Homemade Battery Packs

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

Post by LeftieBiker » Feb 04, 2014 7:30 pm

Good point about the battery "gauge" LEDs. I do like having them, as they are even more useful with the Ping lithium pack than with the SLA pack. I get yellow (but no red) with green in Winter under heavy load, then get lots of yellow with a little red under load as the pack actually gets low (a rare occurrence with 20AH). I only get yellow in Summer as the pack gets low. Still, I'd trade that for a bit more speed in Summer, as I know the limits of the setup well, and even with a new pack could learn them quickly enough, as I have one great route, one longer version of it, and that's it. Everything else is highways with traffic and cops...

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Re: Homemade Battery Packs

Post by DrkAngel » Feb 09, 2014 11:41 am

I have fallen in love with the 33.3V battery for the oem eZips.
They handily meet the 20mph "legal" speed with a 140% of the oem torque.

My previous favorite eZip mods involved 25.9V with a re-gearing mod ... designed to hit 20mph but with an 80% of oem torque ratio.
7s vs 9s 20mph.jpg
7s vs 9s 20mph.jpg (71.99 KiB) Viewed 5098 times
My 33.3V 31.2Ah (18650 laptop cells) pack works nicely ...

Image
but, I would like to take advantage of my NOS laptop Lipo!

25.9V 25.92Ah 7s12p (2160mAh cells) fits tightly in the eZip "RMB" battery pack

Image
However, fitting 9s 33.3V Lipo will only fit 8p or 17.28Ah ...

33.3V eZip Lipo Re-Manufacture
Now, 33.3V 17.28Ah of Lipo is reasonably good ... but these are cells designed and modified for laptop use.
In my testing, after 4C initial surge followed by a sustained 2C+ drain, the built in fuse has blown.
Simply removing the fuses might be acceptable considering the less than 2C brief surge and <.33C cruising draw.
I prefer a better "reliability" margin.
And I do have a stockpile of good condition 3s2Ah RC LiPo.
I can fit 3 of them beside the laptop cells for an additional 2Ah with a 5C continuous rating.
Hopefully, this 10A brief surge "buffer" will remove any excessive strain on the laptop cells.

Even better!
Just did a cell "re-shuffle" ... with fuses removed, cells take up enough less room that I can turn 1 stack and fit a total of 6 RC LiPo packs for a total 33.3V 21.28Ah with Laptop Lipo @1C for 17A & RC LiPo @5C for 20A totaling a 37A continuous capable output.

Before building I will determine actual Amp usage using 33.3V 43.2Ah 6-pack with Volt, watt and Amp meter attached.
Last edited by DrkAngel on Feb 23, 2014 1:05 pm, edited 2 times in total.
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Re: Homemade Battery Packs

Post by LeftieBiker » Feb 09, 2014 5:08 pm

Can't you determine maximum current draw and just use an appropriate fuse? Otherwise if you get a short you have a runaway electrical resistance heater.

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Re: Homemade Battery Packs

Post by Linukas » Feb 13, 2014 6:09 pm

one of my 18650 cells packs, totaly 289pcs of sony cells:
Image
Image
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Re: Homemade Battery Packs

Post by Hwy89 » Feb 14, 2014 10:28 pm

Linukas,
what is the white cell holder material? Looks like it comes in sheets and can be trimmed to size. Please link the source. Is it expensive?

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Re: Homemade Battery Packs

Post by Linukas » Feb 16, 2014 6:32 pm

cells holder is cnc cut from pp plastic, I designed that holder and yes it can be cut according to needed size, these packs I make for my bikes.
total width with 65mm cells is 72mm, (to calculate total pack size, from one cell center to other cell center is 19.5mm) pack also have laser cut paper isolators on cells + terminals, but this type pack is good just for nicel plates weld because there are no place for wires.
If someone will interest in these kits I'll write new theme in "Items for Sale". I think price can be ~0.6euro for 1cell (both sides plastic parts and laser cut paper isolators on + terminals. (for example pack for 100pcs cells will cost 60euro)
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Re: Homemade Battery Packs

