4s versus 6s and runtime

[1truckerdan]

I was assuming the mah of the batteries and wattage to be the same ..only the kv and cell count as the variabiles.

[Erik Aa]

Hi Paul.

Good to hear that your race season is starting. Best of luck. It would be very interesting hear how the compacts performed in the first race. I am quite curious whether these cells will perform competitively or not, and how well they have coped with storage.

Kind regards,

Erik

[NativePaul]

I have some feedback on the longevity of zippy compact 4000mAh, both myself and another racer I know using zippy compacts have found that our cells have deteriorated badly whilst in storage over winter, last year I was putting about 4300mAh into them, first race this year I was short on time, charged up and only put 3200mAh into them, a couple of cycles later and they seem to be recovering a little last cycle I got 3450mAh out of them at 10A, but still well down on last year. It seems they need regular usage and long term storage at 3.8V doesn't cut it.

[Erik Aa]

This is interesting. Thanks Paul. I have just bought 6 a-spec 4500 mah 3s packs. I am very curious as to how they will perform. They will be run as 6s in my new exiga once I get the time to build it. The packs all arrived reasonably well balanced at approximately 3.81 volts per cell. I don't think I will discharge below 3.4 per cell. Agree?

[NativePaul]

They do seem to need 3.4V, they puff up if you take them down to 3.2V.

[Speedracer128]

Something strange is happening in my boat regarding run times that I'm not sure what is going on. I have a MG with a 4082 motor and a seeking 180 amp esc. When I run it on 4s (2 2cell lipo's) the boat runs normal with roughly a 5 min runtime. What I don't understand is that when I put my 2 3cell batts, as it should the boat runs much faster but what I don't understand is the low voltage cuts off the runtime between 1 and 2 min. But I don't understand why, because when I put the 3cell batts back on the charger they are anywhere from 65 to 75% charged. Both sets of batts are fairly new with less than 10 runs on them, haven't puffed up, gotten too hot or anything.

Does anyone know what could be happening? I was recommended to get a programming card and to lower the cutoff voltage to 3 volts instead of it's factory setting. I ordered the card to see if that will fix it. But if that would fix it I don't understand why it's working properly with my 2 cells

[martin]

Common problem on Seaking esc, they have an over sensative lvc that kicks in to early, thats why many that use Seakings turn off the lvc & time their runs. On 6s your drawing more from the batteries with the increase in performance & unless you have good quality packs you get a voltage drop under load triggering the lvc. Sometimes lowering the lvc voltage to 3.2v or 3v works, but make sure you dont go to low on capacity.

[Speedracer128]

Ok thanks for that info. The guy I buy my boat equipment is who told be to turn it down to 3v and that he would get me the programming card this week. As usual he gave good advise.

He just didn't explain it as well as you did. Your rite, about my batts. My 3s packs aren't as good with quality as my 2s's. how my current cut off is set, if it kicks in when its supposed to my batts get drained fairly low. That's why I didn't understand why lowering the cutoff would help. But since that's common with my esc I guess lowering the cutoff will fix it. But I def will have to watch my runtimes to not drain them too much.

So thanks again for the info

[Brushless55]

Hello.

Which set up is most likely to give me a 6 min + runtime? I run a delta force 29 with an octura x440x3.

1. 4s1p 6500 mah with a leopard 3674 2200kv motor.

2. 6s1p 5000 mah with a leopard 3674 1470 kv motor.

Any input on this would be highly appreciated.

Thanks,

Erik.

original posting

remember....... wattage (power) = voltage x amperage .......a lower kv motor on a higher voltage uses less amperage than a higher kv motor on a lower voltage. so you should see a longer run time with the lower kv motor and higher voltage setup.

yes, you are correct

Daniel, if you only want to lug around a set weight of battery say 560 grams then the higher voltage battery will have less capacity, it matters not a jot to the available energy if you have a 67A draw on 4s 6750mAh or a 45A draw on 6s 4500mAh both will give around 6 mins runtime, the advantage to 6s is that of efficiency, either you use the same ESC and wire in which case the lower current draw of the higher voltage setup will waste less energy heating the wire and FETs up, or you use a smaller ESC and wire, keeping the electrical efficiency the same but saving weight which increases the boat's efficiency. The advantage is small and a good 4s driver/boat will thrash a bad 6s driver/boat, but it is there and is noticeable if all else is equal.

this is incorrect
only about 4.8min on both 4s and 6s
and if you did run the same size mah pack say 5000mah on 4s your runs would be 3.58min and 6s again 5.33min
so that's about 50% longer run times on 6s

I was assuming the mah of the batteries and wattage to be the same ..only the kv and cell count as the variabiles.

me to

[NativePaul]

this is incorrect
only about 4.8min on both 4s and 6s

I would like to see the maths you used to work that out, the maths I used is rather simple so I don't believe I got it wrong, 6 minutes is 1/10 of a (60min) hour so if I take the Ah ((amp hour) mAh / 1000) of the cells and multiply it by 10 it gives the average amp draw for those 6 minutes. I just rechecked my maths and stand by what I said 67A average for 6 minutes on 6750mAh and 45A average for 6 minutes on 4500mAh.
The only "mistake" I made is rounding down the 67.5A actual average to 67A instead up rounding it up as is the norm for .5, I did this because you actually need between 6m5s and 6m25s (with mill and in lap) to complete a 6 minute Naviga race so in the real world Eric will need to pull slightly less amps than those above.

