Turnigy Multistar - lightweight 10C cells

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Re: Turnigy Multistar - lightweight 10C cells

Post by DAND214 » Mar 29 2015 4:42pm

Any reports on capacity loss?
Only running 35amp controller 12s1p and no loss yet. But only have about 10 cycles.

Dan

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Re: Turnigy Multistar - lightweight 10C cells

Post by bionicdan » Jun 06 2015 5:58pm

I guess this is in relation to any lipo but it happened to my multistars so thought id ask here.


So I have a few cells that discharge themselves from 3.9 to 3.8v in 6ish weeks. So to boost them up fast I set the charger to nicad and accidentally went out. 4.8v later I came home to a house still standing and no drama. But im sat here trying to get it down to 4.2v and iv taken around 6ah out already. So this 16ah cell has taken 22ah?

Or have I just messed the chemistry up to make the voltage higher. I know lipos die fully charged ie they dont degrade like lead acid but more become locked with charge or something. Imagine in an ev race you could get 20 percent more capacity at the cost of 70 percent of your cycles probably?
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Re: Turnigy Multistar - lightweight 10C cells

Post by Alan B » Jun 06 2015 6:05pm

People have done that for racing. They do store more energy, but there is degradation too, and fire hazard.

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Re: Turnigy Multistar - lightweight 10C cells

Post by bionicdan » Jun 06 2015 6:16pm

I wont do it again as im a 4.18v man max but i expected the non linear curve. So I get around say 3ah from 3.9 to 4.0 and 2ah from 4.0 to 4.1 and 1ah from 4.1 to 4.2. Its stayed linear after 4.2 squeezing in 6ah to 4.8v. Anyway I'm grateful to the battery gods it didnt explode phew
Last edited by bionicdan on Jun 07 2015 5:59am, edited 1 time in total.
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Re: Turnigy Multistar - lightweight 10C cells

Post by Alan B » Jun 06 2015 10:05pm

Never use constant current to charge Lipo. Constant voltage is fine.

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Re: Turnigy Multistar - lightweight 10C cells

Post by bionicdan » Jun 07 2015 5:56am

Due to the resistance in using the balance leads to bring a self discharged cell back up, The charger wont pump much more than 1amp down it due to hitting 4.2v in the cable. Often it drops to 200ma.

So I find myself wanting to go out for a ride as the sun actually came out after the winter lasted 6 months and it takes hours just to correct one cell.

Unless of course I make the charger think its a 4cell nicad. Then I can drop 3.4 amps in and be good to go in 30 mins. Unfortunately I have previously had massive brain damage and am easily distracted and wandered off. It was on a washing machine ontop of the metal chargers psu in a garage. So I had at least taken some precaution.

Im sure theres a better setting I could have used perhaps. Doh just remebered my turnigy reaktor goes to 4.30v if I want but would still take an hour. Anyway this is a testament to the fire/puffing resistance of these cells
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Re: Turnigy Multistar - lightweight 10C cells

Post by Alan B » Jun 07 2015 6:12am

For balancing I find the BC168 to work quite fast, it charges through balance leads up to 8 amps and uses a separate DC-DC converter for each cell. I never go above about 3 amps, but with paralleled packs it is possible to. I suspect they measure the resistance of the leads and compensate for it.

Lipo has improved a lot, good to see the data. It will be interesting to hear how this overcharged cell behaves in the future, whether it shows more damage.

Take care and Be safe.

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Re: Turnigy Multistar - lightweight 10C cells

Post by bionicdan » Jun 07 2015 6:42am

I have a cellpro 10s xp (1 amp bleed current) and turnigy chargers that usually do the job just fine until I got a bunch of these multistars that arrived with a few low cells from new. Even when I ordered 4 all the manufacturer codes where hundreds differnt (ie not from the same batch boo) so I think they could have sent me previous customer returns.

Hobbyking refused to replace them but luckily a badly assembled pack looked puffed and they sent me a new one. Yup I will keep an eye on it but of course this was always an iffy cell anyway. I give up trying to baby things now lol Take it easy
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Re: Turnigy Multistar - lightweight 10C cells

Post by Alan B » Jun 07 2015 6:48am

I have a cellpro 10S and they are great chargers and super precise, but the BC168 handles out of balance packs a lot faster, doesn't need to bleed at all, just charges each cell separately in parallel, but only 6S.

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Re: Turnigy Multistar - lightweight 10C cells

Post by bionicdan » Jun 07 2015 7:13am

I guess as I only have 1 cell in any one config ( 1600mah 12s2p or 16s) I am doing what that bc168 would do anyway. And if I got more than one cell in any one pack il just sell it to someone who uses it more frequently and buy fresh ones. Maybe I have more money than sense ha ha.