Post by madin88 » Feb 17, 2014 7:56 am

Linukas wrote:cells holder is cnc cut from pp plastic, I designed that holder and yes it can be cut according to needed size, these packs I make for my bikes.
total width with 65mm cells is 72mm, (to calculate total pack size, from one cell center to other cell center is 19.5mm) pack also have laser cut paper isolators on cells + terminals, but this type pack is good just for nicel plates weld because there are no place for wires.
If someone will interest in these kits I'll write new theme in "Items for Sale". I think price can be ~0.6euro for 1cell (both sides plastic parts and laser cut paper isolators on + terminals. (for example pack for 100pcs cells will cost 60euro)
awesome battery build! yeah write a theme in itmes for sale would be great. I think the problem is cnc cut is expensive for higher quantities.
It would be a lot cheaper if a company built such big sheets of molded plastic.
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Re: Homemade Battery Packs

Post by madin88 » Feb 17, 2014 7:57 am

doublepost
Last edited by madin88 on Mar 01, 2014 3:18 am, edited 1 time in total.
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Re: Homemade Battery Packs

Post by DrkAngel » Feb 22, 2014 10:39 am

Update - MeanWell S-240-48 does not mod well!

33.3V Charger
As mentioned previously, there seems to be a shortage of available chargers for a 33.3V pack.

An S-Series 36V MeanWell would be perfect, S-350-36 was produced but seems to be very rare.

I just lucked into a supply of MeanWell S-240-48.
48V 5A can be modded to 36.45V 6.5A which would be perfect for my 9s x 4.05V Li-ion pack, typical Winter forays use less than 5Ah.
Or ...

37V Charger
I could easily mod the MeanWell S-240-48 to a 42V 5.7A charger for a 10S x 4.2V battery pack.
Or ...

33.3V - 37V Charger
Best of all ...
At a 39V median, the oem 1K pot gives an 8V adjustment.
Which means I can use the same charger and quickly adjust for a 33.3V or 37V pack.
Or ...

44.4V Charger
Of course, a 12s x 4.2V 50.4V 4.75A charger is simple, requiring a basic current adjustment
And finally ...

48.1V Charger
A 13s x 4.2V 54.6V 4.4A charger is just as simple (with current mod.)

For use as a charger, near maximum output, I will implement a continuous fan mod.
Simply linking the fan neg to the DC neg output works for a 12V fan voltage.
Perhaps, I will Add a diode & 2W resister from the fans neg line to the PS DC neg output.
This will supply a reduced continuous fan speed, leaving intact the oem full speed circuit if temperature rises high enough.

I will post up dedicated thread after my samples arrive.
The Journey: Speculation through results - MeanWell S-240-48

Started a Wiki page.
See - MeanWell S-240-48

Just noticed ... MeanWell S-xxx-48 are "48V - adjustable from 41V - 56V ".
So, without a voltage mod, would be a capable bulk charger for 10s, 11s, 12s or 13s (37V - 48.1V) Li-ion battery packs.
Current mod still required-highly recommended, unless BMS is programmed to regulate.
Last edited by DrkAngel on Jul 15, 2014 7:46 am, edited 1 time in total.
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Re: Homemade Battery Packs

Post by 999zip999 » Feb 28, 2014 7:18 pm

Bump.

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Re: Homemade Battery Packs

Post by parabellum » Feb 28, 2014 10:25 pm

Drkangel.
High discharge cells are excellent to boost slow pack. I use turnigy packs to have more out of Drbass makita packs.

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Re: Homemade Battery Packs

Post by cal3thousand » Mar 10, 2014 2:22 pm

I just finished my battery mounting rack for my Pelican (Peli-Storm Im2075 Case) 24S 10Ah LiPo box. I used ABS for spacers inside between the LiPo packs and closed cell foam for padding. Silicon wires, Genuine Andersons, 8x Turnigy 20C 5Ah packs, 50A mid-mounted fuse and Method's LiPo protection kit were used.

