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View Full Version : RC li-po - what's the verdict?



podolefsky
26 July 2012, 1246
OK, I know this has been discussed here and endless sphere. Info is kind of all over the place, and opinions are always changing. I want to just know the verdict right now, with what we know at this point.

(and yes...I just want someone to tell me - I don't feel like searching the endless threads of endless sphere just to come out even more confused)

On paper, RC li-po seems like the best thing going. It's about $0.40/Wh, does 20C, half the weight and size of LiFePO4. You can go online and order it right now. It comes prepackaged with connectors and balance leads.

But...it likes to catch fire, the failure rate is around 3-5% off the shelf (so I hear), and it takes a lot of them to build a big pack.

All that said, suppose one were to build a BIG pack, like 9.5kWh. Say 32s16p. You order a few extra to replace bad cells. You check them all by doing several hard charge cycles. You monitor them all for LVC (say with 4 cell log 8's). You bulk charge them most days, but balance charge them every couple weeks just to be sure.

What's going to go wrong? Am I going to lose $4000 worth of cells in one big fireball? Am I going to just lose a few cells here and there?

Just for comparison, you could get Kokam or EIG for 2-3x the price. They're larger packs, more stable, lower max C-rate, claim not to be a fire hazard (or not nearly as bad as RC lipo). Harder to get (can't just get online and order them from Hobby King).

There's the opener...tell me why I shouldn't build a 9.5kWh RC lipo pack.

mcharles13
26 July 2012, 1312
I used to be big in the r/c plane arena and one of the best crashes i've ever seen was a plane that burst into flame mid flight because the battery packs were overworked. The plane burned forever, nothing was salvageable, was too hot to get close to and burnt a hole in the ground. It burnt the dirt. That being said when taken care of they are fine.

The only problem i see is individual cell management. If you can keep all the cells individually managed you can pull it off. If a balancer fail, if 1 cell fails and gets over looked that one cell can flame up. In a crash if any of the cells get punctured or twisted or severely damaged you are screwed. With as violent a flame as that is and with THAT much fuel, no way would do it.

With LiFe you can swap out bad cells no problem, condition the packs w/ a few cycles and the new cell falls in line. I did it very often. I flown a plane into the ground (servo failure) full speed, dented up the cells and they still survived.

just my .02

Mike

p.s. i am not a lipo scaredy cat. I love them as well as LiFe. But there is a difference flying a potential flame monster versus riding one.

Athlon
26 July 2012, 1321
On prius owner forum there is a group buy of A123 Pouch for about the same price per wh of hobbyking lipo http://priuschat.com/threads/is-there-interest-in-a-group-buy-of-a123-20ah-prismatic-pouch-cells.110235/page-3 I think is a good compromise between power and safety

Hugues
26 July 2012, 1324
I have 3 7S lipo packs on my mountain bike, for 21S, for about a year now, 10AH, lots of fun but....

The first 6 months everything was ok, i could pull my 8.5 AH out of them. I was only bulk charging, they did not even have balance cables to monitor the cells voltage, gee i was a bit foolish at that time,

Now i have balance cables, i check them regularly , and started to balance charge them , because 2 cells out of 21 are starting to charge faster than others, or discharge faster than others. One day i was bulk charging and found 2 cells above 4.3 while the charger was still going ! They have some kind of BMS built in but no way for the BMS to stop the charger.

I just could not imagine making my 10kwh build with this kind of pack, especially having to parallel some to increase the Ah, not knowing when a lazy cell would bring down the others. Plus the wire harness that becomes quite messy when you parallel cells.

For me it's clear my first motorbike build must be:
- LifePo4 or similar but enclosed prismatic, no loose pouches.
- series only, no harness mess
- full BMS capabilities with communication to charger through CAN port
- constant monitoring during charging and discharging, probably with the torque app on android phone or tablet.

No more lipo bulk charging without balance wires

Allen_okc
26 July 2012, 1400
what about the hobby kings LiFePo4's???

teddillard
26 July 2012, 1402
My conclusion is to keep running the lipo. I looked into the A123 idea, and, though the discharge rate seems about on par, I was told by someone who'd done it that soldering a pack together is something he (and his friends who helped him) would never do again. The biggest advantage the A123 packs have is the fact that you can run them down to really low levels without damaging the cells.

I don't believe that the new generation of lipo packs is as volatile as even pack from a year or two ago, to be perfectly honest, and was posting to a thread about that a few weeks ago. I'll see if I can find it. (edit: here- http://www.elmoto.net/showthread.php?2398-LiPo-fire-FAIL) I do feel that they're a little more needy, in terms of maintenance, but I know Adam (RC) has been running them in a big pack for over a year now, very successfully.

RC lipo, in my opinion, is "there". I also believe that to get a fair view of it, you have to separate a lot of the older information for more current actual use experience. I think that a lot of the drama of older lipo fires has to be put into the correct context - we're not working with those cells anymore.

Nuts & Volts
26 July 2012, 1409
I have quite a bit of experience with LiPo.

Big thing is to order extra and test as many individuals cells as possible. Check internal resistance and cell voltage. Remove duds. 1C cycle cells or packs while monitoring voltage. remove duds. Discharge to 50% SOC and leave packs for 1-3 weeks to find high self-discharge cells. Remove duds.

