Homemade Battery Packs

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

Post by DrkAngel » Oct 27 2011 12:58pm

Kin wrote:Just wondering if you got the PM I sent asking about tips for sourcing used LiPo. Was looking over at RCgroups, thinking they might have some stuff (but a lot of it is excessively high C rating or excessively low Mah).
RC types on ebay auction.
Sometimes a good price, but they are 1 item auctions so might take awhile to collect enough.

Recycled:
Check local recycling centers.
Look for auctions on ebay, craigs list, etc.
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Lipo mAh per 100th V

Post by DrkAngel » Oct 27 2011 4:25pm

Lipo mAh per 100th V completed.
Still graphing data.
Will post numbers and do graph this weekend.
DrkAngel wrote:12V thermostat - safely regulates 12V heating pads.
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Sorry ... tried something different!
Just click on the picture, to be taken to the link!
Inexpensive, thin, flexible, self adhesive, low wattage heating pads.
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12V thermostat - safely regulates 12V heating pads.
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Re: Homemade Battery Packs

Post by Kin » Oct 27 2011 4:54pm

DrkAngel wrote:
Kin wrote:Just wondering if you got the PM I sent asking about tips for sourcing used LiPo. Was looking over at RCgroups, thinking they might have some stuff (but a lot of it is excessively high C rating or excessively low Mah).
RC types on ebay auction.
Sometimes a good price, but they are 1 item auctions so might take awhile to collect enough.

Recycled:
Check local recycling centers.
Look for auctions on ebay, craigs list, etc.
Thanks, I guess, there was no secret that I was missing. Just, it's not super easy :).
New to endless-sphere? Notice a lot of signatures recommending Ebikes.ca? That's because it's the best place for a quality and manageable, (but still 'real'), first build. Justin is a solid supporter of electric bike development, and a good source of equipment.

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Recycled Lipo Homemade Battery Packs

Post by DrkAngel » Oct 29 2011 12:22pm

I'm guessing for maximum life, the Laptop lipo packs charge to 4.13V, then settle to 4.10V.
My mAh per 100thV testing seems this to be a wise choice!

Indeed, when discharge tested from 4.25V, these cells output a mere 1/10th the mAh from 4.2V to 4.1V, compared to the mAh output, from 4.1V to 4.0V.
This was true of the best, and the poorest of the packs I tested.
Guess I'll be lowering the setting on my iMax B8, from "LiPo" to "LiIn", which changes peak charge to 4.1V per cell.
Strangely, my recycled Li-ions seem to charge efficiently to nearly 4.2V ... the "LiPo" setting ... ???

Be aware! These results are for a specific cell type-formulation and might have no relation to other brands-types-formulations!

Sorry ... got excited looking over the discharge stats.
Will have full numbers, and hopefully graph, posted later tonight.
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Recycled LiPo discharge Curve mAh/100thV

Post by DrkAngel » Oct 29 2011 5:15pm

Quick stats on mAh per 100th V.
LiPo 2160mAh used cells.
Charged to 4.2V (charging to 4.25V produced no additional "usable" mAh)
.2C discharge rate
..V... mAh
4.23V ..
4.22V ..
4.21V ..
4.20V ..
4.19V ..
4.18V ..
4.17V .. 1
4.16V .. 1
4.15V .. 2
4.14V .. 4
4.13V .. 4
4.12V .. 7
4.11V .. 10
4.10V .. 14
4.09V .. 17
4.08V .. 21
4.07V .. 31
4.06V .. 39
4.05V .. 40
4.04V .. 59
4.03V .. 68
4.02V .. 82
4.01V .. 45
4.00V .. 75
3.99V .. 70
3.98V .. 60
3.97V .. 90
3.96V .. 70
3.95V .. 70
3.94V .. 75
3.93V .. 75
3.92V .. 70
3.91V .. 66
3.90V .. 68
3.89V .. 66
3.88V .. 70
3.87V .. 80
3.86V .. 100
3.85V .. 110
3.84V .. 120
3.83V .. 130
3.82V .. 75
3.81V .. 80
3.80V .. 75
3.79V .. 75
3.78V .. 75
3.77V .. 65
3.76V .. 55
3.75V .. 55
3.74V .. 45
3.73V .. 45
3.72V .. 45
3.71V .. 36
3.70V .. 39
3.69V .. 35
3.68V .. 34
3.67V .. 29
3.66V .. 28
3.65V .. 27
3.64V .. 26
3.63V .. 25
3.62V .. 29
3.61V .. 26
3.60V .. 27
3.59V .. 24
3.58V .. 24
3.57V .. 27
3.56V .. 24
3.55V .. 21
3.54V .. 20
3.53V .. 20
3.52V .. 16
3.51V .. 17
3.50V .. 14

