...

For a 3.7V (4.2V full charge) 4.05V looks very attractive.
A 280% usable life for an initial 17% capacity loss.

On the other hand ...
Keeping working voltages between 3.7V and 3.9V gives 54% capacity and 800% cycle life.
(Charging to 3.9V retains 62%, but the 8% capacity below 3.7V is not worth the additional wear and tear! IMO!)
With my 31.2Ah builds this still gives me 16Ah+ or about 40 miles @16mph or 20+ miles @ 20mph.
Which is fine for my typical daily use.
And I can always charge up to 4.05V (an additional ~45%) for longer trips, or clip in 2nd battery pack.

Even though I get my recycled cells pretty darn cheap, I spend a goodly bit of time testing and building ...
I'm beginning to view 4.20V charging as a wasteful-needless form of abuse!
Last edited by DrkAngel on Nov 10, 2013 9:48 am, edited 1 time in total.
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Re: 3.6V vs 3.7V Lithium Cobalt cells

Post by DrkAngel » Nov 10, 2013 9:43 am

DrkAngel wrote:3.6V vs 3.7V Lithium Cobalt cells
Apparently there is a difference!

After exhaustive-exasperating research, although there seems to be a lack of definitive sources, the consensus seems to be that:
3.6V cells are designed to be charged to 4.1V
and
3.7V cells are designed to be charged to 4.2V ... !

This might explain why my 18650 Sanyo cells deteriorated so quickly when being routinely charged to 4.20V.
They were oem pack labeled 10.8V = 3.6V.
Charging 4.1V (3.6V labeled) cells to 4.2V would cut usable and manufacturers rated cycles in half!

3.7 - 4.2V would be labeled 11.1V or possibly 14.4V.

Just checked my LiPo cells, that survived 4.20V charging, admirably, and yes, they are labeled 3.7V - 11.1V.

I don't understand how such a basic difference was allowed to continue unexplained so prevalently.

If anyone has found authoritative documentation on this subject, could they please reference it?
Post a link.
As demonstrated in these test results.
The different voltage ratings,
3.6V Sanyo 18650 cells - red line
3.7V Dell recycled LiPo - blue line
Demonstrate a shift of voltages of dense energy capacity.

Image

(It seems that the 3.6V labeled cells are designed to be charged to 4.10V, charging to 4.20V will cut usable life in half! ... ? )

For the 3.6V Red Line 18650 cells 3.90V peak charge appears ideal. = 400% usable cycles
For the 3.7V Blue Line LiPo cells 4.00V, maybe 4.02V, looks more ideal. = 400% usable cycles

Remember!
These are capacity maps for specific brand cells.
All cells vary by formulation.
e.g. - Tested "Winforce" RC LiPo demonstrated a shift towards a much lower usable voltage ...
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Re: Homemade Battery Packs

Post by 2007blueprius » Nov 28, 2013 1:21 am

wonder if you could clear something up for me:

http://www.ebay.com/itm/18650-3-7V-3000 ... 5d4598177f

I opened my laptops battery pack today, It has not took a charge for a while now, so I figured I'd have a look, but I am going about it the oposite way, I was going to replace the cells and fix it, so they measured 6.5 cm, figured they are 18650, so I was looking for replacements.
now I shoped them before, and there are so many out there up to 5000+ mah, now wiky puts them at 2200 to 3400.
my pack says 10.8v, that is 3.6 per cell, so I am asuming they are LiFePo4
87wh that comes up to about, 2000mah,
they are pink in color by the way, there are some numbers on them but nor 2 cells are alike.
my question is, are the higher capacity cells a different chemistry, or false advertising, I understand the 3.7 are a Co chemistry
likely I will have to stick to the same type cells to make it work.
but just out of curiosity I noticed a trend in recomended charge voltage getting lower and lower I thought 3.6v was nominal full charge, 4.1 sounds really high, most of those small charges are 4.2, do you really charge them that high and they hold it?
like these for example, I know they are 3.7 v but inside the laptom they may not make a difference at all http://www.ebay.com/itm/12x-3-7V-18650- ... 19e2f17a4e
so all in all if I were to order some replacement cells, should I bother with the higher rated capacity, or stick with something realistic?

