My first puffer - 200 cycle 4s hardcase review

[auraslip]

Ok, these packs have ~200 cycles at 5c max 1.5c normal. Charged to 4.15v - discharged no lower than 3v and typically to 70% DOD. Never abused to my knowledge.

I pulled these out of my bike with it's enclosed battery box after riding for 6 months. I DID NOT NOTICE IT WAS PUFFED UNTIL THE NEXT DAY. So either it was puffed and I didn't see it until I went to unwrap the tape wrap, or I did something to it when I put it in the storage closet that caused it to puff. At first I was thinking I was 99% sure it wasn't puffed when I took it out, but now I'm only 50% sure.

Battery was removed at ~4v. All cells still roughly balanced at ~4v

What to do with it?

Also, I'm gonna do a capacity test on the 7 other non-puffed 4s packs in the next few days. I'll post info in here.

fyi pack is 22s10ah with 4s packs and 6s packs.

 

[neptronix]

Highly bogus.
I'm curious.. did you capacity test all these packs before using them? Did you number them or make any notes.. if so.. was this one kind of a runt to begin with in any way?

Or were these all perfect shining specimens of what a RC Lipo pack should be, and this one just went sour?

Also, did you charge them at 1C and make sure regen doesn't go over 1C?

If so i don't know what to tell you and that makes me nervous if you treated them totally perfectly and there was not any obvious problem with that pack to begin with.

Well, you know me i never recommend taking any risks with lipo. Some would tell you to pop the cell and keep using it, but smokey the lipo bear says no here. Put this one aside and use it as a spare cell pack, i say.

 

[ZOMGVTEK]

That guy puffed really good. I'd vote for a cell replacement if it was just one cell affected. It's not worth using a cell in that kind of questionable condition. After you remove the affected cell, poke it with a stick in a parking lot and run away screaming. That's how I get rid of bad cells.

I'm also curious as to if you have a new capacity/discharge profile for that pack.

And, I just realized my regen is 3C. Guess its not the best idea to hold onto the back of a car at 50 and hold regen to recharge the bike.

 

[liveforphysics]

Contamination in mfg.

 

[neptronix]

And, I just realized my regen is 3C. Guess its not the best idea to hold onto the back of a car at 50 and hold regen to recharge the bike.

LOL...... do it yourself hybrid?

I bet a lot of people are running regen higher than their batteries can tolerate.
I ended up having to set my EBS limit to '0', which gave me 10 amps in on my magic pie on an EB3 18FET. ( or 'mark 2' in the lyen controller world )

 

[auraslip]

FOR THE LAST TIME EVER:

BATTERIES CAN SAFELY TAKE HUGE PULSES OF POWER FOR SHORT AMOUNTS OF TIME.

HIGH C REGEN IS ABSOLUTELY FINE IN SHORT BURSTS



sorry don't want anyone to miss this point

 

[neptronix]

Actually below 10% SOC, even 1C is hard on a battery rated for 1C. Internal resistance exponentially grows below 3.4v/cell on these RC Lipos for example.

I know you live in Texas, but in other parts of the world you may be descending down a multi-mile long hill with the regen on.. on default settings that is 2C for some battery packs. On my testing hill, it's 7% average grade down for 3 miles. I'll be regenning down that hill the entire time.

Always good to add a margin of safety to every setup so you don't blow shit up anyway.

 

[neptronix]

Suppose i shouldn't have mentioned it since you lived in flatland, usa though

 

[ZOMGVTEK]

BATTERIES CAN SAFELY TAKE HUGE PULSES OF POWER FOR SHORT AMOUNTS OF TIME.

HIGH C REGEN IS ABSOLUTELY FINE IN SHORT BURSTS

Don't worry, brief periods of 3C charging does not concern me. I bulk charge unattended at 2C with nothing monitoring the balance taps, never balance, and my charger is connected to an extension cord that gets mushy after 20 minutes of 2,200W draw.

Worst case is the bike burns a bit. The motor and controller are away from the batteries, the rest of the bike is a $150 Walmart POS. It would be a good excuse to get some snazzy new batteries.

 

[auraslip]

Here is the discharge graph done when the pack had 3-4 cycles on it. Here is a bigger version -> http://i.imgur.com/O7z2s.gif

Cell 3 looks bad, but all packs delivered 5ah. I think the puffed cell is on the outside so it must be cell one or cell four.

 

[neptronix]

Hm, if cell 4 puffed up, that would be odd. That's a weak cell, but not TOO bad.

A weakling over 200 cycles will be pushed harder over it's lifespan. I am surprised that one took 200 cycles. You got off easy

I think that you saw it puff after you unwrapped the tape because the tape was holding the pressure in, and the cell deformed in some other way ( like, sideways ) then became a 'case burster' once you let it hang loose. Maybe next time around you should tape the packs together a little loosely so that you see this warning sign sooner, just an idea.

The puffing gives you a visual warning before mayhem occurs. This is one of the things i like about pouch cells actually.

 

[liveforphysics]

If you were feeling daring, you could follow Aussie-jester's guide for de-puffing, and then post a follow-up graph of the performance afterwards.

