Homemade Battery Packs! ... etc.
I started with cheap eZip eBikes.
Being sadly disappointed with oem battery performance-capacity-endurance I decided to "play" ...
Too many pictures to fit in one post, so supplied links.
36V 11Ah SLA test
36V 11Ah SLA Toolbox
Speed, or range, pushed 150% ... not both at once tho.
24V 7Ah Nimh too small for 450w motor so ...
Doubled it up. worked great till accidental short detensioned the springs.
Now I always build in a fuse.
24V 14Ah Nimh
Weak point is the light duty springs.
Recommend spring contact points "enarmored" by covering and running tinned copper braid between cells, and ensuring good contact with dielectric grease.
37V 10.4Ah Li-ion My first Li-ion build.
Proved too small for 675w motor 35A controller.
Made using recycled laptop battery cells.
37V 20.8Ah Li-ion 2008 vintage build.
Still use on my Winter eBike.
Li-ion vs SLA
37V 20.8Ah Li-ion #
25.9V 31.2Ah Li-ion 2009 vintage build.
Used till 2011 - relegated to reserve status or doubled range for trips.
eZips are designed to carry 2 packs.
25.9V 31.2Ah Li-ion 2011 build.
Made use of recycled eZip RMD battery cases.
37V 26Ah 1kWh Lipo Lico
Prototype: 120 - 2160mAh cells 10s12p.
37V 26Ah 1kWh Lipo Lico
Used tinned copper braid as flexible - durable conduction media.
Laid in a 7/16" layer of waferboard as stable-protective base.
Several of the builds are packaged in insulated bags.
Or at least are padded with closed cell polystyrene or foam.
Packs exhibit markedly reduced performance when cold!
The recycled Li-ion and lipo builds are constructed from laptop technology cells, of a Lithium Cobalt formulation, about 2x the energy density of LiFePO4 ... but designed with a low "C" rate.
Built to expend at .33 to .5C a maximum 1C surge is recommended.
30Ah pack recommended for a 10 - 15A continuous output, surges above 30A for brief periods only.
Still ... 30Ah pack is the size of a 15Ah LiFePO4 or a 6Ah SLA ...
Laptop Lipo 25.9V 26Ah
Going strong after hundreds of cycles.
I did include balance connectors with all Li builds.
After proven reliable, I typically "bulk charge" and occasionally "balance charge".
I did re-design MeanWell power supplies as rapid Bulk chargers.
25.9V 22.8Ah RC lipo
37V 17.1Ah RC Lipo
Got tired of crappy cordless tool batteries
14.4V 1.2Ah Nicd > 14.8V 5.2Ah Li-ion
7s 25.9V 5A charger build
I modified MeanWell power supplies as bulk chargers.
Extended voltage range
Variable current adjustment
Modifications required for running "in Series"
Built in volt meter is nice.
Quick add, in line, amp meter handy for monitoring charge rate.
I "modularized" for maximum adaptability.
2x = 7s 25.9V 10A build
28.9V??? Yes battery capacity mapping showed efficient battery usage to be at a lower peak charge. A "full" 4.2V per cell charge added needless damage for minimal capacity increase!
Every "type" cell has a different voltage range of maximum and most efficient energy storage.
I have mapped several types but mostly the ones I've recycled.
wow! that's some badass tinkering!
How hot do those get and did you build in any protection circuitry?
Heat 'er Up!
SLA is a major heat producer - 40-50% wasted as heat!
Nimh not quite as bad ... but still can get hot.
Li-ion and lipo, at modest rates, near 100% efficient. No noticeable heat production!
..... 25.9V 31.2Ah (9lb 12oz) = 808Wh ..... vs ..... 24V 10Ah** (15lb 2oz) = 240Wh (120-140Wh usable)
SLA (10Ah) - expended in 1 hour = 6.14Ah *
24V x 10Ah = 240wh
.614C drain = 147w output to motor for 1 hour but 93wh wasted heat ~60% efficient
1C drain (10A) = 240w output to motor for 1/2 hour but 120wh wasted heat ~50% efficient
25.9V x 31.2Ah = 808wh (Smaller than and weighs about 1/2 the 10Ah SLA pack!)
