DrkAngel
1 GW
If you have 15 parallel spots, you should be charging 15 paired cells or 30 x 1500mAh @ .5C ≤ 22.5A.dequinox said:
You didn't separate your cells! ... did you?
*Dusting off the 1000lb of laptop batteries
- Thread starter dequinox
- Start date
You didn't separate your cells! ... did you?
dequinox
10 kW
DrkAngel said:If you have 15 parallel spots, you should be charging 15 paired cells or 30 x 1500mAh @ .5C ≤ 22.5A.dequinox said:
You didn't separate your cells! ... did you?
That's about the charge current I came up with too... divided in half of course.
To answer your question: with regard these laptop cells, not yet. The tool pack cells I did separate, but only to be able to recombine every single one how I see fit... and tearing the packs apart almost (again I say almost here) made it necessary. There's only about 50 cells in that set though, and I'll be moving on to the laptop cells (by far a larger qty) with the notion that I'll leave cells together when I can. I do plan to build a tab welder too though... which may negate the extra work in separating cells.
I do see the value in leaving them paired though, I do!
dequinox
10 kW
I thought people reading this thread might like to know what happened to the whole 1000 lbs of batteries I acquired, so here's a rough summary:
So there you have it. I haven't recycled the prismatics just yet, as I'm going to go through and try and find all the apple pouch cells (there was a significant quantity) and see if anyone wants them. I will see if there's enough of any of the others to arrange a sale of them, but I'm betting there isn't enough matched of any other kind to be worth it to anyone. Plus they are a PITA to pull apart. FYI the apple prismatic packs are somewhat similar to these... and there's a buttload (50lb or so) of them.
I may have a few more matched brand cell deals coming, depending on how I use my leftover stock, and I'll price these according to quality/origin of the cells. These will all be individual lots that I come up with later, and I'm guessing it will be in a few month's time when I have my own 1kwhr+pack build done.
So keep an eye out!
- About 300lbs were sold to ES users
I kept for my own use about 250-300 lbs
100lbs were useless cell phone batteries
I'd guess about 20lb were accidental mix-ins of Nimh, Nicad, Lead, and even 2 chargers if you can believe that...
The rest (200-300 lbs) were various kinds of prismatic or pouch-style packs. I knew most ppl wouldn't want these, so I was weeding them out of the mix of 18650 packs.
So there you have it. I haven't recycled the prismatics just yet, as I'm going to go through and try and find all the apple pouch cells (there was a significant quantity) and see if anyone wants them. I will see if there's enough of any of the others to arrange a sale of them, but I'm betting there isn't enough matched of any other kind to be worth it to anyone. Plus they are a PITA to pull apart. FYI the apple prismatic packs are somewhat similar to these... and there's a buttload (50lb or so) of them.
I may have a few more matched brand cell deals coming, depending on how I use my leftover stock, and I'll price these according to quality/origin of the cells. These will all be individual lots that I come up with later, and I'm guessing it will be in a few month's time when I have my own 1kwhr+pack build done.
So keep an eye out!
BSATOM
1 W
Bought 75 pounds. Here is the breakdown of resting voltages.
611 cells total.
0.0v=152cells
under 1.0 volts=13 cells
1.0 to 2.5v = 98 cells.
2.5 to 2.99 volts = 92 cells.
3.00 to 3.99v = 256 cells
I measure the cells from each pack. If all cells are at the same voltage then I leave them all paired. If a laptop battery has a cell pair that reads lower than the others, I separate that pair and wait until the shorting cell reveals itself and chuck it. One cell will rise and the other will stay or lower in voltage.
I use the 3.0v and over cells for bike batteries first, and will use the 2.5v batteries if needed in their own packs. I never mix resting voltage cells in pack builds. These are just the standards I developed for myself.
99 percent of cells resting at 3.0 or over will give at least 1500mah. I conservatively rate all good used 18650 cells at 1.0 ah when building packs, even if they give over 2000mah during discharge. That keeps me in the green there with the combining of dissimilar cells.
About c rating.
Every 18650 cell involved here can discharge at 2.0c which is at least 3.75 amps and up to 5.2 amps according to the PDFs for the cells. I rate 18650s at 3 amps each when building packs. Therefore 15p will be expected to deliver 45 amps and no more, and that is not a continuous rating, but intermittent which works out fine during normal riding conditions. These guidelines provide me with very reliable packs that rarely need cell replacement due to one developing a short and heating up.
By the way, an infrared FLIR camera or like device is very useful for spotting heating cells in a pack.
611 cells total.
0.0v=152cells
under 1.0 volts=13 cells
1.0 to 2.5v = 98 cells.
