Can't get my head around what batteries to use with my F550

[rilot]

I've been reading and reading and reading and I just can't get my head around what batteries to use.
My AUW (with 1 x 4S 5000mah) is 2.4kg with gimbal, camera, FPV gear, legs etc. Using the stock DJI motors, and ESCs. Gimbal and FPV tx are powered from their own 2S 800mah battery.
I'm looking for a flight time of around 10 mins with this setup.

Props I have available in my box are 8x5 Graupner, 10x5 Graupner, 1038 DJI, 8" DJI. It seems to fly best with the 10x5 Graupners.

I only have a couple of batteries available at the moment. A bunch of 3S 2200mah and a single 4S 5000mah. These seem to give about the same flight time of around the 5 mins mark with ultra conservative voltage warnings.

So, would you use 2 x 4S 5000mah in parallel or 2 x 3S 5000mah in parallel with my setup and with which props? I'm thinking 2 x 3S 5000mah with 10" Graupners will give me the longest flight time - due to the lower weight of the batteries - but the least agility. I'm not really interested in sport flying. This is for photography only.

There seems to be a lot of contradictory information about 3S vs 4S on 10" props with some saying it will kill my motors and others saying it will be just fine and they run 4S/10" all day long for ages with no issues.
I've checked the motor temps with 3S and 4S on 10" and they are hotter with 4S after 5 mins of flying around but not hot enough that I can't hold my hand on them.

Just looking for some advice on what batteries to buy. More 4S 5000mah items or drop the 4S and get a bunch of 3S 5000mah.

Thanks in advance.

 

[thehelidude]

I had to go from 3s to 4s when I added a gimbal to my f550 quad (4 arms on a 550 to get props out of view). I'm using 10 inch graupners and a 6000mah 4s and getting 10 mins or so, depending on if im flying far away or more hovering. I am also powering the fpv gear and gimbal off of it. I feel like 2 4s 5000mah might be a little too much considering that you have that 800mah for your fpv gear. I think 6000-8000mah would be more appropriate but it might be ok. I have light landing legs and only 1 battery so I'm probably lighter.

 

[rilot]

I ended up getting a bunch of 5000mAh Turnigy Nano-Tech lipos. I'll run them as singles and see how we go.

 

[Treg]

I am using a 4s 8000mah 30c in mine with fpv and a GoPro, I get about 10-12 min easy flying.

 

[OneStopRC]

Try dropping your Prop size, you are not meant to run 10" on 4s, they over heat your motors due to the props working harder. They spin much faster on a 4s than on a 3s, lower Kv motors will allow bigger props with less draw on the battery, which will also allow for more lift. Saying that, you really can't go much more than a 10" without increasing arm length.

 

[bruce365]

Hi deanot, you are wrong in suggesting drop prop size, the smaller the prop the less efficient the flight system = less time in the air.

rilot, 10" graupners with 4S are absolutely fine. 8" props are good if the F550 has low weight, as it comes with out gimbal camera fpv etc.
I would never use 3S batteries on my F550, what for there are no advantages.

2.4 kg is heavy for the F550 with stock motors (at its recommended maximum) so expect about 8 to 9 minutes using a 5amp 4S battery.

Using larger batteries just adds weight that has to be lifted into the air, you can put 2x5amp 4S batteries on the F550 but you will probably only get 12 minutes flight and the hex will be overweight and very sluggish, not recommended.

Check your "ultra conservative voltage warnings" you may well have this set too high, check how many mah your charger is putting back into your battery after the flight. 20% should be left in the battery.

80% @ of a 5amp 4S = 4000mah (this amount you can use in your flight), so your charger should be putting 4000mah back into the battery when fully charged.

Regards - bruce

 

[rilot]

Thanks Bruce, good info.

I was putting back 3200mAh so I'm too high on my voltage warnings. I haven't flown with the nano-techs yes but I'm expecting the load voltage drop to be less than with the Zippy Flightmax I was using.
I'll set the first level warning to 13.5V, hover until the warning, then measure the voltage of the bats. The difference between my measured voltage and my warning should be my voltage drop. Then I'll measure how much I put back in to the battery and adjust the cutoff accordingly.

 

[OneStopRC]

So why do dji tell you other wise? 8" props on a 4s, 10" props on a 3s?. I Ann quoteing information from the manufacturers, while not trying to call you out, would they not know more about there product than you?

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[Benjamin Kenobi]

The DJI recommendation is for a bare kit with no payload. If payload you up prop. Thought you'd know this Deanot.

