Servo current draw question/issue
 

I had a Hitec HS-8370TH die on me during a race over the weekend, luckily I had a DS1015 in my pit box so I was all good for the A main.

Today I brought the servo into work so that I could call Hitech and get it sent it for warranty/service and I decided to open it up and see if I could see anything...I also brought a lipo and my Viper ProGauge with me and another servo (Solar D770). Well after opening the Hitec servo and not seeing anything obvious on the PCB or in connections I put it back together and plugged it into the ProGauge. Boom the servo snapped to life.

So I'm letting the servo tester run cycles on the servo and one thing I noted was that the current draw seemed awfully high to me, it was reading 4.5A-4.75A for a full sweep. At that point I plugged in the D770 which runs about as fast (as it should by spec) but pulls WAY less current at 2.11A in one direction to 2.65A in the other direction. Now I get that the Hitec servo has WAY more torque (double), does that account for the added current draw? I would think that the fact that the Hitec is drawing more current than my ESC BEC is outputting (HW XERun 150A, 5.75V 3.0A) would be a bad thing. Also I've seen threads about Savox servos (supposedly power hungry) where people have shown current draw graphs where they weren't pulling much more than 2A.

So I guess what I'm really asking here is has anyone use the servo tester feature much on the ProGauge or similar? If so what sort of current draw are you seeing from fast highish (250 oz/in) torque servos?

Ok no responses here...I called Hitec and they seemed to think that the current draw was typical. I'm going to see what a DS1015 does when I get home.

I'm sending the Hitec servo in anyway as I can't rely on it at this point to be solid for racing.

I have no experience running those servos, but I do have an eagletree data logger. If you're so inclined, I can put it in my TLR 22T for a run or 2 and give you the numbers that the logger produces.

That does seem excessively high. Is the servo unloaded at the time of testing, or do you have the car on the ground to simulate load?

Either way, that seems steep.

Totally unloaded, out of car, not even a servo horn.

Something is amiss. That is simply too much current through an unloaded motor of that size. I think for the sake of experimentation, you should mount the servo to the rack and lay the car on the table. See what happens when a small load is applied. It could be that the servo is pulling too much current because it is UNloaded. Not likely, but worth trying. Just a thought.

That servo should stall around 2.65A. Something is wrong with it.

I'm with you on the fact that something is wrong with it...it's on its way back to Hitec for inspection.

Ok so I tried my ds1015 and the result was around 3.0A until I pushed it to the limits and then it got up to 4.09A. This is with the servo in the car turning the wheels on carpet. A Savox 1258tg turning just the unloaded steering of a B4 was also pulling 2.9A-3.0A.

So I fully believe that the Hitec has an issue. Lets see what Hitec thinks.

Update: Just got off the phone with Hitec customer service, they found a broken motor wire and have repaired/replaced it under warranty.

All's well that ends well.

Thanks for the update. Always like to see how these issue threads work out. Wish more would do the same.