I like not having to monitor every single cell on the pack while riding with no bms so id rather be this way around in thinking as my rides are sometimes 70 miles long and the last three miles is 600 feet in elevation. Cant have one cell going down or my mrs gets really mad so I demand perfectly balanced packs with matched capacities ha ha. I love that she takes an interest in all this and try my best to keep it as problem free as possible and least time consuming (sat in the garage staring at chargers). Women eh lol
GEARS? Where we're going we dont need gears!

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Re: Turnigy Multistar - lightweight 10C cells

Post by Alan B » Jun 07 2015 8:26am

A smarter charger will do better as it will adjust for the resistance of the leads and charge at more than 4.2V at the charger end of the wires without allowing the cell to ever become overcharged, and do so safely, without requiring attention from us.

By all means retire the iffy batteries and then a better charger won't be as important, and if funds are limited priorities have to be set appropriately.

One thing that is interesting to think about is that if you know which parallel cell group in your pack is the weakest, then a single meter across that cell tells you exactly when to shut off the motor and save the pack.

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Re: Turnigy Multistar - lightweight 10C cells

Post by bionicdan » Jun 07 2015 11:45am

Maybe my balance boards arnt making a good connection now they have been used allot and are causing the resistance.

Def with you on the monitoring. Iv marked the packs with each duff cell numbered. so when that hits 3.5 I know im pretty much baked. This has been My only reasoning for sticking with them as its just one cell per running pack.
GEARS? Where we're going we dont need gears!

Due to metal plates and a body full of nuts and bolts I am as bionic as my bike. Mxus 4t 120v toshiba fets and 16ah 24s nanotech.

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Re: Turnigy Multistar - lightweight 10C cells

Post by Alan B » Jun 07 2015 1:46pm

JST connectors are designed for a few plug/unplug cycles, not hundreds, so they could easily wear and have higher resistance than they started with.

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Re: Turnigy Multistar - lightweight 10C cells

Post by snejky » Jul 20 2015 7:48am

Some news? Number of cycles etc? Thanks

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Re: Turnigy Multistar - lightweight 10C cells

Post by Alan B » Jul 20 2015 11:20am

I put 2 cycles (40%) per most workdays on mine from March up until the end of June. Much less since then. Great so far.

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Re: Turnigy Multistar - lightweight 10C cells

Post by Offroader » Jul 21 2015 1:25am

Have any of you given thought about building your own pack instead of the multistars.

Can you build a better battery and as light weight with 18650s?

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Re: Turnigy Multistar - lightweight 10C cells

Post by riba2233 » Jul 21 2015 1:31am

Sure you can, even lighter :D
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Re: Turnigy Multistar - lightweight 10C cells

Post by Offroader » Jul 21 2015 11:51am

I just had to repair some of my turnigy packs, which always kind of sucks and they keep making the packs harder to repair with those annoying aluminum tabs.

I'd rather just build my own pack so I can repair bad cells more easily.

I may be leaning towards building my own pack then using the multistars.

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Re: Turnigy Multistar - lightweight 10C cells

Post by miuan » Jul 24 2015 2:23am

I always order 1 more brick so I never have to deal with tab welding. At current price the Multistars are pretty disposable anyway.
My 74V10Ah pack weighs 4300g including bag and costs 220 EUR including the spare brick.
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Re: Turnigy Multistar - lightweight 10C cells

Post by neptronix » Jul 24 2015 2:47am

Not sure if this has been mentioned, but there has been a significant price drop on 6S 10AH packs. They are now down to 70-80 bucks for the USA warehouses.

These packs are the easiest to stuff into a triangle frame bag. Icecube57 even fit 40AH of 12S into a falconEV bag with these. The 16AH 6S bricks are not so fortunately shaped; only 3 of them fit into a typical 19" frame bag.

When i got into RC Lipo, 6S 5AH packs were about $50 each. It's awesome that despite 5 years of inflation, costs for this stuff is actually lower now.
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Re: Turnigy Multistar - lightweight 10C cells

Post by neptronix » Jul 24 2015 2:51am

riba2233 wrote:Sure you can, even lighter :D
Yeah, but you can't get the same low internal resistance at all. If you are looking to build something with high power, you're going to need a lot more extra capacity to provide the same kind of battery performance, and that sucks if you don't need super long range.
On low resistance 18650s like the Samsung 25R, you end up lower total capacity delivery too at equivalent C rates.
It also costs more and is more difficult to assemble, but you do get better safety.

