Zippy Flightmax / Turnigy lipo testing

[mwkeefer]

Hello all,

Just an update on the turnigys...

3S Pack #4 just went, its reading funny on the ohmmeter for internal resistance and if i push hard on the edges where the solder tabs are within the heatshrink the readings go back to semi normal. This is for sure a broken solder joint that was fine prior to use. While these are still high quality and the best value in cells I have found, I plan to open them all now and resolder the tabs properly. I have to do this anyway to a few packs to make a 10S3P configuration so it's not a big deal but... as of now, I would suggest removing the shrink and pulling the silicone pad over the PCB and ensuring good electrical and mechanical connections exist fixing where need be.

Even with this, I would still recommend these batteries and I will post an update when I determine the total number of bad joints in my 10 packs. Guess I do need aluminum flux and solder.

spike,

If you would be so kind as to post your current setup: motor type, drive type, speed controller type, desired top speed, average crusing speed, manor in which you intend to use (power only, throttle only or hybrid) and finally the range you would like to acheive.

Be as specific as possible about your motor and ESC, if you have ratings such as kV (RPM of motor per 1V input) that would be helpful. What model / type of ESC are you using or if your not sure, where did it come from.

You seem to have the right idea with the packs but to give you my best advice I (we) would need a bit more information.

If you can post these details, I will calculate a best case / worst case scenario (usign your use patterns as starting point) and then the real guru / elite on here can correct me if / where I go wrong.

Another item is budget, what are you planning to spend for the batts, chargers and power supplies.

And yes cell level discharge LVC (low voltage cutout) is important because if you develop a bad lipo cell it will prevent over discharging a single cell thereby causing potential damage. That would save your pack (if you have the LVC wired to a power cutout - ebrake connector or such).

Post what details of your intended setup you can and I will work out recommendations tonight.

-Mike

[methods]

PPS: methods - Have you ever had a lipo puff or blow while in use on bike? If so, bad lipo? Electric failure cascade, swollen packs? Did you get hurt?

Never. On a regular basis I am running my 24S2P pack and my 12S4P packs. I have shorted both of them many times at a cell level and at a pack level. There are at lest 10 pictures around here of what I call "Kentucky Fried Finger" and never a problem with the cells.

Btw: My new charging setup does cell level balancing for 12S and 24S via a GoodRum Fechter type shunt balancer. It is not finished yet though so I just charge at a pack with BM6's attached. They will start beeping at 4.25V - which - after the charging current is removed settle down to under 4.20V / pack.

I am using the power supplies below for charging. Each is good for about 1.5KW

---------------> Charger hacks



-methods

[mwkeefer]

methods -

First, thanks for confirming what I thought... most people will not have problems with lipos even with "mild" abuse, ie: KFF (Ive just begun getting my color back after connecting a final 4mm male -> female and shorting a 24AH48V SLA supply @ full charge - I really thought my finger was gonna fall off and I was just in shock).

Second, amazing setup... I recognize the powersupplies, I found them recently while searching for another commercial contract project (need more like 110-220vac -> 100v dc @ 6A, very not cheap!).

I am still working on incorporating a modular BMS (over voltage protection, undervoltage warning then shutdown trigger, etc) which will handle up to 3S @ a time but using individual 4.22V max @ 1C (5A) chargers controlled via a common arduino mini 20mhz dev board (you should see the size of this part, I couldn't hardly find it when it arrived in a box). The idea is handle the charging of the cells individually via the balance taps (5A might be too much, not sure yet) so that I don't need to buck up the voltage to match a particular series count of cells. By incorporating a warning indicator (line drawn high +5v) a simple loom (or flat Cat5 cables, IDE cables, etc) cab be used to run signal wiring to an LED display or, in my particular case ... the arduino is already driving a very nice color LCD screen (cell phone type) which means I can use commonly available open source libs to generate the needed graphics to represent the physical connected pack and which cell has a warning. Now I only need to send back a device id (to assign to each cell in pack) and a reading over a serial bus (2 wire), if I go 3 wire I could then address the device and tell it to cutout or reduce current, etc. At which point the controller will automatically reconfigure for instance if your running 12S and the controller is notified of a failed cell it will essentially remove the cell from the pack and change the pack cutout voltage accordingly.

