here is some info on 20v yardworks lithium ion

I run a big LiMn packs ( not power tool cells ) 20ah cells, and as long as the bike is in the house before you leave for a ride, it has to be damn cold before you notice a difference, and at this point i'm not riding lol..

This morning.. -1 celcius.. brrrrrrrr.. pooor Justin will have to ride daytime for the last leg ! hehe
 
I see NO evidence the YW BMS does cell balancing on charge.

I ran a test using my latest #9 virgin YW battery. All I did prior to this test, since new, was:
(1) Charge on YW charger
(2) Run a test discharge through BMS at 10 ohms which ran 160.5 minutes and gave 4.8 AH before LVC.
(3) Charge on YW charger
(4) Run a test discharge connected directly to batt/cells at 2 ohms which ran 34 minutes before I manually LVCd at 14.37v (with one cell at 2.7v, the rest more like 2.9v) This gave 5.1 AH even at the higher current, presumably because no BMS losses.

For the test I used YW charger with amp-meter to C- charge connection. I charged battery to 20.31v and all 5 cells were showing 4.06v; nicely balanced.

I then applied an aprox 1 ohm load to one cell for maybe 5-10 minutes. After recovery, and using a lower DMM range I was seeing cell voltages in millivolts:

3994 4024 4026 4027 4025

Clearly the pack was unbalanced now, although only by about 30 millivolts on the low cell. I resumed charging with YW charger.

After 1 minute: LowCell: 4.02v, Others: 4.06v

After 10 minutes: LowCell: 4.04v, Others: 4.06v

At this point I thought the batt was being balanced; it looked like it.

After some 12 hours overnight on YW charger:

LowCell: 4.09v, Others: 4.17-4.21v.

Umm, so, unless there is some magic trick to apply, I'm not seeing this BMS as balancing on charge. Balance on discharge doesn't make sense IMO, so I think there is no balancing, and this will help sales of replacement batteries in future.


I'll also note that batt was 17.31v before start of charging and current peaked at 1.87amps, declining slightly to 1.82amps at 40 minutes. This is more or less constant current phase. Constant voltage phase seems to be 4.06v per cell, but it's not really a constant voltage, as V later rises eventually to near 4.20v. So the "constant current" is a range, and so is the "constant voltage". Perhaps this helps protect the battery even without cell balancing circuitry, as long as the cells are in decent shape.

I used my remote temp meter and noted no temps over 69-70 degrees F in my garage that was a degree or two colder than that. I checked the BMS top and bottom, and all components there-on. Also checked battery from multiple angles.

I would think that cell balancing would either show components heating up, or would require fancier circuits and show current anomalies if using some other technique than wasting high cell power to balance.


So, IMO, YW BMS does no cell balancing on charge or discharge. If anyone has evidence otherwise please speak up. Cell voltage readings after a settling period are the best evidence IMO.

I think the C- terminal is just a closer connection straight to battery cells that bypasses the BMS discharge circuitry. It depends on YW charger to keep volts and amps in sane range (although there is a fuse). The 6 small cell wires are for LVC only, and trip when first cell goes below 3v. They are not used for balancing.

BTWs:
- I finally figured out why batts are so hard to remove from case. Some sticky stuff at bottom of case; not tight insertion.
- Virgin battery top cover is offset enough it almost looks a bit pre-bulged. I suspect/hope that is normal, and not really a bulge.
- Finally have two consecutive serial numbers: 89 and 90. :)
- Blade screwdriver worked much better than the large Philips I tried to open battery.
- If your voltmeter probe slips on a negative cell terminal you will get a 1 cell spark etc. Negative cell terminals sit on some plastic insulator above the positive "bar" or whatever it is.
 
how about testing discharge using c-...?
what about clipping lvc wires and go through some cycles?
if there is no balancing going on then this would have no effect right?
 
wasp said:
how about testing discharge using c-...?
what about clipping lvc wires and go through some cycles?
if there is no balancing going on then this would have no effect right?
Click to expand...

C- seems to be a more direct path to battery, so discharge through C- should be more efficient, but I've never tried it, and I don't have much reason to do so, because I've already decided against using the YW BMSs, unless I could somehow get them to do charge balancing. There are some components there; 1 or 2 medium size (smaller than the 3 heat sinked ones) FETs or something, and I'm not sure what they do, or how they might react to discharge out a charge port.

