Zippy 20C LiPo after 10 months

[o00scorpion00o]

Hi Everyone,

I measured my Zippy's pack internal resistance today for the first time and the 4x 6 cell bricks are about 45 MOhms
The 2 x 4S packs were about 33.

I got 2x 6S bricks and used them before I got the other 2, then got the 2x 4S a while later.

All cells were about 6-9 MOhms

I have given the pack a hard enough time, and now for a while I'm running 24S 1P compared to normal 16S 2P, so right now I'm being hard enough on it!

I charge to no more than 4.15v per cell, and mostly bulk charge, but not right now as my bulk charger is set for 16S.

Discharge mostly to 3.6-3.8 volts before charging. I still have a low cell in one of the 6S bricks. I still get 8.6 ah out of it, in 16S 2P before lvc, after that the cells start to go off balance. So still getting the same capacity as new.

Roughly I have about 50-60 cycles ? only guess as I forgot to reset the cycle analyst to 0 when changing to LiPo!

I will have the pack a year I think in June sometime.

So what ye think, pack still good enough ?

[neptronix]

Running 1P on a 20C pack, ( which is really a 10C pack in reality, they totally lie about the C rating since the equivalent turnigy 20C has half the internal resistance ) & high amps will kill a pack in short time. That's how you only get 100 cycles out of a lipo

I think it's fairly cooked. Might want to test them for capacity at a 1C discarge. If you're still getting over 4AH, and no cells have swelled, just keep running them, but put them in parallel with the newer ones, make sure you parallel the balance leads too.

4.15v charging, proper balance, no overcharge/overdischarge and running your packs at half their real C or below is the path you want to take if you want that mythical 500 cycle figure.

[o00scorpion00o]

I think I will get another year out of it though and 2 years out of a pack is good enough for me. Still getting the same ah.

I don't think LiFePo4 would be better for me unless I was commuting and they were pouch cells like ping. LiFeP04 is usually rated at 1C. And the good quality packs are too expensive.

Still The LiPo has given me a lot of thrills that LiFeP04 4 can't! No bms, well I'm used to that now so I don't even think about it. If I had a custom bike frame with the batteries inside then the frame, then a bms might be handy, but other than that it's useless for me!

I will go back to 16S 2P as 24S is really a lot of fun on the pie, but it's too hard on the Zippy's and my torque arms are not so good for that kind of power.

I'm still looking for a suitable frame to glue Doc's torque arms too!

I can forget about finding a frame over here! Hopefully eventually I will have one of the custom frames that the guys are selling here on E.S, or wait until I can get a 2nd hand greyborg!

To think of the money I've put into electric bikes, and I'm still not happy!

[chilledoutuk]

its hard to explain my reluctance with lipo packs from hobbyking and i think this post kind or explains my problems with HK packs.

People say only charge to 4.15v and discharge to 3.5v lvc and the packs can last to 500 cycles but at what cost to delivered capacity.

one of the bigest advantages of lipo is energy density but if you have to baby your pack to the extent your only able to use 75% of its potential capacity then its energy density
becomes no greater than that of for example a123 m1 cells.

for example take this pack
http://www.hobbyking.com/hobbyking/stor ... ouse_.html

it has an energy density of about 144 wh/kg factor in the 75% Hobby King care factor you are left with a battery with 108wh/kg that can do 500 cycles if your lucky. But cheap

a123 m1 cells also have energy density of about 108wh/kg but can be cycled reliably for over 1000 cycles.

High quality lipo packs can be cycled easily into there hundreds and in use at there designed parameters and keep there energy density of about 150wh/kg

Quality 18650 cells typically have an energy density of 185wh/kg or greater and there cycle life puts some of these cheap lipo packs to shame even when run at 2c discharge.

I have been trying to cycle a sanyo 18650 cell so that it is more in line with a couple of other cells in capacity terms and after about 20 cycles it might have lost 5ah if even that.

i am running a 5p 18650 pack built using sony cells from laptop batterys and in use the battery barely even gets warm and thats a pack with some questionable cells (thanks ebay seller for saying they had 100% life remaining lol)

Using a cell matching program kindly uploaded by another ES member i was able to get my 18650 5p banks to be within 2mah capacity of each other and from looking at my cellpro 4s when balancing they seem to remain perfectly balanced in use so far.

[neptronix]

75%?
I use over 90% of the available energy on a regular basis.
4.15 to 3.5v leaves under 5% off the top, 5% off the bottom.

Any pack being ran without a BMS will require this same conservative LVC and HVC. All lithium cells have some capacity variance that makes this necessary. It's not unique to RC lipo whatsoever.