The high self discharge are the hardest to find, because they may not show up until 5-10 cycles and then you have to try to remove them. This is the largest issue our OSU pack had. Keeping the cells compact keep some of the failures from being worse then a simple hole in the side.

I would advice ordering bare cells and paralleling the cells, but you can get the premade packs as well. Tony and Adam seem to have had success. The bare cells will be harder to assembly, but will be lighter, easier to replace, easier to fit and probably easier to test. Jonescg seems to be doing good with bare 40C cells, but I still haven't seen him doing any high load testing on his soldered pack.

As far as discharge I would use the continuous rating as the peak to keep the cells cool and to avoid burning tabs up. I have done some 1C up to 8C cycles on both a 20C and 40C bare cell but haven't really looked at the data yet.

Also from what I have read getting over 500cycles is possible with really good treatment, but no hard data for this. I have only read of ~5 people having over 200cycles in ebike applications.

EVcycle
26 July 2012, 1635
Headway's Rule! !!!! :) :) :)

podolefsky
26 July 2012, 1649
Thanks guys. What you say is similar to what I've picked up trying to read through other more recent threads...but I tend to trust the "sources" over here more ;)

Maintenance and upkeep I can deal with. But a 500 cycle life is a bummer. Kokam and EIG, I believe, get well over 1200 cycles, maybe as many as 2000 or more. So the pricier cells end up being cheaper in the long run.

One good thing on C-rate - with 16p of 5Ah RC cells, 700A would be <9C.


Headway's Rule! !!!! :) :) :)

Yeah, you know for all the size and weight savings of li-po, Headway is still an attractive option. RC lipo, square packed, is about 280 Wh/l and 140 Wh/kg. Headway, hex packed, are 204 Wh/l and 100 Wh/kg. The reliability of lifepo4, plus the fact they're 15Ah and easier to build a robust pack, makes it a tough choice.

liveforphysics
26 July 2012, 1926
IMHO, the answer depends on what your goals for the project are. If you want a racebike that gets pampered with lots of testing when constructing the pack to filter out the will-be-infant-mortality-cells, and you're going to pay attention when you use it, not discharge past ~3.6v and not charge past ~4.125v, you can have a battery with unbeatable performance for the money. But I would recomend storing it away from your home in something you wouldn't mind burning down in the rare event you got a nasty unpredictable cell failure from internal mfg contamination or something.

You also gotta of course buy more packs than you need so you have spares from the same batch of cells as random failures start to occur down the road.


If you accept those things, RC LiPo is the path to record breaking performance on a grass-roots budget.

If you don't accept those things, go with something reliable.

Hugues
26 July 2012, 2141
...Also from what I have read getting over 500cycles is possible with really good treatment, but no hard data for this. I have only read of ~5 people having over 200cycles in ebike applications.

Very good point.

The problems I describe above started after 140 cycles only !

While I don't think we need 5000 cycles , big packs are expensive and you would like to enjoy them 3 years or so before going to the next technology.

podolefsky
26 July 2012, 2201
Very good point.

The problems I describe above started after 140 cycles only !

While I don't think we need 5000 cycles , big packs are expensive and you would like to enjoy them 3 years or so before going to the next technology.


This is like the lead vs lithium total cost. Lithium is 4x as expensive, lasts 10x as long (or so).

Still, if you have a non-race bike with a 10kWh pack, you could expect 80-100 mi range. With 500 cycles, that's 40-50,000 mi.

Would be interesting to know the cycle life if, say, you used 20% of the pack on 80% of rides and 80% of the pack on 20% of rides. That would be the case for me, since on most days I ride less than 15 miles.

podolefsky
26 July 2012, 2208
Besides, even if the cells only last 2 years...maybe by then Kokams will be $0.50/Wh and it'll be time to upgrade (again).

EVcycle
27 July 2012, 0223
I like the fact I will be getting a bunch of cycles on these batteries. It can get too expensive
to build new battery boxes, BMS units (or different chargers in our case) and more potential for me
to have a plasma event swapping them out. I plan to ride the $@*&% out of this bike! :)

Remotecontact
27 July 2012, 1939
I've had more than a year of use with about 100 cycles on my 4.4kwh HK Lipo pack. 30s8p on 30c 5ah cells. The pack is made of 6s bricks. I bulk charge to 4v with my Deltaq and balance about twice a month with 5 cheap hk balance chargers. I've never sagged below nominal even with hard riding on my AC20.

If you precycle the packs, do some IR matching for P groups, have a conservative LVC, balance frequently enough, and protect from puncture, you'll have a great pack capable of ALL the amps.

Adam (RC) not to be confused with RC Lipo :)

billmi
28 July 2012, 0515
Adam, how long does it take you (just in your connect/disconnect time start/stop time, not the actual charging) to do the balancing?

My impression of RC LiPO so far has been that the small cell size means more non-paralleled cells, which translates to more complexity either in circuitry or labor needed to keep the pack balanced.

Remotecontact
29 July 2012, 2159
Even a Tesla pack is made of 18650's. My 6s8p modules are all paralleled through the balance connectors. To my charger 6s8p is the same of 6s1p, just more AH. I made some 7pin Andersons that mate to panel mount 7pin connectors on the battery modules.

DaveAK
30 July 2012, 1609
If you accept those things, RC LiPo is the path to record breaking performance on a grass-roots budget.