The reason I used 4500mAh and 6750mah is that those are the largest capacity 6s and 4s packs (I know of) that are under the 560g maximum weight allowed for the Naviga Mono2 class that Erik is interested in, in his first post he wrote 6s 5000mAh not knowing that the Desire 5000 cells he was thinking of were optimisticly labelled and only actually put out 4500mAh.

Erik, if you are still thinking of coming to Bridlington for our nationals the closing date for entries is looming last day is the 4th of June click here to book in for UK nationals

[Brushless55]

I would like to see the maths you used to work that out, the maths I used is rather simple so I don't believe I got it wrong

all based on your numbers with the 20% rule using this simple tool
http://www.offshoreelectrics.com/conversion.htm

[NativePaul]

Ahh, that is where you are going wrong, we don't use the 20% rule for Naviga racing. It is a good idea and will prolong the life of your cells, but if you leave 20% in your battery in an endurance race you are racing with 20% less power than others have, and will come last by several laps every time.

I know it reduces the lifespan of the packs but we generally run them down pretty close to empty and buy new packs more often. Technology moves on so fast that you lose about 5% advantage per year if you don't buy new packs, so even if they were still as good as new you wouldn't want to keep them forever anyway.

[Erik Aa]

Hi Paul.

My new Exiga is on the work bench with all the required hardware goodies, esc and batteries.
The building has commenced, but in between family commitments, so I doubt that it will be done in time for your nationals. Let alone be dialed in.

I think my maiden "serious m2" season will be spent building, testing and dialing in the hull. My strategy will be to hurry slowly.
The first time I hopefully come to visit you guys I would like all my gear to be in ship shape.

I have started a thread in another forum where I report on the building. It's in Norwegian, but it's got pictures.

http://yellowwhitehead.diskusjoner.c...ellowwhitehead

By the way, are there any races in Britain or continental Europe later in the season that draw an international crowd that could represent an alternative option?

Kind regards,

Erik.

[Brushless55]

Ahh, that is where you are going wrong, we don't use the 20% rule for Naviga racing. It is a good idea and will prolong the life of your cells, but if you leave 20% in your battery in an endurance race you are racing with 20% less power than others have, and will come last by several laps every time.

I know it reduces the lifespan of the packs but we generally run them down pretty close to empty and buy new packs more often. Technology moves on so fast that you lose about 5% advantage per year if you don't buy new packs, so even if they were still as good as new you wouldn't want to keep them forever anyway.

actually I am not wrong at all as the math I posted is correct
no one with common sense tells someone to race there packs all the way to 0% (to your math)
and your actually encouraging a member to ruin their packs and buy more often

most everyone on these forums use their packs season after season
check around and you will find out that's what we do

so many things in this posting that just does not make sense only to back up your run time math
just saying

[NativePaul]

It is a very different type of racing we do with Naviga to the sprint racing you do in the states, and the packs we use are different too.

I do the maths on 100% battery capacity because that is what there is available, I don't know how much of that the reader wants to use, 100%, 95%, 90%, 80%, 70% or some other arbitrary figure, and frankly I cant be bothered to do the maths for all eventualities.

I don't encourage anyone to run to 0% as there is no useful power to be had right at the end, speed has dropped off a cliff long before they get to 3.0v/cell (which is what most manufacturers still consider empty). I use a 3.4v/cell cutoff and agreed with Eriks suggestion of him using the same, I also advise stopping if you see it slow down, not rearming and coming back to shore but pulling inside the course and awaiting rescue. 3.4v/cell wont kill the packs we use (though it will reduce their lifespan and I am not shy in admitting that) it varies from pack to pack but it leaves between 3 and 6% in my packs. Some people I race with run a 3.2v/cell cutoff and are willing to crawl round the course puffing their cells for the extra lap, personally I am not that desperate for one lap or wealthy to do that, as we typically get 20-40 laps depending on the class one lap is not an insurmountable difference especially if it is a slow one, but if you leave 20% in your pack all your laps will be slow and you will be several laps down each heat, maybe you would be OK with that if you raced with Naviga rules, maybe not, I am not.

Most everyone on this forum does use packs season after season, they also sprint race either using the motor as a fuse or with high capacity and currents limited by available ESCs so there is no way to use all your capacity in a race. You also use High C rate packs that we cant afford the weight of in Naviga.