Output is reasonably good from about 4.05V till 3.75V.
Very noticeable, is a muscular bulge near 3.85V.
Decreasing till it reaches minimum usable near 3.7V.

Based on these figures:
For my recycled LiPo,
Charge-discharge voltages should be,
Maximum 4.10V
Minimum 3.7V

I would recommend "bottom balancing", at 3.75V.

Charging above 4.1V looks worthless, and unnecessarily damaging.
Same for discharging below 3.7V.

Be aware! These results are for a specific cell type-formulation and might have no relation to other brands-types-formulations!
Attachments
LiPo.jpg
Raw data graph
LiPo.jpg (24.1 KiB) Viewed 3285 times
Smoothed LiPo.jpg
"Smoothed" to moderate "human error"
Smoothed LiPo.jpg (22.9 KiB) Viewed 3285 times
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Re: Homemade Battery Packs

Post by migueralliart » Oct 30 2011 8:56am

I agree with the results, I've tested single pink cells and the behavior is more or less the same. I USED to charge them @ 4.2 but when loaded they let go easily to 4.15V. Do you think it is a better idea to charge them using the li-ion setting?

Just to share, the picture is a bit blurry but it shows my 26AH "bricks" made from pink samsung cells. I got somewhere around 9-10 of these bricks tested and ready to assemble and 15 laptop packs ready to disassemble and etc etc

Image

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Re: Homemade Battery Packs

Post by SamTexas » Oct 30 2011 9:22am

migueralliart wrote: Just to share, the picture is a bit blurry but it shows my 26AH "bricks" made from pink samsung cells.
26Ah (10 cells) is for brand new cells. What is the actual capacity of your pack? I have also built 10p packs using Panasonic pink cells, and the actual capacity ranges from 15 to 21Ah (at 0.5C discharge)

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Re: Homemade Battery Packs

Post by migueralliart » Oct 30 2011 12:17pm

SamTexas wrote:
migueralliart wrote: Just to share, the picture is a bit blurry but it shows my 26AH "bricks" made from pink samsung cells.
26Ah (10 cells) is for brand new cells. What is the actual capacity of your pack? I have also built 10p packs using Panasonic pink cells, and the actual capacity ranges from 15 to 21Ah (at 0.5C discharge)
My bricks get anywhere from 22-25Ah these cells were tested and discharged individually and grouped together by voltage drop and capacity similarities, just as the OP suggested. I picked the BEST cells for the packs as I bought more than 150 laptop battery packs (all the same type) lucky me they all had samsung 2.6ah cells. I spent countless hours doing the cell harvesting while studying for college.

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Re: Homemade Battery Packs

Post by SamTexas » Oct 30 2011 12:24pm

Excellent job. What discharge rate are you using when measuring the cells' capacity?

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Re: Homemade Battery Packs

Post by migueralliart » Oct 30 2011 12:29pm

SamTexas wrote:Excellent job. What discharge rate are you using when measuring the cells' capacity?

I was discharging at 2 amps each pair of cells so that'll be closer to .5C . I plan on building a 24V pack for my commuter bike I live in FL so I don't need a lot of power my 250w rear geared will do just fine with that voltage and capacity, now if I could find a good DIY on a frame battery case on these forums I'm blessed LOL

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Re: Homemade Battery Packs

Post by SamTexas » Oct 30 2011 12:36pm

migueralliart wrote: I was discharging at 2 amps each pair of cells so that'll be closer to .5C . I plan on building a 24V pack for my commuter bike I live in FL so I don't need a lot of power my 250w rear geared will do just fine with that voltage and capacity, now if I could find a good DIY on a frame battery case on these forums I'm blessed LOL
Do they still make hub geared motor running at 24V? Or is this a Currie type non hub motor?