If you don't accept those things, go with something reliable.
From what I've gathered over the years this about sums it up for me. If I was building a race bike I'd use LiPo, and probably budget for 2 or 3 packs worth. If I was doing a good performing street bike I'd go with A123.

NonPolluter
06 November 2012, 1857
Electric 'cycle roasted:

http://www.liveleak.com/view?i=a40_1216404715
http://www.liveleak.com/view?i=a40_1216404715

damnedfish
10 March 2013, 1520
Hi NonPolluter,

As previously mentioned in this thread, the onder LiPo cell chemistries, and reliability, has changed alot in the last Year+. Disappointing no doubt to see that lovely young lady's bike/scoot catch fire, but that is not implying that current generation of LiPo cells are as likely to catch fire. Especially if they have been treated well, both in regards to, discharge, charge, and balancing, as well as any kinds of physical damages.

Damnedfish

(EDIT: Ooh, this was my first post. YAY!! (I'd probably better go and introduce myself, and check profile info)

podolefsky
10 March 2013, 1727
Hey damnedfish (ha ha...that sounds funny)

Yeah, from what I've heard/read RC lipo has gotten a lot better recently. I'm still not sure I would build a 10kWh pack and charge it in my garage overnight...but I do plan on doing some overcharge / overdischarge tests with the spare cells I have, maybe even a puncture test. Just need to get my shop back together (after moving).

ronny
13 March 2013, 1418
42264227

hey guys going for LiPo this year ! main reason is saveing 34 KG (75pounds) !! i got the Turnigy nano-tech 8000Ahm (25C -50C), 22S4P setting. 8x5S + 8x6S. ordered 16 LiPo alerts for riding and some tuned Medics for charging. if this works i will made a second batterie pack for change on the Track. the right side of the ktm frame got a little more space than the left side, so batterie changes would going very easy. i am in RC sports for a long time (only electric :-)) and can handle these LiPos. on my pedelec i ride a nanotech 10S pack for 1500miles with no problems.

ronny
13 March 2013, 1421
i ride the Headways for two seasons now, bike running very well but this upgrade have to be done ! what you think ?

Athlon
13 March 2013, 1610
Right now I'm building a few 1,5 kWh (12s7p) pack with 65-130C A-spec cells.

I will keep you updated how they will perform.

I'm not a big fan of LiPo , but in this case I was forced because I really need 35+C of discharge current.

ronny
14 March 2013, 0036
THe Aspec are a good choice but very expensive
. The 8000 nanos are 25c - 50c so they easyli can handle 200 Amps current.

damnedfish
14 March 2013, 2043
(Pre-tense: I realise you guys know your maths, but I am running the numbers to understand myself) (Also really not picking on Ronny's Cell's or choices, they just happen to be figures on hand)

Of those of you running LiPo cells currently, how do you find the current handling? Especially regarding the pre-made packs from Hobbyking. Obviously the peak C rating is only for bursts (of whatever time is rated). But it is likely to surprise me, that when running running a " 8000Ah " cell at " 25C " equates to continuous rating of 200A. Im not sure how the leads supplied with the pack can cope with 200A, especially once the pack hovers around 82V up to a max above 90v. That gives a maximum continuous of 18.5kW travelling though the leads of the battery pack, that was designed for 5S 8000mAh 25C = 4.2kW, 6S 8000mAh 25C = 5kW (At peak charge fresh off the charger).

Do you replace the factory leads on the packs? Or am I reading into this too much, and it's actually about the current through the packs, which is 200A(cont) - 400A(peak). Which is what the pack w/leads is designed for?

Damnedfish

PS (Noah, my name is Nick, Damnedfish was a name I created a long time ago and apart from a band I found out about (who shares the name), it is a fairly unique name across the internet. If you find "damnedfish" it is usually me)

Doctorbass
14 March 2013, 2213
I just finished the first 2kWh pack of my battery upgrade project for my Zero DS 2011 electric motorcycle.

Really satisfied with the quality and safety i have built with these A123 pouches.

Measured 1879Wh at 100A discharge. The pack is a 16s2p to match the voltage of the 14s LiMn actual battery of the Zero.

HEre is the thread about the build.
http://www.endless-sphere.com/forums/viewtopic.php?f=10&t=47812&p=713926#p71392642294230423142324233

Doc

Doctorbass
14 March 2013, 2215
http://www.endless-sphere.com/forums/download/file.php?id=102524


http://www.youtube.com/watch?v=bvr-EoLs5pE

Doc

ronny
15 March 2013, 0528
Hey nick , i thought about the wire sizes too.i use original one. The packs came with 10 awg wire and 5mm gold contacters so its easy to connect them in series. My axe controller is set about 425 amps- i have 4 packs every pack has to give about 100 amps so i dont worry about the wires. the pics above are from last weekend i keep you updatet!

lionschasing
17 March 2013, 1356
I could tell you what the verdict is.... :)

Cheap Lifepo4 is a good verdict! I am attaching some photographs of my disassembling of one of the 7s3p a123 modules.
1) I used thinner to dissolve the adhesive gluing the cells to the outer shells.
2) I left the battery for several days half submerged in thinner, this dissolved the glue and allowed easy maneuvering of the battery.
3) The glue dissolved, the batteries came apart easily, using a dremel I cut the tabs separating the cells
4) I plan on resoldering the tabs together to form two 21series 1parallel setup. 75v fresh off the charger. 20ah.
5) This setup should allow to use up to 300A bursts from the cells.
6) I damamged one of the cels early on, and used an adhesive and silicon to patch the cell together... seemingly the battery did not react to this abuse indicating a practical test of how robust these cells are. The pierced cell will not be used in battery assembly.

