Zippy 20C LiPo after 10 months

[ZOMGVTEK]

I'm cycling my packs before I put them on my new bike. Most every 6S 5AH Turnigy 20C is giving me 4.7AH from 4.15V-3.5V. One cell ended up at 4.1AH and has been replaced, but the rest are fine. Probably 50+ cycles on it, lots of 1.5C bulk charging, minimal balancing, quite substantial monitoring. The cells average 3-4 mOhm internal resistance, which is roughly 1mOhm higher than fresh cells.

What's really interesting, is that my bother built his pack the same time I did, probably has <10 cycles on it, but has less capacity. He never monitors it, never balanced it, and stores it at whatever SOC it was at when he was done with it. I just started cycling his packs, and so far 4 of them were evenly discharged down to 4.5Ah. Very few cycles, no bad cells, all with 2-3mOhm internal resistance, but lower capacity than my 'used' cells. One of his packs even had a REALLY weak cell that showed 17mOhm resistance! I'm guessing the remaining packs will show more issues.

The difference? I bulk charge my pack before use, putting only enough energy in so that I come back home around 3.85V/cell. Stored mostly around 3.8-3.9V/cell and generally shallow discharges. My brother had his bike sit in the shed over winter, at 100% SOC, when ambients were below freezing.

http://www.youtube.com/watch?v=OoiSIlL6 ... e=youtu.be
I thought it was interesting that the one 'bad' cell in this pack was binned as lower capacity from the factory. Are most common failures due to these lower capacity cells?

[auraslip]

And ya'll mocked me and told me I was a jack ass when I did that old "life cycle comparison between lifepo4 and lipo" thread. TL;DR lipo won't last long and is dangerous. Now a year and a half later we have had a few ebike fires and the premature deaths of lipo packs.

I'm excited to see how my 48v20ah ping with 10,000 miles on it will do when I take my old bike apart and capacity test it.

That being said, I'm not going back to lifepo4. I mean, I have been thinking maybe the high c-rate headways might be good despite being 10lbs heavier, but they're still too damn expensive.

[voicecoils]

That being said, I'm not going back to lifepo4. I mean, I have been thinking maybe the high c-rate headways might be good despite being 10lbs heavier, but they're still too damn expensive.

Dude... why even mention headways? The 20Ah A123 pouches are pretty much the only LiFe option worth being excited about.

Otherwise RC pack LiCo is still the only other game in town for DIY high current ebike fun.

[o00scorpion00o]

A123's are too expensive.

I have pretty much abused my lipo running a lot in 1p, if I rand them in 2P all the time I would probably get a lot longer out of them. But the 20C Zippy batteries are very over rated and more like 8C but in 2P they are great and don't get hot at all.

I don't care about a 1000 cycle battery that would take me years to make use of, the most important thing for me is weight and compact dimensions and high C, I like to pedal a lot so I need the lightest and most compact battery that will give me the boos I need for cycling or the thrill of full throttle for fun! yeah the bmsbattery NMC stuff is probably the most compact and weighs less than anything else we can get, but the c rate is shit.

If I was commuting then the ping battery or bms battery 20ah packs would probably make the most sense. Or the higher c rate like the A123, but they are very expensive!

[cwah]

Actually I think the new zippy compact weight less than the NMC from bmsbattery. It's more expensive than the standard zippy but still good value. these one may worth a try

[voicecoils]

A123's are too expensive.

I have pretty much abused my lipo running a lot in 1p, if I rand them in 2P all the time I would probably get a lot longer out of them. But the 20C Zippy batteries are very over rated and more like 8C but in 2P they are great and don't get hot at all.

I don't care about a 1000 cycle battery that would take me years to make use of, the most important thing for me is weight and compact dimensions and high C, I like to pedal a lot so I need the lightest and most compact battery that will give me the boos I need for cycling or the thrill of full throttle for fun! yeah the bmsbattery NMC stuff is probably the most compact and weighs less than anything else we can get, but the c rate is shit.

If I was commuting then the ping battery or bms battery 20ah packs would probably make the most sense. Or the higher c rate like the A123, but they are very expensive!

Actually, people have recently been buying A123 20Ah cells for $20-25 each incl shipping. That's US$0.30-0.38/watt-hour which is a fantastic deal. Most Hobbyking lipo packs in the 20-30C rating range are US$0.30-0.50/watt-hour before shipping. Terminating the A123 pouch cells is more effort for the moment, but some people are working on kits and methods to simplify. HK lipo packs are more plug and play, but you typically need 4 cells in parallel to equal 1 A123 20Ah cell. That's a lot more cells and connections to manage and potential for something to fail (even if unlikely).

[auraslip]

Dude... why even mention headways? The 20Ah A123 pouches are pretty much the only LiFe option worth being excited about.