.2C drain = 160w output to motor for 5 hours but 2-3wh wasted heat per hour ~98% efficient
.333C drain = 260w output to motor for 3 hours but 10-15wh wasted heat per hour ~95% efficient
The recycled Li-ions I use are designed for a .25-.33-.5C discharge rate. 2-4 hour runtime.
Surge output, IMIO, should be limited to 1C. 31.2Ah pack for ~30A controller.
During Winter bikin' season, I keep my packs inside, nice and warm ~80*F, when possible. Cold drastically reduces battery performance, so I keep them warm in insulated bags. I leave my bike in sub 32*F, just to prevent ice buildup when warm wheels hit snow. - Cold vs Battery
*SLA batteries are typically rated at a 20hr discharge.
A 10Ah discharged in 1hr, typically, outputs a meager 6.14Ah.
I gave up the small cells now only use the screw together type much easyier to replace,8 cells to 1 say 24v pack with only the signal wires to solder. can't upload a picture but the pack i've made especialy for my own bikes is 4 cells each side of the bottom front bar.Got 1- 6 cells ea side easy made with fibre glass, this for 36v 960w cyclone.---These batteries are near all new but what to do with all the small good ones is bafling me,I just test & keep the good ones for the moment.
I try to understand your enthusiasm BUT
with low C-rated cells:
you have to parallel 2-3 cells to get desired current.
10Ah 1C cell can carry only 10A, right?
so if you need to draw 30A from battery pack you need 3 such cells in paraller, right?
but other words,
You would need to manufacture 10Ah,3C rated cell from 3 paralllel 10Ah, 1C cells, right?
Three 10Ah cells for sure would weight more than one 30Ah cell, right?
if you build 36V 30A capable LiFepO battery you will need:
either 12 10Ah cells 3C rated
36 10Ah cells 1C rated
so 12 3C cells versus 36 1C cells, three times more cells.
many more interconnects /jumpers/ between cells = less reliability.
By other words
if you want to carry say 10 pounds of battery on your bike you want to carry high C cells-made battery.
it is obvous
but high C cannot be pulled from laptops
Best of all cost was about $30 for all the cells.
Lucked out on last batch of cells double connected in foldable 6 packs. Minimal solder connections!
Testing and sorting took many hours.
Fortunately ... I am a computer repair tech, in my own shop.
5% of work is starting test programs, 90% is waiting, while those programs run.
I have to constantly find new projects to keep from being bored stupid.
(Once I feel into a stupor and it was 8 hours before I could pull myself away from solitaire.)
Personally, I'd much rather build my own, checking my cells, charging, discharging and evaluating, soldering my own connections etc. ... as opposed to spending 10-20x the $$$ on something pre-made, with tech support in Chinglish.
Many of the recycled cells, that I find available, come in convenient "packs" of 3, 11.1V (12.6V charged).
Previously I broken up this "natural" package to produce 10s - 37V (3 - 3 packs plus 1 single) or 7s 25.9V (2 - 3 packs plus 1 single).
Given the difference in optimal LVC between SLA and Li-ion, a 24V controller seems ideal for a 22.2V li-ion, similar with a 36V controller for a 33.3V Li-ion and 48V for a 44.4V pack.
So my next batch of pack builds will be modular in construction. 18650 2600mAh cells 3s8p - 11.1V 20.8Ah.
With this I will be able to quickly mod from 22.2V to 33.3V to 44.4V packs.
One project will be 2 - 22.2V packs in a saddlebag configuration for my 44 magnum pack.
44.4V x 20.8Ah = ~925Wh .925kWh. 96 18650 cells weighs about 10lb.
