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.
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?
More Homemade Recycled Builds
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."