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Old 10-28-2012, 10:24 PM   #1
zguy
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Default BLS157HV/256HV OK w/ WR Super BEC?

Planning a build and am hearing/reading mixed results with the WR Hercules Super BEC and the Futaba BLS157HV/256HV servos due to their high current draw.

Anyone have issues with this combo?

Any set up tips to trust this combination?

Planning to run it off of 1 pack at 8.4V setting.

Thanks!
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Old 10-28-2012, 10:34 PM   #2
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i am running a wr super herc on a 7hv at 8.4 volts driving mks hvbl servos.

no issues.

hvbl servos run super efficient.

Sent from my phone using Tapatalk2...otherwise i would of sent it from my home PC.
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Old 10-28-2012, 11:45 PM   #3
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I have that setup, 80 flights so far and no issues.

I asked for my BEC to have a 7.4V output (available from WR as an option) because I read on here that Futaba recommend 7.4V max from a BEC because it's a constant voltage. 2s lipo is OK because the voltage drops from the peak of 8.4V fairly quickly.

I run mine off the 14s source - if you're going to run off one pack check out what MrMel has said about that in this forum to make sure you get it right - a few people have fried electronics when they got it wrong.

The servos are really nice, super powerful and smooth, the whole setup has performed really well for me.
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Old 10-29-2012, 07:42 AM   #4
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Quote:
Originally Posted by zguy View Post
Planning a build and am hearing/reading mixed results with the WR Hercules Super BEC and the Futaba BLS157HV/256HV servos due to their high current draw.

Anyone have issues with this combo?

Any set up tips to trust this combination?

Planning to run it off of 1 pack at 8.4V setting.

Thanks!
I run mine off a 2s lipo direct, no issues at all and if the main pack fails for some reason, I still have full control of the servos
My 157/256 combo draws only 200 MAH per flight so I can't see how there could be classified as high amp draw servos. You will be fine either way you go.....Ron
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Old 10-29-2012, 03:17 PM   #5
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Ron,

If it is possible for a main pack to fail, then isn't it also possible that a 2s rx pack could fail too, making the likelihood of failure just as high? OK with the BEC you are adding one more piece of equipment to the chain which could fail also, but I thought that the possibility of 2s pack failure or user error forgetting to charge the rx pack could give just as much risk?

If a flight pack fails, then normally I guess that means one cell would go bad. If the BEC is picking up the 14s feed from 2 packs, would it typically still see enough voltage to operate the radio gear? I thought that if you had a dead short in a flight pack it would probably fry something and there would be a problem, but a bad cell you could probably land - would like to hear other people's thoughts on this as there is differing opinions.

Ant
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Old 10-29-2012, 04:01 PM   #6
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scorpion backup gaurd FTW!!

Sent from my phone using Tapatalk2...otherwise i would of sent it from my home PC.
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Old 10-29-2012, 08:43 PM   #7
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Yep that's a great idea. There's also this from WR http://www.western-robotics.com/battery_buffer_hp.html which allows you to parallel the BEC and a separate 2s pack.

I think I'm going to get one or the other of those two things - best of both worlds.
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Old 10-30-2012, 07:04 AM   #8
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Ron,

If it is possible for a main pack to fail, then isn't it also possible that a 2s rx pack could fail too, making the likelihood of failure just as high? OK with the BEC you are adding one more piece of equipment to the chain which could fail also, but I thought that the possibility of 2s pack failure or user error forgetting to charge the rx pack could give just as much risk?

If a flight pack fails, then normally I guess that means one cell would go bad. If the BEC is picking up the 14s feed from 2 packs, would it typically still see enough voltage to operate the radio gear? I thought that if you had a dead short in a flight pack it would probably fry something and there would be a problem, but a bad cell you could probably land - would like to hear other people's thoughts on this as there is differing opinions.

Ant
No there is a difference, if the BEC is wire to the 14s setup and a single cell fails, the Heli goes down as they are wired in series. There is a lot more stress on the main packs than on a single dedicated 2s lipo.
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Old 10-30-2012, 08:31 PM   #9
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Thanks. I've never had a problem with WR BEC's or a failed main pack for that matter but this is making me think I should add some redundancy such as a 2s pack and the battery buffer. A failure on any heli could be nasty but would be really bad on a big heli like this...
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Old 11-12-2012, 10:05 PM   #10
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Thanks for all the replies!

Tested this set up now myself and the Vbar reported voltage will drop to a minimum of 6.51 volts (from the 8.4 setting) when pitch-pumping the collective as fast as I can. In flight has shown a minimum of 6.9 volts.

So as you guys reported, this combo seems to be OK, but looks like it's getting close to the max of what the WR BEC can deliver.
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Old 11-12-2012, 11:29 PM   #11
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Interesting. How did you measure the voltage the VBar was seeing in flight?
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Old 11-12-2012, 11:59 PM   #12
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Quote:
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Interesting. How did you measure the voltage the VBar was seeing in flight?
The vbar logs the receiver's minimum voltage.


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Old 11-13-2012, 10:44 AM   #13
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Quote:
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No there is a difference, if the BEC is wire to the 14s setup and a single cell fails, the Heli goes down as they are wired in series. There is a lot more stress on the main packs than on a single dedicated 2s lipo.
If you are using a 2s pack and a single cell fails you lose the heli as well though
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Old 11-13-2012, 01:00 PM   #14
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True BUT like I said before, there is a lot more stress on a main flight pack then on a 2s lipo
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Old 11-13-2012, 08:43 PM   #15
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Thanks zguy, I never noticed that.

If redundancy is really the best solution, does a piece of electronics like the WR battery buffer carry a real risk of failure also? Like for example can you have 2 sources through that, but if that fails do you lose both?

Starting to think about either 2 small 2s lipos with separate plugs into the VBar or Rx, or keep the BEC and add one 2s Lifepo pack (so voltage is less than BEC output leaving BEC to be primary source) and a WR battery buffer to join the two.

Any thoughts?
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Old 12-01-2012, 04:02 PM   #16
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I just use a 250mAh 2S buffer pack straight in to the Vbar. The 8V from the Kosmik BEC keeps it charged nicely and in theory should help stabilise the Rx voltage.
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Old 12-11-2012, 06:16 PM   #17
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Which is why I went with a direct 2s lipo, NEVER a current draw issue
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Old 12-13-2012, 09:02 AM   #18
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Which is why I went with a direct 2s lipo, NEVER a current draw issue
There is if you forget to charge the battery! LOL
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