Something I am doing is re-using the metal plates from the a123 battery to build a robust battery box using a mig welder that I have, this will be an interesting experiment, and I will post more photos in this thread.
There are cell modules that are sold by victpower, cheap, at $14 per 3.3v 20ah a123 amp20ah, these are excellent. I am currently dismantling them. I'd like to share this with you on this forum...I think elmoto is one of the best EV forums out there.

42474248424942504251

podolefsky
19 March 2013, 1956
(Pre-tense: I realise you guys know your maths, but I am running the numbers to understand myself) (Also really not picking on Ronny's Cell's or choices, they just happen to be figures on hand)

Of those of you running LiPo cells currently, how do you find the current handling? Especially regarding the pre-made packs from Hobbyking. Obviously the peak C rating is only for bursts (of whatever time is rated). But it is likely to surprise me, that when running running a " 8000Ah " cell at " 25C " equates to continuous rating of 200A. Im not sure how the leads supplied with the pack can cope with 200A, especially once the pack hovers around 82V up to a max above 90v. That gives a maximum continuous of 18.5kW travelling though the leads of the battery pack, that was designed for 5S 8000mAh 25C = 4.2kW, 6S 8000mAh 25C = 5kW (At peak charge fresh off the charger).

Do you replace the factory leads on the packs? Or am I reading into this too much, and it's actually about the current through the packs, which is 200A(cont) - 400A(peak). Which is what the pack w/leads is designed for?

Damnedfish

PS (Noah, my name is Nick, Damnedfish was a name I created a long time ago and apart from a band I found out about (who shares the name), it is a fairly unique name across the internet. If you find "damnedfish" it is usually me)


10AWG does seem pretty thin for 200A. I've tested 10AWG with gold banana plugs up to 50A continuous, and the plugs/wires get warm, but not hot. At 100A, the wires get too hot to touch after about 20-30 sec, but they don't melt (I haven't run a test longer than that, so it could be they melt after more time).

Power dissipated as heat is proportional to I^2, so if current goes up by 2x, heat generated goes up 4x. I haven't actually tried 200A through 10AWG, but I'll bet that's enough to melt the insulation pretty quickly.


The voltage doesn't matter for wire size, just the current. So technically, power (kW) doesn't matter either (if you have the same current). You could have 12V, 120V, or 1200V - if they're all putting out the same current, you'd use the same size wires. That's why higher voltage systems can use thinner cable - same power with less current.

ronny
25 April 2013, 0114
4350

ronny
25 April 2013, 0143
Testrun#1 very good handling and lots of power ! More to come

jonescg
25 April 2013, 0730
Suppose I should post in this forum about my soldered packs.

They are so far standing up to regular use, but I haven't seen enough cycles to make me say they are good, great or awesome. I do know that they can handle high currents through the busbars - the only limitation is the cables.

http://www.youtube.com/watch?v=pLD1iKYV_cg

A few things to note with RC LiPo, QC is bad so sort them well. A multimeter will tell you who is worth using and who is not. If you have the time to cycle each cell or group of cells then do it, but otherwise you can write the cell voltage down, hold off, and measure them a month later and see who has dropped the most. Leave them out. Then solder the packs together.

I'm building a 9 kWh pack using bare cells as a 15 Ah, 168 cell unit. Yes, 700 V dangerous yada yada but the design of the pack and it's isolation is critical. Making sure the cells are protected by a rigid, puncture-proof enclosure is critical. Making sure the cells are evenly supported and that the tabs don't bear any force is also important.

And in the end, this is a pack destined for a bike which I plan on flogging hard less than 100 times. At that point the batteries will be outdated and dangerous, but who cares? Not bad for $5000. As a commuter bike I might find a way of fitting EIGs in there or something, but it won't be road-going for a long time.

Tony Coiro
25 April 2013, 0855
Having used lipo in my last bike, would I use it again? Absolutely, I don't know if I'd consider much else. I would however be MUCH more careful in pre-screening. Had one bad cell drag down an 8p section in the middle of the pack. A little more care early on would've prevented a ton of headaches in repair. I would say, lipo is great but is absolutely not for a first build, maybe even not a second. But, lipo is certainly addicting once you really understand the power to weight ratios you can achieve.

liveforphysics
25 April 2013, 1153
Having used lipo in my last bike, would I use it again? Absolutely, I don't know if I'd consider much else. I would however be MUCH more careful in pre-screening. Had one bad cell drag down an 8p section in the middle of the pack. A little more care early on would've prevented a ton of headaches in repair. I would say, lipo is great but is absolutely not for a first build, maybe even not a second. But, lipo is certainly addicting once you really understand the power to weight ratios you can achieve.


Yep. Huge amount of work in pre-screening to do it. Then you can still have internal defects in cells that you don't know are going to fail later.

For a race bike, I use RC lipo because for the $ and weight and power delivery, it's simply unmatched. However, the QC on these things as they ship out is barely good enough for an RC plane in my opinion. The cathode blends have become much more stable as new generations of RC Lipo continue to improve with respect to safety, however, it seems like the mfg's have used this increase in safety to let them slack even more on QC.

