Voltage gains vs weight = run time?

[Finnster]

He would be better off with the one pack. It can cert provide the power for that setup, so its just ballast at that point. Run 1 and swap later.

[starscream]

The only reason I would even consider running 4S is to participate in a sanctioned race. I can only guess why 4S became a standard for 1/8th scale racing but the reasoning that if a 10th scale vehicle uses 2S then 1/8th scale vehicles should use 4S doesn't jive. This is because the needed power to propel an object increases exponentially when you introduce additional mass. So, a vehicle with twice as much mass should take more than twice the power to achieve the same speed as a vehice that is half the size. 1/8th scale racing should allow 6S-8S setups.

[lutach]

Originally Posted by starscream

The only reason I would even consider running 4S is to participate in a sanctioned race. I can only guess why 4S became a standard for 1/8th scale racing but the reasoning that if a 10th scale vehicle uses 2S then 1/8th scale vehicles should use 4S doesn't jive. This is because the needed power to propel an object increases exponentially when you introduce additional mass. So, a vehicle with twice as much mass should take more than twice the power to achieve the same speed as a vehice that is half the size. 1/8th scale racing should allow 6S-8S setups.

Is there a sanctioning body putting rules for 1/8 scale racing or is it the clubs like Dirt Runners here in NJ who has put this rule because they use it with their 1/10 scale?

[slimthelineman]

look around and see all the things we run on high voltage. its for a reason. also 100 amp spikes arent realistic for some setups. the trick to all this is Kv. pick the highest voltage you can run and a motor that will give you the 30-35k rpms @ that voltage. HV+low Kv= mas efficiency! lower apmerage always means less heat which is power loss. i dont know about the whole weight issue my 6s 4200 is 585g and fits/balances well with the car. running a 1512 3d i should see spikes in the 60-80 amp range geared for 38 mph. waiting for my V3 so i can confirm amperage while running.

[BrianG]

Probably more of a safety measure than anything. 14.8v isn't bad, but getting up to the 8s+ range, and the voltages start getting pretty serious.

[starscream]

Originally Posted by BrianG

Probably more of a safety measure than anything. 14.8v isn't bad, but getting up to the 8s+ range, and the voltages start getting pretty serious.

Point taken but a dead short is gonna leave a big mark regardless of whether its 4S or 8S

Keep in mind that it isn't volts that kill its current/AMPS

A 12awg wire can only physically handle a finite amount of current

I personally run my 8S lipo's with 12awg wires and 35amp power poles so hopefully that'll reduce the potential damage.

I think 6S would be a reasonable alternative

[BrianG]

Originally Posted by starscream

...Keep in mind that it isn't volts that kill its current/AMPS...

True, around 0.015A to be more precise.

And I'm not saying it is justified, but I think if people start feeling the voltage, they will make more sudden movements in response. I can start feeling it on my figertips at around 30V. It's not enough to jerk my hand away, but other people might. especially if they are already nervous about it (which causes sweating, which lowers your resistance, which creates more current flow, which causes more sweating, etc...).

Also, for a given wire resistance, you get a lot more potential current with higher voltages than with low when shorted.

Yeah, it's reaching, but I can't think of any other reason for the limit.

[starscream]

Originally Posted by BrianG

True, around 0.015A to be more precise.

And I'm not saying it is justified, but I think if people start feeling the voltage, they will make more sudden movements in response. I can start feeling it on my figertips at around 30V. It's not enough to jerk my hand away, but other people might. especially if they are already nervous about it (which causes sweating, which lowers your resistance, which creates more current flow, which causes more sweating, etc...).

Also, for a given wire resistance, you get a lot more potential current with higher voltages than with low when shorted.

Yeah, it's reaching, but I can't think of any other reason for the limit.

8S has been my standard for a while now. I run 8S Apogee 2200's and the 12S sentilon which gets me around 25 minutes in my MBX5T on a small track. I've never felt voltage from any pack and really haven't worried about a dead short. This weekend, like a complete idiot, I connected my 2 4S apogee packs together. There was a small pop on the black powerpole connectors and both sides of the connectors seemed like they latched to one aother as if they were mangetically pulled together. I immediatly pulled them apart and saw no signs of puffing nor any noticable heat. Anyway, I guess all things come with risk, you just have to take the needed caution not to kill yourself
I'm not sure how much damage I did to my packs but they still work, for now anyway...

Note to self: when connecting battery leads to RC you MUST be fully awake and sober

[jhautz]

Originally Posted by starscream

8S has been my standard for a while now. I run 8S Apogee 2200's and the 12S sentilon which gets me around 25 minutes in my MBX5T on a small track. I've never felt voltage from any pack and really haven't worried about a dead short. This weekend, like a complete idiot, I connected my 2 4S apogee packs together. There was a small pop on the black powerpole connectors and both sides of the connectors seemed like they latched to one aother as if they were mangetically pulled together. I immediatly pulled them apart and saw no signs of puffing nor any noticable heat. Anyway, I guess all things come with risk, you just have to take the needed caution not to kill yourself
I'm not sure how much damage I did to my packs but they still work, for now anyway...

Note to self: when connecting battery leads to RC you MUST be fully awake and sober

If your not awake... THAT will sure wake you up.