I think unplugging (no need to clip) the LVC wires would trigger LVC since each pair would read 0v. Haven't tried it though.

If LVC was disabled, yes, I think unplugging the LVC wires would have no effect, since they are only used for LVC (or maybe overcharge detection?) and not for balancing. I think the wires would be thicker if they were used for balancing. Also, the BMS components near where the wires connect would be larger to handle shunting unwanted charging current. Those components are tiny surface mount, and I think they are basically a cap or 2 to filter and voltage divider resistors and some components to trigger on LVC.

I ran a 16-14 amp (1 ohm load on new batt) discharge test this afternoon through the BMS and got 5.1ah before the BMS LVC kicked in. The LVC seems to kick on based on load voltage and not battery voltage; that's a bit wasteful IMO of the last few hundred mAH. It kicked at 15.30v, and the batt voltage was almost 17v at the time.

Yes, that's right; At 16.2amps at start, the voltage drop on the BMS was 1.75v ! That's over 28 watts of power being wasted in the BMS and being turned into component and battery killing heat. I calc the internal resistance at this current level as 127 milliohms per 5 cell battery ! In addition to the battery internal resistance which seems in the same vicinity, depending on current and cell health etc.

I'll respect anyones' right to use whatever BMS or no BMS they want, but IMO, the BMS robs power, threatens the battery, weighs too much, and causes grief with premature shutdowns etc. I only see two useful features in this YW BMS:

(1) Limits current reportedly to 31a. I've never hit this limit in testing or use. My controller is 20a, and now I have a 30a fuse and a 30a breaker. I've never tried a test with more than 16 amps yet.

(2) Provides LVC to protect cells.


For (1), the only plus for me would be some protection against wiring problems before my fuse. Like wire cutting into side w/ batt terminals almost causing bike fire. :oops:

For (2), what's funny is that LVC does not seem to be per cell. In my discharge test, my purposely lowered cell voltage was about 2.7v when LVC kicked in at 15.3v total battery (after BMS, and batt total was about 16.8v at the time), So the LVC really only protects the battery as a whole, and only when you don't have one cell much lower than the others. And LVC can pick the darndest times to cut-out. I'd prefer to manually decide when manual LVC is needed. Have an idea for audible LVC type warnings, AND an LVC type throttle, that would effectively lower my controller current limit as needed to keep cells above 3.0v (or 2.5v or whatever I decide).

I also think YW charger could kill your other cells, if one cell goes really bad (like one of mine) and read 0.01v. YW charger will charger other cells to about 5.2v in that case, since it and BMS assume that 21v on batt is same as 4.2v on each cell.

IMO, YW BMS = Yuck
 
nutsandvolts said:
mikereidis said:
Anyone noticing bad effects from cold ?
Click to expand...

Today I seemed to use more capacity quicker than normal. I'm not sure if it was because of the cold but I will try to figure that out in the next couple of months by retaining some data. Ultimately what I'd like is this:

1) Cycle analyst serial data out with 5Hz voltage, amperage, amp hours, distance data
2) Temp sensor and inclinometer
3) GPS to stamp date/time/position/altitude

These would connect to another microcontroller and store all the data on SD or MMC card.
USB driver would enable easy downloading saved data to PC.
It would then be interesting to look at temp and incline data.
And the position data could feed all kinds of cool applications.

Anyone know of good simple reliable inclinometers?
Click to expand...

I guess we are headed down the same "path". :) I want a bike cam too, for some measure of "protection" against cops or stupid drivers or whatever; recall at least one person did same on his car and regularly posts "stupid driver of the day/week" videos on the net. :)

Maybe we could sell equipped bikes to Google, for the new "Google Bike Path View", and all those side streets etc. that are too difficult in the G Street View cars... :mrgreen: :mrgreen:

I have a $40, 360 degree digital inclinometer that reads to 0.1 degree, has magnetic base and is intended for measuring saw angles. No digital interface though, but I'm tempted to open her up and see what I could attach to it. I have no idea how it does 360 degree and turns it into digital for LCD display.

I do a quick google search on "inclinometer USB", and after a slight detour, and search on "sca100t" I end up on this page: http://parts.digikey.com/1/parts/945451-inclinometer-dual-0-5g-dil12-smd-sca100t-d01.html . Quantity 1 = 64 bucks.
 
