Range Issues

[kentsfreeman]

So did a range test and results were lower than I expected

Here is my current setup

16/44 gearing
NTM 5060 270KV
3s 5000mah 30c batteries x 2
150a Hobbyking ESC
83 Abec 11 clones

Range test was conducted with batteries starting full on day 1. Then resumed range test on day 2 without recharging so total range was 6.3 miles.

Day 1
Did 4.8 miles at average speed of 10.8mph with max speed of 19.2mph. Temp was 64F

Day 2
1.5 miles at average speed of 11.6mph and max speed 17.7mph. Temp was 86F

I weigh 210lbs but thought I would get better range than this. This was mostly flat riding with minor hills. I live in the Dallas, Texas area so terrain is very mild.

Batteries were discharged to 3.35 volts.

Just wondering if my range is expected or if there might be some issues I need to address.

Thanks!

 

[torqueboards]

It's about right. On the low end, you expect about 1 mile per 1000mah.

Are you running 6S in parallel and/or in series? I assume parallel. You are running at 6S 10ah? If you are 10ah, it seems a lot less than it should be. 10ah should get at least 10 miles.

You should definitely get a lot more then that. I should have 36T pulleys by the end of this week. You should probably try it and see if it increases your distance - I assume it would as less resistance.

 

[kentsfreeman]

I think I am running them in series actually. I have a battery connecter like the one below to connect them up.

http://www.hobbyking.com/hobbyking/store/__34450__EC5_Battery_Harness_12AWG_for_2_Packs_in_Series_UK_Warehouse_.html

Guess I should get a parallel connector. Speaking of that what are the differences in performance terms from running in parallel vs series?

 

[torqueboards]

You have 6S 5000mah 30C packs?

If you run in series that's 12S 5000mah.
If you run in parallel that's 6S 10,000mah.

Your HobbyKing ESC is only rated for 6S max.

The difference with series and parallel is in series, you add the voltage for added power. In parallel, you increase capacity of your packs as voltage stays the same. You either use one or the other.

Your typical distance on a single 5000mah would be about 6 miles or more.

Your ESC would of blown and/or not start with 12S voltage or shouldn't have and your top speed would of been a lot higher with 12S.

I would check your connections again and make sure you plug in your battery to your setup properly and how you would want it.

Let us know if you need help.

 

[vedder]

Are you running 6S in parallel and/or in series? I assume parallel. You are running at 6S 10ah? If you are 10ah, it seems a lot less than it should be. 10ah should get at least 10 miles.

For a given load profile, it does not matter whether the packs are wired in series or parallel.

If you run at a given speed, the range will be the same regardless if you run the batteries in series or in parallel even if you have exactly the same setup. To output a given torque at a given speed, you need a given motor current. If you double the battery voltage, you will get the same motor current at the same speed at half the duty cycle from before, and thus at half the battery current. The only way you would get lower range if you wire the batteries in series is if you run at higher speed which gives more wind resistance. Of course there are some differences in the ESC efficiency between the setups, but that difference is very small and most likely unnoticeable.

The range at a given load profile should be calculated from watt hours, not from amp hours. In my experience, I draw less than 10 wh/km (it depends a lot on my speed and the terrain though). Each 6s pack has 6 * 3.7 * 5 = 111 wh, so on two of them you should get about 111 * 2 / 10 = about 20km range or more. For your speeds, you definitely get too low range. If you are running on just one of the batteries, you range sounds about right though.

 

[torqueboards]

Thanks Ben for the technical details.

6S 5ah = 111wh
12S 5ah = 222wh

Average 10wh / km or 10wh/.62 miles

111Wh/10wh = 11.1 x .62 = 6.882 miles

1.24 miles = 20wh
5 wh = .31 miles and/or 5wh = .49 km

111Wh / 5Wh * .31 = 6.882 miles from 6S 5ah pack. 11.07km
222wh / 5Wh * .31 = 13.76 miles from 12S 5ah pack. 22.14km

6.88 miles sounds about right as far as distance goes for a 6S 5000mah LiPo pack.


I still don't know what you mean when you mention for the first half..

If you run at a given speed, the range will be the same regardless if you run the batteries in series or in parallel even if you have exactly the same setup. To output a given torque at a given speed, you need a given motor current. If you double the battery voltage, you will get the same motor current at the same speed at half the duty cycle from before, and thus at half the battery current. The only way you would get lower range if you wire the batteries in series is if you run at higher speed which gives more wind resistance. Of course there are some differences in the ESC efficiency between the setups, but that difference is very small and most likely unnoticeable.

