Input voltage limits Turnigy 8-15A UBEC

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Input voltage limits Turnigy 8-15A UBEC

Postby JensR » Wed Feb 08, 2012 11:35 pm

Hello all,

I hope this is the correct subforum!

In my RC earthmover I use a 12V NiMH as power supply.
I now want to implement a BEC - but it needs to be high-powered.

I was looking at this one:
"TURNIGY 8-15A UBEC for Lipoly"
http://www.hobbyking.com/hobbyking/stor ... oduct=6233

Do any of you you have any experience whether this UBEC would work with an NiMH pack that has a nominal voltage of 12V? As I found out, those have a voltage freshly charged of 14V, whereas a freshly charged 3-cell Lipo has the 12.6V mentioned on the UBEC. This makes me think that 12.6V is the actual (and not nominal) maximum voltage.

Has anyone given this a try?

I am also mildly worried that this and other "Lipoly-optimised" UBECs will think my 12V NIMH is a defective 3s or 4s Lipo and refuse working.

I tried to google it, but I seem to be the only one (?!) who wants to run NiMH with a UBEC - but I actually need the weight in my machine.

Best wishes
Jens
JensR
 
Posts: 55
Joined: Sat Sep 11, 2010 3:41 am
Location: Bath, UK

Re: Input voltage limits Turnigy 8-15A UBEC

Postby JensR » Fri May 18, 2012 7:13 pm

I bought the UBEC a few weeks ago and finally got around to test it.

So, just a quick self-update:
With 10 cells of NiMH, relatively fresh out of the charger (half a day), the four battery-indicator LEDs on the UBEC flashed wildly, but it worked flawlessly.
Now, a day later, the battery voltage is down to 13.5V and the LEDs are lit constantly - as they should be.
The device gets a bit warm, but I am not (not yet) worried about putting this into a non-ventilated compartment.
I have inserted a Watt's Up meter between battery and UBEC.
The UBEC draws around 50mA on its own. The value changes between 30 and 80mA - so I assume that my Watt's up meter is not very suited to these small currents. Still, this should give you an indication on what to expect.

Edit:
When switched off at the integrated switch, the current draw drops to between 0 and 10mA and the four LEDs stay lit.
The four LEDs (2 green, 2 red) stay lit even switched off. I am not sure the LEDs are visible in a flying airplane, but certainly bright enough to see during the day on my table.

Edit2:
There's also a red LED that indicates that the switch is "on". Very useful.

I can detect no interference, currently using my 40MHz radio.
As I am building RC earthmovers, I am not concerned with long range - I cannot take any responsibility for your range needs: You will have to test it yourself.

Hope this is useful to some, looks like a nice device to me.
JensR
 
Posts: 55
Joined: Sat Sep 11, 2010 3:41 am
Location: Bath, UK

Re: Input voltage limits Turnigy 8-15A UBEC

Postby quarry44 » Fri May 18, 2012 8:12 pm

Hi,Jens.If you need the weight,why use a ubec?I'm assuming space is your problem?Otherwise,a 2-cell LiFePo4 rx pack would be a better option.
Anyway,would love to see some pics of your earthmover.
quarry44
 
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Joined: Fri Aug 19, 2011 6:58 am

Re: Input voltage limits Turnigy 8-15A UBEC

Postby JensR » Sun May 27, 2012 9:50 pm

Thanks quarry :)
Yes, space is indeed an issue. If I would know the common distribution between the energy consumed by motors and servos I could probably come up with a system using two separate batteries that are not much larger than what I currently have and would drain at around the same time.
I initially had the two 6V batteries connected to give 12V and then one 6V battery would be the receiver pack of one receiver and the other for the second receiver. That worked well enough, but then I had to change this: One 6V battery now had to power both receivers, which meant that it would drain much faster than the other.

My grader is here:
http://flickr.com/gp/22070130@N07/13BERN
and videos here:
http://www.youtube.com/user/YensR

Best wishes
Jens
JensR
 
Posts: 55
Joined: Sat Sep 11, 2010 3:41 am
Location: Bath, UK

Re: Input voltage limits Turnigy 8-15A UBEC

Postby JensR » Sun Aug 12, 2012 11:38 pm

I have now read (ahem, read the manual they say...) that the flashing lights indicate voltage above 12.6V or so. So within limits, the flashing LEDS are not a problem.

What is a problem is that I have had two instances now where the connected receivers malfunction when the BEC was turned off. I am not sure what happened. I assume it is because the ESCs are still connected to the main battery and some interference makes them go randomly crazy. This might be a general problem, or a problem of my ESCs or receiver or their combination.
JensR
 
Posts: 55
Joined: Sat Sep 11, 2010 3:41 am
Location: Bath, UK


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