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Re: Homemade Battery Packs

Post by DrkAngel » Nov 28, 2013 7:01 am

2007blueprius wrote:wonder if you could clear something up for me:

http://www.ebay.com/itm/18650-3-7V-3000 ... 5d4598177f

I opened my laptops battery pack today, It has not took a charge for a while now, so I figured I'd have a look, but I am going about it the oposite way, I was going to replace the cells and fix it, so they measured 6.5 cm, figured they are 18650, so I was looking for replacements.
now I shoped them before, and there are so many out there up to 5000+ mah, now wiky puts them at 2200 to 3400.
my pack says 10.8v, that is 3.6 per cell, so I am asuming they are LiFePo4
87wh that comes up to about, 2000mah,
they are pink in color by the way, there are some numbers on them but nor 2 cells are alike.
my question is, are the higher capacity cells a different chemistry, or false advertising, I understand the 3.7 are a Co chemistry
likely I will have to stick to the same type cells to make it work.
but just out of curiosity I noticed a trend in recomended charge voltage getting lower and lower I thought 3.6v was nominal full charge, 4.1 sounds really high, most of those small charges are 4.2, do you really charge them that high and they hold it?
like these for example, I know they are 3.7 v but inside the laptom they may not make a difference at all http://www.ebay.com/itm/12x-3-7V-18650- ... 19e2f17a4e
so all in all if I were to order some replacement cells, should I bother with the higher rated capacity, or stick with something realistic?
OEM pink are "3.6V" Samsung 18mm diameter 65.0mm length Lithium Cobalt (variant formulation) ~2400mAh cells.
They have individual serial numbers.
4.1V is recommended charge to attain rated capacity. (3.6V is ~empty - See chart for 3.7V)

Image
I would not trust any advertized mAh beyond 2600mAh unless guaranteed genuine Panasonic.
GTL 5300mAh have been tested as 2600mAh or less! (eBay is rife with "creative labeling".)
Reputable brands include:
Panasonic
Samsung
Sony
Sanyo
LG
Tenergy

Replacing Laptop Cells?
Unless you buy tabbed cells, they will not fit unless you cut off the nipples and the protective circuit disc (if present).
Brand name only! Unless you buy a large quantity and thoroughly test and use only the best.
Your 3.6V pack will accept 3.7V cells and suffer a minor capacity reduction, but ... will enjoy a much extended overall life.
Reputable brand cells will likely cost more than a generic replacement pack.
And!
As often as not, cells are still good and the charging circuit (in pack) has the defect.

Recommendation?
Purchase new "replacement" pack from an reputable "in country" reseller with 1-3 year warranty and don't lose warranty info!
Last edited by DrkAngel on May 03, 2014 9:49 am, edited 1 time in total.
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Re: Homemade Battery Packs

Post by 2007blueprius » Nov 28, 2013 11:02 am

yeah that was pretty much the thought I had If it sounds too good, than I don't want it, so lithium cobalt is rather diferent than lifepo4 I am used to, figured you would know exactly what these were I would not mind sacrificing some capacity for life, 87wh is rather large for a laptop any how, and honestly I had it plugged in for more than a year now, I saw replacements anywhere from $25 ( less capacity knock off ) to 100 genuine, saw one in the middle knockoff $50 but it showed more WH, 110 I believe, from what I gathered so far unless that is made with some who knows what chemistry it's probl a quack too.
and honestly it was more about the project, I followed yours so I figured why not I have a bad battery let's have a look, maybe at the end of the project I'll have a couple single chargers left to tinker with, I have a clue of how to go about tabing soldering, yeah it's pretty tight in there and the tabs they use are slim and clean welds, insulated, looks nice good luck with that solder iron huh?

so I have another pack from another laptop that does not hold much charge either, haven't opened it yet, but label says 10.8 v 55 wh so I recon the cells in it are similar chemistry , looks a lot smaller, 6 cells rather than 12, and apparently higher capacity per cell, 2500mah approximately , you recon I may be able to make one out of 2, or likely they would be incompatible, either way these are old and well used so it's anybody's guess what I got to work with, nor do I trust most of these labels, I figure since they are all same size and chemistry there's no way one has 2200mah and others have 5300mah
thanks for the input
Last edited by 2007blueprius on Nov 28, 2013 11:53 am, edited 1 time in total.

