Extremely low flight times on FPV quad

[ThePenguinNich]

Hello, I'm fairly new to this RC multirotor scene (RC stuff in general as well), and I've recently build my first FPV quad (lacking the FPV gear as of now) from a kit. It's been over a month, and I'm still working out issues with the quad. I've gotten it to run, but not for long.

The flight times I've gotten are ridiculously low. Just hoovering about 7ft off the ground, the flight times average at 25 sec on one battery to 41 sec on the other (I will post the info of my tests as an attachment). From what I understand, those times are abysmal to say the least. I'm running with 5x45 props with SunnySky X2204S 2300kv motors.

I did notice that the quad is wobbling a tad when hoovering, so that leads me to believe that the props are the issue, but I'm not really too sure. The frame was put together fine, and everything is snug and fit on well, so I can only reason that the issue is bad props or bad batteries.

If anyone can help out, that would be fantastic. If anyone needs more info I'll be happy to post it with the best of my ability.

 

[fengshuidrone]

Your 1300 mah batteries should last way longer than they are. What do you charge them with? If they are being balanced properly you should get more flight time. If one cell is way off from the rest they wouldn't charge right. If you are using a sub par crap cheapo charger from HK, that could be a part of the problem. I would first check to see if all my cells are balanced and are charging fully. If all of that is fine I would be looking for a dead short somewhere in your 11.1v wiring. Do you get a big spark jump when you hookup your Li Po? The quad wobbling is usually a sign of PIDs out of tune (depending on what FC and firmware you use.) Of course I don't know your AUW, what FC you use, or almost any other tidbit that might help.

 

[ThePenguinNich]

Your 1300 mah batteries should last way longer than they are. What do you charge them with? If they are being balanced properly you should get more flight time. If one cell is way off from the rest they wouldn't charge right. If you are using a sub par crap cheapo charger from HK, that could be a part of the problem. I would first check to see if all my cells are balanced and are charging fully. If all of that is fine I would be looking for a dead short somewhere in your 11.1v wiring. Do you get a big spark jump when you hookup your Li Po? The quad wobbling is usually a sign of PIDs out of tune (depending on what FC and firmware you use.) Of course I don't know your AUW, what FC you use, or almost any other tidbit that might help.

Sorry, I'm running a modified CC3D (works the same as a normal one) using OpenPilot to program it. AUW is 454 or 470 depending on the battery. I'm using this charger, although I'm not really too sure on how good it is. I've checked the batteries when they are charged to make sure they are 11.1v and they are. I'm assuming that means they are balanced but how would I check for sure? Other than that, I'll go adjust my PIDs (just learned about them when you mentioned them), and I do see a large spark when I plug in my LiPo to the quad.

Thanks for the help.

 

[fengshuidrone]

Yeah, your weight is ok. That charger looks OK. You can check your cell balance in several ways. That charger looks like a good one so there is probably a setting there that reads all three cells. There is probably a balance charge setting too. You should always charge on the balance charge setting. When you store your batteries for any length of time you want them at half charge which is 3.85v (per cell). If you have a volt/ohm meter you can set it to read DC voltage at like 20. Then touch the ground probe to the ground connection in the balance plug on the battery and the positive to the next wire over. At full charge it should read 4.20. Move both probes over one wire and read again. It should read the same. Same for cells three (and 4 if you are running a 4s.) The actual full charge voltage of a 3s battery is 12.60-12.64v measured across the balance connector.
Your batteries sound like they are draining quickly to ground and you have a potentially hazardous/fire situation on your hands until you get the short found and fixed. The large spark tells me that there is high amperage being drawn upon plug in. The FC only draws milliamps and the ESCs should not be drawing much of anything until you throttle up so they do not normally cause a large spark (at least they never have for me.) If I were you I would re check all of my wiring and connections that hookup in any way to the high voltage (Li Po + and -) and pay special attention that no + wire goes direct to - and no - wire goes straight to positive. Re check all of your power distribution connections to make sure that the same holds true for this device. Somewhere your battery is shorting out and there is the potential for ignition. This shorting condition is causing your battery to drain rapidly probably causing some sort of issue with excess heat somewhere. If not you are lucky. I would still be looking for a crossed or shorted wire or connection.
I'm not familiar with PID tuning in OpenPilot so you are on your own there. The usual cause of the wobbling you describe is PIDs in Multiwii firmware. I have no idea what term or algorithm OpenPilot uses to tune flight characteristics.
I was through your town back in the 1970's when I lived in Miami for two years. I used to be an auto saftey inspector for Dade County back then and everybody hated me. Do they still slap inspection passed stickers on folks windshields down there?

