help with first hexa crash

[Dingus]

hello all,
This is my first post.
I apologize if this is in the wrong section.
I should preface this by saying I'm just starting to break into the copter community and what a cool one.

I need a little bit of help diagnosing a problem we had that caused the crash with our hexa.
have a link to a video with captions but here's the story.

we have a really great copter that we like and the designer built it to fly 5 pounds for 20 minutes.
the copter flies wkM and uses 2 turnigy 6s 8000 mah.
we use a Futaba 14 with a long range transmitter
Our pilot is an experienced RC pilot who spends most of his time flying Gas and Electric helicopters.
He also tained for a while on our phantom 2.


we set up a gps test flight with a bit higher wind than usual.
23 waypoints 40 meters up at 10 m/s.
we were using the iPad as a ground station
the copter had a five pound weight secured underneath

the copter flew fineup until the 14 minute mark where after the last waypoint the connection with the ground station was lost and the pilot attempted to return home.
(I understand the voltages are not a good measure of the batteries but at the time of signal loss we still had 22 volts.)

while returning home the pilot reported that he was losing altitude/control and was unable to land successfully.

damage was thankfully minimum with a few props and a snapped landing gear piece all easily replaceable.

the GPS compass tower was a little bit bent but easily mended.

the batteries however were swollen/mushy/hot to touch.

best we can come up with is that we pulled too much from the batteries and they got hot and vented.

both batteries will not take a charge and read 0-1 volts

did we simply need more batteries?

also other than the physical repairs is there anything I should do to ensure our copter is in good operating condition?
http://youtu.be/pKmvkArR67U

 

[Rentakill]

I never run batteries under 20%, what happened to your fail safe with the wkm.

 

[BenSkoning]

always keep track of battery voltage. I always land as soon as battery show 3.65 volts per cell.

-Ben Skoning

 

[Dingus]

I never run batteries under 20%, what happened to your fail safe with the wkm.

I am unsure. Instead of returning home to land, the copter rotated in place.
that's when the pilot took over.

I was still reading 22.xx volts on the ground station when everything cut out.
someone recommended adding a third 8000 mah or running two 12000 mAh.
I have read a lot about issues with the max amps batteries and copters though.
something about burst rated to 50°c but not sustained?
these terms are new to me so I'm sorry if I am misunderstanding.

 

[tombrown1]

When you go for your first flight, fly for about 5 minutes. Go back and charge up the batteries. See how much mAh you put back in. This should give you a basic idea of what your flight time should be. You never want to fly more than 80% of your battery out. You shouldn't be putting any more than 6,400 mAh back into each of your lipos.

Buy a couple of cheap lipo alarms from HobbyKing. Use them.

The only things you really need are a timer and lipo alarms. Telemetry is an added bonus. Turn off your WKM low voltage protection. It does more harm than good.

Sorry for your loss. Crashes suck.

 

[Dingus]

When you go for your first flight, fly for about 5 minutes. Go back and charge up the batteries. See how much mAh you put back in. This should give you a basic idea of what your flight time should be. You never want to fly more than 80% of your battery out. You shouldn't be putting any more than 6,400 mAh back into each of your lipos.

Buy a couple of cheap lipo alarms from HobbyKing. Use them.

The only things you really need are a timer and lipo alarms. Telemetry is an added bonus. Turn off your WKM low voltage protection. It does more harm than good.

Sorry for your loss. Crashes suck.

okay, I've never used the alarms before but I'll try it on. how far away can you hear them alarm?

also I want to understand how you are keeping track of how many mah you are putting back in after that first charge.


your directions:
• with two fully charged 8000mah batteries fly 5 minutes and land.
• remove batteries and recharge.
•keep track of how many mah you put back in
^how do I count this?

also you say that after 5 minutes we should not have to put back in more than 6,400mah.
if I do is that an indication of a bad battery?or does it mean that I need more batteries on the copter?
Thx

 

[vrso2]

put your alarm at front of your FPV camera. You can hear and see as well, when is time to go back and land safely

 

[Dingus]

put your alarm at front of your FPV camera. You can hear and see as well, when is time to go back and land safely

:facepalm
Lol
thank you, how many times has that been asked on this forum before?

 

[tombrown1]

Your charger should tell you how much you put back in. If your charger does not tell you this, then you likely need a new charger - considering that you seem to be serious about this venture. The iCharger Duo is a slam dunk.

You never want to hear your lipo alarm. Never, ever, ever, never, never, ever. I think I keep mine at 3.6. The only time I'll ever hear it is when I am taking off with only a minute or so of battery left - it will go off briefly then stop. If it goes off any other time then there is something very wrong and I land immediately.

The 6,400 mah is 80% of your battery's capacity. It has nothing to do with 5 minutes. You should never in your life need to put back more than 6,400 mAh into your 8,000 mAh lipo.

Allowing a lipo to drain completely in flight is a very grave mistake that should have been taken care of ahead of time. Please find some good "stickies" on lipo care online.

Also, just realized you're doing FPV? If you're going past line of sight then lipo alarms won't help - you'll need telemetry - or like vrso2 said put the alarm near the FPV cam and wear headphones.

Hope I don't sound too preachy. Good luck.

 

[Dingus]

Your charger should tell you how much you put back in. If your charger does not tell you this, then you likely need a new charger - considering that you seem to be serious about this venture. The iCharger Duo is a slam dunk.

You never want to hear your lipo alarm. Never, ever, ever, never, never, ever. I think I keep mine at 3.6. The only time I'll ever hear it is when I am taking off with only a minute or so of battery left - it will go off briefly then stop. If it goes off any other time then there is something very wrong and I land immediately.