Too much info about a totally un-related issue. I haven't pulled the pack apart yet, I am busy with my other pack charging and balancing while logging (this is cycle 9 for this pack) and I want to have this data (internal resistance, charge capacity, discharge capacity, temperature chages, discharge temperatures) all at a cell level for cycle 10 which will be the basis for my "official" and technical review of the packs.

Then I am going to dissassemble the packs and reconfigure into 4 x 1P5S @ 5AH packs which will be connected for discharge in 2P10S @ 10AH. The other packs I am planning will be 4x 1P2S which will be wired into 2P2S configuration for discharge then run in Series with the main 10AH 10S pack.

I have already begun designing a solid state switching system( I guess it would qualify as a Solid State Relay array) to handle switching the packs into charge mode and disconnecting the packs from each other when not in use.

This makes my charger design much simpler as I can simply daisy chain these boards together on a serial bus and provide individual LVC/HVC/LVC Warning for such a large pack at the individual cell level.

Just so you know, my Maximum current draw (at 10S) would be 87A but I don't expect to go that high, more like 70-75 which is perfect for cheap FETS without even paralleling = )

-Mike

[spike]

spike,

If you would be so kind as to post your current setup: motor type, drive type, speed controller type, desired top speed, average crusing speed, manor in which you intend to use (power only, throttle only or hybrid) and finally the range you would like to acheive. Be as specific as possible about your motor and ESC, if you have ratings such as kV (RPM of motor per 1V input) that would be helpful. What model / type of ESC are you using or if your not sure, where did it come from. Another item is budget, what are you planning to spend for the batts, chargers and power supplies. And yes cell level discharge LVC (low voltage cutout) is important because if you develop a bad lipo cell it will prevent over discharging a single cell thereby causing potential damage. That would save your pack (if you have the LVC wired to a power cutout - ebrake connector or such). Post what details of your intended setup you can and I will work out recommendations tonight. -Mike

Hi Mike. Many thanks for the help.

I'm holding off using the RC motors/ESCs for ebike builds until I see what develops. That will probably be the next step. The lipo packs will start on a Hi-Koll/USPD setup on a 27" touring bike. The controller is a Crystalyte 36/72V 45/A controller (analogue not digital). According to EVDeals the Koll motor runs at 3730RPM at 48V/883Watts, but that gets geared down to a wheel speed of ~45Km/hr. I think 72V would be too much for the Koll motor which is why my target is between 60-70V. The bike will be used for commuting a 20Km round trip in busy traffic. I want to keep it light with good torque and acceleration from the lights. Keeping up with the traffic would be useful. The limit is 60Km/hr in built up areas. I can charge the batteries at work if necessary so high Ah won't be necessary. I can just peddle harder if the batts drain down. I had figured on spending around $600 to get started with packs/chargers/monitors, but could spend a bit more if that's unrealistic. Cheers!

[liveforphysics]

If you are going to make your own charging/balance setup, don't set it for 4.2v. Set it for 4.125v peak. Yes, you sacrifice 10% of the potential to store energy. However, your number of life cycles extends by about 10x (yes, 10 times the cycles) according to most manufactures cell life graphs.

Charging from a switching power supply works fantastic. They do the perfect CC/CV curve ideal for charging LiPo.

LiPos are really not a hazard when shorted. A proper LiPo battery is designed to harmlessly vaporize it's cell tab in the event of a serious short, and it vaporizes that tab well before the cell even gets warm. The packs are designed like this so it's as if each cell has its own fuse protection built into the pack design.

I run a 20s, and I made the packs in 20Ah 10s cell groups. I run these cell groups 2s 2p if I want a 74v 40Ah pack, or 2s1p if I want a lighter weight 74v20Ah pack. When I charge, I split the pack into 10s sections if I'm going to balance, or I leave it 20s if I'm not going to balance. My cells never go out of balance, so I generally just charge as a 20s pack.

I set the charger for 82.5v. This brings each cell to ~4.125v.

There are a couple things to be careful about with LiPo. If you over discharge a cell, it's damaged. It will have higher Ri, and it's a hazard to have in your pack the next time you charge. You are not in any danger as you are over discharging, it's when you go to recharge again that you are taking the risk of fire. The second is to not let cells go over 4.3v. Yes, you can generally raise a cell to 4.5v-4.8v before it starts to vent, but exceeding 4.3 is when you begin to damage the cell, and you are risking a venting event.