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Re: Homemade Battery Packs

Post by DrkAngel » Nov 28, 2013 11:34 am

Found a collection of 18650 specs, in pdf

18650 Specs

Of Note:
OEM specs typically rate:
<=.5C charge rate
Up to 2C discharge rate (Though I doubt it to be good for the batteries!)

Most of the specs also chart the effect of cold on discharge capability.
See - Batteries vs Cold
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Re: Homemade Battery Packs

Post by 2007blueprius » Nov 28, 2013 8:43 pm

so I got the solder iron out but before I pluged it in figured I'd take some measurements, go figure, 4.15v each block 12+ total, my computer said it would not take a charge, now what is that electronic ghismo, like a bms? could it be fried?

ok this is odd 11.7v, it is now powering my laptop, yet the computer says it is something wrong with it and I should replace it

now 3.8v, 3.8v, 3.74v display shows 55% remaining, it's only been a few minutes, one block looks a bit behind I guess

3.56v. 3.57v, 3.51v , 6% remaining maybe 10 minutes by now, I droped it and had to restart, voltages went to 3.90 at rest

now voltages went up slightly and it holds steady, what do you recon? could all these 12 cells be evenly trashed, I was hoping I could get away with a couple cells, but that be the case there's a bad cell in each block, they stay pretty close together.

oh and mind you this is a 12v pack, 3s4p

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Re: Homemade Battery Packs

Post by DrkAngel » Nov 29, 2013 6:02 pm

DrkAngel wrote: 4.10V is recommended charge to attain rated capacity. (3.6V is ~empty)

As often as not, cells are still good and the charging circuit (in pack) has the defect.

Recommendation?
Purchase new "replacement" pack from an reputable "in country" reseller with 1-3 year warranty and don't lose warranty info!
Pack might "need replacement" if laptop determines it has capacity below a certain preset limit.
More likely, because 1 bank discharges faster.
All cells seem to have deteriorated, with possibly 1 totally dead.

3.6V cells, apparently, are designed to be charged to 4.10V.
Cells might be charged at 4.20V+ and retained 4.15V by the time you measured.Effectively, this would cut usable cycles in half.

C rate seems to be related more closely to remaining capacity than original capacity.
Higher C rate discharges, and recharges, seem to put more wear and tear on the cells = kill them faster.
18650 manufacturers recommend a <=.5C charge rate (2.5-3 hour full charge) and <.5c discharge rate (~2 hours from new battery.)

As an example:
An extended run 3s4p battery pack might take ~5 hours for a full charge (.25C rate charge).
But might run 4-5 hours on a charge (.2-.25C discharge )
As cells deteriorate the C rate increases from the same charge or discharge.
At near half life-usable capacity charge becomes .5C and discharge nears .5C.
Beyond this point, recommended charge rate is exceeded and discharge rate is increasing higher and cells deteriorate quickly.

Laptop battery pack producing heat, either charging or discharging, is a good indication that it is suffering.
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Re: Homemade Battery Packs

Post by 2007blueprius » Nov 29, 2013 6:30 pm

they got a little warm to the touch during my test, not enough to even mention it, I would say it is normal, the laptop is a few years old, there's no secret that I may have gotten all the use I can get out of it and I need a new one, I'm only tinkering with this pack because I want to learn something while at it.
figured it's allready broken how much worse can it get, besides I like what you did with your packs and figured this would be a nice test since I allready have it.
I am afraid this pack in particular may have served it's purpose allready, no cells got hot, not one block was particularily lower than the others, just sags real bad real fast, it stabilised at about 3.5v and stayed there longer than it took to get that low, but that is below empty, I was just curious if any of those cells may be good for something still.

I looked through your builds, I guess most laptop packs are 3s2p, do you test 2 cells at a time? in your finished builds I could still see the original tabs

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Re: Homemade Battery Packs

Post by DrkAngel » Nov 30, 2013 10:40 am

Some detractors made a brief appearance in this thread for the sole purpose of warning about dangerous 18650 Lithium-ion Cobalt cells.
For a laugh, take a gander at someone trying to show how dangerous 18650 cells are:
"Explosion" - "Fireball" tests! ala LFP

There were defective batches of cells produced for Dell, back in the 20th century, and limited problems with some Sony ~2006.

