Turnigy Multistar - lightweight 10C cells

[Offroader]

Hi guys, just wanted to share my recent experience with Multistars.
About a year ago I bought some 4S stuff: 7pcs 10Ah and 6pcs 5,2Ah bricks.
I had a project going on that turned out redundant, so I put the batteries into my fridge.
After a year of sitting at 3-4 degrees celsius I pulled them out to complete a "fresh" 20S 15,2Ah pack with 40A Greentime BMS.
Well I thought the cells would be "as new" since they were refrigerated most of the time.
I discovered that after sitting for a year, 2 of the cells lost a couple hundredths voltage (well, maybe they were like that from the start).
I measured IR of all cells and all there were some big variatons. The worst of 10Ah cells were up to 50% higher IR than the best, and the same kind of variation was there for the 5,2Ah cells. Nothing serious though, considering I won't be pulling more than 80 amps.
Connected the BMS and manually balanced the cells to 0.01V variance. Discharged the pack to 3V per weakest cell. All cells were well under 3.5V by then, indicating less than 2-3% capacity variance between cells. Then fully charged to 4.19V per cell. The measured capacity was 15.5Ah. Very good for a battery that's over one year old.
Moral of the story is, you DO want to keep your batts refrigerated when not in use.

Modern Lipo don't seem to lose much even if not refrigerated.

What you should have done is test the capacity before putting them in the refrigerator, then test them when you took them out after they warmed up. But you would need to test them at close to the same temperature, as even small temperature differences will change the capacity by a few percent.

So these tests you did are not very useful to be honest.

I'm currently doing a capacity test on 18650 cells and put a lot of thought into this. I've put batteries in different locations, different voltages etc.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=81582

For example, here is a 4s 20C turnigy pack that I had sitting in my basement,

9/21/14 = capout 3494
4/10/15 = capout 3450
7/12/16 = capout 3463

You can see that it lost very little capacity in almost 2 years!, however, I took readings in september, april, and july, so the last measurement had the test done when my basement was 80F or 26C, which may have led to higher capacity.

But either way I'm looking at less than 1% capacity loss a year by sitting at 3.7 volts unused. Putting them in the refrigerator would have been a waste of space in my refrigerator. There is no indication that your packs have done better by refrigerating them.

This pack was also left at around 3.7 volts, which may have been why it saw very little capacity loss.

 

[Alan B]

The capacity losses from voltage related chemical reactions are unlikely to be linear. Chemistry is not a very linear system with respect to voltage.

The shipping voltage for cells was originally chosen for best storage life, too low and they might self discharge into trouble, too high and the chemistry side reactions would take their toll. New shipping regulations are changing that to reduce stored energy which was not a requirement before. Lower voltages are probably better if there is a monitoring/charging system to periodically offset the natural leakage (which is small but nonzero).

 

[motomech]

Useful size for some of us.
I ordered 6) to make 12S/10.4 Ah for $126
$12 to ship.
Total - $138
Luv this stuff :lol:
http://www.hobbyking.com/hobbyking/store/__66476__Multistar_High_Capacity_4S_5200mAh_Multi_Rotor_Lipo_Pack_AR_Warehouse_.html

 

[docnjoj]

My 16 ah Multistars x2 failed after 2 years during summer storage. A number of the cells went to 0 volts and I d/c ed tem and dumped them in saltwater for a couple of days. They are fairly inexpensive but unavailable now for Hobbyking (backordered). So I bought a Luna battery. A little less AH (14 vs 16) buy well within our 20 mile ride limit (around 10 ah). Also has a BMS so I can;t kill these like i did with the Multistars. I forgot to recharge after 20 miles and did it again the next day. Got 16 mile till the trike stopped dead. Bad for the cells. They recovered after a charge somewhat but were never the same. I am old and need a BMS.
otherDoc

 

[silviasol]

I have always used the 5ah turnigy's hard cases for the past 3 years. Never leave these cells at a full charge for more then a few days. Just one summer of riding twice a week and always having them sit a full charge after riding and they were puffed badly. Now I always storage charge them after a ride then charge them up the day I ride. No puff and no bad cells for the past 1.5 years that way.