 

[ThePenguinNich]

Okay, so one of my batteries now lost a cell. The charger only recognizes 2 cells, and the voltage is 7.8ish. I was not using balance charge, as I didn't really understand that 'LiPo Balance' was a for charging upon just looking at the name of it (I was using the one that said 'LiPo Charge' this whole time, so I screwed up there.) I looked up some tutorials, and so I'll be able to adjust the PIDs okay I think.

As for the shortage, am I looking for things not plugged/ soldered in correctly or things that are routed wrong or something else? You said to make sure nothing is going straight from + to - and vice versa, does that mean there should always be something in the way (ie ESC or power dist)?

And for that last bit, I've never seen any inspection passed stickers anywhere.

 

[fengshuidrone]

Yes, there needs to be something in the way.
I wouldn't worry as much about the shorting problem now (but it never hurts to double check that stuff) because it now sounds to me like a simple battery issue (although I still am troubled and you should be as well by the large spark you mention.)
Your battery being down a cell will cause your flight time issues also. If the battery refuses to charge with the balance function it is because one of your cells is too low. There are ways to recover a low cell, but not a dead one, and not one that is too far out of wack.
I was 20 years old then (1974-75.) The state of Florida required all cars to have a yearly safety inspection sticker applied by a state certified inspector. We did it in two to four lane inspection stations. Miami only had about 250,000 people back then.

 

[cootertwo]

You're just getting started in this addictive hobby, and a lot of it is learn by trial and error, so to speak. Do some research on Lipo batteries. They can be finiky little bastards, and some brands are better than others. I keep all of mine in metal ammo cans for piece of mind, and I have one can half full of "puffies". (look it up). I was born in Miami, lived there all my life, until I went into the Army in 1967. Vehicle inspection was a pain. Until they setup real inspection stations, you could find a qualified gas station, and for a few bucks extra, get a sticker no problem. They were different colors every year. One year they were yellow, so I found an ad in the phone book yellow pages that was the right size. Cut that puppy out and taped it on the windshield. Worked like a charm, until I got stopped for speeding! Another trick when I had a job transporting new vehicles to the port for shipment overseas, was to place a wet "T" shirt against the inspection sticker. After a couple hours in the sun, you could peel it off without it leaving VOID on it. Where there's a will, there's a way.

 

[fengshuidrone]

You're just getting started in this addictive hobby, and a lot of it is learn by trial and error, so to speak. Do some research on Lipo batteries. They can be finiky little bastards, and some brands are better than others. I keep all of mine in metal ammo cans for piece of mind, and I have one can half full of "puffies". (look it up). I was born in Miami, lived there all my life, until I went into the Army in 1967. Vehicle inspection was a pain. Until they setup real inspection stations, you could find a qualified gas station, and for a few bucks extra, get a sticker no problem. They were different colors every year. One year they were yellow, so I found an ad in the phone book yellow pages that was the right size. Cut that puppy out and taped it on the windshield. Worked like a charm, until I got stopped for speeding! Another trick when I had a job transporting new vehicles to the port for shipment overseas, was to place a wet "T" shirt against the inspection sticker. After a couple hours in the sun, you could peel it off without it leaving VOID on it. Where there's a will, there's a way.

Wow, I never heard of the wet t shirt trick. I guess wet t shirts aren't only for bra-less babes.
They (the state) used to send fake "drivers" through our station twice a week trying to get one of us to accept a bribe. They would offer $10.00 (an enormous amount back then) if we'd just let this or that slide. The inspectors that the county employed were boyscout types (honest to a fault) like I was back then. They did extensive vetting ahead of time. They did all kinds of background checks on me before I got hired. I ended up quitting that job after a fellow inspector was blown up while getting in his car to go to work. I guess he denied some Cuban drug dealer an inspection sticker so the Cuban guy had him followed home. Next day his car exploded when he left for work. I had a new wife and baby so I quit and moved back to Ohio. I actually had some cuban guy come in one day, lift a towel up on his seat that was covering his Uzi, showed it to me and told me his car better pass or he was going to use it. After he passed my station in the inspection station I snuck in to the lunchroom and called the other end of the station on the phone and told my supervisor what happened. Next thing I know, my supervisor is at this guys window with his great big silver revolver cocked and ready to fire. We got that bad ass cuban out of the car and cuffed until the state po po came and took him away. That was just a typical day there. I was actually employed by both the state and Dade County. We wore State Highway patrol uniforms with a candy stripe down the leg instead of the solid state trooper stripe and a different shoulder patch. At that time we weren't carrying guns but our supervisor had a big chrome revolver for these occasions. After the inspector was blown up there was talk of arming us on and off the job. That's when I quit.
I completely agree with cootertwo on the learn all you can about Li Po thing. It could actually save your life someday by preventing a house fire.

