6Likes
4S to 6S runtime.
08-02-2017, 02:08 PM
#1
4S to 6S runtime.
Thinking of going with a 6S for longer run times.
Approximately how much longer will my run time be if both are geared for the same MPH and using the same 90C / 6700mAh?
Right now I'm getting 15-16mins per run out of a 4S / 90C / 6700mAh lipo.
Approximately how much longer will my run time be if both are geared for the same MPH and using the same 90C / 6700mAh?
Right now I'm getting 15-16mins per run out of a 4S / 90C / 6700mAh lipo.
08-02-2017, 11:40 PM
#2
Tech Addict
iTrader: (1)
The simple answer: Volts*Amps=Watts. Watts are total energy. More watts=more run time.
4S: 16.8v*6.7Ah= 112.56 watt hour
6S: 25.2*4.5Ah=113.4 watt hour
People love to say "higher voltage is more efficient, and it runs a lot longer than the math would indicate"....this is urban legend, with no technical or scientific basis. It'll happen...someone will say it...in just a couple seconds from now!
But is 6S always better? No.
Let me explain by making two theoretical batteries with 3000 mAh cells rated at 15C*. Each cell weighs 40grams. And I will assume a max amp draw of 50A @ 16.8v, which equals 33.3A @ 25.2v.
4S (4S2P) 8 cells 100 watt hours 30C* 6,000mAh 320grams 50amps = 27% of max discharge rate
6S (6S1P) 6 cells 75 watt hours 15C* 3,000mAh 240grams 33.3amps = 75% of max discharge rate
6S (6S2P) 12 cells 151 watt hours 30C* 6,000mAh 480grams 33.3amps = 19% max discharge rate
This example shows that if all batteries are made from the same cells, the 4S2P (normal design) pack will perform much better than the 6S1P pack due to it's "2P" configuration. But if the 6S pack is made as a 6S2P, it will have the same capacity and "C" rating as the 4S, but with higher voltage. The down side is that this pack will also be bigger and heaver, since it will require 12 cells, vs the 8 cells in a 4S pack.
The potential disadvantage of the 6S1P pack is that it needs larger capacity cells to match the capacity of the 4S2P pack, and those larger cells have a lower "C" rating. So if the 6S pack is made from cheap cells, it's real world "C" rating might be very poor, less than 1/2 the 4S equivalent!
For the record, I have a truggy running on 6S. My 6S packs are SMC, and are rated at 85A @4,300 mAh...this translates to 19.7C. I compared these packs to the 112A @ 5,200mAh packs, coming in at 21.5C. In the example of these specific batteries, by running 6S I am stressing my batteries less than if I ran the 4S packs. That is the only difference...more "headroom" for the batteries, something that MIGHT lead to my batteries lasting a little longer.
So yeah, if you already set up on 4S, I would say it is highly unlikely that you will see benefit from switching to 6S that will justify the cost of making the switch.
* This 15C is real world performance of any lipo, although the best MIGHT be as good as 20C. With a 1/8 truggy, with high KV motor on 4S, driving on pavement, maxes at 100A current draw. This means a "real" 20C 5,000mAh is enough. A 4S2P pack with "true" 15C cells, creating a 30C 5,000mAh, would discharge 150A, 50% more than the motor will ever be able to draw. So yeah, "90C" is hilarious....
Last edited by fredygump; 08-03-2017 at 12:13 AM.
08-03-2017, 07:17 AM
#3
However, just throwing a 6S pack in isn't always a good idea even if you change the gearing. What KV is the motor? You can damage the rotor by over-revving it, so it's recommended you switch to a lower KV motor if you go to a higher voltage pack.
08-03-2017, 09:03 AM
#4
The simple answer: Volts*Amps=Watts. Watts are total energy. More watts=more run time.
4S: 16.8v*6.7Ah= 112.56 watt hour
6S: 25.2*4.5Ah=113.4 watt hour
People love to say "higher voltage is more efficient, and it runs a lot longer than the math would indicate"....this is urban legend, with no technical or scientific basis. It'll happen...someone will say it...in just a couple seconds from now!
I'll say it. Higher voltage IS more efficient, but for us it might be 3% more efficient if you used a 4s pack vs a 6s pack that had the same Watt hour capacity and a motor that pulled the same wattage in each scenario. Not enough to matter if you are looking for huge runtime gains. The electronics do run noticeably cooler, though.
But is 6S always better? No.
Let me explain by making two theoretical batteries with 3000 mAh cells rated at 15C*. Each cell weighs 40grams. And I will assume a max amp draw of 50A @ 16.8v, which equals 33.3A @ 25.2v.