 

[auraslip]

I think that you saw it puff after you unwrapped the tape because the tape was holding the pressure in,

I actually unwrapped it once I saw the cell puffing out. Like, "aw gawd dammit."

Here is how I have them wrapped. Color coded just for fun.

I'm testing one of the 2p groups right now. Should be done in a bit.

If you were feeling daring, you could follow Aussie-jester's guide for de-puffing, and then post a follow-up graph of the performance afterwards.

if it's for science, i'll do it.

It might be a bit cause this is almost done, and I'm busy getting it on the road

I can fit a lot of batteries in there. and a charger. and a large HV dc-dc. and probably my cat too.

 

[neptronix]

Holy sh.. you are gonna have the mega tourer i had always dreamed of. Right on!!

 

[John in CR]

The top cell if calling the short portion of the hardcase the top is the same cell that lit up on my pack. It looks like maybe you got lucky too. The other 14 of my packs are fine. I use LFP's method to prevent puffing...compression by electrical tape. I don't have a lot of cycles on mine, but I'm hammering them at 20C discharge and 5-7C regen currents in 3-5 second bursts. DOD is very conservative as is my bulk charge rate.

My test method is quite a bit different from Neptronix's....Mine is to verify balance upon receipt. Then store packs in a safe place with enough distance between packs to ensure there's no chain reaction. Wait for over a month until one cell flames out. Wait a few more months to be sure no others decide to go thermal. Run the packs for a handful of non-stressful cycles bulk charging only. Check for balance and note any lagging cells on the pack itself. Balance charge to 4V (a little extra pressure compared to the normal storage charge to help weed out problem cells). Store in a place that can handle flaming lipo for 9 more months. Check for balance. Use a few cycles and check for balance again. If all seems well then put the cells into packs.

The above method is every bit as valid as Neptronix's method for weeding out bad cells. The problem Neptronix doesn't get is that people are almost as likely to do what I did as they are to perfectly follow the routine Neptronix recommends. It's a lot like the glued on torque arms idea. RC Lipo and glued on torque arms can never be fully trusted even after following exact instructions, and most won't follow the instructions to a T anyway. it's "bogus" to think everyone will.

John

 

[auraslip]

lol john, you never fail to make me crack up. your testing method is more like hoarding. :lol:

 

[John in CR]

lol john, you never fail to make me crack up. your testing method is more like hoarding. :lol:

LOL, I hoard just about everything ebike related except RC Lipo, but I haven't bought any more batteries at all since those $.25/wh 4s hardpacks, which are coming in handy with The Sheriff. I hope to finish the head tube pack tomorrow to go from 10ah to 20ah. Then I'll feel better to explore higher power. 10kw was fun, but 15kw is , and it's none of this peak amps tapering off in the first tire revolution. On launch current doesn't start tapering off until above 40mph. High Kv hubbies in sub 20" wheels are the bomb.

John

 

[auraslip]

Got some capacity testing done today:

RED: 8.15ah
GREEN: 8.17ah
YELLOW: 8.57ah
ORANGE: 8.37ah

Testing done as follows:

Balance charge to 4.2v
Set cell-log alarm port to trigger relay at 3v
discharge with 2 50w light bulbs in parallel

Discharging to 3v means the lowest cell usually rises back up to 3.2v or so when done. I don't feel bad about the wasted capacity when compared to going to 2.7v as the packs are already getting quite warm at this point. Nominal discharge rate is around 7a, so less than 1c.

So, wtf is up with this? 200 cycles and 80% capacity? Does this mean hobby king should be rating their packs at 200 cycles because most cells are rated as # of cycles until 80% capacity.

ALSO, weird - the orange group is the drop in replacement I had sitting on my shelf. The packs have been sitting at 4v since last October. Only a few cycles on them. And yet they fair worse than the USED yellow group packs? I'm thinking maybe my GT power amp meter may be out of whack. I'll try one more discharge with the Icharger to see how closely it lines up.

 

[neptronix]

I found my turnigy watt meter ( your gt power meter is a clone of it ) to be off by 10% according to the iCharger.

 

[ZOMGVTEK]

My iCharger @ 10A is measured closer to 10.46xA, which I consider to be quite substantial. The Turnigy meter was actually closer, but still off a few percent. The voltage on my Turnigy was way off, and lower currents/voltages on the Turnigy meter are very inaccurate.

The voltage on my iCharger was within .005V on every channel, so thats great.

200 cycles is quite a few for cheap LiPo. 80% capacity isnt that bad. The capacity loss from here should be reduced. Cycle life is affected by quite a few factors, and its not like Hobby King has a very sound rating system. They say 5C charge on the 4S packs, when they say 2C on most every other 20C Turnigy cell.

My laptop is rated for 1,000 cycles to 80% capacity IIRC, and its at 92% capacity and 164 cycles. I'm not terribly sure it will only loose 12% after 846 more cycles.

 

[auraslip]

Just did the Icharger discharge with the yellow group at 1a. It reported 10.8ah down to 3.3v.