User "methods" posted these links on another thread:

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6589&Product_Name=Battery_Monitor_2-6S

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7216&Product_Name=Wireless_battery_tracker_(6s_&_up_to_300mtr

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7390&Product_Name=MP_LCD_Battery_Detector_6S

These are Lithium cell voltage monitoring products made for RC usage. At least two of them give audible beep at LV, and 2nd one is wireless (but no voltage reading; just one LED per cell).

IMO, cool inexpensive products, a safer alternative than manual LVC of total batt or pack voltage, but let's you use your grey matter instead of some dumb BMS LVC.

I REALLY want USB connection for cell monitoring, and these products may not be USB interface-able, but they might be useful otherwise.

Did a USB search on that site and found: http://www.hobbycity.com/hobbycity/store/uh_viewitem.asp?idproduct=4641

USB Flight Data Recorder Features

* Standard system includes everything to record airspeed, altitude, RPM, temperature, 4 servo channel movements and glitches, receiver voltage
* All data is logged to permanent memory, which retains the data even when the power is removed
* With accessories available below, monitor amps, pack volts, g-force, EGT, and more!
* Logged channels: 16
* Full support for English and Metric units
* Airspeed from ~9MPH to 290MPH
* USB Live Mode for real time bench monitoring
* Altitude to 25,000+ feet
* USB Plug and Play - No new drivers needed!
* Fully Compatible with Windows Vista, 98SE, ME, Win2K and XPâ„¢
* Lightweight - approx 1.5 ounces with unit and cables
* Simple and quick installation and removal
* Retains flight data without battery
* Graphical flight playback in real time
* Excelâ„¢ compatible data output
* Ultra-low power consumption - around 35 mA
* Built-in status LED indicates battery level on power-up
* Adjustable capture rate
* Powerful built-in graphing
* Expansion port for future enhancements
* NEW: now has 4X the onboard memory of the original recorders, with lossless data compression, for much longer storage time.
* NEW: improvements in airspeed, altitude monitoring mean greater accuracy, and no interference from your model’s transmitter
* NEW: increased voltage and current accuracy

For more information, click below;
http://www.eagletreesystems.com/Plane/plane.html


TRES COOL !! :mrgreen: :mrgreen:

From http://www.eagletreesystems.com/Plane/plane.html :

NEW - Google Earth (TM) Real time and Recorded GPS support! Unleash the power of our Flight systems with the powerful visualization capabilities of Google Earth! Our software now supports live data feed to Google Earth, as well as exporting of recorded data to the Google Earth format!

OMG !! :) :) I imagine inclinometers and other cool stuff possible too.

Did I mention my plans for a 3rd and/or 4th wheel (for 0 MPH stability) and hooking my RC truck or plane stuff to my bike ? No more worries about personal injury (on bike by me at least) doing maximum speed tests !

Watch out Ottawa; There's a ghostly rider-less ebike soon to be seen buzzing around. Wonder if there any laws against that sort of thing ? Who cares, nobody to ticket or jail except the bike itself, and this bike refuses to stop or be taken prisoner. :mrgreen: :mrgreen: :mrgreen:

Knight Rider 2009; the new Kitt is an ebike.

Probably get national coverage (and be much detrimental to ebike perceptions) if it buzzed around Parliament Hill with a big 4 letter sign containing two Bs, one O and one M. Gotta go; Mounties and Blackwater banging on the entrance to my super-villain lair...

(OK, yeah, haven't take my meds yet this morning...)
 
if like you say there is no bms on yw chargers...can i use another charger...a 18v nicd tool charger that charges to
21v? it seems way heavier than yw charger? i am returning one of my 2 yw chargers today and would like to try the other(nicd)charger?
anypitfalls i should be worried about?
also if there is no bms and the lvc uses or drops v by 1.75 per bat than we should be able to disasemble the packs and use conventional chargers
using a ca to judge lvc? if 5 cells charge to 21v than 10 cells would be 42 ect they (the cells could be hooked up in bunches say and use a 36 or 48v
conventional chargers? the cells could be repacked to what we like and what works on a individual basis...is this correct or does it need to be proved?
 
my lvc clipped at 14.66v today...first time it has done this below 15.5...
 
wasp said:
my lvc clipped at 14.66v today...first time it has done this below 15.5...
Click to expand...

Two of my batts had LVC break on them I think; went to 14v or so before I "manually LVCd".