4S (4S2P) 8 cells 100 watt hours 30C* 6,000mAh 320grams 50amps = 27% of max discharge rate
6S (6S1P) 6 cells 75 watt hours 15C* 3,000mAh 240grams 33.3amps = 75% of max discharge rate
6S (6S2P) 12 cells 151 watt hours 30C* 6,000mAh 480grams 33.3amps = 19% max discharge rate
The C rating doesn't change when in parallel. The capacity doubles, but the C rating does not.
This example shows that if all batteries are made from the same cells, the 4S2P (normal design) pack will perform much better than the 6S1P pack due to it's "2P" configuration. But if the 6S pack is made as a 6S2P, it will have the same capacity and "C" rating as the 4S, but with higher voltage. The down side is that this pack will also be bigger and heaver, since it will require 12 cells, vs the 8 cells in a 4S pack.
It performs better because it is a larger Watt hour pack,
not because of the 2P configuration.
The potential disadvantage of the 6S1P pack is that it needs larger capacity cells to match the capacity of the 4S2P pack, and those larger cells have a lower "C" rating. So if the 6S pack is made from cheap cells, it's real world "C" rating might be very poor, less than 1/2 the 4S equivalent!
The C rating is determined by the chemistry and build quality, not the size of the cell.
For the record, I have a truggy running on 6S. My 6S packs are SMC, and are rated at 85A @4,300 mAh...this translates to 19.7C. I compared these packs to the 112A @ 5,200mAh packs, coming in at 21.5C. In the example of these specific batteries, by running 6S I am stressing my batteries less than if I ran the 4S packs. That is the only difference...more "headroom" for the batteries, something that MIGHT lead to my batteries lasting a little longer.
So yeah, if you already set up on 4S, I would say it is highly unlikely that you will see benefit from switching to 6S that will justify the cost of making the switch.
* This 15C is real world performance of any lipo, although the best MIGHT be as good as 20C. With a 1/8 truggy, with high KV motor on 4S, driving on pavement, maxes at 100A current draw. This means a "real" 20C 5,000mAh is enough. A 4S2P pack with "true" 15C cells, creating a 30C 5,000mAh, would discharge 150A, 50% more than the motor will ever be able to draw. So yeah, "90C" is hilarious....
Again, cells in parallel don't double the C rating. A 4S2P pack in your example would be able to produce 75 amps continuously.
4S: 16.8v*6.7Ah= 112.56 watt hour
6S: 25.2*4.5Ah=113.4 watt hour
People love to say "higher voltage is more efficient, and it runs a lot longer than the math would indicate"....this is urban legend, with no technical or scientific basis. It'll happen...someone will say it...in just a couple seconds from now!
I'll say it. Higher voltage IS more efficient, but for us it might be 3% more efficient if you used a 4s pack vs a 6s pack that had the same Watt hour capacity and a motor that pulled the same wattage in each scenario. Not enough to matter if you are looking for huge runtime gains. The electronics do run noticeably cooler, though.
But is 6S always better? No.
Let me explain by making two theoretical batteries with 3000 mAh cells rated at 15C*. Each cell weighs 40grams. And I will assume a max amp draw of 50A @ 16.8v, which equals 33.3A @ 25.2v.
4S (4S2P) 8 cells 100 watt hours 30C* 6,000mAh 320grams 50amps = 27% of max discharge rate
6S (6S1P) 6 cells 75 watt hours 15C* 3,000mAh 240grams 33.3amps = 75% of max discharge rate
6S (6S2P) 12 cells 151 watt hours 30C* 6,000mAh 480grams 33.3amps = 19% max discharge rate
The C rating doesn't change when in parallel. The capacity doubles, but the C rating does not.
This example shows that if all batteries are made from the same cells, the 4S2P (normal design) pack will perform much better than the 6S1P pack due to it's "2P" configuration. But if the 6S pack is made as a 6S2P, it will have the same capacity and "C" rating as the 4S, but with higher voltage. The down side is that this pack will also be bigger and heaver, since it will require 12 cells, vs the 8 cells in a 4S pack.
It performs better because it is a larger Watt hour pack,
not because of the 2P configuration.
The potential disadvantage of the 6S1P pack is that it needs larger capacity cells to match the capacity of the 4S2P pack, and those larger cells have a lower "C" rating. So if the 6S pack is made from cheap cells, it's real world "C" rating might be very poor, less than 1/2 the 4S equivalent!
The C rating is determined by the chemistry and build quality, not the size of the cell.