For the mounting, I used only Aluminum square tube, Aluminum L bracket, aluminum rivets, steel plate, stainless fasteners, ABS plastic sheet, a dog collar, and 4 aluminum 1-1/4" accessory clamps. I also only used cordless electric hand tools (DeWalt) and a Black & Decker WorkMate to handle all the cutting/drilling, as I live in an small apartment. (I also learned how to sew by hand so I could shorten the dog collar)

Credit for the Pelican box and clamp ideas all go to Oatnet. The rest of the genius is mine :mrgreen:

Here's a couple pics of the internal construction of the pack:
Peli-Storm Im2075 Case - 1st 12S.jpg
1st half of the Pelican innards
Peli-Storm Im2075 Case - 1st 12S.jpg (55.48 KiB) Viewed 4563 times
Peli-Storm Im2075 Case - 24S.jpg
2nd half of the Pelican innards
Peli-Storm Im2075 Case - 24S.jpg (72.36 KiB) Viewed 4563 times


Here is a picture of the back of the case showing the 4 neodymium magnets. They help align the pack when loading onto the bike and they also provide gripping force to the keep it there. Each magnet is rated at 23 lbs of pull force. But that is rated at magnet to magnet; magnet to steel, they put out like 13 lbs. 4 of them should hold the battery there without much else, but I put a strap on it to be safe. Notice that they are NOT flush to the box's outside:

Peli-Storm Im2075 Case - Magnets.jpg
Magnets on the back
Peli-Storm Im2075 Case - Magnets.jpg (36.25 KiB) Viewed 4563 times

The bottom of the Pelican box has 2 square channels running from front to back that were perfect for square aluminum tubing. So I used some of that to create an area that the battery slides onto the rack like a forklift on a pallet. The ABS sheet was cut with reliefs for the magnets and then riveted to a steel plate. That steel plate is the magnetic surface that the box grabs onto. I painted the plate and put some small faux silver carbon fiber stickers where the magnets will contact the steel plate, in order to prevent the paint chipping from repetitive contact cycles. When the box slides onto the forks, it slides back and the magnets "click" to the steel plate. The ABS sheet is the exact thickness of the magnets creating a recession for the box to flush mount against the ABS sheet.

Here is a pick of the front of the mount showing the forklift section, the magnet reliefs in the ABS and the 3M sticker in place, and the modified XL dog collar that grabs the Pelican's top handle:
Pelican Battery Mount - Front Bare.jpg
Battery Mount Front
Pelican Battery Mount - Front Bare.jpg (58.27 KiB) Viewed 4563 times

A couple side views:
Pelican Battery Mount - Side view Bare.jpg
Side view far
Pelican Battery Mount - Side view Bare.jpg (70.9 KiB) Viewed 4563 times
Pelican Battery Mount - Side View Bare Close.jpg
Close side view
Pelican Battery Mount - Side View Bare Close.jpg (59.65 KiB) Viewed 4563 times

Notice that the magnets sit flush into the mount:

Pelican Battery Mount - Side View Loaded.jpg
flush magnets
Pelican Battery Mount - Side View Loaded.jpg (60.81 KiB) Viewed 4563 times

The bike is now waiting on a repair since I just found the phase and halls were cut by the stupid Xlyte bearing seal. I'm pretty sure it will work out well. If not, you guys will hear about it :D
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Re: Homemade Battery Packs

Post by kje » Mar 20, 2014 7:35 pm

DrkAngel wrote:"Bleed down" from full charge is my primary condition indicator as well.
I am presently remanufacturing my 2008 builds ... 350+ cells.
These particular 3.7V 2600mah cells retain good energy density above 4.2V.
So I bulk charged batts as 44p, using 4.25V 35A MeanWell, then separate.
After setting 7 days I am segregating into piles of 4.24V, 4.23V, 4.22V, 4.21V, 4.20 4.20V - 4.15 and then "bin jobs".
4.2V minus will be used in some bulk power inverter pack charged to 4.10V, or lower?
After charging laptop cells to 4.20V an setting for "bleed down" several months I`ve segregating into piles of 4.20V -> 4.10V, 4.10V -> 4.00V, 4.00V -> 3.90V, 3.90V -> 3.80V

Battery pack: 3s50p 55A continuous draw. Wich cells is usable? Only the 4.20V -> 4.10V cells? Or can I also use the 4.10V -> 4.00V and even 4.00V -> 3.90V cells?

Balancing wire: what gauge do I need for a battery pack this big? Is this acceptable: http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40

Thanks :)

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Re: Homemade Battery Packs

Post by DrkAngel » Mar 21, 2014 4:33 am

Since I usually charge daily and am only charging to 4.05V ...
I only use cells that maintain this voltage for a full week.