It's possible LVC broke because I was charging (and at high current up to 12amps sometimes) through the discharge terminal. Now that I realize I was doing that, I have suspicions this was a bad thing.
 
wasp said:
if like you say there is no bms on yw chargers...can i use another charger...a 18v nicd tool charger that charges to
21v? it seems way heavier than yw charger? i am returning one of my 2 yw chargers today and would like to try the other(nicd)charger?
anypitfalls i should be worried about?
also if there is no bms and the lvc uses or drops v by 1.75 per bat than we should be able to disasemble the packs and use conventional chargers
using a ca to judge lvc? if 5 cells charge to 21v than 10 cells would be 42 ect they (the cells could be hooked up in bunches say and use a 36 or 48v
conventional chargers? the cells could be repacked to what we like and what works on a individual basis...is this correct or does it need to be proved?
Click to expand...


I'm not too familiar with NiCad Chargers, but my 5 amp, 7.2v RC charger is about as fancy as my diode bridge and heater charger; It just pushes 5-4 amps from 12v source through resistors for 15 minutes.

If the charger open circuit voltage is no more than 21.0v, and there is no way for it to go over 21.0v (and your cells are decently balanced), then it should be fine. If it's over 21v, it should also be OK, ASSUMING you watch batt voltage and disconnect as it approaches 21v. If it can push more than 2 amps in battery 15-18v range, it will be faster than YW charger, with whatever (IMO small, at 6amps or less) risks come from higher current charging. As I've said before though, if you can safely discharge at 20-30amps, I think it's OK to charge at 6-12 amps (and more).

I AM thinking now that lower current is always better for battery life though, but the bigger risk is from continuous discharge at high currents and high temps.

Doug/NutsAndVolts (like most people I think) was rather surprised when Ebikes Justin said he had one charger for all battery types. Conventional RC shop or EBike shop wisdom is you must have a universal charger (perhaps with type switches) or different fixed tech type chargers for each battery type. But electrons at given voltages and currents are just electrons; and at worst, if you closely watch your batt voltages and current, almost any charger can be used with any battery. It may not be consumer-proof and "set and forget" however.

I charged my new batt yesterday with YW charger hooked directly to battery, bypassing BMS. Probably charged a bit faster than usual; I think charging voltage drop through BMS was about 0.2v. Cells still perfectly balanced.

Pitfalls ? I think if you have a volt-meter connected and make sure it never goes over 21v it should be OK. Once again, this assumes your cells are still balanced, and if they are undamaged then they should be OK. To be a bit safer you could limit voltage to 20v or so (I.E. disconnect or add series resistance to keep voltage to 20v or less; switching charger on and off could accomplish this limit also.) The last volt doesn't provide anywhere near the same capacity as the volts from 18v - 20v, which are the real meat of the charge level.

I've backed away from the idea of dissasembling the cells from the batteries. I read somewhere that there is specialized equipment for installing those "compression/bulge bands". I've heard they are REALLY tight and need to be.

Yes, a commercial charger that puts out a max of 42v should work OK with a 2s YW pack. Also, a power supply or DC-DC converter set to 41.6v (for a bit of safety), that is current limited to whatever charging current you want should work. Assuming the current limiting does not cut off power, but just allows voltage to drop to current low battery voltage.

I can't stress enough though that if one of your cells is damaged, it will continue to get worse and worse, unless you monitor it's voltage and ensure it never goes above 4.2v again. I'd highly recommend that anyone comfortable with opening their battery to test cell voltages do so, with battery at full charge. Just watch out for the almost inevitable sparks when a probe slips or similar.
 
wasp said:
my lvc clipped at 14.66v today...first time it has done this below 15.5...
Click to expand...

Hmm... with my Milwaukees I don't think I've ever seen the exact same LVC before the BMS shuts down the pack. I always assumed it depended on how hard you pulled your batts down. Seems if I milk my pack on the flats I get a much lower LVC shutoff (23.6-24v) than if I'm pounding on it (24.4-24.6v) in the mountains.
 
is it alright 2 charge both my bats at same time using only
1 yw charger? i know it will take twice aslong but should be fine...
i broke 1 of my chargers and returned it but instead of getting another
i wish to look for a better option...
 
wasp said:
is it alright 2 charge both my bats at same time using only
1 yw charger? i know it will take twice aslong but should be fine...
i broke 1 of my chargers and returned it but instead of getting another
i wish to look for a better option...
Click to expand...