The 6,400 mah is 80% of your battery's capacity. It has nothing to do with 5 minutes. You should never in your life need to put back more than 6,400 mAh into your 8,000 mAh lipo.

Allowing a lipo to drain completely in flight is a very grave mistake that should have been taken care of ahead of time. Please find some good "stickies" on lipo care online.

Also, just realized you're doing FPV? If you're going past line of sight then lipo alarms won't help - you'll need telemetry - or like vrso2 said put the alarm near the FPV cam and wear headphones.

Hope I don't sound too preachy. Good luck.

not at all. Preach,
I inhale this stuff.
I'm currently using a hyperion charger. I'm sure it says it. I just need to pay more attention to the display.
yes I'm very serious about this
I'm currently reading the lipo sticky by bartman.

now back to the OP
it's possible that my batteries were simply old after operating in hot weather too long
but if this copter cannot sustain 20 minutes, I need to add batteries.

I plan on building my own system but as of yet have not.
on a WKM system the new battery leads wire directly into the PMU?

 

[tombrown1]

Let's look at your system from scratch. List all of the parts on your rig. 20 minutes on a hex with a 5-pound load (not including lipos, right?) is a pretty good flight time. Adding batteries may not fix your problem because bigger batteries means more weight. To achieve high flight times you need big props and low kv motors. If you're flying a 680 hex then I doubt you'll ever get your twenty minutes. Is it y6? Flat hex gets longer flight times.

 

[Dingus]

Let's look at your system from scratch. List all of the parts on your rig. 20 minutes on a hex with a 5-pound load (not including lipos, right?) is a pretty good flight time. Adding batteries may not fix your problem because bigger batteries means more weight. To achieve high flight times you need big props and low kv motors. If you're flying a 680 hex then I doubt you'll ever get your twenty minutes. Is it y6? Flat hex gets longer flight times.

We want to achieve 20 minutes with lipos and a five pound weight.
we currently have 14
WKM system,
2.4g data link
long range video transmitter
1 zippy compact for video
2 nanotech 6s 8000mah
avroto 3520 k 400 motors
we use props from the S 800
here is the copter, motors, small camera
I'm having trouble embedding on my phone but here are some links
Hex
http://i.imgur.com/toNes73.jpg?1
Motors
http://i.imgur.com/cvCTfvG.jpg?1
tiny camera for FPV(we don't care about audio or quality)
http://i.imgur.com/eApQPvJ.jpg?1

 

[Rentakill]

I am unsure. Instead of returning home to land, the copter rotated in place.
that's when the pilot took over.

I was still reading 22.xx volts on the ground station when everything cut out.
someone recommended adding a third 8000 mah or running two 12000 mAh.
I have read a lot about issues with the max amps batteries and copters though.
something about burst rated to 50°c but not sustained?
these terms are new to me so I'm sorry if I am misunderstanding.

I recommend using the timer on your controller, I'm flying a skyjibX4 with 2 8000mah nanotech Turnigy. 10-12 flight time

 

[Rentakill]

Your charger should tell you how much you put back in. If your charger does not tell you this, then you likely need a new charger - considering that you seem to be serious about this venture. The iCharger Duo is a slam dunk.

Exact same charger I use, sync charging also a big advantage for batt life.:livid:

 

[tombrown1]

We want to achieve 20 minutes with lipos and a five pound weight.
we currently have 14
WKM system,
2.4g data link
long range video transmitter
1 zippy compact for video
2 nanotech 6s 8000mah
avroto 3520 k 400 motors
we use props from the S 800
here is the copter, motors, small camera
I'm having trouble embedding on my phone but here are some links
Hex
http://i.imgur.com/toNes73.jpg?1
Motors
http://i.imgur.com/cvCTfvG.jpg?1
tiny camera for FPV(we don't care about audio or quality)
http://i.imgur.com/eApQPvJ.jpg?1

What's the 5 pound weight?

 

[Dingus]

What's the 5 pound weight?

the five pounds is to simulate the max weight of some equipment we are developing. We are experimenting with copter s for agricultural purposes. I'm sorry I can't be more specific

 

[Motopreserve]

the five pounds is to simulate the max weight of some equipment we are developing. We are experimenting with copter s for agricultural purposes. I'm sorry I can't be more specific

What is the weight of the MR without batteries? What is the max prop size the frame accepts? As Tom mentioned, adding batteries is diminishing returns because of the additional weight. You might need to determine your total amp draw, and then research some of the lower C rated batteries (Tattu?) to reduce weight but still provide the mah you need to achieve 20 minutes (if possible).

As everyone has mentioned already, keeping track of consumption and not exceeding the 80% rule is key to battery longevity. Whether simple alarm or telemetry, you need to track the battery religiously to ensure long life.

 

[Dingus]

What is the weight of the MR without batteries? What is the max prop size the frame accepts? As Tom mentioned, adding batteries is diminishing returns because of the additional weight. You might need to determine your total amp draw, and then research some of the lower C rated batteries (Tattu?) to reduce weight but still provide the mah you need to achieve 20 minutes (if possible).

As everyone has mentioned already, keeping track of consumption and not exceeding the 80% rule is key to battery longevity. Whether simple alarm or telemetry, you need to track the battery religiously to ensure long life.

sorry for the delay.
I just heard back regarding the weight of the copter
without batteries it is 9.6 pounds
we used two 6s batteries. each weigh 2.5 pounds
I will hear back about the max prop size shortly.

understood about batteries. I will do some research on that
thank you

 

[Motopreserve]

For some reason I haven't found spec on the Avroto - but if the specs are anything close to the KDE 3520 400kv, it looks lik you should be right on the cusp of the perfect 50% hover with 15" props.

 

[Dingus]

Max prop size the frame will take is 17"