Bulk Capacity Testing

Batteries, Chargers, and Battery Management Systems.
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DrkAngel   100 GW

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Re: Bulk Capacity Testing

Post by DrkAngel » Apr 13 2014 9:08pm

Bulk Discharge - Capacity Test
Updated methodology ...
for testing large quantities of cells - more precise.

Step 1
Charge all cells to identical voltage - 4.10V? - 4.20V? (Yes, 100th's is important)

Step 2
Allow all cell pairs to set for several days.
Remove any with a noticeable voltage loss - bleed down - self-discharge, more than ~2/100ths

Step 3
Test each cell pair with a trial discharge.
1 minute through any device with a substantial discharge amperage ~1000mA or higher. iMax B6 time discharge @ 1A, a 1000 lumen rated Cree XML flashlight, or ... .
Measure discharging cell voltage at 1 - 5 min. Mark cell as comparative IR rating, (4.20V-4.14V = .06V). Also note resultant voltage - 2 minutes(?) after discharge stopped
5 minute test could process a dozen pairs, 24cells, per hour and might indicate all cells liable to fail 2 hour discharge test!. (6 minute 1A discharge = 100mAh)
Important to measure voltages at cell with 100th V capable voltage meter, iMax voltage readings are skewed by multiple factors!
Remove any with excessive sag or lower resultant voltage.
This will confirm at least fair capacity and both cells functional.

Step 4
Prepare soldered 28s2p "strings" of cells. 28 x 4.2V = 117.6V DC
Begin the 1000mAh hour discharge using 2 x 60w light bulbs (120w).

Occasionally check voltage on each pair.
If any pairs getting low at 1 hour, (<3.8V? under discharge might not go 2 hours), remove and put in "1000mAh+" pile, save for continued testing with like cells.
Replace with spare pair, or pairs, make sure to tag them -1000mAh?

Step 5
Resume discharging.
Monitor each pair voltages and repeat replacements, (<3.7V under discharge), at 2nd hour put cells in "2000mAh+" pile, (40%+ capacity).

Monitor cells, you might want to schedule 1/2 hour, 500mAh replacements?

3 hours = 60% of original capacity for ~2500mAh cells.
I think, 60% + remaining voltage, to be a satisfactory capacity rating for recycled cells.
Mark pairs as 3000mAh + ( remaining static voltage eg 3.84v).

Pairs are effectively empty if they read 3.3V under a .2-.25C discharge, (= ~3.7V "static" - not discharging).
If unsure of cell rest voltage, disconnect 120w discharge temporarily.

Rebuild and continue testing strings of previously eliminated pairs, if any, test 2000mAh+ first.
Carefully monitor each pair, If they perform well for next 1/2 hour you can label all as 2500mAh+ their remaining static voltages. Every 6 minutes = 100mAh

Preliminary eliminations, 1st hour removals, if any, might not be worth the bother?

Even a 2 hour discharge, + the remaining voltage, is sufficient to build a nicely 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.

Smaller than 28s will require a watt meter to maintain accuracy

Of course if you add a watt meter to your string you can pull cells at any time.
Make sure you use a 3-wire meter, = self battery powered, or you will lose discharged amount when disconnected to remove cells.

14s2p ~60v or fewer would work nicely, but 1000mAh discharge might require ~300w halogen floodlight.
If you want to maintain a .2-.25 discharge rate.

DC-DC 3.8V-60V (80V if 3wire) 20A Dual-display Digital LCD Power Current Voltage, AMP Meter, watt meter, Ah meter $13.69
I've been using one for several months ... love it!
Many more functions but sketchy instructions are in Chinglish

Image



Still believe this bulk method of capacity testing is not accurate enough?

Well ... then ...
Use bulk discharge method to discharge 28 paired cells for 3 hours (= 3000mAh ~60% of new capacity for pair of 2500-2600maAh cells).
Separate cells and use watt meter to discharge to desired "empty", possibly 1 hour more? (4000mAh = 80% of new rated capacity).

Bulk method would take 2-3 hours for 28 pairs but shows cell pairs of 2000-3000mAh (~40-60%) + resulting voltage, which is great for a comparative capacity between like tested cell pairs. (Discharging a typical sample further, in 100mAh steps and "mapping"resultant voltages, should effectively allow a reasonably accurate mAh rating for all cell pairs in the series!)

