Hobbyking Voltage and Temperature Monitor

Hobbyking Voltage and Temperature Monitor Review
By Metallover



I have owned my VT monitor for a few months now. You can get one at hobbycity for $8.50. It is a low voltage alarm and high temperature alarm all in one. The screen changes from voltage to temperature every second or two. The temperature probe has three wires to it and attaches to the main unit with a 3-pin jst connector like those found in RC radio systems. The device measures temperatures up to 150 degrees celsius and takes 4-26v input. Due to the 26v max rating, this won't be the best for e-bikes. You will have to measure just one cell or a group of cells if you want to take advantage of the lvc alarm.

The unit came neatly packaged in it's own box with lots of padding inside. It comes with an instruction booklet which shows how to program it. Programming is very simple. There are two buttons on the right side of the display. Press and hold the bottom one to set the temperature. After holding the button it will start going through temperatures in increments of one degree. The same goes for the voltage programming, just hold the top button. All of this is explained in the manual and I can't imagine anyone not being able to figure it out. It is very simple.



When the voltage drops below the set voltage or the temperature gets above the set temperature, three bright led's will light up and a buzzer will sound. The buzzer is pretty loud; I don't think the buzzer being too quiet would ever be a problem. Even if you don't hear the buzzer, the blue led's are very bright and they should catch your attention.

One flaw I found is the screen brightness. Under direct sunlight, you can't make out what it is displaying. I don't know if this is due to the brightness of the display or the opacity of the shrinkwrap, but it is a problem nonetheless. This isn't too much of a problem however because the alarm still works and if you want to see what's on the screen you can block the sun with your hand.

This device isn't water sealed. It wasn't meant to be either, however the bottom of the board has some foam glued to it which should prevent any water damage there. If any moisture gets on the other parts it could cause problems and false alarms. I am going to work some magic in the near future with liquid electrical tape, and I'll post on here when I get done. I have also had a few false alarms due to bad connections leading to the sensor, so when running the sensor wire to your motor make sure to take your time and make sure you don't make any bad connections.

_____

The temperature probe is a little over an inch long by 5-6mm wide. I attached it to my windings with some epoxy. To test it I turned it on then I used a hairdryer and warmed up the sensor. I then used my infared temp meter and measure the temp of probe I had just heated up. They were both the same. It seems like a pretty accurate device judging by that one test.

Today I went on a 4-5 mile (round trip) ride. when I got to my destination the meter showed 72*c, which works out to 162*f at the windings. I was riding hard like a usually do in the city, and the temp seemed right. The outside of the motor was just a little warm. I should have brought my other infared temp gauge so I could give you a number but I forgot. When I got back it read 63*c. I had the alarm set, conservatively, at 85*c, and as expected it never went off, because I never neared the set temperature.

Pic of monitor without shrink, there is a scratch I made under the bottom button


pic of temp. sensor installed in motor. It is on the right side






_____

Overall, I highly recommend the hobbyking vt monitor to all e-bikers, especially those pushing the limits of their motors. The low input voltage range limits it's usefulness/compatibility for e-bikes, however the temperature setting is the real reason to get this. The low price tag of $8.50 makes this not only a way to measure your motor temp, but possibly the best way because of the high temp alarm. The screen can't be read in direct sunlight and it only displays temperature in celsius, but those are just minor flaws that shouldn't distract you from the magic that is Hobbyking VT Monitor.

I give The hobbyking VT monitor 5 stars out of 5 and a big thumbs up.

I have the same unit on my internal star delta GM hub and it's been going fine for a few months now with no dramas. I agree they're great value and come well packaged.
The voltage monitor is a nice bonus for up to 6S packs especially in the absence of a proper BMS or to keep an eye on an auxillary battery used for lights etc

Awsome !!..

Next HK order i'm getting a few of these, one for the motor, another for the controller !!

Nice! Just wished I'd included it in my last order... I've been melting a lot of plastic lately and I don't want the motor to be next...