I think a potentially slick and simple and reliable way to deal with LiPo would be 5w 4.2v zener diodes with a 0.1ohm resistor in series across each cell. Then set your power supply to only charge to 4.125v/cell average, and if a cell were to get out of balance for some reason, the zener would clamp it at 4.2v during charging. You could very easily build this tiny cell level over-charge protection right into the pack.

I just did a quicky search on digikey, and found some 5w 4.3v zeners for $0.14/diode. They have an excellent temp/v change curve of about -0.4mV/degC. So, even if your pack got 40defC above room temp during charging, it would LOWER the clamping voltage by ~16mV, which would actually just make things slightly more safe I supose. lol. 10uA leakage current at 1v, does not list a spec for 4.1v leakage current. I would take a wild guess it might be around 100-2,000uA at 4.1v. That would mean it would be safe to stay on a 5Ah cell for months (maybe years) with out leakage current being a danger to draining the cell. It would be a good idea to disconnect it if you were going to store your pack for months, but that's not much of a hassle or concern for most folks.

Unless there is some critical flaw that I've missed seeing, it seems like you could setup indivual cell level over-charge protection for a pack for about $5 in parts.

Does someone see a flaw in my logic here? Any critical flaw that makes it a poor choice to use a simple zener clamp for cell protection? If the 2Ohm impedence seems too high, or 5w limit too low, it would be easy enough to connect 4 or 8 in P, and get that down to 0.5Ohm-0.25Ohms with a 20-40w limit. They are only $0.14 each from rip-off-key, so I'm sure I could do a 1,000 quanity buy on them for like $0.05 each from a real parts supplier.

[ZapPat]

Luke - This is from the diode's datasheet. To me, it looks like the current will be too high even before even hitting 4V. Too bad, as a zener with a very steep curve would have been a nice simple fault protection.

Zener I vs V.jpg

Zener I vs V - The 4.3V one is the fourth curve from the left.

(99.08 KiB) Downloaded 895 times

The chargery BM6's that Methods uses are great little gadgets, and pretty cheap at 13$ per 6 cells. You just have to be in earshot to disconnect the bulk charger if something weird happens. They also have a programmable LVC, so can also be used for discharge protection.

Another great thing about the BM6 vs other RC multi-cell monitors is that it doesn't seem to draw it's power from only the first two cells. This is important if you leave them on the battery for long periods, since the BM6 will not bring your cells into a more and more unbalanced state with use. All the others I've seen will drain maybe ~6mA or so from the two first cells - not much, but a pain nonetheless since it will end up being the biggest cause of cell disbalance in these high-C rate LiPo packs.

Pat

[Jeremy Harris]

Just as an aside, I'm currently working on a LiPo charger, using the same sort of system that Doc came up with for charging LiFePO4 cells. I've found some switch mode DC-DC converters that have a 3.3V and 1.2V output, electrically isolated from the input. The output voltage is trimmable by +/- 10%, which will allow me to trim the series linked outputs between 4.05 and 4.95 volts. These things put out 15 amps, so are only really suitable for high charge rate LiPo cells.

If I trim them for 4.125V per cell then I think I should have a pretty robust high power charger, at a cost way under that of one of the dedicated RC Lipo chargers.

Jeremy

[liveforphysics]

That sounds great Jeremy! What input voltage do they take? Any ideas of the efficiency?

What are the physical dimensions, a rough idea of cost?

Thanks!
-Luke

[methods]

The biggest problem I see with parallel charging is that you need to get to each cell....
You cant push 15A through a JST-XH connector rated for 3A so that means you have to cut into your lipo packs and (in the case of a 24S pack) bring out 25 14awg wires.
Then you need a connector suitable for passing 15A.

Sounds like a lot of work if you have mountains of Lipos.

My vote is for charging off of a regular old power supply and using a shunt type balance like the GGoodrum / Fechter board.
I have my issues with that board but I like it in principle because you can mix and match very easy.

I use power supplies that have "modules" so I can match them up in parallel and run 15A or 20A or I can even pair up supplies and run 40A.
Hypothetically limitless.

How small are those 15A supplies you are using?
Could I put 24 of them on the bike? If I could - that would be a big advantage over my 1/2 shoebox size supplies.

-methods

[Jeremy Harris]

The modules are Power One, 1/4 brick ones, so are quite small, see eBay 160350956570 or the Power One data sheet attached. They run from a 36V input, which happens to be fine for me because I have a big 36V switched mode supply I can use to power them.

