Higher Capacity Lipos

[Kelly Wilson]

I am seeing some 8000 & 9000 MaH lipo batteries on ebay. They are not graphene. Has anyone tried any of these ?

[Fluid]

I see plenty which are graphine, do you not want that chemistry? What C range are you looking for, I see packs from 15C to 150C. What use are you planning, sport running, speed, oval racing, long run times?






.

[Kelly Wilson]

[QUOTE=Fluid;750786]I see plenty which are graphine, do you not want that chemistry? What C range are you looking for, I see packs from 15C to 150C. What use are you planning, sport running, speed, oval racing, long run times?



I am going to need something around 8000 MaH and 100c. Because of space available I want to use a single battery. I just haven't seen any graphene with that capacity. I would prefer the graphene, just haven't found any available over 6000 MaH.

[RaceMechaniX]

Ken,

I would steer you away from a single large pack if you think you need 100C. The mechanical construction of the tabs and solder joints in large batteries cannot keep up with the chemical energy in the battery.
That is to say, if you try and pull 400+ amps the tabs will heat up and unsolder the wire or worse damage the cells with the heat. You would be much better off using a pair of 4000mAh cells and have two parallel sets of batteries.
With the parallel packs you split the amperage and this reduces the heating in the tabs and mechanical parts of the packs.

Most packs that are larger than 6000mAh are paralleled smaller packs inside the shrink wrap.

If you want a single large pack I recommend you give Mark at call at Dinogy. He builds large packs for jets with high discharge cells. Take a look at his BVM jet packs here:
https://www.dinogylipos.com/collections/bvm

-Tyler

[Kelly Wilson]

I am building a boat that is unknown territory for me. I am building a PTI QX400 tunnel. There isn't a class for this boat in our Dist so it is mostly for fun. I am using a K&B 7.5 lower leg and a "Q" ( 6S) 40 X 82 1320 kv motor. The inside trough of the hull is only 2 1/2" wide and 3" deep. The battery needs to be on or behind the c/g as much as possible. On a hard run of 6 laps I would like to not drain the battery below 80% capacity.....this is the reason for looking at the larger capacity single batteries. I estimate I will probably need at least 8000 Mah of battery to give a pull down to around 6000 mah.....that is strictly shooting from the hip.

Kelly

[HTVboats]

I have built and run several 6S tunnels. For heat racing I use 2 3300-3700ma batts in parallel, that will give you 6600-7400ma of power. 2 5000's would do what you want at 10000ma but you start to pay a weight penalty. With a 1320 kv motor youre right where you need to be. Try an M445 -545 or an 1816-45 bar ABC, Try to keep diameters below 50mm and use pitch to gain speed. More speed less run time.
Mic

[Kelly Wilson]

Thanks....good advice. I was wondering about props too. I learned my lessons the hard way on P Spec tunnel and P Spec mono trying to use too much prop and too little battery.

[Alfa Spirit]

[NativePaul]

Kelly Wilson, packs capable of a 100C discharge without killing themselves or while maintaining reasonable voltage don't exist yet, and my guess is that at LiPo's rate of progress 100C is so far into the future that we will have moved on from LiPo before we see any real 100C cells. Currently the best cells available will do 60C a few times, and after a dozen cycles 45C is the best we can get. If you buy 100C LiPos you know that the seller is BSing to you hard, and while the best LiPo sellers tend not to BS quite that hard, they all BS to some extent. There is some very good testing being done on the RCGroups forum and I suggest you research there to find out what is the best LiPo for your budget at the time you want to buy.

Fluid, I don't know of any LiPo packs that actually contain any graphene, at this time it seems to be a meaningless trade name. While it is generally applied to a seller's highest C rate line and thus can indicate a good cell, there are also companies with top end cells that haven't jumped on that marketing bandwagon, so I wouldn't let it sway my purchase.

RaceMechaniX, That is a very good point about the tabs being the weak point in cells at high discharge levels. I believe that localised cell degradation from overheating around the tabs is the reason for the 5000mAh (ish) cells they test on RCGroups dropping in C rate so hard after a dozen cycles at high current.

