Building an electric racing gokart (on my bucket list )

[amberwolf]

ok, i've moved it over to the other thread for you.

i recommeded making the wiring diagram and keeping it updated because it is a huge pita to figure out wiring while troulbeshooting something later on, especially if you're looking for something aused by phsycial damage like in a crash (which we know can never happen in a race on a track :lol: ) i've had to deal with is problem numerous times ove rthe years with my experiments because i don't take my own advice.

 

[ZenaWarrior]

I've finished the build, and done testing, and am quite happy with the speed. I'm going tru the program to make some small changes. Question... on the port settings there's 6 round/squares IO,SW,LA,F,U,D what do they mean ? Since all my gear comes from a scooter, it don't have reverse well it's there on PA0 dot on F, but doesn't work, and I can do without, but PB3 has sport mode, wich I would like, not working. 1-2-3 mode is working and I thought it was working, but it was gear 3. I wanted to have a push to pass

 

[ZenaWarrior]

ok, i've moved it over to the other thread for you.

i recommeded making the wiring diagram and keeping it updated because it is a huge pita to figure out wiring while troulbeshooting something later on, especially if you're looking for something aused by phsycial damage like in a crash (which we know can never happen in a race on a track :lol: ) i've had to deal with is problem numerous times ove rthe years with my experiments because i don't take my own advice.

I've finished the build, and done testing, and am quite happy with the speed. I'm going tru the program to make some small changes. Question... on the Votol 100 port settings there's 6 round/squares IO,SW,LA,F,U,D what do they mean ? Since all my gear comes from a scooter, it don't have reverse well it's there on PA0 dot on F, but doesn't work, and I can do without, but PB3 has sport mode, wich I would like, not working. 1-2-3 mode is working and I thought it was working, but it was gear 3. I wanted to have a push to pass
I don't understand how to put my questions first on the list for people to see, they shouldn't have to go tru 2 pages to find what it's all about, or am I not understanding how to do this.
Thank you for your advise.

 

[ZenaWarrior]

Sorry this may not be the right place to ask, but here goes: what setting in a votol em 100 controller program turns it off automatically. I can load a bin file before and after modifying. I can show more like pictures, but there's some allready somewhere. Motor speed was around 5000, I changed amp from 65 to 85 and a couple of other things, and motor spun up to 7500. Test before changes 81 kph after 100 kph and it shut down, disconnected the batteries 2 off 76 volt 30 amp in parallel, ran again after connection.

 

[ZenaWarrior]

I've finished my racing gokart using motors, controllers and batteries from 2 identical step through scooters. I went racing against modified 4 strokers, but weren't fast enough, so now I've modified the controllers, and gained about 40% more speed, took it for a test drive, switched "gears" and reached 100 km/h when it shut off. I disconnected the batteries and reconnected them and was going again. I tried again, and the same happened.
Here's some settings from the scooter controllers Votol em 100:
Page 2: HDC lowrst speed 5050 which I changed to 6050 but I also disabled HDC. When tested on the trolley it spun 7500 rpm. Should I keep the HDC and make 6050 to 7500 rpm, or is something else I can do.
I need this fixed before next race meeting 27 of April

 

[eee291]

Is the battery spec high enough to even keep up with the load?

Sounds like the BMS shutting off from high current or maybe voltage sag.

 

[ZenaWarrior]

Is the battery spec high enough to even keep up with the load?

Sounds like the BMS shutting off from high current or maybe voltage sag.

I've no idea of the spec, the batteries are from the scooters, 2 from each. The amps was set at 65, I reset it to 85, which is max for Votol 100, so maybe set at 80 or 75, and see how it goes. But I thought there would be a max rpm to be set and I hit it. Mind you 2 battries in parallel both was turned off or it was the controllers that turned off. Had to disconnect and reconnect batteries to go again

 

[eee291]

If you have to reconnect the battery in order to get power from them it's the BMS 100%
You may need a third battery or even fourth.

I personally don't really like grouping a bunch of batteries together, ideally you'd have one capable battery.

 

[amberwolf]

Sorry this may not be the right place to ask, but here goes: what setting in a votol em 100 controller program turns it off automatically.

Turns off the controller?
Or turns off the system?
Is power completely lost (no voltage to controller)?

Motor speed was around 5000, I changed amp from 65 to 85 and a couple of other things, and motor spun up to 7500. Test before changes 81 kph after 100 kph and it shut down, disconnected the batteries 2 off 76 volt 30 amp in parallel, ran again after connection..

If you are using batteries only capable of 30A, two in parallel can only handle 60A. So you cannot set the controller any higher than 60A battery current limit, or you are exceeding the battery capability.

Doing that means either damaging the BMS or the cells, or having hte BMS protect the cells from you by turning off all output so you don't damage the cells in a way that can lead to a fire.

 

[amberwolf]

Did the system actually power off, no voltage to the controllers? If so, it's the BMS that turned off to protect the cells from damage that can lead to a fire (doing it's job).

In this event, you would need to be monitoring the voltage and current to and from the battery from the controller(s) to see which one exceeds the BMS limits.


If the system does not actually lose voltage to the controller(s), then it's a controller setting or hardware limitation being exceeded, so it's shutting off the motor to prevent damage to either motor or controller or battery, depending on what limit is being exceeded.