If you're storing your bike in a place you would be upset if it burned, you probably don't want to be using RC LiPo unless you really know what you're doing and are very comfortable in your pack pre-screening skills. Not saying this to scare people away, I'm currently building a bike with Nano-tech RC LiPo in my garage at home right now, just making sure people understand it's not simply a plug-n-play battery build, you really need to carefully pre-screen each pack before building it into a larger pack.

ronny
26 April 2013, 0627
@liveforphysics what is QC ? Ans what does pre-screening mean ? Sorry for my bad tech english

jonescg
26 April 2013, 0815
QC = quality control.
Pre-screening means making sure each individual cell is healthy before building it into a large (often hard to remove) pack.

Remotecontact
26 April 2013, 1438
mwahahahahahaaa

EVGator
06 May 2013, 1640
I always come back to RC Lipo just because of the weight and power. I've dealt with Hobby King and ordered a couple of hardcase packs to test, but they seem to always be on back order. Are you guys finding other decent places places to get RC Lipo from?

ronny
07 May 2013, 2222
4389 after presreening rode the first cycle on the pack . Very nice handling and lots off power !!! Can pop wheelies from stand. 60min drive offroad but not full power hole time, so i think 30min on a motocross track is possible more to come soon ! Very confidence about my LPo upgrade

podolefsky
19 May 2013, 1815
Doing some poking around to see what the cycle life is of RC lipo. HobbyKing says that normal Turnigy are 160+, nano-techs are 250+. People on endless sphere claim to get upwards of 500 cycles (to 80% of capacity).

So, now that I know that, I'm doing the same calculation I did about 3 years ago for lead vs lithium. Lead was around 1/3 the price and had around 1/4 the cycle life (not to mention, a lot heavier and bigger).

RC lipo is about 1/3 the price and has about 1/4 the cycle life compared to Kokam / EIG (from what I can tell, based on the most optimistic reports of Turnigy users). They're roughly the same size and weight. Can't get 20Ah RC lipo, so you need more packs in parallel. Can't beat the discharge rate of RC lipo (20C even for the low cheap stuff). Although, if you've got 100Ah, that's 300-500A continuous...plenty if you're not racing.

QC has gotten better on RC lipo, but still not on par with Kokam / EIG.

Anything else I'm missing?

liveforphysics
20 May 2013, 1020
QC has gotten better on RC lipo, but still not on par with Kokam / EIG.



Intrinsic safety by improved materials/design has gotten much safer with RC LiPo, but from what many of us have seen, the QC seems worse than ever before. The early LiPo powered ebike adopters (myself included) would only need to buy about 1 extra pack per 10 packs to end up with enough good packs. Now days, it's not too uncommon for people to report they bought say 10 packs and 3-4 arrived with either a 0v cell or puffed cell or self-discharging cells etc. We've even encountered packs with the red discharge lead soldered to negative and black to positive, along with incorrectly pinned JST balance connectors. It may just be that we have a much larger sample size of people buying them in bulk quantity than we used to have, but I think it also may be an indicator QC is lower than ever while the cell design itself is better/safer than ever.

Remotecontact
20 May 2013, 1049
1/3 the price? Link to Kokams for under $1k/kwh? Turnigy 4s 5ah hardcases are less than $300/kwh.

The average 5kwh pack results in about 60 miles for most motorcycles. 500 cycles is 30,000 miles, pretty much the life expectancy of a Ninja 250.

podolefsky
20 May 2013, 1150
Intrinsic safety by improved materials/design has gotten much safer with RC LiPo, but from what many of us have seen, the QC seems worse than ever before. The early LiPo powered ebike adopters (myself included) would only need to buy about 1 extra pack per 10 packs to end up with enough good packs. Now days, it's not too uncommon for people to report they bought say 10 packs and 3-4 arrived with either a 0v cell or puffed cell or self-discharging cells etc. We've even encountered packs with the red discharge lead soldered to negative and black to positive, along with incorrectly pinned JST balance connectors. It may just be that we have a much larger sample size of people buying them in bulk quantity than we used to have, but I think it also may be an indicator QC is lower than ever while the cell design itself is better/safer than ever.

I'd heard the first part of that (increased intrinsic safety), but not the second (QC). Does it seem to depend on the supplier (USA warehouse vs China)?

Averaging over all the people that build RC lipo packs, what would you estimate is the rejection rate for new cells? Is it just a few people with 3-4 out of 10, or a lot of people?



1/3 the price? Link to Kokams for under $1k/kwh? Turnigy 4s 5ah hardcases are less than $300/kwh.

The average 5kwh pack results in about 60 miles for most motorcycles. 500 cycles is 30,000 miles, pretty much the life expectancy of a Ninja 250.

I was basing that on about $0.40 / Wh for regular Turnigy 20C packs. Some hardcase packs are dirt cheap for some reason.

Point taken on 30k miles. That would definitely keep the bike going strong until the next generation of whatever cells come out, and the pack gets rebuilt again.

podolefsky
20 May 2013, 1216
Just to state for the record - I'm not an advocate for ANYTHING. I just want to learn what the real deal is - there's too much (mis)information out there to make sense of whether RC lipo is the best thing since sliced bread, or will burn my house down. Or if it will be a reliable 10 kWh pack for $4k, or if I'll be pulling it apart to replace bad cells every week.