[aqwut]

I just ran my buggy this past weekend at a trophy race, of course I was the only electric 1/8th buggy there.. Anyways, I hope this helps you out.. Going to higher voltage will help you keep the current down. I had 8 minutes on an oval race, before I had to do a battery change. And this data was going full out, finger was pretty much on full throttle most of the time, except for the turns.
Setup was
1/8 Buggy Mayhem Pro
Motor: Feigao 12XL (1390 KV)
ESC: OEM-RC 12S100A ESC
Battery: 4S1P PolyQuest 25C 3700XP
Gearing: 22 Pinion, 46 Spur
Throttle EPA: Cut down to 75%
Cut-Off: 2.85V/Cell
Run Time: 8 Minutes
Temperatures: ESC was ice cold, Motor was warm and battery was cool. it was only a 10 Minute Main, but I could've ran the buggy all day without heating issues. And if it was 6S and a lower KV motor, the motor may have been a little bit cooler as well.

Even with the EPA cut down to 75% it was still the fastest buggy in the straight of the oval track. So if you were to move up to 6S 2450mAh 25C Lipo, and 925KV motor... You'd have a more efficient setup meaning lower current, more efficient and maybe a few more seconds of run time. The move to 6S is definately worth it now, especially when you can pick up a Monster Maxx for about $150... Or one of Lutachs ESCs for around the same price...

[E-Revonut]

Originally Posted by aqwut

I just ran my buggy this past weekend at a trophy race, of course I was the only electric 1/8th buggy there.. Anyways, I hope this helps you out.. Going to higher voltage will help you keep the current down. I had 8 minutes on an oval race, before I had to do a battery change. And this data was going full out, finger was pretty much on full throttle most of the time, except for the turns.
Setup was
1/8 Buggy Mayhem Pro
Motor: Feigao 12XL (1390 KV)
ESC: OEM-RC 12S100A ESC
Battery: 4S1P PolyQuest 25C 3700XP
Gearing: 22 Pinion, 46 Spur
Throttle EPA: Cut down to 75%
Cut-Off: 2.85V/Cell
Run Time: 8 Minutes
Temperatures: ESC was ice cold, Motor was warm and battery was cool. it was only a 10 Minute Main, but I could've ran the buggy all day without heating issues. And if it was 6S and a lower KV motor, the motor may have been a little bit cooler as well.

Even with the EPA cut down to 75% it was still the fastest buggy in the straight of the oval track. So if you were to move up to 6S 2450mAh 25C Lipo, and 925KV motor... You'd have a more efficient setup meaning lower current, more efficient and maybe a few more seconds of run time. The move to 6S is definately worth it now, especially when you can pick up a Monster Maxx for about $150... Or one of Lutachs ESCs for around the same price...

Why do you have your lvc set below 3v/cell?

[stum]

Interesting.. Anyway my tekno v3 8ight buggy gets me 20minutes of HARD racing.. ~30minutes if I'm waiting for the nitro guys to refuel and cool down... this is w/ my medusa v2 60mm 2000kv and 4s 5000mah geared for 40mph. My 8ight-t I Just decided to run w/ my Neu 2.5d, so I plan on playing around for the rest of the year w/ a 4s config geared for about 38mph (17/48) and next year before the races start I will snag a pair of 5s 5k packs and regear to 15/48 for the race season.. that way I have fresher packs for the season. I'm hoping this combo will get me through a 30min a-main, time will tell.

[Finnster]

Hv is nice and has alot of advantages, but more care is required as V goes up. Plugging in a 35V battery into a esc w/ empty caps produces a pretty shocking spark. Even plugging into the charger as well.

I doubt it will be std as its a little too dangerous for the careless n00by masses to play with, and good results can be made out of a LV setup. I really really liked the 2Y on 8S I had tho. Very very eff and always cool.

[lutach]

Originally Posted by Finnster

Hv is nice and has alot of advantages, but more care is required as V goes up. Plugging in a 35V battery into a esc w/ empty caps produces a pretty shocking spark. Even plugging into the charger as well.

I doubt it will be std as its a little too dangerous for the careless n00by masses to play with, and good results can be made out of a LV setup. I really really liked the 2Y on 8S I had tho. Very very eff and always cool.

A anti spark is easy to make and BrianG has made it even easier. I love the sparks and the more for me the better, it lets me know the caps are ok. High voltage is no more dangerous than lower voltage. Higher voltage is safer when being operated mainly because nothing is getting stressed liek they do with lower voltage. I find that AMPs are way more dangerous then voltage. I've been messing with HV for a while now and haven't had any problems with it like I did with my lower voltage set ups I had in the past. Just my opinion and I know we will have others that has never experianced HV like we are doing that will say otherwise, but when they change, I feel some apologies coming up . Hail for HV for making me go crazy and ask the Chinese to biuild my 10S ESC . I would've loved it to keep it in the US.

[Finnster]

Yeah I had an antispark, works well. I think HV really comes into its own the larger the vehicle gets, or the more power is required. A 1600W setup in a light little Revo or truggy for the track is passable on 4S, but when you want to really run it hard and not worry about it, or are looking to go to a bigger truck, you really need HV to make the power and keep it cool.

Even now, my 2.5D/ 5S gets truggy get pretty hot after a while if I take it in the grass for a while, try to do hill climbs or a few other things I've done with it and got it hot enough to have to stop and let it cool for a bit. HV was always reliable no matter what I did to it. I'm going to convert my Savage XL to BL soon enough, and that thing will need pretty high power and efficiency to run really well and reliable where ever I take it. 8-10S on a 80mm can seems like the way to go