Quality 18650's ( sanyo, panasonic, etc ) are expensive, a pain in the ass to solder, and have low discharge ratings, so you cannot really push them too far unless you have a really low power setup, or a mid-power setup with a ton of amp hours.

You can do the same capacity matching with RC Lipo. That's how i went over 90 cycles without balancing a 20AH pack. I only balanced the pack because i felt like it was a good idea to do it after a year. It only took 30 min to balance the whole thing, so it hadn't became very unbalanced during that time anyway.

There is something awesome about a 10S/20AH pack that sags no more than a 1.25v at a peak of 56 amps, cost under $400 shipped, puts out more power than i could ever need, is small, and was super easy to put together.

Nothing beats lipo right now unless you need thousands of cycles. Like scorpion says, if you commute, these aren't so bad. If your bicycle is an errand/grocery getter/pleasure mobile rather than a primary form of transport, 300-500 cycles aren't so bad, especially if you have a really large capacity pack.

[flathill]

75%?
I use over 90% of the available energy on a regular basis.
4.15 to 3.5v leaves under 5% off the top, 5% off the bottom.

Any pack being ran without a BMS will require this same conservative LVC and HVC. All lithium cells have some capacity variance that makes this necessary. It's not unique to RC lipo whatsoever.

Quality 18650's ( sanyo, panasonic, etc ) are expensive, a pain in the ass to solder, and have low discharge ratings, so you cannot really push them too far unless you have a really low power setup, or a mid-power setup with a ton of amp hours.

You can do the same capacity matching with RC Lipo. That's how i went over 90 cycles without balancing a 20AH pack. I only balanced the pack because i felt like it was a good idea to do it after a year. It only took 30 min to balance the whole thing, so it hadn't became very unbalanced during that time anyway.

There is something awesome about a 10S/20AH pack that sags no more than a 1.25v at a peak of 56 amps, cost under $400 shipped, puts out more power than i could ever need, is small, and was super easy to put together.

Nothing beats lipo right now unless you need thousands of cycles. Like scorpion says, if you commute, these aren't so bad. If your bicycle is an errand/grocery getter/pleasure mobile rather than a primary form of transport, 300-500 cycles aren't so bad, especially if you have a really large capacity pack.

There is no way you can run hobby lipo down to 3.5V on a regular basis and get good cycle life. Are you talking down to 3.5V under load or they recover to 3.5V?

[itchynackers]

I've been running the same 20c zippy's for 2 years now. I currently run 30s 12ah. I didn't have the capability to measure Ri initially. I have just under 200 cycles with no seat of the pants degradation. Normally I charge to 4.1v/cell. A couple weeks ago I was curious if I had any loss in capacity, and after a charge to 4.2v/cell, and discharging to 3.3v/cell (average), I got just OVER 12ah capacity. Pretty happy with them. In winter, I store them in a metal cabinet. Temps typically don't drop below 30F. I still have all the lifetime data on my CA, so if/when these ever crap out, I'll know the cycles/total ah used/ total wh used, etc... I'm curious as to the total wh/$ cost over a lifetime.

[neptronix]

There is no way you can run hobby lipo down to 3.5V on a regular basis and get good cycle life. Are you talking down to 3.5V under load or they recover to 3.5V?

Really! my turnigy watt meter must have been lying to me for the past 2 years
That is not under load, that is resting after some time.



I have packs that are extremely well balanced ( the iCharger gets calibrated every year now ) and no cells hit 3.0v until i am around 3.4v/cell. But i never take them that far unless i am really close to home. 3.5 avg. is the lowest i'll go.

I also do not run any funky packs. I have discharge graphed all 28 packs i have bought before using them, and ended up putting 3 aside as spare cell replacements.

I also charge up to 4.18v/cell average fairly often. I'll do this right before i take a ride.
That's how i get a little over 90% SOC cycles without a BMS.



Been preaching my lipo management techniques for a long time now. People that tend to follow similar practices seem to get the same results as me, or better. A few folks on here retired their packs at around 600 cycles, using a bit narrower SOC.

[o00scorpion00o]

Most LiFeP04 specs that I've seen may say 1000 cycles, but that's at 1C !

My main reason for going with LiPo was indeed energy density and small size, and a little less weight. I don't care too much about cycle life, size and weight are more important to me. I don't want a 1000 cycle battery when I know it would take me years to reach that, when I know something better is not that far away. I estimate 5 years before we get our hands on decent C rate NMC cells! So I will be happy if I only have to get another 4 bricks of 5ah, maybe the Zippy compact would do and maybe a few high C rate for the odd blast at 40 mph. Battery costs will get much cheaper in a few years too now that e.v production is ramping up!