More recently, major manufactures seem to stringently safety test their products.
For example, these are the published safety tests (2007) for the Samsung 18650 3000mAh cells:
Samsung Safety.jpg
Samsung Safety.jpg (59.1 KiB) Viewed 4008 times
Of course, not every cell!
Probably every "batch" has a representative sample tested.

Lipo, on the other hand ...
Bargain price RC Lipo seem to have limited QC (Quality Control). I, personally, suspect that some of the Lipo I've purchased are repackaged rejects from some company with better standards. Varied capacity, self-discharge, puffed cells!, 25% of last batch not reliable-usable.
The exception are the Lipo I've been recycling from Dell secondary bay battery packs. 95% of the used packs, (3s2p), still charge & discharge evenly, within a couple 100ths of a volt.
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Re: Homemade Battery Packs

Post by agniusm » Dec 02, 2013 1:11 pm

My first LiPo battery pack for robotic lawn mover, 24V 10AH (6S2P):
Image
Image
Image
More photos @: E-Lawn mover
Last edited by agniusm on Dec 02, 2013 3:42 pm, edited 1 time in total.

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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 02, 2013 3:07 pm

got some questions that maybe themore versed in the mater can answear, inspired by the work posted in this thread I started tinkering with some power supplyes, my first atemp, a $5 Dell I ended up giving up on, could not find any schematics, datasheets nor somebody familiar with them, I looked into purchasing a meanwell at some point but gave up due to availability at the time, recently I got a $15 brand new 400w atx type which have been done before and folowing those examples I managed to tune it just enough to do what I needed it to.

so with the PS set at 3.65v I set out to charge an 80 ah 4s, 20 ah each block of lifepo4

chose to start with 4 of them because I was expecting 25 amp charge current, as the PS is rated for, now these cells were about dead ar aprox 3.28v each, as I first hooked them up the curent bearly got over 5 amps with a combined voltage of about 3.44v, in other words the setup did neithe CC nor CV, at least not the way I thought it would, I was expecting the PS to hold the voltage at 3.65v at least as a CV source, but nope it seemes to work somewhere in the middle, the charge curent has been decreasing as the SOC increased, at the moment my watt meter showa 3.58v still taking 1.5a charge, for an 80 ah block it's neglijable I guess, however I am ok with it at this time as these particular cells were a bit problematic I think, so a tricle charge may not be such a bad Idea.

however I am trying to get a better understanding of what is happening as I do have another 4 cell block to tinker with next and I would like to try something different I guess.

I never found any good material to read as far as CC/CV charging but my understanding is that initialy the CC phase, as the name states pushes a CC into the battery, I am assuming that my test block would only take at most 5 amp due to the relatively small delta v, 3.65-3.28 =0.37v, plus maybe the bateries resistance is nowhere near pulling a 25 amp load regardless of what the PS is capable of.

I know curent flows from the higher voltage to the lower so maybe cranking the PS up may have increased the charge curent, I haven't tryed that yet, but if I do I am assuming I can only go as far as 3.65v combined, as in charging, I know it is not a good idea to push these cells much further, even than I don't think I will get anywhere near the 0.5c charge rate of 40 amps, even if the PS was capable of, I also asume that since done manually I need to monitor it and turn it down as the bateries fill up, either way I guess I do not understand the concept behind CC charging, in order to achieve such curent I'd have to crank the voltage way up, further beyond what I thought would have been reasonable, even if I did one cell at a time

maybe somebody more knowledgeable can give me a hint https://endless-sphere.com/forums/viewto ... 14&t=51172 for more details about my experiment, skip over theDell part and look at the more recent posts

