HobbyKing car ESC cut-out problem

[JeremyParticipant @jeremy15845]

I have been using a HobbyKing 100 amp Quik seies car ESC with a Turnigy D3536-6 brushless motor and a 10 pack NiMh 5000 mah battery. The input voltage of the motor is 7.4-15V (OK) and 4-15V for the ESC(also OK)

However, the ESC keeps cutting out when I throttle up. Sometimes it will restart. Sometimes not. I have had this model for some time and earlier on it worked OK. Any ideas on solving this problem would be appreciated. I could switch to a water-cooled marine ESC and link it into the plumbing of the fire monitors, but would hope not to have to do this.

[JeremyParticipant @jeremy15845]

[Dave MilbournParticipant @davemilbourn48782]

Jeremy

Without giving it much additional thought this sounds very much like "brown-out". Throttling up will cause a sudden surge of current and consequent drop in voltage at the battery pack. If that voltage drop is significant then the Rx will think you've switched it off and go to failsafe. As soon as all that happens the load comes off the battery which then powers everything up again! Or not…

My suggestion would be to replace the NiMH battery pack with an equivalent voltage LiPo pack. In this case that would be a 3S pack. Go for the highest discharge current available. This is indicated in the specs for the battery pack as a value which looks something like "35C". That means that the pack can deliver up to 35 times its own rated capacity. Translate that into Earth-speak and a 4000 maH pack described as 35C discharge capacity will handle up to 35 x 4000ma, or 140Amps. I don't know of a NiMH battery that can get anywhere near this. Don't confuse this with the maximum charge rate, which is also quoted as C but will be a much lower value.

This pack is described as 35C discharge and 5C fast-rate charge. If you look at the technicals you'll see it will deliver 140A continuous discharge current (4000ma x 35) and take a maximum charge current of 20A (5 x 4000ma). **LINK**

The reason why your model used to work OK but now misbehaves is probably that the NiMH pack is being regularly overstretched and therefore losing its capacity to deliver high currents. A few slow discharge/recharge cycles may improve it but I'd still go for the LiPo option if 't were mine.

Fitting an on-board monitor will indicate maximum current and voltage of every session. I use one of these but others are available **LINK**

Dave M

Dave M

[JeremyParticipant @jeremy15845]

Dave

Thanks for your detailed reply, in particular your explanation of why the problem has got worse over time. I will go for the Lipo option.

Jeremy

[Malcolm FraryParticipant @malcolmfrary95515]

If going the LiPo route, if the ESC doesn't already have one, a voltage alarm will be useful. You don't get a lot of warning of imminent full discharge with a LiPo, a low volt alarm gives a chance. Over discharging is not good for the life expectancy of LiPo batteries.

[Dave MilbournParticipant @davemilbourn48782]

I've had a look at the manual for this ESC and it appears that the unit will automatically calculate the number of cells and set the low-voltage cutout at 2.8v/cell. If you use the programming card you can adjust this to a higher value. I set mine at 3.1v/cell. An audible alarm which goes off at a slightly higher voltage would give you time to bring in the model before the motor cut out. Alarms are very cheap – LiPo packs and new models aren't!

DM

[ashley needhamParticipant @ashleyneedham69188]

I have used a wattmeter on several of my air-boat jobbies and it is amazing what difference a LiPo makes, even if the Nimh is not being used to its full capacity.

​Percentage increases in power of at least 25% have been seen, and this percentage increases the bigger the load becomes. One reason has to be the voltage, which holds up under big discharges much better than a Nimh, and may well be your issue as pointed out by a guru.

​Those alarms are good, but do tend to go off under largish full throttle discharges as the battery gets used and can be annoying. Bleeping under NO LOAD is when you need to take the boat in and change batts.

​OR….do you need to change the batt when it bleeps under full load??? is that a question for an expert??

Ashley

[Dave MilbournParticipant @davemilbourn48782]

Ashley

Common sense says that if it beeps at all then the voltage is pretty low e.g. 3.1v compared with a nominal 3.7v working. The V/T discharge curve isn't linear but rather the voltage stays at a constant level (the nominal voltage) for around 90% of the pack's capacity and then falls away quite rapidly. If you want to ignore the alarm then go ahead, but that rather begs the question "why fit one at all?". If price is a concern then try this **LINK** It even has an adjustable cut-out voltage!
Other low-voltage alarms are available, as are wonder-gizmos like Dawnmist's Lithimon http://www.dawnmist.org/rcm.htm#2 I have one of these in Huntress and I intend to fit one to all of my models in future.

Dave M

Edited By Dave Milbourn on 07/01/2018 14:01:28

[ashley needhamParticipant @ashleyneedham69188]

Noted.

Ashley

[harry smith 1Participant @harrysmith1]

Hi Jeremy

AS per the Hobbyking specs the D3536 is 500 watts with a current draw of 34Amps.

You battery does not appear to handle the constant current draw.

For a power and amp onboard meter I use the Turnigy 180A Watt Meter and Power Analyzer(959800004-0).

If you use this with a steady increase in throttle you will get you constant current draw.

If you hit the throttle hard you will get the maximum current draw.

Two of the lipo batteries I have are the Zippy compact 3S 3300mah 60C(9067000038-0)(weight 288 grams) and the 3700mah 60C(9067000041-0)(weight 338grams).

The Hobbyking weights are a bit of bull, as I weight these on my scales.

Low Voltage Alarm, the better one is black 2S-8S) (VOLTAGE-ALARM).

I use the Hobbyking car ESC series(HK-45A, 60A and 100A) with the program card as all our club members use.

My 1920 Gentleman's Runabout (850mm) is running a 3639-1100kv 800 watt, the 3S 3700mah Lipo, HK-60A ESC and a 2 blade 40mm 1.6 pitch prop.

No cutting out problems.

Hope this helps.

Harry Smith

[JeremyParticipant @jeremy15845]

Boat goes like a dream with the new Lipo. Low voltage alarm on order. 4000mah Lipo was down to 38% after maybe 35 minutes running, mainly at full throttle. Each cell was at 3.79v, so effectively no drop-off at that level. Thanks to all for their advice.

Jeremy

[Dave MilbournParticipant @davemilbourn48782]

Jeremy

I'm pleased it's all worked out for you. NOW if you fit one of the Dawnmist Lithimons you can probably stretch that 35 minutes to 55 minutes. I was truly amazed at the run times I got from the LiPo in the Huntress and the motor runs as fast and smooth as greased weasel pooh. I have to say that I'm not in any way connected to Dawnmist. My late, great friend Peter Keirle introduced me to their website a long time ago now and I've been a fan ever since. Check it out for Pete's sake…

DM

[JeremyParticipant @jeremy15845]

Will do, Dave.

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