I agree, the cells may need to have the balance wires beefed up for 15 amps per cell, but if I have quite a few cells paralleled up via the balance connectors I'm hoping that things should even out, allowing the standard wires to be used.

Jeremy

[methods]

but if I have quite a few cells paralleled up via the balance connectors I'm hoping that things should even out, allowing the standard wires to be used.

Jeremy

ahhhh.... I did not think of this.
Good point.

-methods

[mikehains]

A very informative, excellent thread. Hopefully the right one for me to make my first post.

The good news - based on my lurking research here, my 9 x 5000maH 5S Turnigy packs turned up yesterday from Hobby City. 8 of them perfectly balanced. One not so good, with one cell around 100mV low. That has since been ironed out by the 1010B+ charger (also purchased after carefully reading these forums).

I am going to run them 10S4P for a nominal 36v system, and charge them 10S4P with the 1010B+ charger ... balance leads in parallel.

Here's my big question: Can the balance leads stay in parallel when they are in use on the Kart ?

I have 2 x Chargery BM6 (after reading posts from Methods) which are excellent. Given that the pack is 4P, these devices will be enough if the balance leads stay in parallel while the pack is in use.


Thanks in advance,
Mike

[mwkeefer]

Mike,

If I understood correctly you are running 10S but have 4 of them for 4P10S. Currently charging all 4 packs of 10s on the 1010B+ with the balancers in parallel same as discharge of each 10S pack.

If that is correct then yes you can leave (and should) that configuration while discharging also.

If you wired your packs the correct way from scratch (assuming 4P10S not 10S4P there is a difference) then you would first parallel each 4 individual cells (totalling 40 cells) then connect them all in series. In this instance you would add a balance tap at +, - and on each cell inbetween. Basically you would still have 10 taps and they would be wired in at the paralleled cell level.

Your setup is perfect for the balance charging taps and good enough for the discharge side too. The proper way would have been to do 4 cells in parallel, make 10 packs like that @ 3.7 nom ea 20AH then connect 10 of them in series for 12S 20AH. That type of build would be referred to as 4P20S.

Your pack is correctly configured to charge as a 4P20S since they will both tap the same place, I would stick with no more than 1C charge rate to keep the life of your packs (cycles) higher.

It would be better for a discharge perspective if the output termination was based on these 4cell parallel segments but unless you going to move past the rated value (4x20C=80C*5 = 400 Amps Nominal (4P) and max would be 4 x 30C = 120C * 5 = 600 Amps for 15 Seconds.

You have a very nice pack there, now if you have a sufficient power supply that can push over 16.5v and 30-40A continuous... you have a perfect charging system with your 1010B+ (check the post about the power supply onsale for 17.00 at microcenter, quality dual fan unit. Fits nice with charger in trunk on rear rack for my bike.

If your not sure about the top end speed of 10S, you could always make a similar pack of 2S4P and wire in series to make a 12S supply (or 3S, 4S). For testing... use a single 10S 5AH pack and series with single 5AH 2S, 3S, etc. No they wont go more than a few miles (10 or so) at a nominal draw of 30A peaks of 40 but that is fine for an evaluation run.)


Hope it helps!

-Mike

[mwkeefer]

Mike,

Don't know why I didn't think this sooner but the 1010B+ is max charge rate of 10A which I think drops to 7A for 10S, the limit is the voltage buck up and the components themselves and it is right around 300 watts so.

10S Max V required for Charge: 42.4v DC
300 Watts Potential / 42.4v = 7.07 A

lets be nice and assume 100% efficiency and ample DC power to operate the conversion (above 13.5v)

10S4P Capacity = 20AH

7 / 20 = 2.86 Hours or 2 hours 50 minutes (approx) to acheive full charge from empty.

Just as long as your satisfied with the 7A limit always (forget fast charge, you still can't push more than 7A when in 10S mode) this is actually a great setup.

3 Hours Charge Time is nothing compared to my 6 hour Segway charges and you have room to upgrade, modify and play if you want.

An additional item worth mentioning is that you can leave the 10S paralleled tap connected to your 1010B+ set to monitor mode to view realtime cell cluster information and log battery drain, etc using the LogView software so it really is a nice setup.

The slower charging will result in longer battery life. Also, set the lipo charge cutoff @ 4.18 as suggested earlier in the forum, this will greatly increase your packs longevity also.