Just for a ltitle follow up,, I went for a ride yesterday. Coming back up a slight grade with a strong headwind the meter went off. I had it set to 95*c. The buzzer was easily noticed. One thing that might be a problem is if the buzzer is going off and you are in town, people will look at you and think you're crazy. :lol:

When the inside of the motor is close to 90*c (195f), the outside is around 80-85f. Once you've stopped for awhile, the inside will cool down and the outside temp will rise to about 90-95*f. This is my experience, is this normal?

I have this expoxied directly on the windings. In the past, I have had the outside of the motor too hot to hold your hand on it; the outside must have been 150+f. God knows how hot the inside was. How hot should I have my meter set?

If you could test at what temp the motor wires melt and short together ( heat gun ? )

lol, hasn't that test already been done? :lol:

Are the windings the first things to go? With RC stuff the thing we always worried about was the magnet demagnification... With e-bikes I've heard magnet epoxy is important..

Looking at methods sig, , 164c/327f is below-frying temp,, and 215c/419f, is too hot for a (X5) hub motor to take.

The epoxy I used to attach my temp probe to my windings is good for 120c/250f.. After looking around it seems like 120c would be a good temp to set my alarm at??

If you do start running for long periods of time, say 20-30 minuites at 250F and get away with it be sure to let us know in a new thread. For now I'm calling the max 180 F or maybe 200f.

My previous experiences with melted motors showed that brushed Aotema motors would melt the epoxy before winding damage, then the loose magnets caused problems. No telling what temp that was. Since then, running motors with temp monitoring, I have not melted anything down when keeping temps lower that 180F. But I haven't pushed it further than that, since that is about the max temp I'd reach climbing a big hill in 100F weather, using less than 1000 watts. Once you start pushing higher voltages and running 2-3000 watts though, I'd expect the temps to get higher. I can only say at this point, that under 180F is safe for sure.

Another issue is time, getting hot for a few moments and softening the epoxy is one thing, but running continuously at temps over 180 may be another, allowing time for the magnets to get to moving around in there.

Other things could make a difference too, on the aotema brushed, the magnets had lots of space between them to start wandering. But on a brushless hub, they tend to be packed in there pretty tight, and may not move around so easy like they did on the brushed hub. Only by a month or more of commuting in hot weather at 2000 watts could I be able to say if it could be done at higher temps reliably. Right now, I only have about 1200 watts avaliable on my 48 battery.

I got some liquid electrical tape and sealed her all up. Without the shrinkwrap, the numbers still can't be read in broad daylight, but reading is better with an overcast.



The unit is still working perfectly and I notice how much I love it every time I go for a ride.

And sorry for the blurry pic.

Do any of you electronically minded people know what gauge wire is used on these
Thanks

It uses servo wire, which is usually 22ga or 26ga, depending on the application. I always get 22ga and it looks like the power wires on the device are 22ga also.

By the way I just ordered 2 more of these things. Unfortunately there were 7 left when I ordered and now they're out of stock. Hopefully they'll be back in a week or two tho.

This sounds like just what I need, I will get one.

I ordered the wireless pack-tracker voltage meter from Hobby King, and I was very disappointed. I may have just got a bad unit, but there was no web-PDF, and the paper instructions were confusing with small fuzzy pics that were not useful at all. I planned to attach with velcro to the handlebars, so I could slap it on and off without fiddling with plugs. Here a thread about the battery-medic and cell-log, specifically for their feature of tracking low voltage in the pack (which I have done to my first pack already!)

http://endless-sphere.com/forums/viewtopic.php?f=14&t=23838&start=0

i bought the HK VT monitor ages ago but am just now using it. sort of. i installed the sensor in one motor, tested it, and it worked fine. read the voltage and cold motor temp.

then i got another motor with the sensor already installed, and when i hooked up up on just 9V (alkaline test batt only), the temp sensor went nuts flashing blue and reading 164 degrees...

so, is it possible i cooked the motor beforehand and broke the sensor and it got stuck at 164 somehow?

the motor was cold when i tested it, so no chance it was that close...

i will check my first motor and see if it still works while hooked up to that one...

any one know what thermistor they are using ? or the resistance in say boiling water?