 

[ThePenguinNich]

That's a hell of a lot more dangerous than I imagined. Was that the only hazardous incident you experienced?

Anyways, I'm still tampering with the PIDs, but I've balanced the battery I have that works and flew it a couple times. It's getting about 60 sec of flight time. I mentioned there being a spark when I plugged in the battery, but it's not happening anymore. I raised up the power distribution board (the kit came with two sets of pegs for it, I was using the shorter ones that kinda squished the board to the bottom plate).

The spark isn't there, and the batteries are balanced, but I'm still getting a minute of flight per charge, though.

Edit: I did some amp testing with my dad, and here's what we got:

• Idle: 320 mAh
• -90% throttle w/o props: 1200 mAh
• -50% throttle w/o props: 1600 mAh (how is this possible?)
• -90% bottom left motor: 450 mAh
• -90% bottom right motor: 780 mAh
• -90% top right motor: 430 mAh
• -90% top left motor: 460 mAh

So, is 320 mAh on idle too much or is it common for just powering the FC? Also, one motor almost draws close to twice the amperage than the other three. What's up with that?

 

[John Doecliff]

If one motor is drawing twice as much that would be a good place to start. when you land after your battery goes dead check for heat on all of your components. If something is way hotter than everything else that is an indicator as well. A fully charged 3S lipo is 12.6V, It says 11.1 on the battery but that is nominal voltage (3.7v per cell) you should be starting with a fully charged lipo at 12. 6v. Carbon fiber is conductive so like others have already mentioned you may have something going to ground. If you are sucking down a fully charged lipo in under a minute they may start to get puffed.

 

[ThePenguinNich]

Okay, I'll look out for that. Do you know how many mAh just a FC and receiver would pull?

 

[John Doecliff]

No, but its such a small amount that it shouldn't matter. This is an interesting problem and I'm looking forward to learning what's happening. Stick with it until you figure it out so we can all learn too. Just to clarify again, a fully charged (3S) battery is 12.6 v

 

[Bartman]

i'm looking at this thread and thinking that the batteries aren't being charged correctly. even if the props were upside down and the timing on the ESC's was way off the flight times would still be better than they are. hell, even if you doubled the weight of a basic quad the flight times would be better than sub-one minute

what charger do you have?

 

[cootertwo]

Something ain't right. Like John said, look for heat. If you're sucking a fully charged battery down that fast, something is getting hot. I always feel my motors and ESC's after a flight. Warm is OK, hot is not. Do you have access to someone else's charged battery to try? Maybe your charger is bad?

 

[Bartman]

if a battery were going from full to empty in less than a minute the discharge C value would be so high that the battery would be destroyed and not just hot but nearly burning and puffed like crazy! lol

maybe the heli isn't wired up correctly and there's a short somewhere? if there was though the battery would be toast

 

[Bartman]

Okay, I'll look out for that. Do you know how many mAh just a FC and receiver would pull?

can you post a few close up photos of your wiring and installation? and a model number of the charger too would be helpful.

we'll get you going, it'll just take a little time to get your problem figured out

 

[ThePenguinNich]

Okay, here's some wiring. You might want some more, like the motors and stuff, so I'll go do that. From what I can tell, everything that's soldered is soldered right and everything that has a plug is plugged in right. Also, I'm pretty sure my charger is only charging batteries until 11.1. When I charge, I set the value to charge 'til as 11.1v, should I change that to 12.6v if I can?

 

[cootertwo]

Ah Ha !!!!!

 

[ThePenguinNich]

Ah Ha !!!!!

Should I be charging it for 12.6, or should the charger bump it up to 12.6 itself when I say my battery is a 11.1v one? This is my charger, by the way.

 

[John Doecliff]

If you select 3s (11.1v) it should take it all the way up to 12.6 and then stop automatically. You need to set the charge current at 1.3 amps ( for a 1300mah battery) dont set it any higher than that for a 1300mah battery. The battery needs to be fully charged at 4.2 v per cell. in your case that's a 3 "S" (as in series) battery. 3 times 4.2 equals 12.6v You need to select the "balance charge" function and hook up the balance plug and charge lead. Check total voltage before and after charging. should be 12.6vdc when fully charged.