One of the things I like about elmoto is that it's not endless sphere (in that the majority of people on here either genuinely want to learn, or genuinely know what they're talking about). So how about we put that knowledge out there? I promise, no flaming, no bull****.

podolefsky
20 May 2013, 1716
I've been browsing youtube for lipo tests. Some puncture tests cause lots of smoke (http://www.youtube.com/watch?v=c2HVkuW2Nxo) (although no fire), some do nothing (http://www.youtube.com/watch?v=V5mwLcFV8PU).

This overcharge test (care of liveforphysics) shows both the safety and danger. Safety in that you really have to overcharge them (>5V), and danger in that if you do, they explode.


http://www.youtube.com/watch?v=FXrmvuLkSsQ

DaveAK
20 May 2013, 2046
Are Kokam / EIG available for us mere mortals?

teddillard
21 May 2013, 0244
I believe my comment was that, for the substantial gain in power-dumping ability I'm happy to trade-off cycle life, especially when, as Remotecontact pointed out, 200 - 300 cycles will pretty much surpass the lifespan of the bike. It certainly will surpass battery development, with any luck.

My opinion as of this posting, which is several months later after running blue 40ah CALBs all summer, is that I can't wait to dump this pack and go back to a nice, big, RC lipo pack.

podolefsky
21 May 2013, 0854
[deleted]

teddillard
21 May 2013, 0908
...

podolefsky
21 May 2013, 0918
Anyone else want to weigh in...or is this thread just dead and what we've learned is that the first rule of lipo is not to talk about lipo...

ARC EV Racing
21 May 2013, 1002
Well since you asked, I'm all for RC lipo but in the right application and in the right hands. For race bikes run by folks who know what they're doing (or who to ask) it can't be beaten in terms of performance for the money. Cell level voltage monitoring with LVC/HVC is a must though and we always use a balancing BMS.

Nuts & Volts
21 May 2013, 1005
I'm over LiPo pretty much. Mainly because they still use LiCo which is a volitale chemistry. The cells have gotten safer, but it still have more potential to start a fire than other chemistry (NCM, NCA, LiFePO4, LiMn) if you have any type of failure.

The only reason I see to use LiPo is if your number 1 goal is a small initial $ investment. OR you need high power from a small battery (<4kWh).

If life-time cost is important NCM/LiFePO4 is a better choice due to increased cycle life.

If energy density/weight is more important then NCM/NCA is a better choice (>170Wh/kg, HK LiPo is ~150Wh/kg).

If range is more important than you want a large pack so high C rate isn't needed and NCM/NCA works great.

If ease of pack construction is what you want then LiFePO4 is the best with large format NCM (20Ah+) coming in second in my opinion.

If you want a middle ground, good starter pack then LiFePO4 large format is the best choice (good energy, good power, good cost, good safety, good availability, great cycle life, good track record). Headway

I've used a 14kWh LiPo pack, it was a horrible experience for me. I've also done testing with about 8 diff LiPo cells. All performed great in those tests. I also used some HK Turnigy packs on an ebike and they performed great. I even over discharged (<3V) a lot of them and only one cell died. But I have seen a number of cells once installed a pack fail (tabs ripped, high self discharge, puff up and break the seal) and then the pack was pretty much useless.

I have an NCM pack that is very configurable which makes my project very flexible and much easier to use than LiPo bricks. I even crashed with this pack and scrapped up one cell which I easily removed from the pack. It swelled up, but I still used it for 15 cycles or so with little issue (little extra voltage sag it seemed). I am planning out my next pack with NCA 18650 cells at the moment because I want a large pack for both racing and commuting. And I just like to design these things.

I like LiPo, but there are better cells for what I want in a racing machine and a commuter bike. Both of which I have worked/designed on.

I've got more information but have to go...

podolefsky
21 May 2013, 1019
Thank you! That's good information. Keep it coming.

__Tango
21 May 2013, 1125
Kyle, can you give examples of the NCA/NCM cells? EIG and Enerdel are NCM, right? What are examples of NCA?

Nuts & Volts
21 May 2013, 1136
Also with my NCM cells I do not use a BMS and probably won't for awhile. If I do add one in it is either because I will start pushing the limits of the cells (higher current or larger DOD >90%) or I want more data about the cells/pack. I do not use a BMS because the QC is great, cell variance is very small and I trust the safety of the cells. This brings the cost, weight, and complexity smaller on my pack too. I do not think I would trust a LiCo (LiPo) pack without some form of HVC/LVC.

Also manual balancing and reconfiguration of packs is a little bit harder with smaller format cells. The HK packs and a balance charger make things easier, but still a lot of cells to deal with.

RC LiPo is nice to because it can be easily handled with lower risk of shock and mechanical cell damage then say a 20Ah EIG or A123 cell. These are a lot easier to bend or set on a piece of metal and short than the bullet connector and shrinkwrapped nature of the RC LiPo.


