4s 8000 lipo what brand?
 

Hi, I need 4s 8000 lipo but not blow my wallet, I know truerc has 4s 8000 but 10c only dun think it's enough for 1/8 CRT.

Maxamps is too expensive so any advise?thx

Any reason that you "need" 8000mah.... You could buy 2 4000 zippies and run them in parallel for 8000. What is this going it, cause that much lipo will be heavy and dimensionally big.

i m running a 30min main, i was using 6s 5000 zippy most prob cant finish the race, if i swap batt i will lose out( not a very good driver) i noticed maxamps has 4s 8000 at 700g same as my 6s 5000 with that i dun hv to swap batt.

maxamps 4s 8000 is us399, 4s 6500 us279 its alot

i cant run parallel as theres no space, any advise?

4s 8000mah batteries are not going to provide much more runtime then the 6s 5000mah.
(assume 3.7V per cell "nominal" voltage then 4x3.7Vx8A-h= 118.4Watt-hr
and 6x3.7Vx5A-h=111Watt-hr, only a 6.7% increase in storage)
They end up weight about the same because the store about the same amount of power...

what size battery area do you have to work with? could you put the pack(s) on their side to increase size? (aka do you have the height available). Any pics of your setup?

If you can fit it Mike has a 6s 6000mah battery for $309, my rough estimate is it should give you 30% more runtime (due to more stored capacity). It is pretty sizable though.... 168 x 48.5 x 66.5 mm

here is the link http://www.rc-monster.com/proddetail...pq25c6s6000mah

BTW if any of the battery Gurus disagree with my math/reasoning, please correct it. Thanks

i ran the 4s2p 8000 true rc pack, hate to tell you but its the same cells as the maxamps pack, it has excellent punch, but only runs for about 24 mins, thats with a 1y, so you might get another min or so with your 2000, but it wont cut it

Mike has a 7800mah 30C or 35C batts in his store. Way better and cheaper than maxcraps.

But the above is true, its not going to give you much mroe runtime (assuming you are not hitting the LVC early due to zippy's poorly matched cells)

Plus, if you are using that 1600 kv motor, 4S is a bit slow for it, esp if you are using 6S now. 5S really seems to be the sweet spot IMO. A 5S 7800 batt would get you there, but its quite heavy. Perhaps think about two small batts and a batt swap? What are the rules you are running against? Do you have to "courtesy pit" if you are running against nitros? Maybe the race director will excuse those if you do a batt swap.

spc has 2s 20C 8000mah for $72-75 :)

I m not sure how but I was told 6s 5000 won't run longer than 4s 8000 becoz of the amount of Mah, per cell does not increase run time but speed coz more cells. Correct me if I m wrong.

I can only take up to 750g which is one sided. 6s 6000 is 900g way too heavy. I can't parallel coz my setup is 1 sided batt n they are 150mm long.

I m racing against nitro already no pit stop is a advantage, but with a batt swap abt 40sec I lose 1 lap already.

I will post my setup pics later now using my crappy iPhone. I m chosing between truerc 4s 8000 n maxamps 4s 8000( but wallet empty)

If there's any other batt abt truerc price or abit more I dun mind thx guys

I'd buy TrueRC before Maxamps...

But why not try these in series?
http://www.rc-monster.com/proddetail...00sp302s3p7800

760g for 2 in series.

dont buy the maxamps, the true rc will hold up just fine as maxamps rates the pack at 160 continuous ans true rc is 80, but really the pack is good for about 120 continuos, you just wont make 30 mins with it, it is about the same runtime as your 6s 5000, it has about the same total energy stored.

I have a pair of those coming in the mail for my buggy, hope they are as good as eveyone says (since Mike is selling them I am sure they are).
But it still does not solve the additional runtime issue.

A truggy requires around 250w average power (typical from most people's runtime vs battery capacity figures). At 250w and 4s, that equates to ~17A average current. With 5Ah cells, that should give you around 17 minutes of runtime. With 8Ah cells, you should get around 28 minutes of runtime - still a bit short of 30 minutes.

But don't forget that with added capacity comes added weight, which adds to the load and will reduce the runtime. Track conditions (high grip vs low grip), drivestyle (lots of heavy throttle starts vs smooth throttle finger), ESC settings, etc all play a role too. Set the punch control high to allow the ESC to more gradually apply power (helps limit burst current and increase runtime).