Pushing an eZip 24V 450w motor to 44.4V will output 832.5watts = 1.11hp
Object is to assist a properly geared Haro Express Deluxe* to a sustainable 30mph.
* Yes, I did relace an eZip type hub into a 700c wheel.
Homemade Batterry Packs - Rebuild
I decided to rebuild all my 2008 era "homemade" 18650 packs.
Most have been sitting a couple years.
I noticed a bad "balance" on my 37V 20.8Ah build.
So I have decided to rebuild my 3 - 37V 20.8Ah and 2 - 25.9V 31.2Ah packs, a total of 408 18650 cells.
I still have another 100+, unused cells.
1. Disassembly of hundreds of solder connections
2. Charge all cells to 4.2V
After I disassemble all packs, I will gang together 1s40p cells and charge with my modded MeanWell S-150-5 @ 4.2V 30A. (Note: recycled Lipo cells will be tested at a modest 4.1V per cell, but monitored for self-discharge for a considerably longer time period, several days, a week?)
3. Test all cells
a. After fully charging, separate, let set ~24 hours, any noticeable self-discharging cells will be eliminated. (Degree, and depth, of self-discharge has proven to be a reasonably reliable "yardstick" of cell condition!)
b. Apply a .5C, timed, drain to each cell, low ending voltages will be eliminated.
4. Build packs
I intend on a modular construction.
3s8P 11.1V (12.6 fully charged) 20.8Ah modules
(I plan on using 25.2V*, 37.8V*, 50.4V* builds)
I will install balance plugs, but after thorough testing I intend on bulk charging ... with scheduled balance charges.
5. The builds (eZip pack capable)
a. 22.2V - 6s16p 96 cells 22.2V 41.6Ah 923.5mAh
b. 33.3V - 9s8p 72 cells 33.3V 20.8AH 692.64mAh +9s1p 5700mah RC Lipo 5.7AH 189.81MaH = 26.5AH 882.45MaH total - Hybrid Pack
c. 44.4V - 12s8p 96 cells 44.4V 20.8Ah 923.5mAh
6. I intend to streamline pack build using flat tinned 9-10ga copper braid, replacing 10ga insulated stranded copper. 22ga tinned copper wire for balancing.
* Fully charged
Any cells not rated as grade A, but reasonably good, will probably be allocated to other applications such as:
Lanterns - florescent, LED etc.
Power inverter - pulled 36Ah SLA out of a 200watt pack, could pack in 11.1V ... 100Ah Li-ion?
22.2v! ... ?
22.2V (25.2V full charge) might sound pretty wimpy compared to to oem 24V SLA (26V+ full charge).
But considering the voltage sag from the SLA under use, the minimal sag from the 40Ah Li-ion, and the typical 24V controller LVC of 20.5V, I believe that the 22.2V will outperform the oem SLA in every way ... plus 6.5X the range. (OEM with 15mile range - ~100mile Li-ion range!)
I believe that the 22.2V Li-ion is also a better fit for the typical 24V controller!
A controller LVC of 20.5V leaves a 12V SLA at a dangerously rundown 10.25V.
While a 22.2V Li-ion still retains a 3.4V+.
Now ... 3.4V is below what I consider optimal, but when you figure voltage sag under throttle 3.5-3.6V actual capacity sounds ideal.
Oh! My Trailz with 25.9V & 16T mod cruises at 22mph, 22.2V will drop that to a "legal" ~19mph.
22.2V - 41.6Ah eZip pack rebuild will consist of 2 - 6s8p modules, will install connectors for quick switch to 44.4V - 20.8Ah. - TURBO mode!
Alternately, 2 - 22.2V packs with switches from parallel to serial.
Yes 2 - 41.6Ah packs, ~10lb each, should provide a possible 200 mile range!
A little better than the oem SLA at 15 miles, with a 16lb+ pack!
i admire your knowledge on batteries, I've heaps of cells that I'd like to re -use but am frieghtened i'll ruin them without paying more to get new BMS for them. How low a current would you use without BMS.