 

[rilot]

Using ecalc, with 4S you could put more current through the motors than they can handle, but only in a full-throttle climb.

Mine seems to fly fine with 10" on 4S and the motors barely get warm.

 

[OneStopRC]

I am running 9x5 on my 4S, getting around 16 minutes air time on a 4500. I am running slightly heavy also, but increasing the props would increase the load on the motors, also increasing the draw on the battery which would equal shorter flight times and premature failure of the motors and battery.

If you want to do it the right way, increase your prop size and change out your motors to a lower KV....

 

[RobertsUp]

My first build is an F450 with the Aerial Media Pro's heavy lifting conversion kit. It has only flown on 4S batteries. It flies like a beast and for 15 minutes. (Carrying no load)

It has flown with both 11x5 Graupners and Xoars. My first build is a success. I'm still flying it in test mode but I plan to put a camera on it.

I don't obsess about the details of motor to battery matching. After a flight the motors and esc's are cool. The LiPo is just noticeably warm.

My plan is to adjust my power to whatever load my quad carries in the future. Always testing and adjusting. Maybe bigger LiPo's, maybe smaller Props. Always finding out what works best in the real world of flight. Science as defined by Prof Feynman: "Guess, then test"

 

[Benjamin Kenobi]

Here here! Well said! What does work and what should work are often different.

 

[rilot]

I flew the F550 last night after doing some voltage protection calculations.
I rigged up the watt meter and measured the voltage drop in flight to be 0.4V. I punched this in to the Naza as my drop and set 14.0V as my level 1 warning. I also set 13.6V as an alarm on my DX8 from the telemetry.
I maintained a hover for 12 minutes with an AUW of 2.34kg with Graupner 10x5 props until the alarm went off and the Naza started flashing.
I measured the battery with a multimeter and got 14.0V so, spot on @ 3.5V / Cell. This also agreed with the watt meter and the Naza.

I stuck the battery on charge and it took 5200mah to full. Or 104% of the capacity!!!!
I've probably killed the battery. Damn.

I thought keeping the batteries to no lower than 3.5V / cell would be fine. I guess not. I'll set a new limit of 3.7V / cell = 14.8V and see where we go from there.

 

[Quantumlight]

This is one reson i just got a fule guage to my rig. but im using Futaba 14SG so with this sensor i will get the reading down to controller in mAh. no more time calculations or voltage protection in Naza.
0.4 v load seams a bit low on a 2.34 kg rig. I use 0.8 with raupner 9x5" props. wight 2.9kg so a bit heavy rig. will change out to better motors etc. soon

 

[rilot]

I'm not aware of any telemetry adaptor for the DX8 that supports mAh used information. There is a current monitor but it does just that, gives an instantaneous reading of current.

I'll re-calculate my voltage drop tonight. I thought it was a bit low. I relied on the watt meter to show me the voltage drop before. I'll do it the old way by setting a warning at 1V below fully charged, flying until the alarm goes off, then measuring the pack voltage and subtracting.

 

[Quantumlight]

ya thats the way to go
1. Fully charge battery
2. Open Naza assistant
3. Click on "Voltage" tab
4.. Turn on Naza voltage monitor (it's probably on already)
5. Calibrate fully charged battery and note the voltage of the battery
6. Set the First Level No Load protection at fully charged battery voltage Minus 1.2 volts (4s) AND SET THE LOSS TO 0 (ZERO) (make sure that the second level protection is at least 1 volt or more below the above No Load setting)
7. Fly until LED is flashing red
8. Land immediately
9. Hook up to Naza assistant and click voltage tab
10. Check the voltage of the battery within Naza assistant
11. Subtract the First Level protection voltage from the above (higher) battery voltage
12. Enter this difference in the First Level Protection Loss field (backspace and delete all the red numbers and you can enter values greater than "0.50")
13. Enter (3.6 volts per cell x 4(s) = 14.4) volts in the First Level No Load field.
14. Enter (3.5 volts per cell x 4(s) = 14) volts in the Second Level No Load field AND the same Loss value as in #12 (above).
15. It's not good to discharge LIPO batteries below 3.5 volts per cell!
16. During Flight, the observed battery voltages are temporarily lower and fluctuating because of the motors having to lift the weight of your aircraft. These voltages are always lower than when your aircraft is not flying. The entries in the Loss fields reflect and estimate the above differences to extend your flight time!!
17. For other batteries (3s), the above voltages should be re-calculated accordingly.