HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Apr 22, 2011, 12:57 PM
Registered User
United Kingdom, England, London
Joined Nov 2006
163 Posts
Question
How do i connect a UBEC in a 2 pack setup

I had my UBEC connected as shown in diag 1 with the +ve input lead on the +ve side of the ESC and the -ve on the series connection.

Last night while browsing Castle Creation site i saw this article(diag at bottom of article) http://www.castlecreations.com/products/ccbec.html
which warned against connecting the way i had the UBEC connected.

The way Castle say to do it is to connect the -ve input lead on the UBEC to the -ve side of the ESC and the +ve on the series connection.

Castle say that connecting the UBEC the way how i had it will boost the ground voltage in a disastrous way.

My UBEC is western robotics, so i had a quick read of the manual and found out that they warn against connecting between battery packs period.

So i decided to tap from the balancing leads of both batteries (they are 22AWG) using only 3 cells from each battery to reduce the work load of the UBEC. So i wired up the UBEC as shown in diag 2 and plugged in B2 first as i normally do. However, when i attempted to pug in B1, there was a big spark as soon as the +ve on the deans connectors touched. This happened with the 5mm and 1mm connectors open. The usual sequence is B2, then B1, then the 1mm plug to arm the ESC without sparking, then the 5mm plug and finally opening the 1mm plug.

At first i thought i had made the series connector incorrectly, but that was ok. So i then drew a diagram similar to diag 2 and realised that by tapping off the balancing leads of both batteries i was completing a circuit and causing a short. So i unplugged one of the taps and tried again and it worked ok.

However, looking closely at diag 2, i realised that tapping off the balancing leads is the same config as diag 1, in that the UBEC is between the packs.

The only way i can see to install the UBEC without conflict, is to use a separate battery, which defeats the purpose of the UBEC.

So my question is how to install this UBEC? should i do it like how Castle say with the -ve lead on the -ve side of the ESC? and in layman terms exactly what is boosting the ground voltage in a disastrous way?
bajinuk is offline Find More Posts by bajinuk
Last edited by bajinuk; Apr 22, 2011 at 01:03 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 22, 2011, 01:18 PM
Registered User
Harry H's Avatar
Los Angeles
Joined Oct 2010
1,518 Posts
The Castle warning is for connecting the bec with over 25 volts. In there diagram, there are (2)- 6S in series making 12S which is over voltage for the CC bec. I have mine hooked up this way but totol is 6S. You need to know the max voltage for the bec you are using and figure it out that way with the batteries you are using.

Harry
Harry H is offline Find More Posts by Harry H
Reply With Quote
Old Apr 22, 2011, 01:20 PM
Registered User
Harry H's Avatar
Los Angeles
Joined Oct 2010
1,518 Posts
PS, you should not get any kind of spark - check to make sure you did not fry anything

Harry
Harry H is offline Find More Posts by Harry H
Reply With Quote
Old Apr 22, 2011, 02:47 PM
Registered User
United Kingdom, England, London
Joined Nov 2006
163 Posts
the max voltage for my UBEC is 6s which is why i had it between the the two 5s packs. However there are 2 ways in which the UBEC can be wired between the 2 packs. The +ve input of the UBEC can be connected to the +ve side of the ESC and the -ve input to the series connection wire OR the -ve input of the UBEC can be connected to the -ve side of ESC and the +ve input to the series connection wire. Castle say that the latter is the correct way as the former will "boost the ground voltage in a disastrous way".

My UBEC is western robotics and they say not to connect between packs period. So part of my question is what exactly are castle talking about in layman terms and wether it would be safe to connect my UBEC as castle recommend. I have also sent an e-mail to western robotics but in the mean time if i want to fly to be safe i will be connecting the UBEC to a separate 3s batter which defeats the purpose of the UBEC.
bajinuk is offline Find More Posts by bajinuk
Reply With Quote
Old Apr 22, 2011, 03:01 PM
Registered User
Harry H's Avatar
Los Angeles
Joined Oct 2010
1,518 Posts
Yes this is confusing. I think I contacted Castle some time ago and that is why I use my config. Best to double check and be safe. I would like to know what the responce is so please post.