That should work, but it's best to ensure they are about the same state of charge/voltage when you do it. If you hook 2 batts in parallel (with no charger or charger off), the weaker one will be charged by the stronger until they are in equilibrium. Often considered a bad thing as it wastes power, but for charging, who cares ? I presume these are 2 batts from the same 2s pack so they should be roughly equal. When charging, one will probably take more current than the other, but no big deal about that.

It actually shouldn't take twice as long; only the constant current phase will take twice as long. The perhaps longer constant voltage phase should be almost the same length as for a single batt. (With higher current charging like mine CV phase is DEFINITELY longer; I can fill the first 1 amp hour in 7 minutes at 11 amps or so. 2nd AH takes 10 minutes more).

So it might only take 1.3-1.8 times as long; maybe 4.5-6 hours.
 
wasp said:
how about testing discharge using c-...?
what about clipping lvc wires and go through some cycles?
if there is no balancing going on then this would have no effect right?
Click to expand...

Tried this yesterday. Disconnected LVC wires. Discharge would not work; voltage was there for DMM, but try to pull any current and LVC prevents discharge. So you'd think that open wires are interpreted as 0volts, right ?

So then I tried charging with YW charger through official terminals. No go. Charger said "green; battery ready". Voltage not rising so clearly no charging was happening. So for charge, open wires interpreted as 4.2v or more ? Or some failsafe mode ?

So it appears that BMS won't work for charge or discharge with sensing wire plug disconnected from BMS.
 
I think I've finally got my range/battery issues "under control" now.

With 9 batts, I finally have one 4s pack that seems pretty good and balanced. Except for one unfortunate "sacrificial cell". So it appears I ended up damaging 6 of my 8 original batts with "dangerous charging". Let that be a lesson... LiMn get's it's revenge if you let it boil over 4.2v per cell.

With one bad batt (plus one bad cell) in my 4s, I got 17 KM up and down my street yesterday, targetting 32 KMH. With only the one bad cell, I got 20 KM and may have been able to push it a few more KMs. In both cases, pack started about 82v; I.E not full charge.

I found a use for marginal batts; Big Bike Lights ! :) Can Tire is discontinuing their 10.8v (nominal or max w/ 3 cell?) Lithium tools, and I bought 5 "Compact Light Bars" for $12 each. They each have 24 white LEDs, and when hooked to 12.5v from 3 YW cells, they consumed 270 mA. That results in 1.5 watts to the 24 LEDs and 1.5 watts to 12 surface mount 270 ohm resistors.

I ran them at 20v (5 cells' full YW batt), current was 600 mA (25 mA and 75 mW each LED, I tested one at 200 mA and it didn't burn after a few seconds!). I figure the LEDs were getting 3.6watts and the poor 1/10th watts SM resistors about 0.75 watt each, for total of 8.4watts wasted. Should run for 8 hours or so, perhaps 24 hours without wasteful resistors. In my 50 minute ride tonight, 10 of the 24 LEDs went dark and I presume 5 SM resistors burnt. Fine by me, I'm going to bypass resistors and use straight voltage and see how long these LEDs last at higher powers. Might also be useful as charger cell balancing shunts; but I have doubts; these aren't zener LEDs.

The light output is WONDERFUL, and I'm only running 1 of the 5 at present, at less than the max power they can tale ! MUCH better than my previous "best cheap bike light", which was a Stanley 369 Tripod flashlight currently selling for $30 that I got a few years ago for a bit more. This flashlight does not get good reviews; Tripod and 369 are great but LED tech is aged.


I'm starting to wonder if it might actually be "NCC sanctioned" to charge random things like cell phones, laptops etc. at NCC facilities. I charged up a bit for 15 minutes tonight at Lac Des Fees Information booth. Nice handy double outlet at back (with some burn/melt marks NOT from me) next to the rackboard where a pay phone used to be, in the days before everyone but me had a cell phone. No sign saying "You can't plug in here". I asked guy at info booth on Sunday about using the outlets and he was taken aback, his answer was garbled and he mentioned he was a Biology student. I bought a $5 map for his trouble... :)

Ebikes may technically be banned on the NCC paths, but they can't ban them on the same NCC roads the cars use. So, just "possessing or riding an ebike" on NCC property can't be banned either. So I see no issue with ebike charging at NCC facilities, unless they also ban cell phone etc. recharges on those outlets.