 

[deepfraught]

Echo Silviasol, for any other lipo consumer device it's a convenient habit as well. Partial discharge storage from last use, charge less than full before next use.

Unfortunately even notebook power management doesn't have battery preservation profiles, so little hope of smaller devices having it.

 

[miuan]

Echo Silviasol, for any other lipo consumer device it's a convenient habit as well. Partial discharge storage from last use, charge less than full before next use.

Unfortunately even notebook power management doesn't have battery preservation profiles, so little hope of smaller devices having it.

So sad but true. I wonder if there is any android app or a native app for Samsung phones that shuts off charging at a preset SOC.

 

[Ykick]

Echo Silviasol, for any other lipo consumer device it's a convenient habit as well. Partial discharge storage from last use, charge less than full before next use.

Unfortunately even notebook power management doesn't have battery preservation profiles, so little hope of smaller devices having it.

So sad but true. I wonder if there is any android app or a native app for Samsung phones that shuts off charging at a preset SOC.

I've desired this for years with lithium powered portable devices. Dunno Android but I try to manually maintain my laptop battery between 60-85%. It would seem to be a simple thing to implement automatically?

 

[miuan]

[I've desired this for years with lithium powered portable devices. Dunno Android but I try to manually maintain my laptop battery between 60-85%. It would seem to be a simple thing to implement automatically?

I think my Dell laptop has a kinda lower SOC battery charge mode.
For single cell devices, maybe putting a diode in series on 5V charger cord could decrease voltage enough so that the cell would never reach 100%.

 

[bionicdan]

iv got an ebay "genuine samsung "BS"" android cable. It charges at about 150mah and never goes over 92 percent. Its great when Im using it as a modem to avoid heat and sitting at 100 percent when I havnt realised. Maybe it got tugged or something but that must be resistance at play

 

[Ianhill]

All my multistars I received from hobbyking uk have been around the 3.9v per cell mark and up to 5mv or so out of balance, so I dont know how they first charge them is it to 4.2v then discharge test the cells to 3.9v for an initial stress test of each cell or do they charge to 3.9v and do an IR test but what ever they do they end up around 3.90v.
When I fully charge to 4.2v and then proceed to discharge to 3.7v my coulomb counter says I have discharged 90% or 14.4ah of my 16ah pack so I believe the storage charge is set a little high to allow being sat on a shop shelf for months because we check our cell weekly or daily I believe anywhere between 3.7v-3.75v is a safe range to store at if you check them regular. After 6 months I have no noticeable IR loss yet according to my Icharger using this method.
Main thing is to make sure you never let the pack get to hot under discharge or rapidly charge them, for my 4s2p 16ah packs I find 60amp continuous to be their threshold any more and they start to become warm and I charge at 10amps and no heat gathers at all, not sure on other models specs or how they act but I'm happy with them for the price u can not go wrong a 16s 16ah pack for around £170 delivered.

 

[motomech]

Great info.
Thanx

 

[DAND214]

I have 6 - 6s 16ah packs. They came at 2 at a time about 6 months apart. All came at about 3.93 per cell. One set year and a half and still balances without a balancer, just bulk charged at 10amps. newest this last spring balances perfect and maintains it. So far I can say that these have been the best Turnigy's I have had.