PITA to terminate. Questionable QC. The high c-rate headways are supposedly on par with a123.

[voicecoils]

Dude... why even mention headways? The 20Ah A123 pouches are pretty much the only LiFe option worth being excited about.

PITA to terminate. Questionable QC. The high c-rate headways are supposedly on par with a123.

ZZZzzzz... the poor packing density of those cylindrical cells is making me sleepy.

I guess you mean http://www.greencarreports.com/news/1074491_a123-systems-to-recall-electric-car-battery-packs-for-fisker-others when you talk about 'questionable QC'. Lucky for them it only degraded performance, not safety.

I've only had first hand experience with the Korean made A123 pouch cells and they've been rock solid.

[auraslip]

I know what you're saying, but I'm reading through the threads where people use the pouches and I'm thinking to myself, "they're spending as much money terminating these damn cells as they are on the cells themselves!"

[voicecoils]

Could you just test at 5C from 4.15 to 3.3V? I'm trying to see what's the maximum capacity I can get from lipo.

I'd use them for daily commuting, no need to pump super high C. Thanks for that

Zippy 5C 25A discharge.JPG

(89.79 KiB) Downloaded 2 times

There you go, the cells are rated for 18.5v5Ah = 92.5 Wh new.

85.2Wh between 4.15v to 3.3v They're still doing pretty well!

There's little to gain by going below 3.5v on my cells, judging by the discharge test.

[cwah]

92% of initial capacity remaining after 2.5 years?? That is sooooo goood. And much better than NMC or LiMn2o4 that have poor calendar life.

That means that lipo has very good calendar life. Not sure with the cycles as you only have 50... but that's really great.

I think I'm going to get the Zippy compact very shortly

[o00scorpion00o]

I don't think anyone knows the calendar life of NMC yet ? I would have thought it would be a fairly long time!

[cwah]

Few data from Battery University:
http://batteryuniversity.com/learn/arti ... hemistries

Lithium Cobalt Oxide (LiCoO2):


Lithium Manganese Oxide (LiMn2O4):


Lithium Iron Phosphate (LiFePO4):


Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2):


Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2):


Lithium Titanate (Li4Ti5O12):


Wh/kg comparison:



Not sure to which one of these charts belongs the lipo, but you can see clearly that NMC lifespan is shorter than Lifepo4 although higher than LiMn2O4.

[o00scorpion00o]

Few data from Battery University:
http://batteryuniversity.com/learn/arti ... hemistries

Lithium Cobalt Oxide (LiCoO2):


Lithium Manganese Oxide (LiMn2O4):


Lithium Iron Phosphate (LiFePO4):


Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2):


Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2):


Lithium Titanate (Li4Ti5O12):


Wh/kg comparison:



Not sure to which one of these charts belongs the lipo, but you can see clearly that NMC lifespan is shorter than Lifepo4 although higher than LiMn2O4.

Thanks for that.

I wonder how long in real life conditions NMC will last in cars ?

It's a pity that that's the best there is for E.V use!

[o00scorpion00o]

I was out on the bike today and I didn't charge it because I needed it right away. Anyway I had used up about 5ah out of the usable 8.5ah out of the 10ah pack. I noticed it chucking a little and realised it was lvc kicking in. I have it set for around 54 volts for 16S.

The controller was keeping the power at a level that I wouldn't exceed the lvc.

I'm getting around 6 volts sag at about 45 ish amps, after only 5ah used. On a full charge I can easily get 80 amps.

If I turned the amps down I would still get full capacity, and probably would if I kept going, the controller would be limiting my power until the pack was empty.

But the 33-55 MOhms I'm seen is telling me the pack is close to being useless, so I reackon I would get a total of about 100-120 cycles and not full ones either. Probably 200 cycles If I run the pack at 30 amps and then less and less, but that would be no fun!

Sure I probably could have being much easier on the pack to begin with, running the first 3 bricks in parallel for a few weeks until I got my other 3 bricks for 2P was probably not a good idea.

The next LiPo buy will probably be the Zippy compact, 4S x 4 for 16S , maybe the hard case if they are available in the compact version. I have all the charging equipment and so it would be a waste not to use it again. I will take better care of the next batch of LiPo. But it has been fun abusing it!

[auraslip]

Battery university is always behind the curve. Don't trust anything they post. Lipo would be li-co.

[voicecoils]

Battery university is always behind the curve. Don't trust anything they post. Lipo would be li-co.

Lipo (lithium polymer) includes any lithium ion battery in a foil pouch. It's not specific to one type of active material. LiCo, LiMn, and others are available in lipo and li-ion can cell formats.

[kevo]

cwah wrote: the new zippy compact

Thanks for mentioning cwah, I haven't been checking HobbyKing batteries for a while and missed these