Thoughts on 4s versus 6s in large scale RC
 

Hello all, I'm looking to get some responses from those of you that have experience on runtime and durability/lifespan of batteries.

Question - assuming the same Mah rating of say 5000, will a 6s battery have a longer runtime than a 4s? Meaning, if i drive my RC at the same speed and never tap into the harder acceleration and higher top speed, will a higher voltage battery give me longer runtimes?

By virtue of not running it as hard, will the 6s battery as compared to the 4s last longer because I will not be running it as hard?

I'm getting into larger scale and I'm not a speed freak, but if more voltage and cells means a longer life for my batteries (assuming I can stay out of the throttle) then I'm all for it!

One can set up the same drivetrain performance with 6cell and 4 cell batteries in the drivetrain. The key is picking the correct wind of motor to match the selected battery voltage. Where the experience will be different is the 4s setup will run hotter, and if the mAh are the same between the two packs the run time will be shorter.

In reality, usually for the same weight of pack, the 6S has a lower capacity than the 4s, but the higher voltage operation is more efficient so you still get longer run time.

No battery pack likes a lot of mechanical abuse, and I can't say I've noticed a difference in life between 4s and 6s in this regard. Enough hard landings eventually kill everything.

A few thoughts -

To make the same power, at a lower voltage, you need more amps. V*A=W. So, at the same power output, the higher voltage system will run cooler, and have less stress on electrical components.

Also - our batteries are generally rated in mili-amp-hours(mah). To look at total stored power, it can be useful to use mili-watt-hours(mwa) or watt-hours (wa). So if the cells are 5000mah, each cell has (nominal) 18.5wh, so a 4s battery would have 74wh, and a 6s would have 111wh. So if the watt load (power load) is the same for both packs, the 6s will last longer.

Personally, I have antidotal proved this out to my self - at my local track, I often run my 4s 1/8 buggy and truggy at 70% throttle. Once, I tried to run 3s at 100%. Performance on the track was y similar. Runtime was noticeably shorter ( I didn't time it, but was surprised when it LVC'ed). Also, my motor truggy motor normally comes off the track about 110-130, that day it was 160f - lower voltage needs more amps to make the same power, which means more heat.

My .02

There is a Radio and Electronics section, this question should really be posted there.

4s setups are common because that is what ROAR went with for electric 1/8th scale. Personally, if I were to drop the $$$$$$$ on an ebuggy setup, I would go for 6s. Power levels would be similar, but a 6s system will not have to work as hard. If you are not bound by ROAR's antiquated 4s rules, go 6s.

Anecdotal, the term you are looking for is anecdotally.

On large scale 4s is for servos. :nod:Are we talking like a true 1/5 scale?

Hahaa no, not really large scale as in 5th scale and 8s. I just picked up a Traxxas ultimate desert racer. I have option of 4s or 6s and I'm thinking from my experiences with my tekno sct and scte as compared to my 1/8 buggy, that 6s is easier on electronics. Just wondering if 2s to 4s logic still applies from 4s to 6s. I'm more concerned with longevity than power, and would rather not buy a battery that will be overworked in it's application. I have 2s packs already, but I'll need to get more batteries for the new ride, and im looking to make a smart purchase based on replies here.

According to the reviews that I read on the Traxxas UDR, 4s gives just the right performance and it's over powered with 6s.

Best regards,
Brian

To really gain the benefits of a 6s pack (more efficient, cooler, longer life), you need to go to a lower kv motor. Also, like others said, it isn't a fair comparison to take a 6s 5000 mah pack and compare it to a 4s 5000 mah pack. The 6s pack in that example straight up has 50% more energy (and weighs 50% more as well).

If you can fit a 6s 5000 mah pack into the battery tray, then a 4s 7500 mah pack should fit as well. The difference between the two will be within 5% for run time and durability if you don't swap the motor and just rely on using less throttle/epa adjustments to reduce the power with the 6s pack.

When you use the EPA to limit the power, you end up with more switching losses. At 2/3 throttle (to roughly mimic 4s power on a 6s pack) the FET's are switching on and off thousands of times more per revolution than if you were actually at full throttle with a 4s pack. The switching losses eat up any benefit gained by going to the higher voltage.