I did the math here, because i was really curious if 18650s really were better:
Turnigy multistar vs. Samsung 25R

I figure i can stuff 1.88kwhrs of multistar ( 12S, 40AH ) into a frame bag. Maybe it will be 1lb heavier, but it'll perform like a beast and cost me $608 before shipping. All i need to do is build a wiring harness, cycle them to filter out any bad packs ( if any ), and i'm good to go. Rather than soldering about 163 cells together.
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Re: Turnigy Multistar - lightweight 10C cells

Post by riba2233 » Jul 24 2015 2:57am

30Q, HG2, that's all I'm gonna say.


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Re: Turnigy Multistar - lightweight 10C cells

Post by neptronix » Jul 24 2015 3:14am

That graph is atrocious and that battery should never be operated like that without some form of liquid cooling, or it is toast in short order. In that condition, you are blowing over 10% of your energy as heat. If you are drawing 1000W, the battery is producing 100W of that energy as heat and giving you 900W out to your controller in reality.

A cell that drops from 4.2v to 3.7v immediately upon getting hit with a 3C load is an entirely unacceptable cell for very high performance bikes, unless you're willing to fill your triangle and a rear rack and accept a very heavy and bulky bicycle that has massive voltage sag, and thus does not give you the top speed you could achieve with a stiffer battery like a 10C or 20C lipo.

Image

This is what a 3 year old 20C lipo looks like at 1C at 51 degrees. The middle bar is when it gets hit with a 1C load.
We see about a 0.025 volt drop per cell.

Image

I tripled the internal resistance by freezing the battery, thus simulating the sag of a 3C load here.

We see almost 0.1 volt per cell of drop here, but not quite, lol.

Expect a 10C multistar to perform about half as good as that.

Those high density cells are only useful for lower power bikes. Guys who are interested in RC Lipos usually aren't buying them to power a 500-2000W setup, but that's what they're good for.. unless you are OK with a super heavy high power bike.
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Re: Turnigy Multistar - lightweight 10C cells

Post by riba2233 » Jul 24 2015 3:36am

What the hell man, are you blind, or are you doing this on purpose?! I've posted a 20 A graph, which is 6.6 C, not 3C!
In reality, nobody is going to draw 20 A continuous from these cells, and they have better energy density than multistar, and similar power density.

And it's clear that they are better than 25R which, as you've said, have same power density as multistars at high C rates (although you've never showed 8 C discharge for multistars).

Please, don't run this conversation with lies, thanks.
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Re: Turnigy Multistar - lightweight 10C cells

Post by neptronix » Jul 24 2015 4:45am

I made a mistake thinking that your graph is 3C. Simply did not check a number. It is not an intentional lie. My bad. By that, i also understated the watt hours that the cell would be wasting by a large degree. Do you notice that my story was consistent? :mrgreen:

But.. do you think that my, what.. ~0.8v at 3C scales up to anywhere near the ~0.45v sag at 6.66C though?
Nope, it's probably under 0.15v on a new 20C cell that isn't 3 years old, don't you think? ohm's law and all that..
I can provide you a proper test, but this is a linear math problem from what i have experienced. So we can do simple multiplication here based on IR.

Hobbyking lipos are rated similarly, so let's do some theoretics on the multistar ( sorry, i don't have any in my possession, but i know a lot from icecube57 who tested them extensively ). My 20C turnigy registered at 1-2mOhm when new, i'd expect a 10C multistar of the same capacity to have 3-4mOhm. We'll make assumptions and calculations based on that.

The samsung 30Q is rated at 20mOhm, but that's a 3ah cell and not a 5ah - we've got a 40% difference in cell size, so if we scale the batteries to an equal AH, you're going to see about 12mOhm. This math works because IR scales downward proportionally to amp hours when the amp hours increase.

12mOhm and 3-4mOhm are clearly not the same. To get power density, we have to do a little math on the multistars to compare a 190whrs/kg to cell to a.. i'm guessing.. 230-250whrs/kg cell? and then that depends on whether you are thinking about power density in volume or weight. mmm.... yeah, given that these cells are not immensely different in size and weight, i'd say that you can't bridge the gap between a difference of 300% by doing that math. You can try though. Just make sure to show your math :mrgreen:

You can call me a liar, but you did make a statement that was much more far off than my statement was, and probably didn't do any math to get there. So..
riba2233 wrote:What the hell man, are you blind, or are you doing this on purpose?! I've posted a 20 A graph, which is 6.6 C, not 3C!
In reality, nobody is going to draw 20 A continuous from these cells, and they have better energy density than multistar, and similar power density.

And it's clear that they are better than 25R which, as you've said, have same power density as multistars at high C rates (although you've never showed 8 C discharge for multistars).

Please, don't run this conversation with lies, thanks.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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