Of course originally I planned on using the mac for cycling and the 5ah was going to be plenty. Cycling a lot with the mac saw me easily 20 miles using only 3ah or less depending on wind.

Then I realised how powerful the mac was and wanted more power for the occasional bit of fun. So I added more LiPo.

I really miss the mac and can't wait for the new parts to arrive.

Considering it can do 40mph on 16S and have tonnes of torque is really good, obviously running it at 3500 watts, while highly addictive, was always going to kill it, I hope to have it back running in a few weeks!

But anyway, the mac 8T would do 28 mph on only 12S which is pretty good, and have plenty of torque.

The most I got out of the pack (8.5ah) without charging was around 110 miles using it only for assistance.

So Lipo is more than good enough and I have not exactly been kind to it, when I first got the LiPo I was running only 1P and it was quiet hard on it, so I could have been kinder to it, but it still gives me 8.5 ah in 16S 2P and the last week I've been pretty hard on it with the pie in 24S 1P pulling 6-10c It was pretty warm.

Neptronix,

I must hook the bricks up to the Icharger and log a 1C discharger. If only I could find the usb cable and driver.

Anyone know where I can download the driver ?

[chilledoutuk]

i was going to mention that the problem with some turnigy packs going bad could be down to poor cell matching coupled with poor balance chargers.

If however you were to get the single cells and test the capacity of each cell you could build packs with very accurately balanced cells.

I do however think some of these cheap lipo packs have shelf life issues that the higher quality ones don't seem to suffer as much.

[flathill]

Hey Neptronix,

What was capacity now vs new? IR vs new? How many C are you pulling when the pack is almost discharged? Do you baby it as your pack runs down? All I'm saying is you should not recommend to the average user to discharge down to 3.5V on a regular basis. Cell life doesn't probably doesn't matter in your case because you are not pushing the cells very hard.

Just a rough example, if you were pushing the cells at 20C and only got 200cycles if ran down to 3.5V vs 350cycles if ran down to 3.7V it might make you more conservative. If you only pushing a 20C cell at 1C average then your cycle life is 500+ you start not to care. I'm coming more from the average user RC world where you push a cells much harder than the average ebike. In the serious racer RC world guys charge up to 4.35V because winning is more important than cycle life (money).

[mvly]

its hard to explain my reluctance with lipo packs from hobbyking and i think this post kind or explains my problems with HK packs.

People say only charge to 4.15v and discharge to 3.5v lvc and the packs can last to 500 cycles but at what cost to delivered capacity.

one of the bigest advantages of lipo is energy density but if you have to baby your pack to the extent your only able to use 75% of its potential capacity then its energy density
becomes no greater than that of for example a123 m1 cells.

for example take this pack
http://www.hobbyking.com/hobbyking/stor ... ouse_.html

it has an energy density of about 144 wh/kg factor in the 75% Hobby King care factor you are left with a battery with 108wh/kg that can do 500 cycles if your lucky. But cheap

a123 m1 cells also have energy density of about 108wh/kg but can be cycled reliably for over 1000 cycles.

High quality lipo packs can be cycled easily into there hundreds and in use at there designed parameters and keep there energy density of about 150wh/kg

Quality 18650 cells typically have an energy density of 185wh/kg or greater and there cycle life puts some of these cheap lipo packs to shame even when run at 2c discharge.

I have been trying to cycle a sanyo 18650 cell so that it is more in line with a couple of other cells in capacity terms and after about 20 cycles it might have lost 5ah if even that.

i am running a 5p 18650 pack built using sony cells from laptop batterys and in use the battery barely even gets warm and thats a pack with some questionable cells (thanks ebay seller for saying they had 100% life remaining lol)

Using a cell matching program kindly uploaded by another ES member i was able to get my 18650 5p banks to be within 2mah capacity of each other and from looking at my cellpro 4s when balancing they seem to remain perfectly balanced in use so far.

upsides to using Lipo:
Weight, ease of use, no BMS required, low series cell count to get high voltage.

downsides:
balance charge one in a while, potentially unstable, need to care for the battery

But you are right in terms of energy/dollar. It's probably similar if you only allow to charge to 4.1V and discharge to 3.6V to get similar charge cycle as LiFePo4.

[chilledoutuk]

Hey Neptronix,

What was capacity now vs new? IR vs new? How many C are you pulling when the pack is almost discharged? Do you baby it as your pack runs down? All I'm saying is you should not recommend to the average user to discharge down to 3.5V on a regular basis. Cell life doesn't probably doesn't matter in your case because you are not pushing the cells very hard.