For the record, I have a truggy running on 6S. My 6S packs are SMC, and are rated at 85A @4,300 mAh...this translates to 19.7C. I compared these packs to the 112A @ 5,200mAh packs, coming in at 21.5C. In the example of these specific batteries, by running 6S I am stressing my batteries less than if I ran the 4S packs. That is the only difference...more "headroom" for the batteries, something that MIGHT lead to my batteries lasting a little longer.
So yeah, if you already set up on 4S, I would say it is highly unlikely that you will see benefit from switching to 6S that will justify the cost of making the switch.
* This 15C is real world performance of any lipo, although the best MIGHT be as good as 20C. With a 1/8 truggy, with high KV motor on 4S, driving on pavement, maxes at 100A current draw. This means a "real" 20C 5,000mAh is enough. A 4S2P pack with "true" 15C cells, creating a 30C 5,000mAh, would discharge 150A, 50% more than the motor will ever be able to draw. So yeah, "90C" is hilarious....
Again, cells in parallel don't double the C rating. A 4S2P pack in your example would be able to produce 75 amps continuously.
08-03-2017, 09:11 AM
#5
The simple answer: Volts*Amps=Watts. Watts are total energy. More watts=more run time.
4S: 16.8v*6.7Ah= 112.56 watt hour
6S: 25.2*4.5Ah=113.4 watt hour
People love to say "higher voltage is more efficient, and it runs a lot longer than the math would indicate"....this is urban legend, with no technical or scientific basis. It'll happen...someone will say it...in just a couple seconds from now!
But is 6S always better? No.
Let me explain by making two theoretical batteries with 3000 mAh cells rated at 15C*. Each cell weighs 40grams. And I will assume a max amp draw of 50A @ 16.8v, which equals 33.3A @ 25.2v.
4S (4S2P) 8 cells 100 watt hours 30C* 6,000mAh 320grams 50amps = 27% of max discharge rate
6S (6S1P) 6 cells 75 watt hours 15C* 3,000mAh 240grams 33.3amps = 75% of max discharge rate
6S (6S2P) 12 cells 151 watt hours 30C* 6,000mAh 480grams 33.3amps = 19% max discharge rate
This example shows that if all batteries are made from the same cells, the 4S2P (normal design) pack will perform much better than the 6S1P pack due to it's "2P" configuration. But if the 6S pack is made as a 6S2P, it will have the same capacity and "C" rating as the 4S, but with higher voltage. The down side is that this pack will also be bigger and heaver, since it will require 12 cells, vs the 8 cells in a 4S pack.
The potential disadvantage of the 6S1P pack is that it needs larger capacity cells to match the capacity of the 4S2P pack, and those larger cells have a lower "C" rating. So if the 6S pack is made from cheap cells, it's real world "C" rating might be very poor, less than 1/2 the 4S equivalent!
For the record, I have a truggy running on 6S. My 6S packs are SMC, and are rated at 85A @4,300 mAh...this translates to 19.7C. I compared these packs to the 112A @ 5,200mAh packs, coming in at 21.5C. In the example of these specific batteries, by running 6S I am stressing my batteries less than if I ran the 4S packs. That is the only difference...more "headroom" for the batteries, something that MIGHT lead to my batteries lasting a little longer.
So yeah, if you already set up on 4S, I would say it is highly unlikely that you will see benefit from switching to 6S that will justify the cost of making the switch.
* This 15C is real world performance of any lipo, although the best MIGHT be as good as 20C. With a 1/8 truggy, with high KV motor on 4S, driving on pavement, maxes at 100A current draw. This means a "real" 20C 5,000mAh is enough. A 4S2P pack with "true" 15C cells, creating a 30C 5,000mAh, would discharge 150A, 50% more than the motor will ever be able to draw. So yeah, "90C" is hilarious....
4S: 16.8v*6.7Ah= 112.56 watt hour
6S: 25.2*4.5Ah=113.4 watt hour
People love to say "higher voltage is more efficient, and it runs a lot longer than the math would indicate"....this is urban legend, with no technical or scientific basis. It'll happen...someone will say it...in just a couple seconds from now!
But is 6S always better? No.
Let me explain by making two theoretical batteries with 3000 mAh cells rated at 15C*. Each cell weighs 40grams. And I will assume a max amp draw of 50A @ 16.8v, which equals 33.3A @ 25.2v.