2.5 to 2.99 volts = 92 cells.
3.00 to 3.99v = 256 cells
I measure the cells from each pack. If all cells are at the same voltage then I leave them all paired. If a laptop battery has a cell pair that reads lower than the others, I separate that pair and wait until the shorting cell reveals itself and chuck it. One cell will rise and the other will stay or lower in voltage.
I use the 3.0v and over cells for bike batteries first, and will use the 2.5v batteries if needed in their own packs. I never mix resting voltage cells in pack builds. These are just the standards I developed for myself.
99 percent of cells resting at 3.0 or over will give at least 1500mah. I conservatively rate all good used 18650 cells at 1.0 ah when building packs, even if they give over 2000mah during discharge. That keeps me in the green there with the combining of dissimilar cells.
About c rating.
Every 18650 cell involved here can discharge at 2.0c which is at least 3.75 amps and up to 5.2 amps according to the PDFs for the cells. I rate 18650s at 3 amps each when building packs. Therefore 15p will be expected to deliver 45 amps and no more, and that is not a continuous rating, but intermittent which works out fine during normal riding conditions. These guidelines provide me with very reliable packs that rarely need cell replacement due to one developing a short and heating up.
By the way, an infrared FLIR camera or like device is very useful for spotting heating cells in a pack.
DrkAngel
1 GW
Oops! Forgot to post up "Step 3"
Step 1 - Bulk Charging
Step 2 - Comparative IR (Quick Condition-Capacity Estimate)
Step 3 - Bulk Discharge-Capacity Testing
"Batch" cells of similar manufacture capacity and "comparative IR".
a. Rig as 30s = 126V, (tabbed as 2p = 60 cells per batch - 3p = 90 - 4p = 120), or 28 x 4.2V = 117.6V DC , and discharge with 2x60w light bulbs 120W / ~120V = 1000mAh per hour for accurate capacity (3 hours discharge = 3000mAh + remaining voltage (EG 3000mAh + 3.75V)).
Cells can be rated by discharged mAh + remaining voltage or further discharging individual pairs using metered discharge device (3000mAh + 1458mAh = 4458mAh saves 3 hour per additional pair)
or
b. Rig as ≤20s and discharge using a cheap V-A-mAh meter using discharge source, multiple light bulbs? (meter requires external power supply to retain readings while cells being removed)
See - Bulk Capacity Testing for full and various testing methods.
Even a 2 hour discharge, + the remaining voltage, is sufficient to build a fairly balanced pack.
Line up all cell pairs, best to worst.
Starting with best, lay them into banks ...
12s = ...
1 2 3 4 5 6 7 8 9 10 11 12 12 11 10 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 10 11 12 etc
9s = ...
1 2 3 4 5 6 7 8 9 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 9 8 7 6 5 4 3 2 1 etc
etc.
Unless you have a few exceptionally good or bad cells, this should build banks of nearly identical capacity.
Reshuffling ... adding or subtracting cells from any variant bank can "tune-up a pack easily!
If using various brands, try to distribute a representative sampling of each into every bank.
This helps banks retain a reasonably equal IR - important for building a battery that doesn't need a BMS to maintain equalized banks.
Cheap - ~$12 IR meter, V-A-mAh meters etc - See - EBike Toolbox - Bargains! $
Step 1 - Bulk Charging
Step 2 - Comparative IR (Quick Condition-Capacity Estimate)
Step 3 - Bulk Discharge-Capacity Testing
"Batch" cells of similar manufacture capacity and "comparative IR".
a. Rig as 30s = 126V, (tabbed as 2p = 60 cells per batch - 3p = 90 - 4p = 120), or 28 x 4.2V = 117.6V DC , and discharge with 2x60w light bulbs 120W / ~120V = 1000mAh per hour for accurate capacity (3 hours discharge = 3000mAh + remaining voltage (EG 3000mAh + 3.75V)).
Cells can be rated by discharged mAh + remaining voltage or further discharging individual pairs using metered discharge device (3000mAh + 1458mAh = 4458mAh saves 3 hour per additional pair)
or
b. Rig as ≤20s and discharge using a cheap V-A-mAh meter using discharge source, multiple light bulbs? (meter requires external power supply to retain readings while cells being removed)
See - Bulk Capacity Testing for full and various testing methods.
Even a 2 hour discharge, + the remaining voltage, is sufficient to build a fairly balanced pack.
Line up all cell pairs, best to worst.
Starting with best, lay them into banks ...
12s = ...
1 2 3 4 5 6 7 8 9 10 11 12 12 11 10 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 10 11 12 etc
9s = ...