Bulk method + metered per each pair would take 3 hours + 28 hours = 31 hours for 28 pairs

Metered discharging each pair from full would take 4 hours x 28 = 112 hours for 28 pairs
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douglashart   100 W

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Re: Bulk Capacity Testing

Post by douglashart » May 07 2014 12:44pm

I got my s-150-5 meanwell and I switched the R25. great! just thought id let you know- the r25 in this one was 1.2K , the resistor pack I received had only 2.2K so I tried that and Perfect -- 3.7 to 4.3 volts. Question: If you've read about the fletcher board could you tell me how it could improve on this seemingly complete unit. Am I missing something? Another Question: On the 90/20 ammeter, after disconnecting the jumper from the 'vext' will I still need a diode in the mix? thnx again doug

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Re: Bulk Capacity Testing

Post by douglashart » May 07 2014 12:47pm

another question about the 90/20 , can I simply hook up 3 or 4 lico cells for the external power source?

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DrkAngel   100 GW

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Re: Bulk Capacity Testing

Post by DrkAngel » May 07 2014 2:47pm

Fletcher board is for "lesser" power supplies, mainly as a replacement for the R33 mod.

Diode not needed if solder "jumper" removed.
I use 2s or 3s Li-ion as external power.
3s probably better because they drain relatively fast. Monitor battery level to estimate time between rechargings.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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douglashart   100 W

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Re: Bulk Capacity Testing

Post by douglashart » May 14 2014 6:19pm

hi DA, need help again . just hooked the s-150-5 backwards for a sec and poof. it seems to be the item 'scr1' any ideas? or am I sol ? my new hyperion wont balance either so im bummed and without chargers thnx again don't mean to be a nuisance but you the man

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Re: Bulk Capacity Testing

Post by DrkAngel » May 14 2014 6:29pm

Powers on?
Indicator light on?
Check fuse.

But, most likely ...
Check Diode behind wire connector block.
See - Shorted Diode
Last edited by DrkAngel on May 16 2014 7:04am, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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douglashart   100 W

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Re: Bulk Capacity Testing

Post by douglashart » May 15 2014 12:05pm

thnx , im sure your right. I got full continuity both ways.

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DrkAngel   100 GW

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Re: Bulk Capacity Testing

Post by DrkAngel » Nov 07 2014 10:39am

Testing up my latest 12 x 3s4p batteries in bulk.
(2 batches of 6 x 3s4p)

Image
1. Removed from packs
2. Used imax B8 to balance charge to LiPo voltage 4.17V per every cell.
(with 1 exception, all cells in each pack began within 1/100thV )
3 Ganged cells in parallel 3s24p to precisely equalize to 1/1000V
4. Re arranged in series, 18s4p
6x12_2.jpg
6x12_2.jpg (239.7 KiB) Viewed 2354 times
5. Connected 90V 20A V-A-W-Ah meter and 100w light bulb and 150w heater which supplied a 1.35A discharge.
6. Monitored voltage until 1st cell dipped to 3.65V

1st batch (Sony) metered at 8.43Ah with all 72 cells within 2/1000th V of median.
3.658 - 3.661
This demonstrates an excellent degree of quality control in manufacture!!!
And a very modest 4.17V to 3.66V metered discharge showed 81% of rated capacity.
Probably 90%+ if I pushed voltages to what most consider usable.

Next up, 2nd batch, (Sanyo) using same procedure.
Attachments
6x12.jpg
Last edited by DrkAngel on Nov 08 2014 6:53am, edited 2 times in total.
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There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

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Re: Bulk Capacity Testing

Post by DrkAngel » Nov 07 2014 6:14pm

DrkAngel wrote: Testing up my latest 12 x 3s4p batteries in bulk.
(2 batches of 6 x 3s4p)

Image
1. Removed from packs
2. Used imax B8 to balance charge to LiPo voltage 4.17V per every cell.
(with 1 exception, all cells in each pack began within 1/100thV )
3 Ganged cells in parallel 3s24p to precisely equalize to 1/1000V
4. Re arranged in series, 18s4p

Image
5. Connected 90V 20A V-A-W-Ah meter and 100w light bulb and 150w heater which supplied a 1.35A discharge..
6. Monitored voltage until 1st cell dipped to 3.65V

1st batch (Sony) metered at 8.43Ah with all 72 cells within 2/1000th V of median.
3.658 - 3.661
This demonstrates an excellent degree of quality control in manufacture!!!
And a very modest 4.17V to 3.66V metered discharge showed 81% of rated capacity.
Probably 90%+ if I pushed voltages to what most consider usable.