When bulk charging, it is important to not have any cells that bleed down below charged voltage.
If you rely on balance charging, this is not as important.
Though I can't recommend using any cells that bleed down below working voltage between uses ... weekly(?).

Balance wire gauge is not important ... balance amperage is so low that even the smallest gauge is adequate.
If you manually balance, by applying 1s voltage directly to a bank, then you would bypass balance wire and connect directly to each bank with alligator clips.
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Re: Homemade Battery Packs

Post by ridethelightning » Mar 21, 2014 7:48 am

subscribed 8)

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kje
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Re: Homemade Battery Packs

Post by kje » Mar 21, 2014 9:09 am

DrkAngel wrote:Since I usually charge daily and am only charging to 4.05V ...
I only use cells that maintain this voltage for a full week.
Thank you DrkAngel.

The number of cells after "bleed down":
4.20V -> 4.15V: 101
4.15V -> 4.10V: 8
4.10V -> 4.00V: 43
4.00V -> 3.90V: 10
3.90V -> 3.80V: 17

Do you recommend me to use just the cells between 4.20V -> 4.15V?

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Re: Homemade Battery Packs

Post by DrkAngel » Mar 21, 2014 10:16 am

kje wrote:
DrkAngel wrote:Since I usually charge daily and am only charging to 4.05V ...
I only use cells that maintain this voltage for a full week.
Thank you DrkAngel.

The number of cells after "bleed down":
4.20V -> 4.15V: 101
4.15V -> 4.10V: 8
4.10V -> 4.00V: 43
4.00V -> 3.90V: 10
3.90V -> 3.80V: 17

Do you recommend me to use just the cells between 4.20V -> 4.15V?
Yes, charge to 4.15V.

Use others for ... other project?
4.00V plus for axillary or emergency "limp home" battery.
Charging to 4.00V does provide "decent" capability.
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Re: Homemade Battery Packs

Post by parabellum » Mar 21, 2014 4:19 pm

kje wrote:
DrkAngel wrote:Since I usually charge daily and am only charging to 4.05V ...
I only use cells that maintain this voltage for a full week.
Thank you DrkAngel.

The number of cells after "bleed down":
4.20V -> 4.15V: 101
4.15V -> 4.10V: 8
4.10V -> 4.00V: 43
4.00V -> 3.90V: 10
3.90V -> 3.80V: 17

Do you recommend me to use just the cells between 4.20V -> 4.15V?
How many over 4.17? Makita konions go down to ~4.16 (but it is not laptop cell)

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Re: Homemade Battery Packs

Post by liveforphysics » Mar 21, 2014 5:23 pm

kje wrote:
DrkAngel wrote:Since I usually charge daily and am only charging to 4.05V ...
I only use cells that maintain this voltage for a full week.
Thank you DrkAngel.

The number of cells after "bleed down":
4.20V -> 4.15V: 101
4.15V -> 4.10V: 8
4.10V -> 4.00V: 43
4.00V -> 3.90V: 10
3.90V -> 3.80V: 17

Do you recommend me to use just the cells between 4.20V -> 4.15V?

There is no good or safe self-discharge mechanism for a cell. All self-discharge is indicative of something very wrong in a cell that you do not want in your pack EVER. They won't always become safety issues, but they will always become pack-health issues and risk killing all the other cells in that group with it, and hopefully it's mechanism of self-discharge doesn't go into runaway while paralleled with the other cells in the group or things can go thermal impressively fast. The little can's are nasty when they are exploding.

Any cell that exhibits abnormal self-discharge should definitely be destroyed or recycled. Seriously.
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Re: Homemade Battery Packs

Post by kje » Mar 21, 2014 6:26 pm

parabellum wrote:
How many over 4.17? Makita konions go down to ~4.16 (but it is not laptop cell)
The numbers between 4.20V and 4.11V: (these cells have been charged to 4.20V and then resting for 4 or 5 months)
4.20V: 3
4.19V: 12
4.18V: 11
4.17V: 12
4.16V: 16
4.15V: 27
4.14V: 16
4.13V: 5
4.12V: 0
4.11V: 6

I will now apply 1A test on each cell with my Imax for 2min exactly and write down voltage reading. I guess bad cells shows low voltage reading after 2min of discharge, so I`m sorting out the good ones.