1 2 3 4 5 6 7 8 9 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 9 8 7 6 5 4 3 2 1 etc
etc.
Unless you have a few exceptionally good or bad cells, this should build banks of nearly identical capacity.
Reshuffling ... adding or subtracting cells from any variant bank can "tune-up a pack easily!
If using various brands, try to distribute a representative sampling of each into every bank.
This helps banks retain a reasonably equal IR - important for building a battery that doesn't need a BMS to maintain equalized banks.
Cheap - ~$12 IR meter, V-A-mAh meters etc - See - EBike Toolbox - Bargains! $
999zip999
100 TW
Not a fan of used cell packs as it takes many hours, hours ? days. And I'm very hard on batteries. These packs do better with a 20amp controller for a commuter. The Makita packs can handle more, but still a 40amp controller. This is a great learning experience that only a hands on approach can deliver. Good luck be careful as they are alive and do bite. Don't get sloppy.
DrkAngle I'm a big fan of your's
DrkAngle I'm a big fan of your's
DrkAngel
1 GW
Laptop cells ...
"Go big or go home"
Laptop cells are designed for and do well at their designed discharge rate.
2 - 3 hour laptop run time = .33 - .50C discharge rate.
I have always recommended a ≤.50C continuous and ≤1.0C surge discharges. (≤.5C charge rate)
30Ah battery for 30A controller or 15A cruising drain.
For example:
These very common Sanyo cells at a 2C discharge rate almost immediately sag to their "empty voltage" of 3.60V.
42V "full" battery sagging to 36V.
Higher discharge rates are damaging and induce rapid degradation!
A 40Ah battery might last 400% the usable life of a 20Ah battery (30A controller)
Further! I must add, these C rates should be based on actual present capacity, rather than original ratings!
"Go big or go home"
Laptop cells are designed for and do well at their designed discharge rate.
2 - 3 hour laptop run time = .33 - .50C discharge rate.
I have always recommended a ≤.50C continuous and ≤1.0C surge discharges. (≤.5C charge rate)
30Ah battery for 30A controller or 15A cruising drain.
For example:
These very common Sanyo cells at a 2C discharge rate almost immediately sag to their "empty voltage" of 3.60V.
42V "full" battery sagging to 36V.
Higher discharge rates are damaging and induce rapid degradation!
A 40Ah battery might last 400% the usable life of a 20Ah battery (30A controller)
Further! I must add, these C rates should be based on actual present capacity, rather than original ratings!
BSATOM
1 W
I perform a full discharge test at 3 amps continuous, which is much harder than what they will see in my ebike.
Right now I am running a very low budget 72v pack consisting of 3 6s11p packs. I consistently get 10 amphours out of it at 35 amps max discharge into this oil filled steel geared BMC I have pictured. No cell in this 198 cell pack was over 2.5 volts when harvested.
Also, that Sanyo chart shows more voltage sag at 2c continuous, but still over 2000mah of usable capacity. You can decide yourself that it is not feasible or prudent to do, but the manufacturer says it is fine with a chart to show what to expect when designing a pack at 2c continuous discharge.
I have had no problem with 1.5c intermittent peaks. This is my real world experience even with half capacity cells.
Right now I am running a very low budget 72v pack consisting of 3 6s11p packs. I consistently get 10 amphours out of it at 35 amps max discharge into this oil filled steel geared BMC I have pictured. No cell in this 198 cell pack was over 2.5 volts when harvested.
Also, that Sanyo chart shows more voltage sag at 2c continuous, but still over 2000mah of usable capacity. You can decide yourself that it is not feasible or prudent to do, but the manufacturer says it is fine with a chart to show what to expect when designing a pack at 2c continuous discharge.
I have had no problem with 1.5c intermittent peaks. This is my real world experience even with half capacity cells.
DrkAngel
1 GW
I am more concerned of cell damage than output capability.
At .2C average discharge voltage is 3.8V x 2450mAh = 9.31wh (discharge efficiency is near 100% = ~0% damaging heat production.)
At .5C average discharge voltage is 3.7V x 2350mAh = 8.695wh (discharge efficiency is near 93.3% = ~6.7% damaging heat production.)
At 1C average discharge voltage is 3.55V x 2250mAh = 7.987wh (discharge efficiency is near 85% = ~15% damaging heat production.)
At 2C average discharge voltage is 3.3V x 2150mAh = 7.095wh (discharge efficiency is near 76% = ~24% damaging heat production.)
With my recent 108 cell pack, 33.3V 31.2Ah = 1038.96 wh
At .2C that is approximately ~0 watt of heat per hour.