Next up, 2nd batch, (Sanyo) using same procedure.
Sanyos tested up.
Not quite as good as the Sony.
While all cells in each pack maintained equal voltage, within 1/100th V, ...
2 packs hit 3.65V at 7.8Ah
3 packs metered, within 100thV, with noticeable reserve (7.8Ah+) and
1 pack showed notable, better capacity (7.8Ah++).
(3 "noticeable reserve" packs - all cells within 1/100thV) - (I did not feel it necessary to "fully discharge" to 3.65V)

So ...
33.3V 31.2Ah, (more like 25Ah with the cell voltages I intend on using),
will be constructed with 9 banks of 8 Sony and 4 Sanyo cells.
This utilizes the 6 Sony packs of excellent equal capacity and the 3 Sanyo packs of excellent equal capacity.
Recharging cells at present and will hopefully have pack assembled this weekend.

IR? (Internal Resistance) With all cells being of same brand-age-manufacture-capacity, I did not fell it necessary to individually test-rate IR

Will also build a 36V 12A 36.45V - 37.8V dedicated charger, for same.
Pack has better capacity than I will typically use, so I will attempt to greatly prolong usable life by charging to 4.05V per cell ... possibly lower ...
I will need to create a capacity map of the Sony cells to determine optimal voltages.
Last edited by DrkAngel on Nov 13 2014 8:02am, edited 1 time in total.
A little learning is a dangerous thing;
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There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Bulk Capacity Testing

Post by DrkAngel » Nov 09 2014 7:46am

Rather than soldering cells together to bulk charge ...

Image
I picked up a pile (stack) of 8mm neodymium magnets as nibs for bare 18650 cells, for good contact in battery holders, flashlights etc.
Well, seems these magnets and some steel wire should gang together batches of cells nicely.

This would handle voltage equalization of a large batch of cells nicely ... without soldering - de-soldering etc.
Should work, at modest rates, for in series also.

100pcs 8mm x 1mm Neodymium = $6.50 delivered

Image

Also works good to attach alligator clips to batteries etc.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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DrkAngel   100 GW

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Re: Bulk Capacity Testing

Post by DrkAngel » Dec 06 2014 10:13am

DrkAngel wrote:Rather than soldering cells together to bulk charge ...

Image
I picked up a pile (stack) of 8mm neodymium magnets as nibs for bare 18650 cells, for good contact in battery holders, flashlights etc.
Well, seems these magnets and some steel wire should gang together batches of cells nicely.

This would handle voltage equalization of a large batch of cells nicely ... without soldering - de-soldering etc.
Should work, at modest rates, for in series also.

100pcs 8mm x 1mm Neodymium = $6.50 delivered

Image

Also works good to attach alligator clips to batteries etc.
Magnets work well!
They appear to be chrome plated.

Image

I used thin steel wire to connect ends and as replacements when cells removed.

"A" on meter is Amps = A -1.37A @ ~80V (100w light bulb & 150w heater)
"C" on meter is Capacity = Ah - 0.09Ah

Neodymium magnets lose their power when accidentally shorted! - Thin steel wire turns bright red! ... then evaporates? ... !
.
Attachments
Li_magnets.jpg
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Bulk Capacity Testing

Post by okashira » Dec 08 2014 4:04pm

Yeah, I would stick to low currents when using the magnet method.
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Tesla Model S 18650 cells - like new - and custom packs from Tesla cells for sale. Any shape Any power Any capacity.
PM me or search my threads.

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2015 Testing Methodology

Post by DrkAngel » Apr 30 2015 8:24pm

2015 - My, presently, favorite developed best-fastest cell testing method.

Stage 1 - Charge cells
Charge all cells equally to a voltage above preferred use voltage. ... (4.20V?)
I charge 40p ... or 56p using modded 5V MeanWell (combine cells when of nearly equal voltage)
I am testing combining using steel wire and 8mm round Neodymium magnets during testing, rather than soldering.
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 - eliminate leaky cells
Separate and allow cells to set and self discharge - the longer the better. (Minimum of several days )
Eliminate all with notable 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 Comparative IR
Test cell pairs for a comparative internal resistance.
While monitoring cell voltage, apply modest drain (2A?) and note voltage sag.
Remove any with notably greater voltage sag. These are likely very poor capacity cells or one of pair is bad. Separate and test for alternate use, flashlight etc.

Stage 4 - Capacity rate cells
With all cells at equal voltage, discharge at a measured rate.