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Re: Homemade Battery Packs

Post by parabellum » Mar 21, 2014 7:17 pm

Thanks. Nice info.

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Re: Homemade Battery Packs

Post by NaturalPath » Mar 21, 2014 8:18 pm

I think I remember reading somewhere that the self-discharge rate for these type of cells is about .01V per week, so I'm wondering how, after months, you would still have cells reading 4.20 unless they were over-charged to begin with?

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Re: Homemade Battery Packs

Post by alsmith » Mar 21, 2014 8:26 pm

that may be the cell discharge but bms's can have losses too.

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Re: Homemade Battery Packs

Post by e-beach » Mar 21, 2014 9:58 pm

NaturalPath wrote:I think I remember reading somewhere that the self-discharge rate for these type of cells is about .01V per week, so I'm wondering how, after months, you would still have cells reading 4.20 unless they were over-charged to begin with?
Depends on the cell. Turns out, at least from my experiments that computer lico holds a charge for a long time. Even bad cells don't necessarily lose voltage even after weeks. I have cells that will only charge to 4.16 and only discharge at .45C for 10 minutes but will hold that 4.16v for weeks. This is why IMHO the "Bleed Down Test" is an inaccurate determination of the health of a cell.

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Re: Homemade Battery Packs

Post by DrkAngel » Mar 21, 2014 11:48 pm

e-beach wrote: Depends on the cell. Turns out, at least from my experiments that computer lico holds a charge for a long time. Even bad cells don't necessarily lose voltage even after weeks. I have cells that will only charge to 4.16 and only discharge at .45C for 10 minutes but will hold that 4.16v for weeks. This is why IMHO the "Bleed Down Test" is an inaccurate determination of the health of a cell.

:D
All battery types self-discharge!
Test is to determine rate and depth of self-discharge ... to eliminate dangerous cells by diagnosing abnormal self discharge.
I recommend self bleed down test only to eliminate the obviously bad cells.

My, presently, favorite developed best-fastest cell testing method.

Stage 1
Charge all cells equally to a voltage above preferred use voltage.
I charge 40p using modded 5V MeanWell (combine cells when of nearly equal voltage )
Keep eye, or finger, on cells, remove any that start getting warm, 40p 2600mAh = 104Ah so 30A Meanwell will not create heat while charging unless cells are bad.

Stage 2
Separate and allow cells to set and self discharge - the longer the better. (Minimum of several days )
Eliminate all with substantial voltage loss - keep only cells that maintain above your preferred use voltage.
I used to charge to 4.20V but have begun charging to 4.05V for certain cells and 4.15V for others.
(Different variations in formulation produce different optimal charged voltages)

Stage 3
With all cells at equal voltage, discharge at a measured rate.
I began using 28s2p, discharging with 2 - 60w light bulbs (~120V DC discharging 120w = 1A=1000mA per hour)
2x2600mAh cells = 5200mAh, 1000mA discharge = ~.2C
Monitor each cell voltage, remove any that fall below 3.5V (voltage will drop suddenly at this voltage, so monitor carefully) and mark time, 1000mAh capacity for each hour
Discharging for 2.5 hours(50%+ oem rated capacity), 3 hours(60%+ oem rated capacity), or, if very good cells, 4 hours(80%+ oem rated capacity). Then rating cells by residual voltage, works nicely.
If cells don't last 2.5 hours, less than 50% capacity, probably not worth building into pack? (unless large bulk pack?)
Mark rated capacity on cells-pairs. (eg "3H 3.82V" or "3000mAh + 3.82V")
Method provides a fairly accurate comparative capacity ... 56 cells capacity tested in 3 hours.

Stage 4
Recharge all cells to equal voltage.
Build banks of equal capacity.
Line up all cells, best to worst. Shuffle into banks.
6s = 123456654321123456654321 etc
Should provide reasonably well balanced capacity banks.

Stage 5
Test full pack discharge, if not perfectly balanced at deep discharge, reshuffle cells to equalize, or add cell-cells to any weak bank.

Quick and easy and reasonably accurate method to test cells.
Last edited by DrkAngel on Apr 04, 2014 7:35 am, edited 5 times in total.
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