I have built 2 triangle frame battery/controller boxes, but I was not happy with either. They look too add-on, too crude for me.

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Re: Homemade Battery Packs

Post by migueralliart » Oct 30 2011 12:51pm

SamTexas wrote:
migueralliart wrote: I was discharging at 2 amps each pair of cells so that'll be closer to .5C . I plan on building a 24V pack for my commuter bike I live in FL so I don't need a lot of power my 250w rear geared will do just fine with that voltage and capacity, now if I could find a good DIY on a frame battery case on these forums I'm blessed LOL
Do they still make hub geared motor running at 24V? Or is this a Currie type non hub motor?

I have built 2 triangle frame battery/controller boxes, but I was not happy with either. They look too add-on, too crude for me.
I got it from BMS battery. Well I guess I should stick to using the rear rack for battery storage.

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LiCo vs LiPo Discharge Profiles.

Post by DrkAngel » Oct 31 2011 10:58am

Please note:
The LiCo is a 2600mAh cell,
compared to the LiPo cell which is 2160mAh.

So, for a direct comparison, the LiPo line might-should be moved up, about 25%?

Image
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Re: Homemade Battery Packs

Post by DrkAngel » Nov 05 2011 6:37pm

DrkAngel wrote:
neptronix wrote:So basically this data might be useful to you, but needs to be in a different format in order to actually compare with the other 99.9% of battery graphs on the web, on manufacturer spec sheets, etc.
Exactly my point! ........ Useful!
I think my type graph might be more useful ... to everyone!
In fact, I specifically decided to create this type of graph, because the "standard" type was so useless!
I would think everyone would consider this type of graph to be more useful than the "standard" type.

I think it would be very useful if we could develop a database (mAh/.01V)
If you would like to determine the functional capacity of your type battery, (mili-Amp hours per 100th volt), I would recommend the following standards:

List the Brand, mAh capacity, formulation - LiPo, LiCo, LiMn, NiMh, SLA etc.
Use a regulated discharge (digitally metered) I used an iMax B6 - about $25
Discharge at a low rate to reduce "voltage sag"(.2C = 5 hours)
Digitally meter voltage at the cell - much more accurate than through the discharge device

Graph program is a free download from http://www.padowan.dk/graph/.
Last edited by DrkAngel on May 06 2013 7:26am, edited 2 times in total.
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Re: Homemade Battery Packs

Post by DrkAngel » Nov 05 2011 9:35pm

Latest mAh per 100th Volt test was with the rather common WinForce 5700mAh cell.

Yellow is the laptop recycled Lipo, that I use. - 4320mAh
Pink, is the laptop recycled 18650 cells that I use. - 5200mAh
Green, is the new, RC type, LiPo, that I was considering using. - 5700mah
Combo s.JPG
Combo s.JPG (41.37 KiB) Viewed 2980 times
I found it, almost, ... disturbing, that the best capacity, was at a point, below what is "usable", on an alternate brand of LiPo.

See the full specs & stats here - Lithium - mAh/100th V - Discharge Test
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Li-ion Capacity Maps

Post by DrkAngel » Nov 07 2011 8:38am

DrkAngel wrote:Latest mAh per 100th Volt test was with the rather common WinForce 5700mAh cell.

Yellow is the laptop recycled Lipo, that I use. - 4320mAh
Pink, is the laptop recycled 18650 cells that I use. - 5200mAh
Green, is the new, RC type, LiPo, that I was considering using. - 5700mah

Image

I found it, almost, ... disturbing, that the best capacity, was at a point, below what is "usable", on an alternate brand of LiPo.

See the full specs & stats here - Lithium - mAh/100th V - Discharge Test

Due to the extreme variance in usable voltages, I would highly recommend testing your own battery!
Capacity at different voltages differs substantially.
Different brands, supposedly of the same type-formulation, can vary wildly.
The LiPo, I use, are at "empty" voltage, before a different LiPo, starts into its greatest capacity voltage! ... ???

My testing procedure explained, up 2 posts.