Dan

 

[sketchism]

Time to check the cells after 1 year and 150+ hard cycles (26S2P at 180Apeaks) always charged to 4.1 and taken down to 3.6 at most although usually 3.7 or higher, with 32Ah i rarely run it low so the 80% -/- DOD is doing them well

Spent the morning checking cell balance and Internal Resistance for my white bike, time consuming but considering i hadn't balanced in months, (just bulk charging to 4.1 every ride) i figured it was due for a good going over. (the black battery in the pic is a 4S i made from a 6S that had a physically damaged cell at the start of last year)

I wanted to check the IR individually to see how the lifecycle is going for the multis, especially seeing as they are worked hard, up to 180A block bursts (90A each)
In Brief, the lowest cell of the 52, was 3.83 and the highest was 3.87 in different packs, the biggest difference in a single pack was 0.03 which is lovely

The Average IR per cell is 3.2 with a low of 3.1 and high of 3.5 within range, One pack however (coincidentally one that i used on a test run with a diff motor as 1p and really hammered at about 150A till it puffed) is mildly puffed/squishy and is reading almost double the lowest reading at 5.5 on 3 cells, i will be keeping an eye on this one. it is still within the range of (12000 / cell mAh) but is above the rest of the bike which is what i was checking for.

Getting the discharge test ready, I can pull 33A for the length of the cycle just over 2C (might need to throw some ice in the bucket it gets toasty)

I'll see how close to the rated 16000mAh we actually get

The short answer is 15.5ah

discharge load between 35Ato 30A so just over 2C in 29min 10 sec
From 4.2 to 3.0v/cell with cells 1 and 3 hitting lvc first and pack temp at 51c (load water temperature at 90c and I was pouring cold water into it non stop haha )
As soon as I let the load off the lowest cell jumped back to 3.34 so at a 1C discharge I have no doubt it would have been well over 16ah

This is after a year and 150+ hard cycles, I'm impressed with these batteries still and glad i took the time today to record these, ill check again in another few months and have a comparison figure.

 

[Ianhill]

Thank you sketism some cracking info by there and the thermal pic is a delight.
You can see the heat from the load bleeding back through the cable and into the cells, so the cells tabs must be a bit more toasty than the 50°c under the wrapper but that's a nice test the capacity has turned out well, but your at nearly 100% deplete with a cell voltage of 3.4v, I try to keep to 3.6v lvc that's normally around 80% deplete on mine then I find or about 13ah.

 

[motomech]

Great stuff!(the post and the batteries)

 

[redline2097]

Is it ok to connect 6s 8000mah graphene pack (internal resistance 5mΩ) to 6s 16000mah multistar (internal resistance 9mΩ)? I would use these pack three in series so it would total 18s 24000mah.

 

[miuan]

Is it ok to connect 6s 8000mah graphene pack (internal resistance 5mΩ) to 6s 16000mah multistar (internal resistance 9mΩ)? I would use these pack three in series so it would total 18s 24000mah.

As long as the discharge curves match each other and the parallel wiring doesn't have to handle excessive current, it should be fine.

 

[redline2097]

Is it ok to connect 6s 8000mah graphene pack (internal resistance 5mΩ) to 6s 16000mah multistar (internal resistance 9mΩ)? I would use these pack three in series so it would total 18s 24000mah.

As long as the discharge curves match each other and the parallel wiring doesn't have to handle excessive current, it should be fine.

I measured the packs internal resistance again. They look like this:

Graphene 8000mah 6s

PACK 1: 2mΩ, 1mΩ, 3mΩ, 2mΩ, 2mΩ, 1mΩ
PACK 2: 2mΩ, 1mΩ, 3mΩ, 1mΩ, 1mΩ, 0mΩ
PACK 3: 2mΩ, 1mΩ, 3mΩ, 1mΩ, 2mΩ, 0mΩ
PACK 4: 2mΩ, 1mΩ, 3mΩ, 1mΩ, 2mΩ, 0mΩ
PACK 5: 2mΩ, 1mΩ, 3mΩ, 1mΩ, 2mΩ, 1mΩ

Multistar 16000mah 6s

PACK 1: 5mΩ, 4mΩ, 5mΩ, 4mΩ, 5mΩ, 4mΩ
PACK 2: 4mΩ, 4mΩ, 5mΩ, 4mΩ, 5mΩ, 4mΩ

And they are connected like this:

Pack 1: 3 x 8000mah graphene
Pack 2: 1x 8000mah graphene and 1x 16000mah multistar
Pack 3: 1x 8000mah graphene and 1x 16000mah multistar

And those 3 packs are wired in series totaling 18s 24ah

Also checked hobbyking forums that both pack types should have about the same discharge curve. Should I worry how much?