I now make my own battery packs (some i've sold) that wrap a around front bike stem work even for rear suspention bikes from fibre glass using the big screw together cells. I'm not good enough with the pc to upload the pictures.
But i've always thought the battery has to be as far foward as possible & low as the first one used to topple from stand & left no room for Bags of stuff etc.
No BMS ! ... ???
A great tool is the wonderfully cheap, 1-8s voltage monitor-alarm, mulitple for larger packs. 8 wire ethernet cable lets you mount on the bars. (note - draws additional power from cells 1 & 2, minimal, but accumulates over many cycles.)
Are you risking a fire?
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Siu Blue Wind
Preliminary charges - discharges are monitored, then each bank rearranged for equal capacity.
Then, typically, I charge each bank to about 4.1V per cell.
This is to prolong lifespan, some estimate double the number of cycles.
Even if 1 cell totally fails, on a 10s8p 36V pack, maximum voltage on the damaged bank is less than the rated 4.2V.
So ... barring traumatic or dramatic damage or failure, there is an extremely slight chance of any possible overvoltage reaching, even near to, danger level.
I've built 4 Li-ion packs and 2 LiPo packs, and run hundreds and hundreds, maybe 1000 recharges. (37V and 25.9V builds)
Nearly 15,000 recycled Li miles over the past 5 years.
Right now I am rebuilding my 2008 builds. (2 - 37V and 1 - 25.9V)
Separation and re-evaluating all cells individually.
Voltage bleed down test
Note - I did use a PCB (BMS), to begin with, but quickly went to monitored bulk charging. Balance circuitry was minimally effective and only worked at full 4.2V and only if cells were closely matched already. I was disgusted at the cost and lack of effectiveness. The last straw was the balance circuit did absolutely nothing when I switched to a less damaging, life preserving, 4.10V per cell.
To charge each cell you mean the 4-6 or what ever that are there in paralell , this would be hard like 4-6 different places to charge , after each time using the bikes.As it is I get sick of charging,controllers cutting out, replacing BMS & cyclone parts & think how amazing the fossil fuel combustion motor is----& cheaper ---hard to change an obsessions though.---It like giving in.
Bulk charging refers to the method of charging by the process of applying a single connection-voltage to an entire pack.
My builds do use balance connectors, so all the parallel cells are connected.
Typically I bulk charge to the preferred voltage.
Balance charging is an available option but no longer used.
Especially with a new build, I do monitor initial charges.
Rather than charging to the "rated" 4.2V per cell (s7 29.4V) I prefer the life preserving 4.1V per cell (7s 28.7V). Any failed cell and the pack is buffered to a safe voltage, preventing any dangerous overvoltage.
So the entire pack is directly charged from a single 28.7V power supply.
Under normal operation all cells will recharge to the same equalized condition that they began with. Exceptions include abnormally drastic charge-discharges, damaged packs, excessive discharge depth etc.
I do monitor DOD with the aforementioned voltage monitor-alarm.
With all Lithium battery packs, there is a recommended charge voltage.
With Li-ion and Lipo, this is typically 4.2V per cell.
This voltage is the manufacturers "maximum capacity" rating.
However, this is not the best voltage for maximum battery life ... or for best, sustainable, capacity!
Many recommend lower voltages for best battery durability and life.
Several sources go so far as to claim that reducing voltage from 4.2V to 4.1V will double the number of usable cycles!
At an initial 10% capacity loss!
I decided to fine tune my battery voltage by capacity mapping my cells.
My most common 18650 Sanyo cells tested as optimal at a 4.05V per cell top voltage, an 18% initial capacity loss for a 300% usable lifespan!
My recycled laptop Lipo was less clear with a minimal capacity loss and 150% usable life by reducing voltage to 4.15V.
On the other hand, reducing to 4.05V produced a 300% usable life but required a 28% initial capacity loss!