One other thing I wanted to add. I went with the NCM cells for a few reasons that I've already mentioned, but I also got them because they will safely last me for 20yr+ in various applications. I myself will probably update my battery pack every 3-4years with the latest and greatest. But the NCM cells still have plenty of life, what do I do with them? My plan is to use them as a battery pack for a solar array and hopefully get my house off the grid. I would never want to use RC LiPo in my house as a battery back-up system for 10yr+. So over 10-20yrs the cost of my NCM (EIG) cells will be much lower than RC LiPo. The cells fit my needs and I really think they will fit other people's needs on this forum very well.

lugnut
21 May 2013, 1140
I'm over LiPo pretty much. Mainly because they still use LiCo which is a volitale chemistry. The cells have gotten safer, but it still have more potential to start a fire than other chemistry (NCM, NCA, LiFePO4, LiMn) if you have any type of failure.

I thought LiPo stood for LiPoly or Lithium Polymer which includes a broad spectrum of Lithium chemistry all of which would use a polymer electrolyte, even some LiFePO4.

And I was also wondering what NCA is.

Good discussion. I like it.

Nuts & Volts
21 May 2013, 1146
Kyle, can you give examples of the NCA/NCM cells? EIG and Enerdel are NCM, right? What are examples of NCA?

NCM, Mixed Metal, LiNiCoMn cells
EIG, Kokam, Enerdel (?), Zeros new supplier, Brammo's supplier are all NCM battery cells

NCA, LiNiCoAl cells
I have only seen these in 18650 cells made by Samsung, Panasonic, Sanyo, and maybe LG. Like those used in the Model S- Panasonic NCR18650

Nuts & Volts
21 May 2013, 1154
I thought LiPo stood for LiPoly or Lithium Polymer which includes a broad spectrum of Lithium chemistry all of which would use a polymer electrolyte, even some LiFePO4.

And I was also wondering what NCA is.

Good discussion. I like it.

You are correct. LiPo is a broad term that might include other chemistries. I have seen it most associated with LiCo and LiMn cells. I generally just link LiPo with LiCo because that is what HobbyKing cells use. I'm just going to stop using the term LiPo and use the actually chemistry when I talked about cells from now on.

I talk a little NCA above, but the PDF below shows most of what I know about NCA chemistry

https://docs.google.com/file/d/0ByrXDM_gdAHEMTZJTERKTG5EN1k/edit?usp=sharing

DRZ400
21 May 2013, 1216
I have been using RC Lipo for several years in my planes and choppers. Always balance charge and never over discharge. I have tons of puffed packs laying around, several with dead cells (both new and old) and even a few that after 3 years are still perfect other than some loss in capacity. No question they perform but I would never trust putting a 22S8P pack in my bike based on the quality and reliabilty issues Ive seen in my RC stuff.

ARC EV Racing
21 May 2013, 1421
We did 25s16p and 30s8p with our last couple of race bikes. One cell went down during the season with the first pack, the second pack used the best of the old cells and two went down that year. Nothing dramatic just high self-discharge which we spotted before it got too low. We took to having spare parallel blocks on standby so we didn't have to find the bad cell in the parallel string while at the track.

Our new bike uses 5ah turnigy cells which are paralleled into blocks first using our own design. The initial configuration of this one will be 40s12p, and no bullet connectors or jst balance leads!

theFREElaker
21 May 2013, 1430
Somebody earlier on asked whether or not mere mortals could get their hands on EIG and Kokam cells. Im not sure about EIG but I called a Kokam plant near my house in Kansas and the sales rep said they sel to anyone who can pay. He quoted me the following prices for a quantity of 40-80 cells
$173.00 - 75Ah high power cells 6c continuous 10 peak
~$150.00 - 60Ah high power cells 8C continuous 12 peak
~$120.00 - 40Ah high power cells 8C continuous 12 peak

Im not exactly sure about the pricing on the 60 and 40Ah packs because i was primarily interested in the 75Ah.

podolefsky
21 May 2013, 1446
Really? That's $0.62 / Wh for 75 Ah cells. I've never seen Kokam for less than $1 / Wh, and that was in a bulk buy.

ARC EV Racing
21 May 2013, 1456
Those prices make a kokam pack sound realistic

picaroon
21 May 2013, 1456
Our new bike uses 5ah turnigy cells which are paralleled into blocks first using our own design. The initial configuration of this one will be 40s12p, and no bullet connectors or jst balance leads!

Are these new single cells you are using or are you breaking up your 5s packs to parallel?

ARC EV Racing
21 May 2013, 1510
Are these new single cells you are using or are you breaking up your 5s packs to parallel?

They're new single cells. A bit more expensive than using the 5s packs but I couldn't face trying to de-solder 480 cells. Most of the used 5s packs were still giving good capacity so we sold them off cheap.

picaroon
21 May 2013, 1657
They're new single cells......... 480 cells.

That's a much bigger pack you'll be using for this race bike then...
Were there any cells dead on arrival?

jonescg
21 May 2013, 1745
Like ArcEV, I've been building RC LiCo packs from Turnigy / Haiyin cells using individual, unadulterated cells for about a year now. It is a MUCH better way to go than trying to plug pre-built 6s packs together.

Here is a 14s3p LiCo pack for an e-bike:
http://i285.photobucket.com/albums/ll53/jonescg/48V15Ahnearlydone003_zpsf5f1a71e.jpg (http://s285.photobucket.com/user/jonescg/media/48V15Ahnearlydone003_zpsf5f1a71e.jpg.html)

It also means you get to sort out any dud cells before you put the pack together - something the prebuilt packs don't have going for them.