Lac Des Fees parking lot not as pleasant as McKenzie King; too much traffic, especially now that Blvd Des Allumetiers provides a nice shortcut for general traffic. I leaned my bike to charge, accidentally banged the door a few times and wondered how sensitive the alarm was. 10 minutes later, red and blue flashing lights ! :shock: As I ponder ripping out my plugs and looking innocent I see the cop has someone pulled over. After the ticket I see cop back into fire route, watching for stop sign roll-throughs. (In Quebec ?? !! National pastime here !) As I plan my "super duper legal" departure with a full stop at sign and a hand signal to turn, cop has next customer so I chuck the formalities. Did a nice thorough scan farther on doing an illegal U-turn at St. Raymond exit.

The mid trip electron top-up wasn't strictly needed, but gave me the confidence to go heavy on the throttle on the way back. Total 19.9 KM, runtime: 47+ minutes, avg speed: 25.3 KMH, top speed 51.4 KMH.
 
:shock: :shock: :shock:

Dayum ! So much for my "good" 4s pack. This is what happens when you forget and accidentally overcharge at 6-7 amps for 1 hour 7 minutes using 800 watthours of AC. And then you get the bright idea of lowering the voltage to safer levels by discharging at 8 amps adding fuel to the heat fire.

Thank the gods that LiMn doesn't explode and burn. It just pops, crackles and sparks a bit. External batt temps were as high as 140 F. I think I'll have to buy some more batts with cash and/or on my wife's credit card.

IMG_1246.JPGIMG_1247.JPGIMG_1249.JPG
 
omg thats some swollen cells...
for the amount of "testing" you are doing
on these yw bats i feel the need to donate
to the cause because the info learned is
great and the mfg would never show pics
of thier cells abused this way...lol
keep up the great work
 
mikereidis said:
Some pics of bulged batteries:View attachment 2View attachment 1
Click to expand...

Is this all the result because you charged over the 21v mark of each group of 5s pack or because you where charging at to much of a high current (6-7amps)

I was reading on a prior post somewhere that they were tested to charge at up to 12amps.

thanks
steveo
 
steveo said:
mikereidis said:
Some pics of bulged batteries:View attachment 2View attachment 1
Click to expand...

Is this all the result because you charged over the 21v mark of each group of 5s pack or because you where charging at to much of a high current (6-7amps)

I was reading on a prior post somewhere that they were tested to charge at up to 12amps.

thanks
steveo
Click to expand...


AFAIK, I'm the only one who has charged at 12a. With a pretty much discharged pack, IE. each batt about 17v and each cell about 3.4v open circuit (which tends to drop to LVC 3v per cell under a bit of load), I can pump 10-12 amps in for the first 7 minutes or so. At that point I always have at least one cell that is at 4.20v and I drop my current to 7-8 amp range for another 10 minutes, before dropping more.

Then I continue with dimmers all the way down to the point I lose patience with being a manual CV mode component and the cells are out 4.1v anyway, so that's virtually a full charge.

So current in and of itself was not the issue. Over-voltage over 4.2v per cell was primary cause, and the current pushing that voltage combine to create too much power the cell can't absorb, turning into heat, which expands the cells permanently and increases their internal resistance.

In this extreme case, much more happened I'm sure. :mrgreen:

The worst battery was the newest one; bottom photo. It popped it's compression bands which probably takes lots of force. Since my batt pack is wedged in the bike frames with only 5 mm or so of clearance, I had to use a hammer to bang the deceased pack out of there. :shock:

The pack might have semi-survived at much reduced capacity and much higher resistance if I hadn't gotten the bright spontaneous idea of applying an 8 amp discharge load to reduce cells to "safe voltage". That really got the popcorn machine popping.

Just for a larf I checked to see if there were any cells showing voltage just now. Holy Shmidt ! 18 out of 20 are showing a pretty good charge ! The two 0v cells are in the middle and above the middle cell in the worst batt. I was expecting them all to be dead. It's not dead ! It's just sleeping ! (Monty Python)

I'll have to test those cells and see how they're doing now. Increased resistance mostly important for high current discharge, so low current uses like bike lights should be fine with damaged cells/batts.