But, for a solid 30 minutes, 6s paired with the proper motor and gearing is the key IMO. For the same 250w figure, 6s requires only ~11 average current. You still would need a little over 6Ah to get 30-35 minutes.

Hi Brian,

So if I m not wrong u r saying 6s 5000 will last longer than 4s 5000?

I m running a x2 CRT with 50slip diff n 12pinion, medusa 2000kv motor n watever batt that will last 30mins or more

If you have those batts running different kv motors that both end up spinning the same max rpm and the same gearing on each the 6s pack should give you half as much time again, say 30 mins vs 20 mins on the 4s. You have half as much voltage again with the 6s compared to the 4s.

A 1500-1600kv motor would be the best bet, along with a 5-6k mah 6s lipo. That will yield the longest runtime to the lightest weight. Plus you could get away with a 25c rated packs for track speed, that will also help with weigh/size as the higher c rated cells tend to be a little heavier/larger.

Yes. Like linc said, 6s 5Ah will have more runtime than 4s 5Ah paired with the right motor geared for the same speed. No matter how you slice it, it takes X amount of power to run your vehicle the way you want, for the length of time you want. Since power is V X A, higher voltage requires less current for the same power output.

... and cheaper.

I ran 1600kv on my main it was slow as I geared 12t n during my heats I use 16t n was slow. If I run 1600 I hv to gear higher (my heats is 10mins)

It means I may hv to do motor swap during my heats n main

As a former racer....changing motors between heats/mains I found to be personally a PITA...changing pinions is much easier. Find the correct motor so you only have to gear up or down a bit as the track permits

yes i used to change motor but now i change pinion, but i think its overgear for a 1600kv at 19t for 34.5mph, if i use 2000kv i worried abt my 30mins main.

But at 6s i can get 38mph at 14pinion

The joys of racing! The hardest part of racing is balancing performance and runtime

this is my setup n amain videos, i think its slow i m running 6s 5000 with 12pinion medusa 1600kv n 50slip diff on x2 crt.

i was 2nd in 20mins b4 my motor wire got desouldered, its a 25min main(usually 30mins)

its the pinky car with black rims



http://www.youtube.com/watch?v=uCQWdB1FvFw

http://www.youtube.com/watch?v=kDkW3-12eEU
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http://www.youtube.com/watch?v=t1giRI6bJ-Y

http://www.youtube.com/watch?v=tLZQM3lnULQ

http://www.youtube.com/watch?v=WwAvZsHiDpo
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wow i am new and you guys get down with the info , lost me a 5000,6000 lol
some guy is trying to sale me 2 4s 5000 for 120.00 and said to run them in parallel wow lost me at 4s help i just want to run the main rc911

lol, it may be a bit daunting to a newb, but it's not that bad unless you get really deep into it. We're just trying to say that it may be difficult to get 30 minutes on a 4s pack depending on various factors. It's not simply how much mAh your battery has, but the voltage, motor kv, gearing, drive style, weight, etc.

Personally, I was able to get over 40 minutes on 4s 8Ah with a Neu 1512/2d geared for ~40mph, but that was on a buggy. I always felt it was too heavy with those batteries, but I wasn't specifically looking for 30 minutes either.

Be careful about buying used lipos, or if they are too-low priced, unless you know how they were used (or abused). Were they balanced all the time? Were they ever used close to or over their max current rating? You usually get what you pay for. But, two 4s 5Ah in parallel would be 10Ah total. Should be plenty for 30 minutes.

Also, what kind of track is this? Is it big with lots of straights and not many turns? If so, setting it up for ~35-40mph would be advisable. If the track is small with lots of tight corners, set it up for ~30mph because you'll never hit top speed and the lower gearing will be more gentle on your batteries (and increase runtime). No matter what, use gentle throttle to keep the current bursts down.

Any advise guys n Brian? Can I use a amp meter n count backwards to see if it's better on 6s 5000 or 4s 8000?

Short of using something like an Eagletree device, the easiest thing to do is run whatever 4s pack you have at the track you plan to run at and measure the runtime. Then use this page to figure out your power requirements and average amp draw. Post that info here and we can help you choose the proper size lipo as needed.

