Choosing the right battery

[Raptor4184]

so i have 2212/920kv motors (the black ones), for the dji f550 (aluminum arms so its a little lighter) so what battery should i get for longest flight. what is a trustworthy lipo manu? its a film drone and peak power wont be used as in flying fast or crazy maneuvers, mainly hovering or slow movement. Please help thanks


my drone is very similar to the one pictured, running dual battery or single, same gimbal and gopro, and same props and motors (i have the red ones too)

-Taylor

 

[jamesb72]

Pretty sure you are limited to 3S with those props/motors, so flight time is a factor of weight/capacity not voltage.

 

[moonpie57108]

I have had good luck with Pulse and just started using Tattu. I have also had good luck with Turnigy for a cheap battery.

They are batteries and at that they aren't the most stable battery in history (in my opinion) and probably all brands have had problems or at least had people blame their abuse on the battery. That said, battery brand might matter but your care for the battery is more important in my experience.

 

[moonpie57108]

3s vs 4s question, would probably just come down to the weight of the drone. Do you need the thrust the 4s system can create? If the 3s system would put you under 2:1 thrust to weight, run 4s.

To just hover around, I would think the flight time would be similar as you are running the motor at the same RPM for the same Thrust regardless of 3s or 4s. (Using the same motor and prop). You would need a little heavier duty 4s battery because the 4s rig could pull more amps on the battery, if you don't wield the throttle like a baton, you should be fine.

 

[jamesb72]

... you are running the motor at the same RPM for the same Thrust regardless of 3s or 4s. (Using the same motor and prop).

I think this isn't what you meant, as 3S vs 4S you cannot typically use the same motor/prop, as RPM would be ~25% higher - so would be like trying to pull away in 3rd gear - you can do it, but its not efficient and will not give best service life.

3S packs are nominal 11.1v, 4S are 14.8v so for the 920kv motor the unloaded RPM would vary from 10,212rpm to 13,616rpm (voltage x kv is unloaded rpm), so would need different props to run efficiently.

Typically the 920kv motors (which were used on Phantom1+2/F450/F550) would run 9x45 - 10x47 props for 3S, for 4S you would run smaller props (8"?) as RPM will be higher.

Running oversize props will dramatically increase the current draw and reduce efficiency, you may get slightly more thrust on 4S but you will be cooking your motors/ESC/battery with much higher current load for little or no benefit.

There are a ton of tools online you can enter motor/prop/battery and get an estimate of current draw/thrust/efficiency, or you can use a wattmeter/thrust stand and test different props with your motor to work out the best efficiency for your total weight and flight time requirement, but the easiest way is to copy existing known good setups.

 

[Raptor4184]

I think this isn't what you meant, as 3S vs 4S you cannot typically use the same motor/prop, as RPM would be ~25% higher - so would be like trying to pull away in 3rd gear - you can do it, but its not efficient and will not give best service life.

3S packs are nominal 11.1v, 4S are 14.8v so for the 920kv motor the unloaded RPM would vary from 10,212rpm to 13,616rpm (voltage x kv is unloaded rpm), so would need different props to run efficiently.

Typically the 920kv motors (which were used on Phantom/F450/F550) would run 9x45 - 10x47 props for 3S, for 4S you would run smaller props (8"?) as RPM will be higher.

Running oversize props will dramatically increase the current draw and reduce efficiency, you may get slightly more thrust on 4S but you will be cooking your motors/ESC/battery with much higher current load for little or no benefit.

There are a ton of tools online you can enter motor/prop/battery and get an estimate of current draw/thrust/efficiency, or you can use a wattmeter/thrust stand and test different props with your motor to work out the best efficiency for your total weight and flight time requirement, but the easiest way is to copy existing known good setups.

Thanks, so I am
Getting 1047 props and the 2212/920kv motors. May get the E310 motors tho from DJI. Thoughts? I'm running now 5000mah 3s 25-30c batteries. Can I run dual and get more flight time? What's the benefit of dual batteries?


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[jamesb72]

The only advantage of the E310 is they are a known good setup, but so are your 920kv motors, as they were the predecessor of the E310 on DJI props.

Dual batteries will give more capacity but higher weight, so you won't get double the flight time with double the mah as the extra weight will take more power to lift.

I suspect there isn't an exact way to calculate flight time, but its definitely diminishing returns. Generally the best way to look at this is start with the camera gear you need to lift (payload) and the flight time you want to achieve and then backtrack from there to work out best frame (x4/Hex/X8 etc) motors, props and batteries to achieve it.

You can google F550 flight times and get an idea, but just guessing I'd expect 10-12 minute flights with that hex, I'm sure you can get more but the weight will hit flight performance as you start to carry a lot more battery weight.

 

[Raptor4184]

The only advantage of the E310 is they are a known good setup, but so are your 920kv motors, as they were the predecessor of the E310 on DJI props.

Dual batteries will give more capacity but higher weight, so you won't get double the flight time with double the mah as the extra weight will take more power to lift.

I suspect there isn't an exact way to calculate flight time, but its definitely diminishing returns. Generally the best way to look at this is start with the camera gear you need to lift (payload) and the flight time you want to achieve and then backtrack from there to work out best frame (x4/Hex/X8 etc) motors, props and batteries to achieve it.

You can google F550 flight times and get an idea, but just guessing I'd expect 10-12 minute flights with that hex, I'm sure you can get more but the weight will hit flight performance as you start to carry a lot more battery weight.