2014 - I began using 28s2p, discharging with 2 - 60w light bulbs (~120V DC discharging 120w = 1A=1000mA per hour)
2x2600mAh cells = 5200mAh, 1000mA discharge = ~.2C. Capacity metered by time discharging till "empty" 3.60V*.

2015 - $12 90V V-A-W-mAh meter, (w/external power to maintain mAh reading), and various AC devices to provide ~1A discharge rate for 20s2p cells.

Monitor each cell voltage, remove any that fall below 3.60V* (voltage will drop suddenly at this voltage, so monitor carefully) and mark mAh from meter.
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 ... 40 cells capacity tested in 3 hours.

Stage 5 - Build equal banks
Recharge all cells to equal voltage.
Build banks of equal capacity.
1. Using mAh rating of cells, build banks of equal total mAh.
or
2. Line up all cells, best to worst. Shuffle into banks.
7s = 1234567765432112345677654321 etc **
Should provide reasonably well balanced capacity banks.

Stage 6 - In Service test
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.

* See - Capacity Mapping (Optimal Charge-Discharge Voltages)

** See = Cell interconnections for cans - ES Wiki

Updated INDEX
Last edited by DrkAngel on May 05 2016 8:39am, edited 2 times in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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DrkAngel   100 GW

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Quick Checklist

Post by DrkAngel » Jun 30 2015 6:50am

Check list for bulk testing
Multi-Meter
MeanWell S-150-5(w/Mega-Mod - optional)
V-A-W-Ah meter w/external power (or dual 60w light fixture)
Jumper wires w/alligator clips
Neodymium magnets (100?) and a box of steel paper clips make a great tool. (tough to find good paper clips - got plastic coated then some poor conductivity ones. I need to find a source for proper clips)
Bleed down device - to lower bank voltage (12V headlight etc.?)

Handy
MeanWell S-150-12
Infa-red meter

Check List for building
~14 & ~10ga tinned copper braid (dependent on pack size and power demand)
≥50W soldering iron, 60/40 rosin core solder & soldering flux
Small chrome plated probe (screwdriver?) to stabilize soldered components
Clear 2" boxing tape
Duct tape - 3" preferred

Will update - fill-in after coffee!

PTR! (Points To Remember)
Test for self-discharge!!!
Leave cells with tabs connected! (wires too!) - makes testing and building much easier!!!
Cells of 0V are "iffy" at best. You can try to charge ... but monitor closely!
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - February 2019

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Endless Sphere Wiki - Lost?

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DrkAngel   100 GW

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Re: Bulk Capacity Testing

Post by DrkAngel » Jul 31 2018 7:13am

.
...
Updated Quick Bulk Cell Testing Method

Test cells the way I test used cells

1. self discharge
Charge all cells to same exact voltage
Let set several days
Discard any with noticeable voltage loss

2. IR (Internal resistance)

Comparative IR - identical cells under identical discharge will sag in voltage to the same voltage
With cells of identical voltage
Connect discharge device to cells, individually, in turn
check and note cell voltage at a specific time during discharge
Discard any with excessive voltage sag

3. Capacity
From full voltage, run a metered discharge
discard any with substantial capacity loss
or
after marking each cell with capacity, build banks of identical capacity

Bulk testing
After self-discharge test
String batches of 30s cells in series = ~120V
Discharge using 2x 60w light bulbs = 120w
Monitor all cells
Each hour of discharge = 1Ah of capacity
Stop discharge when any cell hits low voltage
3.40V - very safe discharge point, don't recommend below 3.00V
Label each cell with residual voltage
1hr = 1000mAh + 3.95V?
2hr = 2000mAh + 3.75?
3hr = 3000mAh + 3.45?

Bulk building
With all cells identically discharged
Sort all cells from best remaining voltage to worst
Sort into banks with best cells to worst
10s >> 1 2 3 4 5 6 7 8 9 10 10 9 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 10 etc
This will create banks of nearly identical capacity ... banks will safely balance if within ~.1V ... barring any cells of radically different voltage ...
Combine cells - since all cells are free of self-discharge and were identically discharged, simply bulk charge to full pack voltage
Good Lithium cells, discharged at moderate rate will bulk recharge right back to their starting voltage!
Should have good solid pack of reliable tested cells.
Best news ...
Should be good for bulk charging ... with no need for balance charging!

Oops! I forgot, good for bulk charging if pack of sufficient size for moderate discharge rate.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - February 2019

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