Been wondering how I'm going to cram those batts back in their cases. :mrgreen: Guess I can just remove the best cells first to "compact" them. (No I've never read the CTire warranty terms, assuming they exist somewhere; nor did I ever explicitly agree to them. :wink: )
 
wasp said:
omg thats some swollen cells...
for the amount of "testing" you are doing
on these yw bats i feel the need to donate
to the cause because the info learned is
great and the mfg would never show pics
of thier cells abused this way...lol
keep up the great work
Click to expand...

Oh, I love testing, measuring, analyzing and designing... I can't take a bike ride without checking speed and voltage umpteen thousand times. Continuous data logging will eventually allow me to relax more (I hope), but I'll also want a busy real time display too showing all cell voltages, ride stats, live streaming pr0n off some random wifi somewhere. etc.

I've ALWAYS learned stuff from pushing limits, breaking things, learning to how to fix them or design to prevent damage etc. At the best times, I learn from other's mistakes, or at least my own that others have to pay for... (Sounds bad, but meaning stuff like breaking things on the job. In my early 80's electronics tech days I blew up stuff accidentally, like capacitors that go bang and at least one circuit board for a terminal that I saw every chip glowing red from a bad power supply. Just part of business; stuff happens.)

So here's some stats from the other day, just before the big LiMn meltdown; using the pack that popped, before it popped:

It was a nice day so I went full throttle almost all the way, except maybe 2 KM on a dirt road.

Starting voltage on 20 cell pack: 82v, which is what I target now. Ending voltage 72v, but recovered later to 75v.
11.27 KM, 18:40 run-time, 36.2 KMH average, 56.5 KMH maximum, a new high for me.

Max speed was going down a smallish hill, full throttle, somewhat tucked, but was midway through trip so voltage under load was only 70v and current was 17.5amps or so.


After the meltdown I assembled my former 4 worst batts (with 1 cell at 0v; I bypassed it for a 19 cell pack). I charged to 78v (2v under 80v max for 19 cells). I rode much slower, 15-20 KMH my target range, and I pedalled up hills, assisted by the motor. My ebike "hyper-miling" strategy (esp on damaged batts with higher resistance) is basically keeping the amps down. I accelerate very slowly, used the brakes only once really, near end of biggest/fastest hill and tried to avoid unneccesary hills up and down.

I ran 1:24:26, (84+ minutes), distance 22.67 KM, avg speed 16.0 KMH, max speed on 1st big hill ~ 38 KMH tucked, 2nd bigger hill 40.6 KMH. My batts ended up about 70v recovering to 72v, but with only 19 cells so 3.7v per cell pre-recovery. Towards end I speeded up a bit and up a smallish incline I was dropping to 60v, about 3.2v per cell.

Not REALLY sure how much AH is left at 72-75v or so; maybe 10-15% of full 6ah, so about 0.6-0.9ah. Hard to do hills at that voltage though; mostly via concern about cell under-voltage.

I'll be ebiking to flatter part of Gatineau Park tonight to continue the tests/biking fun, a bit faster tonight. Will be thinking of how to build a SAFE charger/balancer; I'm extra motivated now. I'm considering using the YW chargers again, to see if I can get more than 3a from them and use them as 21v power supply, 1 per batt; $30 is hard to beat. I'll recheck to see if I can get a BMS to balance, but I'll probably find a way to connect 5 cell balancers of my own design in series for each 21v supply. Whatever works, and is safe to the cells.


Canadian Tire has a $10 sale on a somewhat newer version of the DMM I use on my bike this week. Sign said $15 inexplicably so I thought I might get another $10 off deal, but cash reg was good so no dice. :) Clerk knew nothing of policy.

I like this cheap DMM because I've used the 10a current function continously on the bike and it's never blown, even though the 10 milliohm shunt they use makes them say you shouldn't use it at 10 amps for more than 15 secs each 15 minutes. Works fine for me, even with virtually full throttle runs and 15-16 amp discharge testing etc. My better DMMs blew their fuses pretty fast; this one doesn't bother with a fuse. Also, it reads to 19.99amps even though spec'd for 10 only.

