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Old 09-23-2019, 06:56 PM
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Question from a first time large scale gasser about batteries

Hi there guys (and gals), I'm new to this large scale gas engine stuff and I'm currently putting the finishing touches on my Hempel 25% L4. My question is around my batteries and if I have enough "power" for my setup.

I am running (2) 6.6V LiFe batteries, each with 3000mAh that will be running through a Booma RC flag switch. I am also running a Tech-Aero IBEC supplying ignition power to a DA50. Each control surface has their own 645MG for a total of 6. Those will be running through a AR8010T receiver and an Aura8 Gyro.

This will be for scale flying, no advanced acro. (yes I know the DA50 is more than needed for scale flight)

I'm hoping that my current setup will be ok as I am cramped for space and I'm not sure I can fit any bigger batteries in there.

Also looking to know how many flights I should expect (with flight times around 10 min I'm guessing)

I appreciate any advise!
Thanks, Joe
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Old 09-23-2019, 07:02 PM
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That will be fine you will have loads on power on board could probably fly for 2-3 hours

With A123/ Life batterys the best way to work out what current your drawing per flight and what run time you can expect is to do a flightm say 10 mins with charged battery's then land and charge,
The amount you put back in will equate to roughly what you consume per flight, Then you can do some simple maths to work out how many flight @ 10 mins you can get.

But work on a margin of 30-40% left just so they never go FLAT.

Hope that helps.
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Old 09-23-2019, 07:06 PM
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Sounds good to me,shouldn't be any problem with battery power.If your cramp for space one battery would be just fine too.I run 30% planes all the time with just one 2500 a123 battery for rx and ignition.
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Old 09-23-2019, 07:13 PM
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I appreciate the quick replies fellas! I'm sure I'm stressing over nothing but the last thing I want is something to go wrong because of my ignorance. And just FYI I'm running 2 batteries simply for redundancy.

Thanks Again!
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Old 09-23-2019, 07:15 PM
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Wrong thread.
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Last edited by Judge; 09-23-2019 at 07:17 PM. Reason: Posted in wrong thread. Deleted
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Old 09-23-2019, 09:27 PM
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I'm using two of the Spektrum 2200 2S LiFe packs in the BH L4. Using the DLE 55 RA for the power plant. So your setup should would be a little better than what I am using.

https://www.horizonhobby.com/66v-220...spmx22002slfrx
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Old 09-23-2019, 09:33 PM
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Quote:
Originally Posted by Aero_Joe79 View Post
I appreciate the quick replies fellas! I'm sure I'm stressing over nothing but the last thing I want is something to go wrong because of my ignorance. And just FYI I'm running 2 batteries simply for redundancy.

Thanks Again!


I run a 35cc, tech aero, 1270's, with one 6.6 2500 A123 on a 3D plane and I calculated about 320 mAh per 10min. I've flown basically an hour on this setup before a recharge, I tell myself to top it off after 4-5 flights.
So you'll see pretty similar numbers, except you have another battery!!
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Old 09-24-2019, 05:54 AM
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Originally Posted by MarksHangar View Post
I'm using two of the Spektrum 2200 2S LiFe packs in the BH L4. Using the DLE 55 RA for the power plant. So your setup should would be a little better than what I am using.

https://www.horizonhobby.com/66v-220...spmx22002slfrx

Nice looking bird! Any quirks about the L4 that I should be aware of? Where did you put your CG? The suggested 4 mark?
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Old 09-24-2019, 07:25 AM
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Yes, that is what I used. Page 67 of the build guide is where I got the info from as there were no instructions with the plane nor directly on BH's web site at the time I bought mine 3 years ago.

https://www.flyingrc.net/graphics/re...Y%20MANUAL.pdf

For me, it aligned with the wing bolt locations and I was able to balance the plane by placing the two LiFe's to the left-hand side of the side door opening making them easy to charge too.

I centered the tank under the wing tube and installed the receiver between the tank and the rudder servo. The only thing that I had to search around for was the O-rings for the landing gear. I ended up getting them from Home Depot in the plumbing department and used two per side. The O-rings are DANCO #96735, #18 O-rings and come in a pack of 10 for around $5.00.

For the wing strut attachment point, I use these from HH. They are easy to install and remove so assembly time is toolless for me.

https://www.horizonhobby.com/han4563

The L-4 takes off in just a few feet with 1/4 throttle and then I add power and climb away, landing is simple and easy, no issues with this plane.
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Old 09-24-2019, 07:30 AM
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Quote:
Originally Posted by MarksHangar View Post
Yes, that is what I used. Page 67 of the build guide is where I got the info from as there were no instructions with the plane nor directly on BH's web site at the time I bought mine 3 years ago.

https://www.flyingrc.net/graphics/re...Y%20MANUAL.pdf

For me, it aligned with the wing bolt locations and I was able to balance the plane by placing the two LiFe's to the left-hand side of the side door opening making them easy to charge too.

I centered the tank under the wing tube and installed the receiver between the tank and the rudder servo. The only thing that I had to search around for was the O-rings for the landing gear. I ended up getting them from Home Depot in the plumbing department and used two per side. The O-rings are DANCO #96735, #18 O-rings and come in a pack of 10 for around $5.00.

For the wing strut attachment point, I use these from HH. They are easy to install and remove so assembly time is toolless for me.

https://www.horizonhobby.com/han4563

The L-4 takes off in just a few feet with 1/4 throttle and then I add power and climb away, landing is simple and easy, no issues with this plane.


Thanks so much for the info. Believe it or not Ive actually been looking for a cotter pin system that would help with the wing strut. When I ordered it a month or so ago, Bill emailed me a build manual. I can forward it to you if you would find it useful.

Thanks again!
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Old 09-24-2019, 12:49 PM
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What I've been doing for quite a while now, with new packs, and when I'm not sure about how long they might take to drain, is take alot of notes on the packs, starting with how much power (in Mah's) they take in initially, then first flights are short... maybe 5 minutes..(set and use your timer), then I take it home and charge it again, and take notes of the data on the recharge(as well as the number of flights...)... If you use your timer religously, you can easily gauge the time you've used the system.. (IE.. 3 ten minute flights=30 minutes use).


Once I confirm via the data I'm getting from the charger when I recharge(modern technology is wonderful like that).. and I'm confident I can get more flight time, I'll set the flight timer for a few more minutes, and/or maybe get another flight in, then I recharge and take more notes... until I've developed a track record, and am confident I actually have enough power to fly X amount of flights at X amount of time... and that pretty much establishes my routine. It usually takes 10 or so flights to gather my confidence that everything works properly. I/you can even get a reasonable gauge of average Mah's used per flight. Then you can use that when you move on to the next project.

I have small spiral note pads for each substantial plane I own... and another note pad that has info for all my smaller models. There's just too much pertinent information to remember... and I write down significant dates and repairs/modifications.. (IE...battery swap, engine work, servo/radio work, etc...). Also, write your date of first charge on your new batteries... Then there's no question when you put them into service.


I also have telemetry onboard with alerts and warnings set accordingly.. of which I've never got any using my above method. It's seemed to work pretty well for quite a while, once I started realizing the data is available on most modern chargers, I've tried to take full advantage of it all.

You're definitely in the ballpark with your batteries, and as mentioned you should be fine from what I'm reading, but do yourself a favor and jot down that data, create your track record. The information you're needing is probably closer then you think.

I also believe if a battery is going south(fading/wearing out), I/you would probably have an indication well before that battery fully fails. It's part of why we pay the big bucks right.

Good luck with your plane, it sounds nice.
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Last edited by DGrant; 09-24-2019 at 01:07 PM.
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