If you don't have a wattmeter on the system that can at minimum remember max amps, min voltage, max watts, etc., I'd recommend installing one between battery and controllers. You can get cheap ones on amazon, ebay, etc., like this one that I've bought and verified power up of but haven't used on a system yet https://www.amazon.com/dp/B013PKYILS so can't say how well it works. There are lots of similar ones out there.


Also, from your other post on the subject in a different thread:

Motor speed was around 5000, I changed amp from 65 to 85 and a couple of other things, and motor spun up to 7500. Test before changes 81 kph after 100 kph and it shut down, disconnected the batteries 2 off 76 volt 30 amp in parallel, ran again after connection..

If you are using batteries only capable of 30A, two in parallel can only handle 60A. So you cannot set the controller any higher than 60A battery current limit, or you are exceeding the battery capability.

Doing that means either damaging the BMS or the cells, or having hte BMS protect the cells from you by turning off all output so you don't damage the cells in a way that can lead to a fire.

 

[ZenaWarrior]

I don't know the max current of the batteries, there's no info on them. I use the two batteries which come from one scooter, 30 amph X 2= 60 amph. I've 4 identical batteries. Today I ran the kart on my dyno to see how much current it would use and to see if it would switch of. Measuring was not succesfull, don't really know what I'm doing. The numbers didn't make sense.
What size battery should I iam for ? if the motors make 4000 watt each (2 of and 2 Votol em 100 controllers) ?

 

[AdR]

Power(watts)=volts x amps. You need to aim for a battery that can deliver 8Kw + losses for as long as you want to keep the motors running.
My pull out of my derriere rule of thumb.
motor power + 10% to 20% =controller power + 10% to 20%=battery power in all my setups.

 

[amberwolf]

I don't know the max current of the batteries, there's no info on them. I use the two batteries which come from one scooter, 30 amph X 2= 60 amph. I've 4 identical batteries.

Well, the Ah is just the capacity, or how much range they can give you (if you know how many Ah/mile your system uses, from the readings on a wattmeter vs the distance you travel).

To know what they are capable of, you'd need to know the A (not Ah) rating. Most batteries can do at least "1C" which means equal A to the Ah rating, but not all of them can. Some can do up to several times that.

If they came from a scooter, what current did the scooter draw? If it was never measured, what was the original controller's current limit?


If you have four of them, then using all four in parallel quadruples the current capability (and capacity) of a system using just one, or doubles what two can handle.

Today I ran the kart on my dyno to see how much current it would use and to see if it would switch of. Measuring was not succesfull, don't really know what I'm doing. The numbers didn't make sense.

What numbers did you get?

What was the exact complete testing method? (including how the current measurement device was wired into the system)

What size battery should I iam for ? if the motors make 4000 watt each (2 of and 2 Votol em 100 controllers) ?

Is 4000w what you measure on the dyno under load for actual motor power produced?

Or is it what the dyno measures for battery power output?

Or is it what a wattmeter measures for battery power output while riding?

Or??

Speculation since no numbers available:

If 8Kw is the actual power the motors deliver, you can assume anywhere from 20-50% more than that will be needed from the battery to give you that 8Kw. Let's say the system is really wasteful and you need 50% more, so you'd need 12kW out of the battery. Assuming 72v batteries, then 12000w / 72v = 167a.

If the batteries are each capable of only 30A, then the best you can get is 120A with all four. If you're only using two in parallel at a time, you'll only get 60A, and the system would be trying to draw almost three times as much current as it can handle, so the voltage sag would be bad enough that the controller *should* stop trying to drive the motor if it's LVC is setup properly, but otherwise the battery's BMS should turn off the output to prevent cell damage, either from overcurrent or voltage drop.

 

[ZenaWarrior]

I didn't get any numbers because the multimeter numbers fluctuated. Need a person who knows how to. I may be racing again on Saturday, so I'll change some settings on the controllers and bring the laptop to the track and try different settings. Thank you for all your help.

 

[amberwolf]

I didn't get any numbers because the multimeter numbers fluctuated.

Even if they fluctuated instead of settling, you would still see them on there--what range of numbers did you see? The highest numbers are the most important ones, as your battery has to handle those.

If you use a meter that can send data to a computer to log, then you will get useful dyno results (without some form of logging to create charts from, dyno data is not usually very useful).

Most wattmeters will at least show you the most important things even after you stop--the max and min of the various things being monitored (usually watts, volts, amps). Those you can get cheaply don't remember this data after power off without rigging up some sort of backup battery to them, but some including the CA (below) do, and have other functions as well.


Some wattmeters (like the cycle analyst from ebikes.ca) can send data realtime over the serial port, and there are many logging applications to capture the data. The CA also monitors speed, and torque, and temperature, so if you have a wheel speed sensor, thermometer, and torque sensor on the dyno setup, you can capture all this data at once to see what is actually happening with your system, and use the dyno to tune it for best performance without stressing the parts.


Even if you don't use it as part of the dyno setup, you can isntall the wattmeter on the kart itself to monitor actual usage and see what's really happening.


But just the cheap wattmeters would still show you the max amps, and that would tell you what capability battery you must have. Then you can get batteries that can handle that without cutting out or being damaged or catching fire from overload, unlike the ones you have now.