I'm not sure if the newer version can do the same, but I'll try it soon enough. If not I imagine it could be modded to work, and I'd LOVE to find a way to disable the auto-off function. On these DMMs you have to flip dial all the way back to off. Grrr.
 
my latest issue is uneven battery lelel's after run...
starting from yw1 20v yw2 20v sla13.60v
after 8km at 45kmh strait no cooling breaks(motor is hot)
ending volts...yw1 16.01v...yw2 18.60v...sla 12.63v
they are wired just as shown and i think the bottom yw bat
is taking the brunt...? i think i will rearange my wires
so sla is bottom bat and see if it takes the hit and my
limn's even out some in discharge? does that make sence?
 
mikereidis said:
steveo said:
mikereidis said:
Some pics of bulged batteries:View attachment 2View attachment 1
Click to expand...

Is this all the result because you charged over the 21v mark of each group of 5s pack or because you where charging at to much of a high current (6-7amps)

I was reading on a prior post somewhere that they were tested to charge at up to 12amps.

thanks
steveo
Click to expand...


AFAIK, I'm the only one who has charged at 12a. With a pretty much discharged pack, IE. each batt about 17v and each cell about 3.4v open circuit (which tends to drop to LVC 3v per cell under a bit of load), I can pump 10-12 amps in for the first 7 minutes or so. At that point I always have at least one cell that is at 4.20v and I drop my current to 7-8 amp range for another 10 minutes, before dropping more.

Then I continue with dimmers all the way down to the point I lose patience with being a manual CV mode component and the cells are out 4.1v anyway, so that's virtually a full charge.

So current in and of itself was not the issue. Over-voltage over 4.2v per cell was primary cause, and the current pushing that voltage combine to create too much power the cell can't absorb, turning into heat, which expands the cells permanently and increases their internal resistance.

In this extreme case, much more happened I'm sure. :mrgreen:

The worst battery was the newest one; bottom photo. It popped it's compression bands which probably takes lots of force. Since my batt pack is wedged in the bike frames with only 5 mm or so of clearance, I had to use a hammer to bang the deceased pack out of there. :shock:

The pack might have semi-survived at much reduced capacity and much higher resistance if I hadn't gotten the bright spontaneous idea of applying an 8 amp discharge load to reduce cells to "safe voltage". That really got the popcorn machine popping.

Just for a larf I checked to see if there were any cells showing voltage just now. Holy Shmidt ! 18 out of 20 are showing a pretty good charge ! The two 0v cells are in the middle and above the middle cell in the worst batt. I was expecting them all to be dead. It's not dead ! It's just sleeping ! (Monty Python)

I'll have to test those cells and see how they're doing now. Increased resistance mostly important for high current discharge, so low current uses like bike lights should be fine with damaged cells/batts.

Been wondering how I'm going to cram those batts back in their cases. :mrgreen: Guess I can just remove the best cells first to "compact" them. (No I've never read the CTire warranty terms, assuming they exist somewhere; nor did I ever explicitly agree to them. :wink: )
Click to expand...

Hey

thanks for all your info; I've convinced my neighbor to purchase these batteries today; he bought 3 packs for his electric scooter. I have quite a bit battery experience when i buit my dewalt packs; i've test over 200+ dewalt cells .. oh the fun times that was.

anyways .. this is what i remember off my memory

I opened a pack fresh of the charger;

voltages reading anywhere from 4.04 - 4.07

(I really hate using chargers/bms's that comes with a battery pack like this or even like the dewalt dc9360 cells; the only electronics stuff i trust on my own batteries while testing was trusted r/c stuff; Myself i have a modded megapower sr960 with balancer (modded to get more accurate internal resistance)

I plugged this 5s pack into my balancer and charged at 1amp after charge was completed on the Yardworks charger;

1.5hours latter i check my results; 4 of the cells where at 4.2-4.23 and once showing 4.16; my charger was still trickle charging the low cell at 0.16a(it keeps trying to get them really close) but it had beeped so i took it off

My particular pack showed an internal resistance of approx 107mohms; BELIEVE it or not I got an extra approx 1500mah into the pack after using my charger; this can make quite a difference in run time on the battery

BASICLY IMO

YW charger (crap.. don't waste your time)
YW bms (again Crap don't waste your time, I had nightmares with my dewalt bms, I don't trust anything yardworks is going to include with this $109 battery; Use a 3rd party balancer for god sakes; I think a lipo blinky balancer will do a heck of a better job.

Battery testing to come...

p.s. What would you say is a safe charge rate for these cells? What it the safest discharge rate for these batteries also say for a 20s pack?
Have you found any specs on the batteries? I wish i had the battery info here with me just curious to find some info on the cells themselves.

-steveo
 
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