More Homemade Recycled Builds
25.9V 22.8Ah New RC LiPo - proposed build - 7s4p - 2011
37V 17.1Ah New RC LiPo - proposed build - 10s3p - 2011
Power tool rebuild - 4s2p - 2011
14.4V 1.2Ah upgraded to 14.8V 5.2Ah
22.2V 41.6Ah - 6s16p - 2013
22.2V just didn't do it for me ... so I re-shuffled into ...
29.6V 31.2Ah - 8s12p - 2013
33.3V 43.2Ah - 9s20p - 2013
oh dear god.. he spreads his wings........
This has been debated to death on ES, countless warnings, and safety concerns expressed...
Can used laptop cells be used for an ebike ? Yes
Is it a good idea? .. NO>
For the 1% of the population who will be willing, able, and determined enough to deal with the risks, it can be done.. but the rest of the world should not follow the advice above... there are way too many details missing, and far too little warnings.
For starters. 4.1v vs 4.2v is not accurate enough... and saying that the first several charge cycles were monitored is also not sufficient info.
I personally have multiple high powered ebikes, running on RC lipo, i bulk charge them all, and none of them use a BMS... I am part of that 1% group.
Before, and After, EVERY cycle, i check cell voltages with a cellog, i always remain present during charging ( not sitting staring at the pack, but am within range at all times, and i NEVER go to bed while a pack is charging ) .. I set my bulk charger to get an average cell voltage from 4.15~4.18v, without balancing, but if at any point, a single cell/group goes outside this range i hook up the RC charger to that cell/group and bring it back into proper range, if it remains in check for another dozen or so cycles i keep doing this.. but if after 1 or 2 cycles that cell/group drops out of range again, i open the pack and repair it.
When i ride, all my bikes have Cycle Analyst meters, so i monitor Amp/Hour used very closely and never exceed 75% of my known available capacity.
If any of the above seems like too much work or bother... you belong to the 99% group and should not copy the efforts above.
ps: SLA is not wasting power as Heat ( entirely... ) , it's a reaction called Peukert Effect :
18650 cells dangerous! ... ?
A couple ES members warned about dangerous 18650 cells!
One, went so far as demonstrating how dangerous they are!
"18650 cells dangerous! ... ?
I have to compliment Liveforphysics for trying to prove his point using the scientific method.
First, he considered all the ways, that he believed, that the 18650 cells might be hazardous.
Then he devised tests ... tests that were specifically designed to show 18650 cells burning, exploding etc.
18650 cell -
crushed in vise
skewered with a screwdriver
pounded - crushed-mangled by heavy hammer
18650 cell -
hyper-charged with V & A
placed under a heat gun
finally with torch applied!
Sadly, for LFP, his failure to demonstrate any hazardous results caused me to consider 18650 cells to be even safer than I had previously believed.
Except for when he applied a torch directly to a cell ... which I don't intend on doing!
It did shake my spirit tho ...
LFP scientifically formed his hypothesis, devised tests to test his hypothesis, diligently performed these tests and noted the findings ... but then ... apparently completely ignored his own results ... by standing steadfast in his assertion that 18650 cells were dangerous and liable to burn and explode???
I'm afraid that he, himself, severely degraded my opinion of him.
After my disappointment wore down and I accepted it ... I was able to watch the 2nd video again and laugh at the "stupidity" of performing flaming-exploding tests in the midst of gasoline cans and nitrous tanks."
it's not always a happy ending
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:
Of course, not every cell!
Probably every "batch" has representative samples 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.
Tested to death on E.S. , no.
E.S. battery forum is mostly debate, little testing.
And all the useless debate has chased many of the testers away from that forum.
Ypedal, have you done or posted any laptop cell tests ?
If you want the E.S. battery forum to be a HK lipo only forum then keep it up.
Gave that up back in 2011..... i need to update that page with recent info.. but as you can see.... yes i've done my share of testing with used cells..
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