Alternate test method is to ...
Plan a specific route, of limited length.
Check fully charged battery voltage.
Carefully measure and note voltage, after each "lap".
Run each lap in identical manner, same speed-acceleration, etc.
100th's Volt used each lap should give you a "map" of usable voltage.
End test, when 100ths volt used increases sharply.

Shorter "lap" will produce better "map".
Around block?
Recommended length varies by battery size.
Method should work with all "types" battery.

1/100ths Volt preferable!
Some digital meters won't meter 1/100 V at pack voltage.
1/10 V should give fair idea.
Laps per 10th volt, on full pack voltage.
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Re: Homemade Battery Packs

Post by DrkAngel » Nov 12 2011 11:34pm

I found a new toy!
A different type of battery, an offshoot-improvement? of the LiFePO4.

I accidentally picked up a couple kWh of LiFeMgPO4 (lithium iron magnesium phosphate)

One feature, is that they seem to be designed to be directly usable at 12V, and multiples thereof.
There is some indication that sla chargers and devices are compatible! ... ?

More info - mAh per 100th Volt graph, etc > LiFeMgPO4
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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LiFeMgPO4 Projects?

Post by DrkAngel » Nov 14 2011 8:04am

DrkAngel wrote:I found a new toy!
A different type of battery, an offshoot-improvement? of the LiFePO4.

I accidentally picked up a couple kWh of LiFeMgPO4 (lithium iron magnesium phosphate)

One feature, is that they seem to be designed to be directly usable at 12V, and multiples thereof.
There is some indication that sla chargers and devices are compatible! ... ?

More info - mAh per 100th Volt graph, etc > LiFeMgPO4
DrkAngel wrote:Confirmed manufacture by Valence Technology.
Damn ... only got 2kWh worth.

Supposedly:
they have an overvolt charge capability,
a degree of auto balancing,
do well with a "100% DOD",
are designed "capable" as SLA replacements, (SLA charger resilient?)
2500 cycle, at normal temperatures

Damn! Only got 2 kWh worth!
The cells, 12 thick, are about the size of the 12V 7-8Ah SLA batteries, used in the common, personal use, APC UPSes.
If indeed, they are undamaged by SLA type chargers, my little UPS (Uninterpretable Power Supply), can be upgraded from about 3Ah usable to 15Ah.

Doesn't take advantage of the 2500 cycles ... hmm ...

Could replace the, less than, 6Ah usable, SLA, in my EZip pack, with 15Ah.
Almost 3X the capacity.
2500 cycles = 8 years - daily cycled.
Should outilve a few ebikes!

Enough cells for 5 EZip packs! But ... gotta think of some better use ...

Daily, or multiple, daily cycles, to take advantage of, extreme "cycles", capability?
Solar storage?
Hybrid vehicle buffer?
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Saphion LiFeMgPO4 Cells

Post by DrkAngel » Nov 15 2011 8:20am

Unfortunately, I think I was just lucky, when I found my little supply of these cells.
More, to play with, would be nice ...

Valence Technology does not specifically rate these cells.
However, their current production of their LiFeMgPO4 cells, advertise:
2C continuous output.
3C surge output.
12.8V - 3.2V per cell
13.8V - 3.45V per cell float voltage
14.6V - 3.65 charge voltage
.5C - standard charge

Charging voltages look compatible with SLA chargers.
Charge rate is much higher than SLA recommended - a good thing.

The Valence LiFeMgPO4 technology - cells are Patent - branded Saphion.

The company - Valence Technology
A little learning is a dangerous thing;
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Re: Homemade Battery Packs

Post by SamTexas » Nov 15 2011 10:47am

Sounds like an excellent replacement for Lead Acid battery in ebike application.
But the whole thing is pointless. It's a product that can not be bought by a normal consumer! Why? Too expensive to buy? Too expensive to maintain? Too dangerous? Whatever the reason is, it must be a serious one.