I hv a amp meter by watts up, n can tell u d amp drawn for both 6s n 4s is that ok?

Unless you can take current samples every 1/10 second or so, it really won't tell much.

it will take d highest amp drawn any good?

Not really. The only thing that will tell you is the C rating of the battery you'll need. Like I said, all you need is the runtime you get, the voltage of the pack, and the mAh of the pack, and plug those values into that link I posted above. That will tell you the average current and power. Then we can go from there.

Sure man u got me all excited I dun feel like going to wrk just go track LOL but luckily my track is closed, they went for femca selection. No Ep:(

should start with my 6s 5000 on 1600kv or 2000kv on 35mph?

i would just use the 2000 kv and turn your epa on your radio down for 6s, this is like changing the pinion, it just controls the motor rpm back to what it was running on 4s, so really its like gearing down 3 teeth

I would run the 1600kv motor on 6s geared for 35. I think it will give you the best result.

You need to write a guide on how to lower your efficiency dude. Dropping the epa will only heat the esc up more, and is a poor substitute for a properly setup system.

I am guessing (since I do not race) that you benefit from having a faster truck for qualifying in order to get a better placement for the main? I am also guessing the qual is shorter than the main? Yet another quaint but pointless method to determine the starting grid, IMO. Race officials should not allow gearing or setup changes for the qual to the main, IMO. Get racing back to skill, not equipment... Probably why I do not race...

i have never noticed the mmm getting any warmer dropping the epa, ive heard that about old speedos but dont agree with it on the mambas, ive heard multiple others say the same thing but never noticed this among me and a dozen or so others around here doing it

Ok, at anything less than full throttle the esc has to switch the fets to chop the voltage down. That is what warms up escs, and that chopping has a by product of heat. No way to get around that. And making heat means that you are losing runtime...

Dropping EPA is a method of limiting the power of the motor but there is this concern that it may lower efficiency in the motor or esc. To my understanding, the motor will not be affected much as long as it is running within its optimum rpm range - where there is no significant predominately iron or copper loss.

As for the esc, switching loss of the mosfets is the main cause of concern when lowering the EPA. According to my findings, other than switching to rotate the magnetic field within a brushless motor, the esc varies the input power to the motor by doing pwm switching when powering each phase of the motor coils. Usually pwm is done at a constant frequency - only the duty cycle is varied. But at 100% duty cycle, the mosfets are turned on all the time. Anyway, a well designed esc will operate its mosfet at an efficient pwm frequencies while maintaining good performance. And to top it off, with advancement in mosfet technology, good quality mosfets can switch at high frequency with minimum switching loss as long as the switching current is of an acceptable range. Switching loss goes up as switching frequency goes up/switching current goes up. Switching loss due to gate capacitence is neligible at constant on or off state but becomes significant when switching at high frequency. This explains why mosfets heat up more when running at a lower than 100% duty cycle. At 100% duty cycle, the mosfets are still switching to rotate the magnetic field of the motor around the rotor but the switching frequency of the mosfets is reduced.

I doubt that there will a big difference in esc temp by lowering the EPA in todays well designed escs with quality mosfets. Many reported that running their brushless setups at half throttle seems to heat up the motor/esc more.
I am thinking that maybe there is lesser air flow (lower speed) or that the motor's efficiency is lowered due to it running at a lower than optimum RPM (copper loss). But then again, I highly doubt that the temperature increase will be a lot. Probably just 1 or 2C depending on the setup. I will test out different EPA values once I get my HW150A.

Slap me hard if I got it wrong. :D

I use heats as practise rather than push d car to it max becoz in main it's more endurance than quick dash.

The setup is heavier n safer driving, always stay away from crowds

Wats the safe cut off for racing? 3v per cell or 3.2

Low current application, 3V.

High current application 3.2 - 3.5V to be safe. For your case I think 3.2V will suffice.

I've been setting the LVC to 3V for all my lipos be it they are used in 1/36 or 1/10. So far no damage. My 1/10 e-savage (modded) is geared for 40 over mph.

thx man, so how's ur car going to any race?

that was a good write up, as for it dropping efficiency, your not wot barely at any tracks i run on, so i dont think it will do much difference