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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 02, 2013 8:27 pm

ok so I am going to post my preliminary results here just so I can have a point of refrence later and maybe get some input on what I am doing here.
I stopped charging my first batch when the combined voltage reached 3.6v, and the curent was at 1 amp, I verified my PS was still set for 3.65v once unpluged, after a few minutes together the 4P bundle settled at about 3.47v, I was a bit bummed about that, all this for .2 v but I guess it's much higher than it ever was last I had it as a part of the pack it bearly reached that on the charger, long story there too the pack was way out of balance, they used to settle at about 3.3v, so it is charged more than it ever was.
now the 4 pouches are separated, I'll check them in an hour, and again tomorrow see what we got.
as for my second batch figure'd I'll try a little faster charge, starting voltage 3.27v, once on the charger I cranked it till about 3.66v, amps was reading alittle over 10, the voltage did start to clime shortly after so I turned it down to 3.59 and keeping a close eye on it amps was about 7.4
even at the maximum "safe" 10 amp which is bearly 1/8c, the voltage was at 3.66 and climing and it would take 8 hours in theory to chatge it, so my question is how does one actually go about charging at 1/2 C in theory regardless of cell type, seems to me that the voltage would be crancked way up for that, my charger for the whole 16s4p is rated at 55v, 15 amps, there's no way it pushes 15 amps at 3.47v average per cell, or there is something here I do not understand, the voltage difference would have to be much higher to even come close.
maybe one of you can clear that up for me, when you speak of 4.2v for those lipo cells, do you mean while on a charge? towards the end? where does it stand in between? during CC stage? and when it does reach 4.2v how far back will they normaly sag when charge is removed?
one thought that comes to mind I am only using 2 computer fans for a dummy load, I know if not enough it wont regulate properly, they are rated ar 12v 0.13 amp 1/4 together at 3v it's neglijable, maybe I need a couple 5w resistors on on the 5 v one on the 12v just to make sure, I was under the impression these were regulated PS , maybe not the $15 ones.

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Re: Homemade Battery Packs

Post by Hillhater » Dec 02, 2013 9:01 pm

The basics of Ohms law still applies. V=IR
If you want a certain charge rate (amps) and the load (cell internal resistance) is fixed, then you have to increase the voltage (above the cell voltage) to give you the amps you want.
If you are seeing a low current at reasonable voltages, then that is suggesting your cells have a high Ri
Also that voltage fall off after charge would worry me.
Have you tested these cells at all for condition, Ri, etc. ? ..maybe they are dud.
CC charging a LiPo the charger voltage will "display" the actual cell voltage at that time.
A liPo, charged to 4.1 4.2 v will hold that voltage within 0.05v when removed from the charger and for days after.
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LiFePO4 - Worn Out?

Post by DrkAngel » Dec 02, 2013 9:41 pm

Cells that are "worn out" might be resistant to accepting a charge.
Look for any weak link in your charging rig.
A 24g jumper wire might not allow more than a 5A throughput?
Check input voltage at the cell!

Start at a lower voltage and try each cell individually.
Last edited by DrkAngel on Dec 02, 2013 11:26 pm, edited 1 time in total.
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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 02, 2013 9:46 pm

Hillhater wrote:The basics of Ohms law still applies. V=IR
If you want a certain charge rate (amps) and the load (cell internal resistance) is fixed, then you have to increase the voltage (above the cell voltage) to give you the amps you want.
If you are seeing a low current at reasonable voltages, then that is suggesting your cells have a high Ri
Also that voltage fall off after charge would worry me.
Have you tested these cells at all for condition, Ri, etc. ? ..maybe they are dud.
CC charging a LiPo the charger voltage will "display" the actual cell voltage at that time.
A liPo, charged to 4.1 4.2 v will hold that voltage within 0.05v when removed from the charger and for days after.
there's no secret to me that these cells may be damaged, long storry with this pack but there's a reason it is apart, if anything this is more like a post mortem autopsy that is why I am posting here I am curious to learn what can be salvaged, these 2 block are part of a 4 kwh pack, that was set up more like a joke advertised and sold to your average housewife as a plug and play.
I bought it used, and I allready aquired a good used pack which I am building a zephyr for, just testing to see what can be salvaged, repurposed, prettymuch same Idea as the laptop packs.
I get the theory that's why I was baffled, it is my first hands on experiment thou, it makes sense, where voltage is constant higher resistance lower curent, this is actually what I am trying to acomplish but in order to test them I had to get them charged first, and I believe they were so far gone to where I would not even try to charge them as a whole pack, the resistance may also explain the voltage sag.
now the charge was terminated at 3.6v combined, 1 amp curent the cells themselves didn't even come close I don't think, they were probls still at about 3.55v, reverse lag so to speak.
so would you consider these voltages reasonable, would you expect more current at these settings? I thought the PS will be maxed out honestly, I have yet to get to the better cells to see how they behave but all in all I am trying to gain some experience to be able to manage my new pack better.
what would be a proper procedure to charge them? I think I will try them individualy next, so where shoud my PS be set? is 3.5 good? say they will settle at about 3.45v eventually, what kind of amp should I see if they were good, considering they have some charge, maybe 5 amp each 20 ah cell? would that be reasonable. I'll see how much I can charge the so I can do a resistance test see what we got here.