At .5C that is approximately 33.5 watt of heat per hour. (My recommended maximum sustained)
At 1C that is approximately 150 watt of heat per hour. (My recommended maximum for limited periods)
At 2C that is approximately 480 watt of heat per hour.
Heat in lithium batteries is the source and indicator of damage-deterioration.
Even mild discharges in hotter regions (90 - 100 ºF ) can cut battery life in half.
The equivalent of a 500w heater inside a battery the size of a lunch box has got to be severely damaging!
At .2C average discharge voltage is 3.8V x 2450mAh = 9.31wh (discharge efficiency is near 100% = ~0% damaging heat production.)
At .5C average discharge voltage is 3.7V x 2350mAh = 8.695wh (discharge efficiency is near 93.3% = ~6.7% damaging heat production.)
At 1C average discharge voltage is 3.55V x 2250mAh = 7.987wh (discharge efficiency is near 85% = ~15% damaging heat production.)
At 2C average discharge voltage is 3.3V x 2150mAh = 7.095wh (discharge efficiency is near 76% = ~24% damaging heat production.)
With my recent 108 cell pack, 33.3V 31.2Ah = 1038.96 wh
At .2C that is approximately ~0 watt of heat per hour.
At .5C that is approximately 33.5 watt of heat per hour. (My recommended maximum sustained)
At 1C that is approximately 150 watt of heat per hour. (My recommended maximum for limited periods)
At 2C that is approximately 480 watt of heat per hour.
Heat in lithium batteries is the source and indicator of damage-deterioration.
Even mild discharges in hotter regions (90 - 100 ºF ) can cut battery life in half.
The equivalent of a 500w heater inside a battery the size of a lunch box has got to be severely damaging!
BSATOM
1 W
Per hour? That is continuous. We are intermittent duty cycle here in the Ebike world. Please take off the propeller hat and get into the field. My battery box has never got more than slightly warm. Yes I feel it after a ride. 2c is totally OK as per manufacturer specs, especially for intermittent field use. Your concerns are unfounded, and I have already proven this to myself. Limit yourself as much as you want, but please do not come off as law to others with your conservative opinions and calculations. If I went by your limitations, I would have to go much slower or build a battery pack twice the size. What power do you draw from your packs when riding? What size packs? What motor?
I actually came here to say that I accidentally drew 6 amps from each cell last night on a 10 minute test ride. I ran an 18s 14p pack on a trike that I soldered the shunt on. I went for a ride and it hauled ass. It pulled my hill like nothing. I got home and saw 84 amps max draw. About 4500 watts with voltage sag under load. So far the packs are testing fine on the charger. The packs were warm but not hot. I will post whether the capacity is lowered in discharge tests. I bet I shortened the cycle life, but since these are already recycled laptop cells, there is really no way to determine this.
I actually came here to say that I accidentally drew 6 amps from each cell last night on a 10 minute test ride. I ran an 18s 14p pack on a trike that I soldered the shunt on. I went for a ride and it hauled ass. It pulled my hill like nothing. I got home and saw 84 amps max draw. About 4500 watts with voltage sag under load. So far the packs are testing fine on the charger. The packs were warm but not hot. I will post whether the capacity is lowered in discharge tests. I bet I shortened the cycle life, but since these are already recycled laptop cells, there is really no way to determine this.
999zip999
100 TW
I golden a bmc at 2,800 watts. I would put sense wires on that for monitoring and ez balancing. Balancing... plus I couldn't think of running 15ah or less.
DrkAngel
1 GW
Not any "law" ... just my experienced recommendation for satisfactory performance and long reliable life ....
"I am more concerned of cell damage than output capability."
Range-durability-reliability are my concerns.
"30Ah battery for 30A controller" my recommended. (1C max and .5C maximum sustained)
Most durable that reached ... retirement age ... so far.
25.9V 26.2Ah (10 lb 9oz including battery box) ...
(28A controller) build ran my eZip at 18-20+ mph for most of 4 years > 7000++ miles.
Hundreds of bulk charges, with bank level voltage monitoring.
Did a "tune-up" balance charge probably ... twice a year.
Retired to 2 "12V" occasional use power supplies for 12V lighting, power inverter etc..
"I am more concerned of cell damage than output capability."
Range-durability-reliability are my concerns.
"30Ah battery for 30A controller" my recommended. (1C max and .5C maximum sustained)
Most durable that reached ... retirement age ... so far.
25.9V 26.2Ah (10 lb 9oz including battery box) ...
(28A controller) build ran my eZip at 18-20+ mph for most of 4 years > 7000++ miles.