4S (4S2P) 8 cells 100 watt hours 30C* 6,000mAh 320grams 50amps = 27% of max discharge rate
6S (6S1P) 6 cells 75 watt hours 15C* 3,000mAh 240grams 33.3amps = 75% of max discharge rate
6S (6S2P) 12 cells 151 watt hours 30C* 6,000mAh 480grams 33.3amps = 19% max discharge rate
This example shows that if all batteries are made from the same cells, the 4S2P (normal design) pack will perform much better than the 6S1P pack due to it's "2P" configuration. But if the 6S pack is made as a 6S2P, it will have the same capacity and "C" rating as the 4S, but with higher voltage. The down side is that this pack will also be bigger and heaver, since it will require 12 cells, vs the 8 cells in a 4S pack.
The potential disadvantage of the 6S1P pack is that it needs larger capacity cells to match the capacity of the 4S2P pack, and those larger cells have a lower "C" rating. So if the 6S pack is made from cheap cells, it's real world "C" rating might be very poor, less than 1/2 the 4S equivalent!
For the record, I have a truggy running on 6S. My 6S packs are SMC, and are rated at 85A @4,300 mAh...this translates to 19.7C. I compared these packs to the 112A @ 5,200mAh packs, coming in at 21.5C. In the example of these specific batteries, by running 6S I am stressing my batteries less than if I ran the 4S packs. That is the only difference...more "headroom" for the batteries, something that MIGHT lead to my batteries lasting a little longer.
So yeah, if you already set up on 4S, I would say it is highly unlikely that you will see benefit from switching to 6S that will justify the cost of making the switch.
* This 15C is real world performance of any lipo, although the best MIGHT be as good as 20C. With a 1/8 truggy, with high KV motor on 4S, driving on pavement, maxes at 100A current draw. This means a "real" 20C 5,000mAh is enough. A 4S2P pack with "true" 15C cells, creating a 30C 5,000mAh, would discharge 150A, 50% more than the motor will ever be able to draw. So yeah, "90C" is hilarious....
There is so much wrong here I'm not even sure where to begin.
Stop commenting on things you know nothing about, it makes you look like an idiot.
08-08-2017, 04:43 PM
#6
Going from a 4s 6700 mah pack to a 6s 6700 mah pack will increase your runtime by about 50%.
However, just throwing a 6S pack in isn't always a good idea even if you change the gearing. What KV is the motor? You can damage the rotor by over-revving it, so it's recommended you switch to a lower KV motor if you go to a higher voltage pack.
However, just throwing a 6S pack in isn't always a good idea even if you change the gearing. What KV is the motor? You can damage the rotor by over-revving it, so it's recommended you switch to a lower KV motor if you go to a higher voltage pack.
I'm running a MM2 with a Castle 2200kV motor.
I'll think I'm fine with going 6S. I've ran the same system in my Savage flux and Vorza flux.
Now I'm confused about SMCs ratings. When they say 90C why is that number so high if most lipos are 20C? From my math below they're not even 20C packs? And when SMC lists their amp rating is that what a load can pull upto?
Ex:
I'm looking at getting 2x-3S packs. It's between their 7200mAh 131A/90C or 6700mAh 145A/90C.
7200x20=144A
6700x20=134A
I'm currently using their 4S 6700mAh / 131A / 90C. When really pushing my truggy the lipo was getting in the high 130s at the end of the run. My LVC was set at 3.5V. My ESC and motor were well below max temps. It was recommended I go with a 6S setup.
Really confused and don't want to waste money on something that won't help.
I appreciate the help so far everyone!
08-08-2017, 08:52 PM
#7
Tech Addict
iTrader: (1)
I'm currently using their 4S 6700mAh / 131A / 90C. When really pushing my truggy the lipo was getting in the high 130s at the end of the run. My LVC was set at 3.5V. My ESC and motor were well below max temps. It was recommended I go with a 6S setup.
Really confused and don't want to waste money on something that won't help.
Try writing to SMC. They should get back to you pretty quick. They know their batteries better than anyone. They can tell you if switching to a 6S will be an advantage. They can tell you exactly which battery will work best.
I think there is a small advantage, if you get the right packs, but I'd be curious to know what they say.
About the rating, I recommend you read the info supplied by SMC. It's all the text you have to scroll past to view their battery selection! I trust them over the entire rest of the internet and RC industry!
The summary is that "90C" and "131amp" ratings are completely unrelated. The 90C is not a real; he says it straight up.
SMC calls it "90C" so you can compare it to other brands. He says his packs will perform as well or better than other brands' "90C" batteries
The "131 Amp" rating provided by SMC tells you what the REAL discharge rating is. You can calculate backwards: 131 / 6.7 = 19.55. I'll be generous and round it up to 20C. And that is a GOOD rating.
Here's the shocker:
131 Amps is more than you will ever need in 1/8 buggy or truggy! You MIGHT use up to 110A in a 1/8 truggy using roar approved electronics. Average is a lot less.