Harry
Harry H is offline Find More Posts by Harry H
Reply With Quote
Old Apr 22, 2011, 03:09 PM
Registered User
USA, MO, Florissant
Joined Nov 2010
1,618 Posts
The UBEC connects the -v input to its -v output, which would raise the ground potential of the receiver to the voltage of B1 in your first diagram. Because the ESC has its ground from the receiver cable connected to its -v input, this would short B1 through it.

Connect the -v input of the UBEC to the -v of B1 and the +v of the UBEC to either the +v of B1 or B2 (however much voltage it can take), and that makes all the ground levels common.
Wintr is offline Find More Posts by Wintr
Reply With Quote
Old Apr 22, 2011, 04:13 PM
Registered User
United Kingdom, England, London
Joined Nov 2006
163 Posts
Thanks.

I think i understand what you mean. The way how i had it, the -ev output of the UBEC would be +something volts feeding the receiver and that of the ESC would be 0V now which is also connected to the receiver acusing some sort of current to flow between the two potentials.

Before i came across the castle article, i must have had about 20+ flights with the wrong config.Would this have caused damage to any of the components. I am really worried now and thinking about changing the electronics; alot cheaper than losing the whole lot.
bajinuk is offline Find More Posts by bajinuk
Reply With Quote
Old Apr 22, 2011, 04:55 PM
Registered User
Harry H's Avatar
Los Angeles
Joined Oct 2010
1,518 Posts
That reply makes sense. Looking back on your diagram, you have a jumper that is wrong. One of these Dean's Ultra Battery Harness would simplify your set up. I think http://www.maxxprod.com/mpi/mpi-21.html near bottom of page.

Harry
Harry H is offline Find More Posts by Harry H
Reply With Quote
Old Apr 22, 2011, 07:38 PM
Registered User
United Kingdom, England, London
Joined Nov 2006
163 Posts
it is not that the series harness is made up incorrectly, but that the UBEC is connected incorrectly. The -ve input of the UBEC must be connected to the -ve side of the ESC and the +ve input of the UBEC must be connected to the series wire that joins the +ve and -ve of the two deans connectors.

This ensures a common ground.

If the -ve input of the UBEC is connected to the series wire that joins the +ve and -ve of the two deans connectors and the +ve input of the UBEC is connected to the +ve side of the ESC, then there is no common ground, as the -ve side of the UBEC would be at a higher voltage that the -ve side of the ESC. This is because the -ve side of the UBEC is connected to the +ve side of the first battery in the series connection. The series connection is +ve on one side and -ve on the other.

As the output of the UBEC and the ESC are connected to receiver some sort of current flows which will damage the components. This is what castle means when they talk about boosting the ground voltage in a disastrous way. Castle go on to say "please connect the correct way to avoid expensive damage to your entire system".

As i said, i have had about 20+ flights with the UBEC connected incorrectly but i dont know what damage has been done to the ESC, receiver and UBEC even though they seem to work fine.

Something seems to have melted in the UBEC even though it appears to work fine and there is no burning smell. Wether it was caused by by the first installation where there was no common ground, or by the second installation when i tried tapping from the balance leads, which resulted in a spark, i dont know, but I will definitely be changing the UBEC for another, or using a receiver pack, as i ended up carrying lead in the cowl anyway. I dont know if i should change the receiver and ESC as well.

The positive thing is that i stumbled across the castle articel before it was too late.