Hundreds of bulk charges, with bank level voltage monitoring.
Did a "tune-up" balance charge probably ... twice a year.
Retired to 2 "12V" occasional use power supplies for 12V lighting, power inverter etc..
dequinox
10 kW
So I developed a bit of a blue collar method for pulling cells out of these packs...
[youtube]9fDEnIqEgoI[/youtube]
[youtube]9fDEnIqEgoI[/youtube]
DrkAngel
1 GW
Please note:
It is extremely important to accurately determine the "valley" between cells.
Blade height-cutting depth should be set at the absolute minimum necessary!
Ironic huh!
I'm usually the one being berated & reprimanded for promoting dangerous methods ...
without proper safety warnings and disclaimers.
Problem in my mind is that those most in need of warnings are:
illiterate - can't read warnings;
have short attention spans = get bored and never finish reading long-winded warnings and disclaimers written in legalese gobbledygook;
simple minded - can't understand warnings;
believe that warnings are only for stupid people = people more stupid than themselves!
Warnings must be brief, simple and to the point!
Latest recommended warning:
Potentially dangerous, so don't act stupid. Yes, this means you!
Latest recommended disclaimer:
If you are stupid, try only under non-stupid person supervision.
You are warned! So, not my fault if you do something stupid.
It is extremely important to accurately determine the "valley" between cells.
Blade height-cutting depth should be set at the absolute minimum necessary!
Ironic huh!
I'm usually the one being berated & reprimanded for promoting dangerous methods ...
without proper safety warnings and disclaimers.
Problem in my mind is that those most in need of warnings are:
illiterate - can't read warnings;
have short attention spans = get bored and never finish reading long-winded warnings and disclaimers written in legalese gobbledygook;
simple minded - can't understand warnings;
believe that warnings are only for stupid people = people more stupid than themselves!
Warnings must be brief, simple and to the point!
Latest recommended warning:
Potentially dangerous, so don't act stupid. Yes, this means you!
Latest recommended disclaimer:
If you are stupid, try only under non-stupid person supervision.
You are warned! So, not my fault if you do something stupid.
DAND214
10 MW
DA, I never saw a warning not to cut my laptop battery with a table saw~
Dan
Dan
DrkAngel
1 GW
Hoe lee crap! Stop helping stupid people be a danger to themselves!DAND214 said:
Now they know they need to find something called a "table saw".
Too late now ...
So ...
Table saw info (WARNING):
Knife sharp teeth (7.25" diameter blade@5600rpm = 120mph) are potentially capable of:
irritating ears with loud noise;
throwing sawdust plastic etc into eyes;
spattering you with a sticky red fluid;
trimming fingernails or fingers drastically;
sending ≤120mph projectile into stomach, face or groin:
dequinox
10 kW
If someone is stupid enough to lop their fingers off in a table saw because they went out and bought one to copy this trick, but were too stupid to execute it with some level of common sense, it's not my damn fault.
There's your warning.
There's your warning.
DrkAngel
1 GW
"Common sense" is increasingly becoming something of a rarefied commodity! ... ?dequinox said:
Used to be ... natural selection would weed out those lacking common sense.
But, warnings and child proof (more like adult resistant) packaging seems to be proliferating the numbers of those lacking "common sense".
or
Just lowering the bar for "common" sense?
DAND214
10 MW
DrkAngel said:
That sure makes sense to me
Dan
999zip999
100 TW
So to get this straight I need a table saw to cut my 20ah in two for 10ah packs. I was thinking of putting one each on the sides of my bike. ? What do I do with the wires ?
Skalabala
1 kW
999zip999 said:
You can only do that with 50C Lipo bud. :lol:
agniusm
1 MW
I wander why laptop battery scavengers dont use tools to speed up process tenfold like this:
sbworkshop.com
All the needed data stored in EEPROM, cycle count, remaining capacity for individual cell, probably 20 parameters, sure more than enough.
Schematics are quiet simple:
sbworkshop.com
All the needed data stored in EEPROM, cycle count, remaining capacity for individual cell, probably 20 parameters, sure more than enough.
Schematics are quiet simple:
Attachments
Skalabala
1 kW
agniusm said:
What is this sorcery you talk of?
Link does not work.
agniusm
1 MW
Doesn't allow URL without www. Try this one (just copy paste):
sbworkshop.com
sbworkshop.com
Skalabala
1 kW
agniusm said:
Hmmmm, but I doubt it will show a tested capacity figure? Only what is left with the current state of charge?
But I can see it to be helpful to know condition of pack before opening, like detecting all cells are under 2v etc
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