 

[Jestronix]

I've decided to go 4 x 4s 20ah for my new build. I was almost going to get the 16ah but realised these are 4s2p, meaning if one of the 8 cells in the 4 cell pack went bad I'd be looking at a possible situation of thermal runaway etc. I've decided on multistars again, this time using the big 20ah cells in serial only. I balance charge every time, I'll never bulk charge again, I've killed packs before in bulk and it makes me nervous.

I think they are good value and do well if you don't stress these packs, most I'll do peak is 6c. I'll stay within the 80% discharge cycle and charge to 4.16 rather than 4.2. Really 4.1 is even better.

20ah packs allow for a pretty nice serial pack with nice capacity.

Also leaving packs at 3.8 rather than 4.2 helps. I'm over soldering 18650 packs

 

[amigafan2003]

Echo Silviasol, for any other lipo consumer device it's a convenient habit as well. Partial discharge storage from last use, charge less than full before next use.

Unfortunately even notebook power management doesn't have battery preservation profiles, so little hope of smaller devices having it.

So sad but true. I wonder if there is any android app or a native app for Samsung phones that shuts off charging at a preset SOC.

I've desired this for years with lithium powered portable devices. Dunno Android but I try to manually maintain my laptop battery between 60-85%. It would seem to be a simple thing to implement automatically?

For many people, laptops and mobile phones are disposable devices, so they'd rather have maximum capacity over a few years rather than 80% capacity over 7 years.

I've never kept a mobile phone for more than two years for example, so I don't care for the longevity of the battery.

 

[rainmaking]

Hello,

I have a different sort of bike that for various reasons am considering an electric conversion. One battery option I’m considering is to use 96S multistars, 24 x 4S. I believe I need about 30A on average with few second bursts up to 80-90A.

From what I have read on this and other relevant threads this seems around the limit of either the 16Ah or 20Ah bricks. I am curious which would be the better pack? I have space for either but the 20Ah setup would be around 100# which is pushing my desired load limit. It seems that there is more experience so far with the 16Ah. I know it’s 4S2P but still a lot of people seem to be having great success with it, even at higher current levels than the larger cells in some cases posted. They must match those parallel cells or anyway they seem to perform as one pretty well. Having the extra capacity of the 20’s would also be nice.

I want to make a custom machined aluminum sealed case for the battery and make a PCB for the interconnect. I also want to build bms into the board, although need to figure out what devices to use and how to isolate them given the ~400 peak volts. One benefit of using these multistars is that if/when I get a bad cell it is just a matter of unplugging and replacing the relatively inexpensive brick. 18650’s would be a lot harder to set up and maintain, and I’m not sure I could get the discharge rate. Of course fire risk is the chief drawback of the lipo….how high is this risk if I am watching all cell voltages?

Thanks for your insight

 

[wineboyrider]

Of course fire risk is the chief drawback of the lipo….how high is this risk if I am watching all cell voltages?

Very high! Never charge without checking voltages and always charge where you can expect fire and flames.

 

[rainmaking]

Of course fire risk is the chief drawback of the lipo….how high is this risk if I am watching all cell voltages?

Very high! Never charge without checking voltages and always charge where you can expect fire and flames.

Well I think I can mitigate the problem during charge. I'm more concerned about being miles out in the ocean discharging them....a bad enough fire would mean swimming. There must be some kind of warning in cell voltage?

 

[wineboyrider]

Well saltwater should discharge them very fast ! But, these are not a safe chemistry for those that are not informed of the risks. HK cell logs or balance charging every time is one safety precaution, but even then it has risks.