I have designed my race bike battery around these 5 Ah 40C cells, but that was back when EIG or the like wasn't available. I will still go with the LiCo pack for the racing, but longer term it has no place in a road going bike. I will re-design the pack for EIG later on. ...after my car conversion... which will be in about 2017...

podolefsky
21 May 2013, 2037
I just happened to be browsing Evolve Electrics and they're now selling Enerdels (http://evolveelectrics.com/Enerdel.html), in singles and modules.

CP155-365 power cells (15.5 Ah, 5C continuous, 15C max) are $22.48 in quantities of 100-499. $0.40 / Wh

http://evolveelectrics.com/Enerdel_CP155-365_Moxie.html

Skeezmour
21 May 2013, 2119
I have always had good interaction with Justin. Those seem like some very good prices

robo
21 May 2013, 2142
Justin had mentioned these were coming when I met up with him in Feb,, but I agreed to not say anything (although the specific manufacturer was not mentioned at the time). I had the impression they did a fair amount of due diligence before carrying them, but this is not an endorsement.

__Tango
21 May 2013, 2252
Holy smokes, go here: http://evolveelectrics.com/Enerdel.html to see all of the options.

The sale price on the CE-165-360 "energy" cell (higher energy density, lower C rate) is freakin smokin! it's $0.36/Wh!

The Enerdel cells are what the Lightning bike uses for their superbike for TTXGP/e-POWER/whatever-its-called-now (I think for IOM, they run the 18650s since the density is even higher with those.) The Lightning guys swear by the Enerdels, they are putting them in everything they can.

Interestingly, on the Enerdel website, they only list the 17.5Ah "Energy" cells and the 16Ah "Power" cells. I wonder if these are old stock or something...

podolefsky
22 May 2013, 1534
I wonder if you can get the parts separately to build your own custom modules? 43.8V is kind of hard to work with. x2 it's only 87.6V, x3 it's 131.4, just over the limit of my Curtis.

lugnut
22 May 2013, 1752
I wonder if you can get the parts separately to build your own custom modules? 43.8V is kind of hard to work with. x2 it's only 87.6V, x3 it's 131.4, just over the limit of my Curtis.

Fully charged is like 50 V for the block. The nominal voltage seems a bit low due to a fairly steep slope of V vs Ah down to below 3 V/c. It looks like EVolve sells cells and modules. The plastic frames are really nice and only available if you buy the modules or blocks as some call them. You could take it apart and configure to the cell count of your choice. See: http://liionbms.com/cgi-bin/moin.py/CustomProducts/EDI/EnerdelBattery#head-5c4b017c9f3c02caf73aac63cb87f518f09bd642-6

http://elithion.com/battery_blocks.php

This shows a guy who reconfigured the modules for his Sparrow. http://howman.com/sparrow/enerdel/

podolefsky
22 May 2013, 1935
Thanks for the elithion link - that looks like a sweet setup with the BMS integrated. I wish they listed prices for the modules (might email just to find out).

Too bad the curent limit on the terminals is so low. Ideal would be something like blocks of 6S4P, 5 of those to make about 110V and 64Ah. But looks like the terminals will only handle 450A, and I'd want 700A for my Curtis 7601. So that would mean 2 strings of 16S2P modules with high current terminals - and 2x as many BMS boards.

Not that I'm placing an order tomorrow or anything. Just thinking.

liveforphysics
22 May 2013, 2040
Fully charged is like 50 V for the block. The nominal voltage seems a bit low due to a fairly steep slope of V vs Ah down to below 3 V/c. It looks like EVolve sells cells and modules. The plastic frames are really nice and only available if you buy the modules or blocks as some call them. You could take it apart and configure to the cell count of your choice. See: http://liionbms.com/cgi-bin/moin.py/CustomProducts/EDI/EnerdelBattery#head-5c4b017c9f3c02caf73aac63cb87f518f09bd642-6

http://elithion.com/battery_blocks.php

This shows a guy who reconfigured the modules for his Sparrow. http://howman.com/sparrow/enerdel/

Nice looking cell modules. Good to see this stuff getting sold to the DIY EV builder market.

lugnut
23 May 2013, 0330
Too bad the curent limit on the terminals is so low. Ideal would be something like blocks of 6S4P, 5 of those to make about 110V and 64Ah. But looks like the terminals will only handle 450A, and I'd want 700A for my Curtis 7601. So that would mean 2 strings of 16S2P modules with high current terminals - and 2x as many BMS boards.

As long as you're modding the module, do this. http://howman.com/sparrow/enerdel/2_bolt_lug_on_plate.jpg That appears stout enough to handle all the current your Curtis could manage.

podolefsky
24 May 2013, 1542
I just spoke with Davide from Elithion. Elithion won't sell small quantities (<10 kWh), but you can get them from Evolve. The super cheap ones from Evolve are slightly below spec - Davide said that's why you see 15.5 Ah instead of 16.

You can get them configured with the Elithion BMS boards pre-installed from Evolve. I'm inquiring about pricing.

podolefsky
01 June 2013, 2137
Justin at evolve said the 450a rating is continuous, so 700a peak would be fine. I'm double checking though, because on Elithion's site is says the high current terminals are 480A peak.

Can get 8s4p modules assembled with BMS boards for about $1050.