The only real problem I see to using the parallel balance tap (not for your application, for mine) is that having 3 good cells and 1 dead or dying in the cluster of 4 and the 3 good ones will mask the failure cell. My intent is to monitor each individual cell (in your case that would be 40 monitor leads and analog to digital conversion. My final config will also be 10S but wired as 4P10S and tapped per cell not per cluster. Charging will be handled by dual 1010B+ chargers running off a 750 waltt modified PC power supply (portable) and charged in non balance mode without plugs most of the time but using the paralleled method to charge 2 of the 10S packs per charger (1.5 hr full charge)

This will all be replaced once my pre-controller is working with it's own charger = )

-Mike

[mwkeefer]

10S4P Lipo Nominal 37v or 3.7v per cell
Manu Spec Max Charge: 4.20v per cell or 42v
Suggested Max Charge Cutout: 41.5-41.8 - 4.18-4.15 (should extend the life of your packs)
Maximum Low voltage cutout: 30v or 3.0v per cell
Suggested Low Voltage Cutout: 31-32v or 3.1-3.2v per cell

[methods]

I am a bad, bad, man...

I just bought 4 more of the 6S 5000mah 20C packs
They are only $60 !!!!!!!!!!! WTF?

I did it completely on the whim... One minute I was downloading wedding songs and the next minute I was entering my PayPal info on Hobby City

I am going to string those into my 24S 2P pack to make a 24S 3P pack

88.8V 15Ah is one hell of a pack.....

I also picked up 23 more 6S JST-XH 12" balance tap extenders for building stuff.

I hit the 4KG mark right on the spot for the best shipping compromise of price and speed.

-methods

[Hyena]

2 days ago I ordered another 3 of the 5S 5ah packs too.
If all 3 work (got a pack with a dud cell last time ) I'll be able to run 20S2P for a 74/84v 10ah pack

Although the plan is still to build a new bike with the new golden motor magic pie hub and 60v 15s pack

If I get another dud I'll scream the house down. I packaged up my last bad pack to return only to get rejected at the post office because under new laws they will no longer ship anything with lithium in it, not even phone batteries
Had I have known they weren't psychic when they asked if I had lithium batteries in the packet I would have lied...
Ah well, I guess I'd then risk it getting bounced at customs. I suppose I'll salvage the working 4 cells to power my lights or something

[Ypedal]

Lipo Sluts !

[mwkeefer]

I have to agree with ypedal (on more than just the lipo sluts comment)... seriously methods my man, do we need to hold an intervention? As I understand it there is a 12 S, I mean 12 Step Program for this problem... you are not alone = )

Sorry for the humor, just finished a day from HE**... I would get into it but it's so damn confusing that I'm not sure I can even recount it (and I lived it).

Update:
No response from Hobby King yet in regards to:
1.) Loose solder joints (easily fixed)
2.) Broken solder tabs (not easily fixed, but fixable)
3.) One further issue which I won't discuss openly until I hear back from them with regards to an engineering issue (nothing that should affect our use of the packs)

I would also like to give some more info about the packs (mine are all 3S 5A 20/30C) design and engineering and ask that if anyone else can measure and report if they have similar findings...

I was looking at the charts of my battery packs individual cell impedances and noticed an odd trend, on 6 of my packs (some are broken right now, some are just not tested yet) the cells have up to a 3 mohm impedance while others (most) have between 0-2 mohm. All the packs live up to the 4mohm claim so there is no problem there. The potential problem is their distribution within the individual packs, for example ... 1 pack I have measures cell 1 as 0 mohm, cell 2 as 3mohm and cell 3 as 1mohm = 4mohm. By putting the cell with the highest internal impedance in the middle position they have eliminated 80-85% of the cooling area. At the same time they sink the added heat of the higher impedance cell into cells 1 and 3 thereby heating them without cause.

If they put the higher impedance cells at the outside of these packs they would have nearly 50% more surface area exposed to dissappate heat. This would result in lower overall pack and individual cell temperatures and as a direct result, longer pack life.

My question is: Can someone else check this with the 5S and 6S packs to see if this is coincidental or more standard of their assembly process?

Thanks in advance!

- Mike

[liveforphysics]

Mike-

You can't take any Ri measurements on LiPo cells seriously until you've got at least 10cycles on them.

