Siposupra

iTrader: (2)

Hey guys,

Im new here and not exactly sure where to find the answer to this... I purchased a hpi blitz recently and it came with a Hobbywing 35a-sl ESC, 10t 3900kv hobbywing motor... sorry if my terminology sucks.

I have programmed the esc for the lipo voltage cutoff at 3.6volts and the car seems to go die after about 5 minutes of driving. I measure the voltage with my trusty multimeter at 7.0v and it goes into limp mode where it doesnt move and only has steering response.

I then tried to turn off the lipo cutoff and same thing happens. My battery is a 7.4v 2000mah li-power. I can turn off and on the car and it will have a small burst of power for about 30 seconds. then will stop completely

Is it a bad battery causing the problem or the esc??? Is this a common problem and i do i just need to browse the forum more?? Is the small battery stressing the esc because its cool to the touch.

thx guys

justpoet

iTrader: (16)

I don't know the answer to your question, but there's a Hobbywing thread with some pretty active HobbyWing reps in it here.

rctech2011

iTrader: (3)

Hi
Sounds like bad battery or not charging.
See HW link below for ESC info.
I have hobbywing and voltage cut is set around 3.0 or 3.2 to be safe.Your's sounds like it's just set to high and battery is not charged.Recommended not to turn off low voltage "cut off".
My 2s 5000mA Lipo batteries charge to 8.4volts.
The 2s is 2 Series cells which give you total volts.If you set cut off at 3.6volts you should measure around 2x3.6=7.2 when it stops.
hope this helps
good luck

http://www.hobbywing.com/product_show.asp?id=254

Dave H

As mentioned, the lipo cutoff of 3.6 volts is per cell, or 7.2V for a 2 cell lipo like you have. Depending on gearing, driving style, etc, 5 minutes with that combination is probably about right.

Safe to turn the lipo cut off down slightly, to around 3.2 to 3.4V per cell, should get a couple more minutes. 3.0V is the lowest I would recommend, but typically won't make much additional difference in run time, lipos hold voltage well and then die very quickly at the end of the discharge.

Do not turn the cutoff off, and do not try to keep running, don't turn the RC off and on. Lipos can be easily damaged if ran too low. Recharge it.

Also suggest trying to get a more standard sized lipo in the 5000mAh or slightly higher range. Will dramatically increase run time.

By the way, is the lipo getting warm or hot at any point?

Siposupra

iTrader: (2)

thank you, i have a 5000mah lipo on the way. I did not think about the voltage being split between the two cells. I have only owned the car for a couple days. The battery does not get warm and i usually only charge it to 7.4 volts. I had no idea it cutoff at such a high voltage.

So if i charge it to 7.4 volts and i set my cutoff at 7.2volts then it makes perfect sense why my car only runs 5 minutes.

I will mess around with it more when the new battery arrives.

thx

Dave H

Good to hear the lipo isn’t getting warm, with a relatively heavy RC and smallish lipo. If it was too much load for the lipo it would heat up, which is bad news.

I’m assuming when you charge to 7.4V, that’s just the charger setting for a 2S lipo. So called nominal voltage. It should actually charge to 8.4V (4.2V per cell), and hold there as the current drops off. CC/CV charge routine, constant current then constant voltage as it tops off.