A battery discharged in 15 min = 4C discharge rate. For a 5,000mAh pack, this is a 20amp average discharge.
And battery temps--Lipos discharge most efficiently at 130F. My 6S set-up, at the lowest torque setting, puts my batteries at ~115-120F, assuming 75F ambient temps.
And to the haters:
A 5,000mAh pack rated 90C translates to 450amp "safe" discharge.
Do you really think an RC car battery can dump 450amps through a 10ga wire? Do you know how much energy 450 amps is? (If you want to see what high amps do to a wire, check out Photonicinduction on youtube!)
Think about it. A 90C discharge translates to draining your entire pack in 0.66 seconds! Yes, less than 1 second. A capacitor can do that, but not an RC battery.
I assume y'all are kids, so I encourage you to learn about physics and electricity. Not everything people say about RC is true. There is a TON of wrong info out there! Just because you hear it everywhere doesn't make it right!
Last edited by fredygump; 08-08-2017 at 09:13 PM.
08-09-2017, 05:48 AM
#8
And to the haters:
A 5,000mAh pack rated 90C translates to 450amp "safe" discharge.
Do you really think an RC car battery can dump 450amps through a 10ga wire? Do you know how much energy 450 amps is? (If you want to see what high amps do to a wire, check out Photonicinduction on youtube!)
Think about it. A 90C discharge translates to draining your entire pack in 0.66 seconds! Yes, less than 1 second. A capacitor can do that, but not an RC battery.
I assume y'all are kids, so I encourage you to learn about physics and electricity. Not everything people say about RC is true. There is a TON of wrong info out there! Just because you hear it everywhere doesn't make it right!
A 5,000mAh pack rated 90C translates to 450amp "safe" discharge.
Do you really think an RC car battery can dump 450amps through a 10ga wire? Do you know how much energy 450 amps is? (If you want to see what high amps do to a wire, check out Photonicinduction on youtube!)
Think about it. A 90C discharge translates to draining your entire pack in 0.66 seconds! Yes, less than 1 second. A capacitor can do that, but not an RC battery.
I assume y'all are kids, so I encourage you to learn about physics and electricity. Not everything people say about RC is true. There is a TON of wrong info out there! Just because you hear it everywhere doesn't make it right!
I agree with your other information for the most part.
08-09-2017, 07:09 AM
#9
Sorry for some reason I never got a email notification.
I'm running a MM2 with a Castle 2200kV motor.
I'll think I'm fine with going 6S. I've ran the same system in my Savage flux and Vorza flux.
Now I'm confused about SMCs ratings. When they say 90C why is that number so high if most lipos are 20C? From my math below they're not even 20C packs? And when SMC lists their amp rating is that what a load can pull upto?
Ex:
I'm looking at getting 2x-3S packs. It's between their 7200mAh 131A/90C or 6700mAh 145A/90C.
7200x20=144A
6700x20=134A
I'm currently using their 4S 6700mAh / 131A / 90C. When really pushing my truggy the lipo was getting in the high 130s at the end of the run. My LVC was set at 3.5V. My ESC and motor were well below max temps. It was recommended I go with a 6S setup.
Really confused and don't want to waste money on something that won't help.
I appreciate the help so far everyone!
I'm running a MM2 with a Castle 2200kV motor.
I'll think I'm fine with going 6S. I've ran the same system in my Savage flux and Vorza flux.
Now I'm confused about SMCs ratings. When they say 90C why is that number so high if most lipos are 20C? From my math below they're not even 20C packs? And when SMC lists their amp rating is that what a load can pull upto?
Ex:
I'm looking at getting 2x-3S packs. It's between their 7200mAh 131A/90C or 6700mAh 145A/90C.
7200x20=144A
6700x20=134A
I'm currently using their 4S 6700mAh / 131A / 90C. When really pushing my truggy the lipo was getting in the high 130s at the end of the run. My LVC was set at 3.5V. My ESC and motor were well below max temps. It was recommended I go with a 6S setup.
Really confused and don't want to waste money on something that won't help.
I appreciate the help so far everyone!
Personally, based on the info you've presented, I would go with the 3S 6700 mah packs. Make sure you gear down appropriately and you will have a vehicle that runs longer, cooler overall, and has more power.
Be aware you will put more wear and tear on your truggy, between the extra weight from the packs and additional torque from running the higher voltage setup. I would play with the torque limiting on the speed control to help mitigate the effect.
Ideally, if you could pick up a 1600-1800kv motor (same size as your current one) you will really benefit from the higher voltage setup.
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