Nicholas
bajinuk is offline Find More Posts by bajinuk
Reply With Quote
Old Apr 22, 2011, 08:02 PM
Registered User
USA, MO, Florissant
Joined Nov 2010
1,618 Posts
The printed wire that connected the -ve into the UBEC and the -vo to the receiver probably melted, but the UBEC must still be getting a ground through the receiver and ESC so it works. It is running at the full voltage of both batteries. If that is more than the rated voltage, it's running on borrowed time.
Wintr is offline Find More Posts by Wintr
Reply With Quote
Old Apr 23, 2011, 03:04 AM
Registered User
United Kingdom, England, London
Joined Nov 2006
163 Posts
Thanks; ive binned it.

Would the receiver have been damaged as well?
bajinuk is offline Find More Posts by bajinuk
Reply With Quote
Old Apr 23, 2011, 11:27 AM
Registered User
USA, MO, Florissant
Joined Nov 2010
1,618 Posts
Hard to say; the radio itself will be fine, especially since the UBEC was still powering it. The ground path on the receiver is usually a pretty broad section of printed circuit, connecting all the common posts for the output channels, so all the current would have passed through that path from the UBEC directly to the ESC. Take a close look at that part of the circuit board for heating; if the solder looks like it was weakened from heat, a touch-up with an iron may be all that's needed.
Wintr is offline Find More Posts by Wintr
Reply With Quote
Old Apr 26, 2011, 05:56 PM
Registered User
United Kingdom, England, London
Joined Nov 2006
163 Posts
Quote:
Originally Posted by Harry H View Post
Yes this is confusing. I think I contacted Castle some time ago and that is why I use my config. Best to double check and be safe. I would like to know what the responce is so please post.

Harry
This is the reply from Western Robotics

Hello Nicholas,



Thank you for your interest on Western Robotics Hercules BECs.



We do not recommend connecting the BEC as suggest by Castle Creation. What we found due to the different battery chemistries, even though if you connect the BEC to one of the 6s battery pack from a total series 12s pack, the 6s pack voltage has a potential to swing to the full 12s series battery back ONCE EMI is introduced back to the battery from the connected ESC motor. If back voltage is introduced by the motor, the actual voltage from the middle battery pack is unknown and unstable.

If you wish to connect a series 2 pack setup, it is recommended to connect the BEC to the whole series battery pack setup, in this case you need to make sure that the BEC is rated for your entire pack. For the Hercules Super Mini BEC (WRL-HBECM), you will be limited to a 6s lipo pack and the Hercules Super BEC (WRL-HBECS) is limited to a 14s lipo pack.



Regards,



Western Robotics Information

Western Robotics Ltd.

207A-12837 76th Avenue

Surrey, BC V3W2V3

Canada
bajinuk is offline Find More Posts by bajinuk
Reply With Quote
Old Apr 26, 2011, 07:02 PM
Registered User
Harry H's Avatar
Los Angeles
Joined Oct 2010
1,518 Posts
bajinuk - thanks for posting the reply you got. This makes perfect sense but have to wonder why Castle recommends a different set up. I personally think Western is on the money, but then I only know enough about electronics to be dangerous..

Harry
Harry H is offline Find More Posts by Harry H
Reply With Quote
Old Apr 26, 2011, 07:34 PM
Registered User
USA, MO, Florissant
Joined Nov 2010
1,618 Posts
Those transients can be elusive, but damaging. Take Western's advice and get a 12S rated BEC. Although unlikely, a transient like that is possible, and would slowly damage a BEC not rated for that much voltage.
Wintr is offline Find More Posts by Wintr
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion How do I setup the ailerons and everything for thermaling? KillerCut Thermal 22 Apr 13, 2011 07:17 PM
Discussion How do I reduce Rf in Video with this setup????? LexusFPV FPV Talk 6 Apr 08, 2011 07:27 PM
Discussion How do I connect the TP610C to a Lipo pack? Jon 10-50 Batteries and Chargers 5 Feb 14, 2010 03:32 PM
How do I connect 2 etec 2sp1 in parallel Goleith Batteries and Chargers 4 Jul 18, 2003 01:41 AM
How to connect the 7th cell in a stick pack? JoeR Power Systems 4 May 20, 2002 10:09 PM