Just a rough example, if you were pushing the cells at 20C and only got 200cycles if ran down to 3.5V vs 350cycles if ran down to 3.7V it might make you more conservative. If you only pushing a 20C cell at 1C average then your cycle life is 500+ you start not to care. I'm coming more from the average user RC world where you push a cells much harder than the average ebike. In the serious racer RC world guys charge up to 4.35V because winning is more important than cycle life (money).

Im sorry what are you talking about?

Having an lvc setting of 3.5v per a cell is very conservative already and completely unneeded in HQ Lipo packs.

I have Kokam packs that i discharge to 3v and charge to 4.2v and they have done hundreds of cycles in rc applications where they get used pretty hard.

If you were to set the lvc in your RC car to 3.7v per cell you would very likely loose a lot of power towards the end of the discharge as the controller limits the current to protect the battery voltage.

[flathill]

Hey Neptronix,

What was capacity now vs new? IR vs new? How many C are you pulling when the pack is almost discharged? Do you baby it as your pack runs down? All I'm saying is you should not recommend to the average user to discharge down to 3.5V on a regular basis. Cell life doesn't probably doesn't matter in your case because you are not pushing the cells very hard.

Just a rough example, if you were pushing the cells at 20C and only got 200cycles if ran down to 3.5V vs 350cycles if ran down to 3.7V it might make you more conservative. If you only pushing a 20C cell at 1C average then your cycle life is 500+ you start not to care. I'm coming more from the average user RC world where you push a cells much harder than the average ebike. In the serious racer RC world guys charge up to 4.35V because winning is more important than cycle life (money).

Im sorry what are you talking about?

Having an lvc setting of 3.5v per a cell is very conservative already and completely unneeded in HQ Lipo packs.

I have Kokam packs that i discharge to 3v and charge to 4.2v and they have done hundreds of cycles in rc applications where they get used pretty hard.

If you were to set the lvc in your RC car to 3.7v per cell you would very likely loose a lot of power towards the end of the discharge as the controller limits the current to protect the battery voltage.

Yes, the LVC can be set well below 3.5V. The LVC setting is where it cuts out under load. What I'm saying is the resting voltage should recover to 3.7V

[neptronix]

1) Capacity: same @ 1C.
2) IR has doubled in the 2 year old packs, which isn't atypical for a high C rate chemistry.. so my 20C packs are now more like 10C.
3) I run about 1.75-2.5C maximum at all times since i always run a particularly large pack ( typically 20AH, sometimes more. )
4) I don't baby it as it runs down, unless i need to, if i don't really have the amp hours to get home. My C rate is so low and the batteries are so wonderfully overspecced that the max discharge doesn't affect them too much.

I see why you think of lipos differently. I see them as a cheap, low weight, low size pack for long distance, since i can't get my hands on NMC which has a higher wHr/KG, yet still has decent output ( over 2C ). These are not throwaways to me, like they are in RC car usage. A very large pack will age quite gracefully over a long period of time, rather than trying to suck 50-100A out of 5AH worth of lipo.

Hey Neptronix,

What was capacity now vs new? IR vs new? How many C are you pulling when the pack is almost discharged? Do you baby it as your pack runs down? All I'm saying is you should not recommend to the average user to discharge down to 3.5V on a regular basis. Cell life doesn't probably doesn't matter in your case because you are not pushing the cells very hard.

Just a rough example, if you were pushing the cells at 20C and only got 200cycles if ran down to 3.5V vs 350cycles if ran down to 3.7V it might make you more conservative. If you only pushing a 20C cell at 1C average then your cycle life is 500+ you start not to care. I'm coming more from the average user RC world where you push a cells much harder than the average ebike. In the serious racer RC world guys charge up to 4.35V because winning is more important than cycle life (money).

[neptronix]

Yes, the LVC can be set well below 3.5V. The LVC setting is where it cuts out under load. What I'm saying is the resting voltage should recover to 3.7V

3.5-3.6v resting is a totally safe cutoff point unless you are running a bunch of packs with defective cells, running a crappy uncalibrated hobbyking $30 balancer, or doing something equally atrocious.

As my discharge graph showed, you still have a notable amount of energy 'till you hit 3.6v... 3.5v's got a little still.. 3.4.. forget it, and if you are running packs with funky cells or a low-quality balancer, then you prolly dipped some cells below 3.0v..

[o00scorpion00o]

Hey Nep,

How do you get those graphs in the logging program. The graphs I have are completely different !

The Icharger 208B can only discharge at about 1.2 amps max, I Don't know what resistor values to select, and I'm afraid to burn the charger.

