Car accelerates for half a second before stopping
 

Hi all,
I have a HPI Sprint 2 Flux. I got back into the hobby today after 7 years however my car wouldn't drive. I took it to a shop and they put a new radio/transmitter in and this fixed the issue for the first half an hour of use. After this, I took it inside, charged it and then came back another couple of hours later and used it again. It was fine for the first 10 minutes and then I noticed that I couldn't get it to go anywhere near as fast as it was earlier. It then kept stopping randomly so I took it inside. Now it only accelerates for the first 0.5 seconds of me holding the trigger down after plugging the battery in and then after that, nothing. I was wondering if anyone knows what the issue could be? and potentially how to fix it?

Thank you,
Dylan

Hi Dylan,

This could be so many things. I would start with the more basic stuff and go on from there.

1. Is your battery holding charge normally? If you get it to 100% charge this problem still persists?
2. Is your drivetrain free? If you remove the pinion from the motor, will the motor spin for more than 0.5s?
3. Is your radio system working properly? Problems in this particular area could be in a lot of "places". For starters, could you tell us if you're able to turn left/right normally, even after the car stop?

I would say answering this questions should give us a good starting point.

If you are charging the battery (is it a NiCad, NiMH or a Lipo?) and then driving it for 10 minutes then you have likely drained the battery. That is a long time to run a car on one charge. Additionally, the electronic speed control in the car likely has a low voltage safety that cuts power to the motor but leaves steering.

3rd vote to start with battery. If a modern ESC it could be on LiPo protection mode which would cause it to stop running when the voltage drops. If an old battery, it could easily be not holding a charge or it could have a dropped cell.

Check ESC for LiPO mode and check battery for quality of charge.

Hi mr.rev,
thank you for the reply.
1. I believe my battery is holding charge normally, and I don't think thats the issue as it feels charged when I accelerate but it also feels like something is telling it to stop accellerating.

2. I honestly would have no idea how to check this and what this means, sorry, lol.

3. It should be, I bought a new one yesterday to fix the original issue it had and it was working fine and seems to still be. I can turn the wheels fine.

Thank you.

It sounds like it could be this protection mode you're talking about. It is a LiPo battery and it is quite old so maybe this is the issue but the guy at the store said the battery seemed fine just yesterday. Does this mean I need a new battery? can I check for any other issues first?

You might get 4-8 minutes of run time from a healthy fully charged lipo depending on how heavy-handed you are with the throttle, so it is likely you are draining the battery too low.

lipo cutoff on a esc usually cuts power by 50%.
id check the battery . check its internal resistance also. how many milliamps goes in battery Id be going to battery .. buy a cheap battery buzzer they can be had for as little as 4$... its not a fix but lets you know how long your battery is lasting .if its a old battery like said thats what id guess as issue

I think the battery might be the issue. The car works fine for about 2 minutes and then goes into this mode that I've spoken about. Until that point the car runs normal. The battery used to last about 15-20 minutes on one charge so I guess its just worn down. I'll look into getting a new one. Thank you guys for the help!

Many things here : Esc burnt... TX batteries not sanded ??? No rx glitch capacitors ? No fan on esc with gearing too high for the drivetrain friction...Maybe dendrites on motor timing board(happens to old novak motors)...Motor timing too high...Runtime too long(reduce to less than six minutes)...Drivetrain bearings catching when heated or pinching inside tight hubs....Radio bec overloaded too fast..lipo connectors no good...etc.....

Hey Dylan
sound like you are running brushes motor? check your brushes and see if they are not brunt and check the springs they are not heat damage.