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Re: Homemade Battery Packs

Post by DrkAngel » Nov 15 2011 4:09pm

SamTexas wrote:Sounds like an excellent replacement for Lead Acid battery in ebike application.
But the whole thing is pointless. It's a product that can not be bought by a normal consumer! Why? Too expensive to buy? Too expensive to maintain? Too dangerous? Whatever the reason is, it must be a serious one.
Extremely Safe!
Too expensive-too good ... for normal consumer ... ?
Tested at 100% DOD for 3000 cycles, still 80% capacity = daily charging for 8+ years!
Few ebikers would feel "satisfied" handing down the same battery pack, through several generations of ebikes.
15-20 years might be more typical, which might induce "age degradation"?
And battery price drops, every year.
I believe these batteries are designed, and marketed, towards heavy users, multiple cycles per day etc.

Some lucky few will find and recycle these gems. ... :D

Just gotta think of worthy applications ... only got about 2kWh worth.

Valence
Last edited by DrkAngel on Nov 15 2011 8:34pm, 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

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Re: Homemade Battery Packs

Post by SamTexas » Nov 15 2011 5:51pm

DrkAngel wrote: Some lucky few will find and recycle these gems. ... :D

Just gotta think of worthy applications ... only got about 2kWh worth.
When and if I found them I would put them in my motorhome. No more worries about 50% DOD.

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Re: Homemade Battery Packs

Post by Skysurfer » Nov 15 2011 6:30pm

Hi, folks. Very interesting. I've just bought a used wheelchair package, 24v. I was amazed to open it up to find 64 cells of A123's. I have no idea how they're wired at the moment, they're throwing out 26+v, so I've a bit of time yet, no panic. I need to put together some kind of BMS, as there's no electronics in the box, no balancing circuit at all.
Does anybody know how these might be wired (series/parallel) to give the 24/26v -ish I'm getting? Then I can plan for a BMS (I'd like to get a balancing circuit in there, somewhere). Anybody got any ideas on this BMS + balancer?
Yup, I might have bitten off more than I can chew, but I'm gonna give it the good ol' college try... :shock:
Image attached
Cheers, y'all
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Re: Homemade Battery Packs

Post by The Mighty Volt » Nov 15 2011 6:56pm

Skysurfer wrote:Hi, folks. Very interesting. I've just bought a used wheelchair package, 24v. I was amazed to open it up to find 64 cells of A123's. I have no idea how they're wired at the moment, they're throwing out 26+v, so I've a bit of time yet, no panic. I need to put together some kind of BMS, as there's no electronics in the box, no balancing circuit at all.
Does anybody know how these might be wired (series/parallel) to give the 24/26v -ish I'm getting? Then I can plan for a BMS (I'd like to get a balancing circuit in there, somewhere). Anybody got any ideas on this BMS + balancer?
Yup, I might have bitten off more than I can chew, but I'm gonna give it the good ol' college try... :shock:
Image attached
Cheers, y'all
Pete (Manchester UK)
Hello from Dublin, Ireland.

Paul, those don't look like A123 from here.

If they are A123, then it is an 8s8p pack {24v, 17.8Ah}

To make 24v with LiFePO4, you need 8 cells in series.

The remaining cells {56 in your case] are then added in parallel to each cell in turn in the series line until all the cells are used.

Another way to look at it is that 8 groups of 8 cells in parallel are made up {8 cells connected to each other, positive to positive, negative to negative} and then the groups are connected to each other in series {positive of first group to the negative of the second, positive of 2nd group to negative of third group etc etc}

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DrkAngel   100 GW

100 GW
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Joined: Dec 15 2010 11:14am
Location: Upstate-Western-Southern Tier NY. USA

LiFeMgPO4 Discharge Graph

Post by DrkAngel » Nov 16 2011 9:58am

Oops forgot to post the discharge graph ... here.

Most impressive is the massive amount of energy, concentrated at full voltage!
LiFeMgPO4%20smooths.JPG
LiFeMgPO4%20smooths.JPG (10.75 KiB) Viewed 6026 times
Sorry, I didn't have a "standard" LiFePO4 to compare against.
Pictured is a comparison with my standard use recycled LiPo -
vs%20LiPos.JPG
vs%20LiPos.JPG (12.51 KiB) Viewed 6026 times
.

Larger size below, as attachments.
Attachments
LiFeMgPO4%20smooth.jpg
LiFeMgPO4%20smooth.jpg (41.73 KiB) Viewed 839 times
vs%20LiPo.jpg
vs%20LiPo.jpg (48.11 KiB) Viewed 839 times
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