They will often read all over the place, then once cycled a few times, Ri and voltages all settle out pretty consistantly, unless you have a bad cell. Never judge a cell until it's been cycled a number of times though. Your higher Ri cells might become your lowest Ri cells.

Capacity always increases as well. I find a 5Ah zippy/hobbycity cell might have 5,500mAh on it's first 1-2 cycles, and by cycle 15, it's getting a full 6Ah, and I'm not using any different HVC/LVC on the testing.

Since you have a 1010b (very nice choice in charger), set that sucker to cycle mode, throw everything in a big clay pot on your back porch (or somewhere else safe) and set it to run 20cycles, and forget about it. In a day or two when it's finished, swap new packs onto it, and set it to 20x cycles again. Remember to disable the auto-time-off thing, so it doesn't time-out before it gets all 20cycles done. I also set it for fairly shallow cycles, like 4.1v-3.3v, it takes less time, and the cells still get broken-in just fine.

Best Wishes,
-Luke

PS: I am also a LiPo slut. I have around 80 LiPo packs, and I'm around the $13,000usd spent at hobbycity point... RC helicopters and planes are worse than a drug habit.

[mwkeefer]

Luke,

Thanks for the info... I had already determined that lipo needed to be properly cycled 5-10 times before they develop stable characteristics. I have cycled in the manor your mentioned (I used my oven then, it is flame proof) each of the 4 3S packs 8 times before first use on eBike.

I would be doing the same with my other cells to make a 10AH pack (I think the added capacity will make all the difference when presented with 35-40A continuous max) but since 3 of my HK cells are beyond repair (2 broken weld tabs, 1 with a problem I dont even want to mention until I hear back from HK) I can't build my 10AH pack (or my 10S 15AH which is my final power configuration for my lightweight and ultra powered (4+ hp) ebike.

Sadest part is, my company was looking to HK as a vendor for lipo packs (large quantities 200-800 packs at a time, and you guys think your lipo sluts... lol) with 3/10 unusable and 5/10 which had to be repaired (solder tabs came off durring shipping I suppose but packaging was not damaged, eh) and they haven't responded to my emails yet... well, for the company purposes I think the packs would be perfect (if 1/2 didn't require resolder on arrival) even without the cycling they deliver their rated power and then some so they fit the bill... I can tell you they only puff when overcharged, no heat, no flame though I wouldn't want to breathe whatever its venting but I did deliberately overcharge (V and A) one pack just to see what would happen, I was surprised at the lack luster nature of the event.

I don't think we can use them as suppliers though based on their recent shipping issues, response delay and quality control but if they atleast make good on the 3 unuseable packs they sent me... I will continue to order their cells for my own personal uses.

Again thanks for all the info, nice to have expert confirmation = )

-Mike

[Hyena]

Sadly I dont think we can expect much out of hobbycity in terms of warranty without alot more expense on our part for return shipping. They claim to replace and resend a lipo pack that's faulty on arrival, but only after you fork out another $30 odd on return shipping to China. I even offered to video testing each cell voltage, and showing the BM6 alarming and showing the dud cell, but they weren't interested. Return it or nothing. And if you've tried to repair it then don't even waste your time on return shipping because they won't take responsibilty.

Reading on other forums a few people have received packs with one more more cells wired with the polarity backwards. They claim to test all their batteries before shipping but clearly this isn't the case. Yeah ok the cheaply made tabs could break during shipping, but there's absolutely no way they've done any sort of checking/ quality control if they're sending out packs with cells wired in backwards.

[liveforphysics]

It seems you guys have terrible luck, or HC goes out of there way to test every pack they send me, and they always have loads of protection in the shipping boxes.

I might just be on a perfered customer list or something, but the few times I've had issues with various RC parts, I've just sent an email, told them what I wasn't happy with, and they said they would send out a new one to me later that day.

About 3 years ago, everything they sold was offered with free replacement and they covered shipping, you just had to tell them something was bad/broken. I think perhaps people abused this system to the point that they have to demand things to be sent back to avoid fraud warentee claims.

[Ypedal]

Next time i order from there i'm making a video of me opening the box and testing each cell on the spot ! ( may or may not help with warranty, but i'm sure if these start to show up on youtube they may take notice !! )

[GGoodrum]

Luke -- You are truly the centerpiece in a bouquet of LiPo sluts... Even Patrick is a "slut-in-training", in comparison.

-- Gary