The cells seem to be much more static with the racing you do compared to the racing I do, taking 4s for example as 6s has only recently been allowed, 5 years ago I believe Hyperion VX 45c packs were arguably the best you could get or nearly if not, and while there may be better value cells today I believe that for performance they are up there with the best, so obviously you want your cells to last 5+ years. We have a very different situation, Naviga was trialing LiPo 5 years ago and the weight was the same as it is now 560g for a 4s pack, but back there there weren't any packs over 5000mAh underweight, but there was quite a choice of 5000mAh packs within weight, the various Enerland packs probably the most popular so you buy a flightpower 5000mah pack, then next year Overlander 5400mAh were available offering 8% more power than your FP, the year after Zippy and ETTI had 5800mAh offering 16% more power than your FP, the next year ETTI bring out 6300mAh cells offering 26% more power than your FP, and this year there are Turnegy 6600mAh available, so even if your FlightPower 5000mAh magically hadn't lost a single mAh you would still be 32% down on power compared to those that bought new cells this year. I wonder if you would still be running the FP pack or if you would have upgraded, and if so when, and how many times? If you had to run to 20% in order to keep that FP pack going for 5 years, the people that don't and upgraded this year have 65% more power than you. Does that arbitrary 20% rule still make sense?

Personally I tend to upgrade my cells every other year on my normal boats, though batteries for Minis are so cheap I upgrade whenever improved cells are available. I have Killed a few packs, but more often than not I relegate perfectly good packs to car duty because I want a shiny new bigger mAh pack.

Whatever way you look at it buying new packs sucks but it might not be as bad as you think, I bought a Thunderpower 65c pack for SAWs a couple of years ago, and as the high capacity cells we race with are all low C rate lightweight cells they are cheaper, I could have bought two packs of 5800mAh for the price of the TP 5000mAh and had change left over.

I have campaigned for a capacity limit since the start to increase cell choice and stop the mAh wars, but it is impractical to tech and a weight is easy so I doubt it will happen any time soon, and have proposed a sprint class which would allow us to be competitive and leave 20% in the cells but there is little interest in shorter races in England.

[NativePaul]

Erik I am not the best person to ask about races in mainland Europe as the worlds (Gent, Belgium 1-11 August) this year will be my first foreign event, I know the LiPoMasters in Moers, Germany, is pretty international but it was a couple of weeks ago, I guess most countries will have there own nationals many with an international contingent, ours was moved forwards to make way for the worlds but some may have moved back later in the season. I will ask around the frequent travellers at the next race.

[Brushless55]

So back to the original OP of the thread and not to boar this thread with smoke and mirrors

it is possible to get longer run times on 6s vs 4s like the original question asked..
specially with the same sized Mah packs....
and never figure runtimes with the math that takes lipo packs all the way down to 0% as damage most certainly will occur and you may not be able to finish a race with your boat out on the lake with empty packs.... or worse yet burnt packs with a burnt smelling hull and done racing for the day...

[Erik Aa]

Thank you Paul for your informative input and generosity. I appreciate it a lot. My exiga build is progressing, albeit slowly.
Kind regards,
Erik.

[Brushless55]

My exiga build is progressing, albeit slowly.
Kind regards,
Erik.

are you going to run the 4s setup?
that would be my choice with the bigger lipo
like to see this run when you are finished

[Erik Aa]

I'm setting it up to be competitive in Naviga racing. It will be run on 6s 4500 mah. I will run a 42 mm alu prop and 1400 kv initially. Will go up to 1700 kv eventually.
Regards,
Erik

[Brushless55]

Sounds good!

[urbs00007]

It's actually very close, but without knowing the current draw of the motor it is a toss up. Both configurations have roughly the same RPM, but I believe the single 6S pack will give you longer run times.
TG

considering the weight loss with 4-s compared to 6-s, does that make a difference for sport running?

[NativePaul]

There is no weight loss between the batteries being discussed here, 4s 6600mAh weighs the same as 6s 4500mAh, both are the highest capacity you can currently buy and stay under the 560g Mono2 battery weight limit.

[Erik Aa]

A small update on my 4500 mah 3+3=6S Aspecs. After winter storage all 3 of my 6S packs suffer from one cell with higher IR. It is really quite annoying. I try every time I charge to "after charge" the bad cell through the balance plug as Paul suggested in another thread, but it only works somewhat. It is a shame that one bad cell spoils an entire pack...

[Brushless55]

A small update on my 4500 mah 3+3=6S Aspecs. After winter storage all 3 of my 6S packs suffer from one cell with higher IR. It is really quite annoying. I try every time I charge to "after charge" the bad cell through the balance plug as Paul suggested in another thread, but it only works somewhat. It is a shame that one bad cell spoils an entire pack...

I agree, that's a bugger to happen while sitting in storage
I've had the same thing happen with a Giant Power/Dinogy pack