I'm assuming you mean something different and/or based off what I said before.

Because it seems adding a pack to a setup in either series or parallel would increase the watt hours which would mean longer distances in this case.

Could you elaborate? I think I'm getting confused somewhere.

 

[kentsfreeman]

Sorry guys. Had a typo in my original post.

I am running 2 - 3s 5000mah packs in series.

 

[vedder]

It sounded like you are saying that you will get much more range if you wire the battery packs in parallel instead of series, so I'm just pointing out that it doesn't matter how they are wired if the load profile is the same. If you drive a lot faster when they are wired in series because you have more power this is true, but if you have the same driving style it does not matter range-wise.

 

[vedder]

Sorry guys. Had a typo in my original post.

I am running 2 - 3s 5000mah packs in series.

Then your numbers seem about right.

 

[kentsfreeman]

Thanks Vedder. If I go to parallel what could I expect with regard to range and top speed?

 

[torqueboards]

That's about right as far as range Kent. That's what I've been averaging with those packs as well for this reason I tend to carry extra spare packs to swap out as I prefer not to have all packs on the board.

I believe, most others are avging that as well.

It sounded like you are saying that you will get much more range if you wire the battery packs in parallel instead of series, so I'm just pointing out that it doesn't matter how they are wired if the load profile is the same. If you drive a lot faster when they are wired in series because you have more power this is true, but if you have the same driving style it does not matter range-wise.

ahh yes.. I only meant that if the current riding style was the same even with higher voltage - the distance would be longer.

Same riding style avg 6S 5ah = 6 miles and 12S 5ah or even 6S 10ah same riding style would be almost double the distance 12 miles? That's right, right?

Thanks Vedder. If I go to parallel what could I expect with regard to range and top speed?

Kent in your situation. On 6S 5ah you use 6 miles. Ben is saying at 3S 10ah (if you wire in parallel) your load profile (dependent on your riding style) requires 6S voltage and/or replaced with current.

By keeping the same Watt hours (6s * 5ah = 111wh) your load profile would be the same with either setup. You would need to add double the watt hours 222wh or equivalent for double the distance.

You would need 6S 10ah to increase your range at your current load profile vs your original 6S 5ah or you can also increase voltage which increase watt hours but you would need to upgrade your ESC.

*On a side note - 3S voltage is too low, so you most likely wouldn't want to run your board with such little voltage. Running them in parallel wouldn't solve your issue.

 

[kentsfreeman]

I think I got it. Parallel lowers voltage but increases amps and runtime.

Series increases voltage output but at the cost of amps and overall runtime.

Makes we wonder what is the most common battery people are using and how many of them?

 

[torqueboards]

6S 5ah is common. 8S 5ah. 10S 5ah. 8S/10S would get a bit more run time if you weren't heavy on the throttle and maintained the same riding as a 6S pack.

Mainly, people use them in twos to keep the main height for one pack thinner. Wire in series for higher voltage.

Ideally, you want both higher voltage + higher capacity but that adds to weight, cost, space available.

Any voltage over 6S also requires more expensive ESCs which allow for voltage higher than 6S.

People who want more distance wire them as in 2 in series and 2 in parallel. An example 4S 5ah pack using 4 packs wire 2S2P would be 8S 10ah.

Easiest is to use bigger packs. Ex. (2) 4S 10ah or 4s 16ah multistar packs. However, the packs are bigger which require more space.

Just depends on what you need.

 

[vedder]

Same riding style avg 6S 5ah = 6 miles and 12S 5ah or even 6S 10ah same riding style would be almost double the distance 12 miles? That's right, right?

Yes

I think I got it. Parallel lowers voltage but increases amps and runtime.

Series increases voltage output but at the cost of amps and overall runtime.

No. If you have the same driving style, the range will be the same. However, if you run on higher voltage on the otherwise same setup, you will get more power and higher top speed. So if you drive faster (because you can with the higher voltage), you will get lower range since driving faster gives more air resistance.

What is often misunderstood is that the ESC together with the motor inductance become a current transformer. For example, if you run at half throttle (assuming that duty cycle control is used), the motor current will be twice as high as the battery current. Suppose you have a 6s2p setup and you run at full throttle - then the motor will have the same current as the battery current. If you rewire the same setup to 12s1p and run at half throttle, the motor will behave exactly like the 6s setup at full throttle, but it draws half the battery current at the same motor current and speed because only half throttle is used. The difference is that on the 12s setup, you get more power on full throttle than on the 6s setup.