But 1.2 amps is way too slow.

[cwah]

1) Capacity: same @ 1C.
2) IR has doubled in the 2 year old packs, which isn't atypical for a high C rate chemistry.. so my 20C packs are now more like 10C.
3) I run about 1.75-2.5C maximum at all times since i always run a particularly large pack ( typically 20AH, sometimes more. )
4) I don't baby it as it runs down, unless i need to, if i don't really have the amp hours to get home. My C rate is so low and the batteries are so wonderfully overspecced that the max discharge doesn't affect them too much.

I see why you think of lipos differently. I see them as a cheap, low weight, low size pack for long distance, since i can't get my hands on NMC which has a higher wHr/KG, yet still has decent output ( over 2C ). These are not throwaways to me, like they are in RC car usage. A very large pack will age quite gracefully over a long period of time, rather than trying to suck 50-100A out of 5AH worth of lipo.

Any idea about the battery total capacity after 2 years? Is it very far from the initial capacity?

[neptronix]

Hey Nep,

How do you get those graphs in the logging program. The graphs I have are completely different !

The Icharger 208B can only discharge at about 1.2 amps max, I Don't know what resistor values to select, and I'm afraid to burn the charger.

But 1.2 amps is way too slow.

I'm using logview, i've modified some settings quite a bit, and i'm in the iCharger's monitor mode, using an array of halogen lamps as a discharger. Due to this, the curve is just slightly skewed, but gives you a very close idea of how these look under discharge in a real world situation. ( in reality, the cliff is much sharper, and the curve it a bit less flat. )

Try dropping the the below logview file into your c:/program files/logview v2 folder and see if the look & feel changes for you to what i've been using..

http://neptronix.org/forumpics/DesktopDefault.lvd

[o00scorpion00o]

Thanks,

I'll give it a go next week.

[voicecoils]

I recently got a datalogging Cell-log 8S to complement the non-logging versions I've used previously. I figure it may be handy to log whichever pack seems to perform worst in the bunch I run but for the first trial, I just picked one at random.

The cell log data was recorded during a short ride then recharged and later transmitted to the logview program, then exported into Excel to make an easier to read graph.

The lipo 'bricks' used were these: Zippy 5000mAh 5S1P 15C (92.5Wh) $40/pack + postage

They are 2.3 years old, with less then 50 cycles on them, mostly stored at ~3.8v when sitting unused.

A total of 5 were used, run as 25S1P under the following conditions:

Peak discharge power: 120 W/cell 6.5C (3000W / 25S1P pack)
Peak charging power: 16 W/cell ~0.8C (400W / 25S1P pack)

And here's the graph:

cell-log-test.jpg (75.46 KiB) Viewed 281 times

As you can see, I wasn't terribly scientific...my starting and ending voltages were different 4.05v vs 4.15v and I didn't discharge fully during the ride but IMO I wasn't far from the lipo cliff beyond 3.6v. The bulk of the energy was clearly delivered between 4v and 3.7v (unloaded voltage).

The other thing that's clear is that all 5 cells are pretty well behaved, none seriously lagging.

What's the point of all this? I'm not really sure but it's a nice graph and a bunch of info that might be of interest to others.

[cwah]

Do you know what's the capacity of the battery after 2.5 years? Do you still have 5AH?

[voicecoils]

Do you know what's the capacity of the battery after 2.5 years? Do you still have 5AH?

I can do a discharge test with my iCharger 3010B. What C-rate do you want me to test at (ie what discharge current) and what starting and ending voltage? It's worth remembering that I've done very few cycles on my packs.

I can test at 7.5C, starting at 4.15v/cell and ending at 3.3v/cell for example. That would be half of the of the rated constant discharge rate and within a very conservative voltage range. A full test would be 15C from 4.2v to 3.0v but would stress the cells much more and exceed the iCharger's 1000W discharge power ability with a 5S lipo pack.

[cwah]

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

[Bluefang]

Hello, I have 6x 6S 5ah 20C, 12s15AH Zippy lipos that i have had for around 1yr or more and they still put out almost the full 15AH. I balance charge all the time using a hyperion charger to charge in 12S format and usually only drain them down to 20% max but i have had a few times where i have drained them down to 0. On the group ride i went on recently i drained them down fully and when charged they accepted 14432mah, so just shy of the 15ah at the start.

FYI these batteries have not really recieved the best treatment, the battery pack has fallen from my bike afew times, some packs have bits missing from the heat shrink around them from heavy falls and just about all the packs are puffed something shocking. Yet they have comfortably output ~10C when i was playing around with a bigger controller and would not get above slightly warmer then ambient.

Derek