docnjoj
1 GW
C rates are off to the right side of the graph, at least on my image.
otherDoc
otherDoc
DrkAngel said:liveforphysics said:DarkAngel- Just for fun, where would you place the maximum usable C-rate for this LG 18650?
You forgot to list the C rate usage, for each different colored line!
Which is the entire purpose of the graph!
Well, that depends on the chemistry. LiCo doesn't work that way, AFAICR, though there are versions of Li chemistries that do (LiMn? whatever the "Konion" cells are made of, IIRC).DrkAngel said:I would thing that, with 2 amps, into an 31ah pack, it is possible that any possible overvoltage might be safely dissipated, as moderate heat?
liveforphysics said:DarkAngel- Just for fun, where would you place the maximum usable C-rate for this LG 18650?
It has 3.05watt-hours usable energy at 3C (and can only deliver that much energy if you're hitting it continuously so the cell stays hot from the initial voltage drop heating it).
Or, 7.7 watt-hours usable energy at 1C.
Or, 9.4 watt-hours usable energy at 0.2C
Also, would you continue to call it maximum C-rate if the cell sagged below 1/2 resting voltage at that C-rate (normally these little feces cells just saturate the current collector and fall on their face before this happens), so that as current output increases, the amount of power you're getting from the cell is decreasing?
neptronix said:Wow, that is horrible. 1C is stressing it out. And that's a *new* cell.
neptronix said:I cannot argue with the price, then again i would never want to solder together all those cells.
First off, I would highly recommend, same model-brand capacity cells, most importantly, of the same ah rating. ex. 2600mah cells.18wheeler said:Alright, I am a total newbie and want to replace the old, heavy LA pack on my ezip trails.
I got ~45 batteries from two local computer service shops. about half is free, another half is $1 a piece. Not bad!
Now I take them apart and ready to do test and build a battery pack for my ezip trailz from walmart.
However, I'd like to ask a few questions before I make mistakes and burn down the house.
if I want to build a 25.9V 12Ah pack from, say 2000mAh Lipo cells, I need to put 6 cells in parallel and 7 in series, right? I'd also like to add PCB (with equilibrium function http://www.batteryspace.com/PCM-wit...r-Only-CU-J185-Battery-Pack-at-10A-limit.aspx) to the pack. From what I heard, I should wire them like the following picture:
So my questions are:
is it the right way?
18wheeler said:If one cell in the parallel went bad, wouldn't it affect / destroy all other cells in the parallel? or the PCB will prevent bad cell affect other cells?
I am not sure how equilibrium works here. I mean, those 6 cells are in parallel, how the PCB determine each individual cell is at the same voltage? or I understand it wrong?
18wheeler said:How do I charge this? is a smart charger all I need (http://www.batteryspace.com/smartcharger28afor259vli-ionpolymerrechargeablebatterypackstandardfemaletamiyaplug.aspx)?
I have heard balance chargers. Aren't they redundant to the PCB here (regarding charging only)? I imagine they like smart charger with build in PCB?
I know there are a lot questions. I have read some literature. but I am far from understand all this stuff. a pointer or two would be very appreciated!
Thanks a lot!
DrkAngel said:"Homemade" 25.9v 31.2ah Li-ion pack.
Just finished my first trial run. Took 2 days. Cruised at an average 18 mph. Of course I was "forced" to take a few "runs" at 22+mph.
Cruised for about 30 miles, then spent today riding around town, checking out the local "Community Yard Sales Weekend" ... another 11 miles - 41 miles - total. Finally decided to recharge, after red battery level led flickered under moderate throttle, red led indicates 24v level.
Residual voltage was measured at 25.8v, down from 29.4v. Using a, very safe, 24.5v as empty, (3.5v per cell).
Wow! That figures to 55.8miles per "full charge" ... without pedaling!!!
edit: "Empty" recalibrated as 3.6V (25.2V pack voltage).
"Motor only" range 45-50 miles!
DrkAngel said:Wow!
I hadn't expected it, but at my typical usage of .33C, It would appear, it is possible, to be getting, close to 100%, (of battery rated), efficiency from Li-ion 18650 cells! (97-98%+ of rated!)
Based on graph.
And! ... my maximum surge usage is still at, better than 92% efficient!
As performed by my 450w EZip Trailz
w/homemade
10lb.
Li-ion 18650 cell,
25.9v,
31.2ah battery pack,
average speed of 18mph.
40-50 mile range - without pedal assist!
DrkAngel said:Of course, still in the offing is an etrike conversion. Schwinn Meredian with eZip motor added. Nice cargo space and hanging big SLA batteries below the axle will greatly increase stability.
SamTexas said:DrkAngel said:Of course, still in the offing is an etrike conversion. Schwinn Meredian with eZip motor added. Nice cargo space and hanging big SLA batteries below the axle will greatly increase stability.
Stability? Why can't you achieve the same thing with LiCobalt? There is no upside, not even cost given that you are able to get laptop batteries at close to nothing.
DrkAngel said:Ballast!
The main complaint on these bikes is the risk of tipping.
10lbs of li-ion helps very little, compared to the 60lb, of comparable SLA.
SamTexas said:DrkAngel said:Ballast!
The main complaint on these bikes is the risk of tipping.
10lbs of li-ion helps very little, compared to the 60lb, of comparable SLA.
I know what you mean. But why not 60lbs of Li-ion? What's the harm of have 6x range?
DrkAngel said:Tenergy 25.9v 2A charger
No major complaints.
No cells charged above 4.2v.
Cells remain nicely equalized, within a couple 1/100ths of eachother.
Seems to charge to about 4.15v, charging light turns green but continues slowly charge-equalize till all cells attained 4.17v - 4.19v.