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Re: Homemade Battery Packs

Post by Hillhater » Dec 02, 2013 11:19 pm

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)
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33.3V 43.2Ah LiPo Pack

Post by DrkAngel » Dec 02, 2013 11:27 pm

Finally got a 33.3V pack built!
9s20p 2160mAh 33.3V 43.2Ah recycled Lipo.
I capacity tested, then selected 30 3s2p and shuffled them into 3 equal 11.1V ~40Ah modules.
They fit precisely into a reinforced 6 pack cooler.
Base is 22.2V with 11.1V on top in removable module.
22.2V ~40Ah pack is available for prolonged cruising with 24V controller.

33.3V 43.2Ah will replace the 36V 20.7Ah Li-ion pack I've been running on my Winter slogger.
The large capacity should handily offset the advantages of the higher voltage smaller Ah pack.
22.2V should give great range, during good weather, on my Comfort Cruiser ... it also will run at 33.3V for a spiffy ~25mph.

I intend on prolonging this packs lifetime for several years.
Last pack using these same batch of cells, (25.9V 25.92Ah), ran for nearly 3 years and 6000++ miles.
By reducing charge to 4.05V per bank, (~32Ah), 280% cycle life is projected.

Oh! I finally modded a S-350-48 MeanWell as it's charger. (36.45V 9.1Ah)
I filled out the directions and specs on all the major mods for this model.
Last edited by DrkAngel on Dec 12, 2013 1:28 pm, edited 1 time in total.
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There, shallow draughts intoxicate the brain,
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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 03, 2013 12:40 am

I am runnung it through one of those http://hobbyking.com/hobbyking/store/__ ... lyzer.html using a totat 7 red wires from the PS and 7 black , my ampmeter is only good for 10 amp, I'll do a test straight through, I was orriginally expecting 20+ amp.
those are Realforce cells, 20 ah 3.2v , 3.65 is supposed to be full, I got some laptop cells to tinker with next we'll see how they do.

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33.3V 43.2Ah Lipo Pack

Post by DrkAngel » Dec 03, 2013 3:58 pm

Gittin' er done!
33.3V 43.2Ah recycled Lipo pack.
9s20p 2160mAh lipo cells = 180 cells
(3.7V x 2.16A) x 180 = 1.44kWh
In case - 20lb 11oz

The Brick - 6s20p 22.2V 43.2AH .96kWh
I modularized, beginning with this 22.2V 43.2Ah 13lb "Brick"
The Brick!.JPG
The Brick!.JPG (97.83 KiB) Viewed 3717 times
The Frosting - 3s20p 11.1V 43.2Ah .48kWh
Then folded and tacked on this 11.1V 43.2Ah 6.5lb featherweight for my 33.3V
The Frosting.JPG
The Frosting.JPG (70.71 KiB) Viewed 3717 times


Buttoned up and ready to go ...

33.3V 43.2Ah Lipo.JPG
33.3V 43.2Ah Lipo.JPG (83.74 KiB) Viewed 3717 times
All components are modular.
I used "Dean's Plugs" (T-Plugs) an color coded all connectors using various heatshrink.
Yes, there is a fuse hiding behind the wire in second picture (40A).
Last edited by DrkAngel on Dec 03, 2013 10:58 pm, edited 3 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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2007blueprius
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Re: Homemade Battery Packs

Post by 2007blueprius » Dec 03, 2013 5:14 pm

score couple of calls and a 2 mile trip to a local computer store, 50c each
WP_20131203_004.jpg
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Re: Homemade Battery Packs

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

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 ~3.7V 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.
Last edited by DrkAngel on Dec 04, 2013 11:10 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

EBike Toolbox - Bargains! $

Endless Sphere Wiki

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