Alpha Spirit, I question your advice. That 15C drone pack is probably not a good idea for the OP that wants 100C.

[plinse]

Ken,

I would steer you away from a single large pack if you think you need 100C. The mechanical construction of the tabs and solder joints in large batteries cannot keep up with the chemical energy in the battery.
...
-Tyler

I must confirm what Tyler wrote.

Honest vendors already reduce the expectations on 5000mAh cells saying that the chemical energy is more powerful then the tabs. I just read in a shop that 65C cells 5000mAh should maximum be used for 20sec @ 65C.
On the other hand that is an established brand here in Germany. It is our local shop to go for when you want quality LiPo.

I have not seen real 100C cells to be honest. Real 100C continuous means you could completely discharge them without a break in 36 Seconds and repeat that multiple times without killing the pack.

I have some real 130C Peak- Applications and I have tried quite a number of cells. Many fancy C-Ratings in the Internet are barely worth half the number that is written. The best cells around can do 60-70C continuous and twice of that for short peaks.

The most powerful packs according C-Rating can be build with cells of ~2000-4000mAh, best value for money is using 5000mAh and to be honest, this is what I do.
My boats almost all use 5000mAh cells and I don't have specific packs for certain boats.
With this strategy I can operate all the boats I wanted so far, the only limitation is that package and weight might dictate which number of cells I should use, defining kV of the motor and a suitable ESC as a consequence. On the other hand I dont have high numbers of packs lying around and being dead after 3-5 years just by being forgotten
This happens to a lot of friends by the way

...
RaceMechaniX, That is a very good point about the tabs being the weak point in cells at high discharge levels. I believe that localised cell degradation from overheating around the tabs is the reason for the 5000mAh (ish) cells they test on RCGroups dropping in C rate so hard after a dozen cycles at high current.
...

I have some cheap 60C Packs - 60C continuous by the way, not Peak ...

They started to balloon being operated at 60C peak with about 3min runtime having a cell voltage of 3,8V afterwards as the hardest requirement they ever had to deliver. These cells were only 1 1/2 seasons old.

I stopped buying packs from brands giving fancy ratings and being less time on the market then I want to keep my packs

By the way we had 3 rapid thermal issues with LiPo at our flying field last season
All of them happend using packs from brands purchased from the Internet that hardly a second club-mate knew

[Kelly Wilson]

Thanks guys for all the input. I understand that the "C" ratings on many of the batteries is not only bogus, but meaningless. I am not hung up on "C" ratings, but was looking for more capacity in a single battery vs parallel batteries for a particular application, I use Giant Power batteries in most of my boats, but they are no longer in business, at least the battery business. I run two of their 6000 mah pack in series in my 1/8 scale FE and their 6500 mah 4S packs in my P Spec boats with excellent results. Usually a 6 lap race pulls about 4000/4200 mah from the 6500 pack and remains cool.

Several of you have given me a couple of good recommendations for me to look at. I appreciate the suggestions.

Thanks,

Kelly

[MarkF]

Kelly

I make big packs using 2 smaller packs in parallel. I make 8,000. 9,000 and 10,000 using my 65c formula. Check out my site and you can see a sample of what I carry. If I don't have what you want, I will make them for you.
https://www.dinogylipos.com/collecti...00mah-65c-lipo
My packs are same company as Giant Power.

Mark

[Kelly Wilson]

Thanks Mark....I will do that.

Kelly

[larryrose11]

Since the OP is not racing, no need to fit in a class.
What about going to a HV setup? double the voltage, half the KV on the motor.
1320/2 = 660 kv motor, 12S. Same (or better) power, half the current, less heat because power dissipation = I^2 * R.
instead of a parallels cells, put them in series.
Just an idea to throw out.

[Kelly Wilson]

Interesting idea, but I already have the 1350 kv motor and ESC to match, but might be a fun project in the future. Thanks for the input.

Kelly