So why would someone use 2 batteries?


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[jamesb72]

People will use two batteries for more flight time (just not double/triple flight time as you add batteries, as the weight goes up), the exact flight time increase depends on many variables, but for a sensible example (say a F450 on 3S 2200) running two batteries would give 50% more flight time (not 100% more) as a reasonable starting estimate, a third battery may add 15% flight time (not 50%) and would fly like crap, and 4th would probably then not fly at all due to weight.

The other main reason to use dual batteries is for large MAH its more managable/flexible to use say two 8000mah or 5000mah batteries than one huge battery (which you may not be able to buy anyway due to freight limits on Wh in one unit) - you can charge them seperately on two chargers etc, also you have a bit of redundancy if a cell fails in one pack, the other battery would hopefully give you power to land under control (voltage would drop so you would need telemetry/voltage alarms to know in flight).

 

[Raptor4184]

People will use two batteries for more flight time (just not double/triple flight time as you add batteries, as the weight goes up), the exact flight time increase depends on many variables, but for a sensible example (say a F450 on 3S 2200) running two batteries would give 50% more flight time (not 100% more) as a reasonable starting estimate, a third battery may add 15% flight time (not 50%) and would fly like crap, and 4th would probably then not fly at all due to weight.

The other main reason to use dual batteries is for large MAH its more managable/flexible to use say two 8000mah or 5000mah batteries than one huge battery (which you may not be able to buy anyway due to freight limits on Wh in one unit) - you can charge them seperately on two chargers etc, also you have a bit of redundancy if a cell fails in one pack, the other battery would hopefully give you power to land under control (voltage would drop so you would need telemetry/voltage alarms to know in flight).

Cool, thanks for the help can I use batteries with slight differences in c and mah?


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[jamesb72]

As long as the voltages are close between packs when you connect them - ie within .1v or so (so you don't get a big spark/dump of voltage from one battery into the other) then you can mix C and mah much like when parallel charging, but obviously its ideal to run as close as possible to the same packs (ie adding an 850mah pack to a 5000mah would not be sensble). C rating you can also run lower with a bigger mah 'pack' as it multiplies out.

Say your quad hovers at 25 Amps on your 5000mah 3S pack that is 5C, if you added a 3000mah 3S pack in parallel to make 8000mah total, your weight will increase so just say current goes up to 30Amps hovering, this is effectively 3.75C. Obviously the max current will be much higher than this, but will also multiply out, which is why the big quad packs (12000-16000mah) are often only 10-20C rated, where smaller miniquad packs (1000-1300mah) are marketed as 45-90C.

 

[Raptor4184]

As long as the voltages are close between packs when you connect them - ie within .1v or so (so you don't get a big spark/dump of voltage from one battery into the other) then you can mix C and mah much like when parallel charging, but obviously its ideal to run as close as possible to the same packs (ie adding an 850mah cell to a 5000mah would not be sensble). C rating you can also run lower with a bigger mah 'pack' as it multiplies out.

Say your quad hovers at 25 Amps on your 5000mah 3S pack that is 5C, if you added a 3000mah 3S pack in parallel to make 8000mah total, your weight will increase so just say current goes up to 30Amps hovering, this is effectively 3.75C. Obviously the max current will be much higher than this, but will also multiply out, which is why the big quad packs (12000-16000mah) are often only 10-20C rated, where smaller miniquad packs (1000-1300mah) are marketed as 45-90C.

Ok so a 6000mah 3s 25c and a 5000mah 3s 25-30c are ok with eachother? Could you point me to a good pack (5000mah at least) inneed some new ones and idk what to get now


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[jamesb72]

Electrically they would be fine, I don't know how well the hex will fly with the extra ~600g weight though, but you can certainly try it.

If you are using Naza FC its important to remember your left stick is not a true throttle, its a 'climb demand' control which the Naza then controls the ESC to whatever throttle setting is required to either hold height or climb, so you can be hovering at midstick but if the hex is too heavy the motors could be almost 100%, so you have no power in reserve for manouvres/stability.

The std way to test is to hover a sensible height say 30ft up, then flick into manual mode (remember you will have no attitude hold and may drop rapidly if its overweight so be ready to switch back to atti/GPS quickly) and see if the craft will hold a hover at 50% stick (which in manual mode is true 50% throttle), the general rule of thumb is you want to be hovering at 50-60% true throttle to have good control/performance in GPS/atti modes.

 

[Raptor4184]

Electrically they would be fine, I don't know how well the hex will fly with the extra ~600g weight though, but you can certainly try it.

If you are using Naza FC its important to remember your left stick is not a true throttle, its a 'climb demand' control which the Naza then controls the ESC to whatever throttle setting is required to either hold height or climb, so you can be hovering at midstick but if the hex is too heavy the motors could be almost 100%, so you have no power in reserve for manouvres/stability.

The std way to test is to hover a sensible height say 30ft up, then flick into manual mode (remember you will have no attitude hold and may drop rapidly if its overweight so be ready to switch back to atti/GPS quickly) and see if the craft will hold a hover at 50% stick (which in manual mode is true 50% throttle), the general rule of thumb is you want to be hovering at 50-60% true throttle to have good control/performance in GPS/atti modes.

Thanks that makes much more sense. So on the topic of esc, what range of Motors are ok to use with 30A esc (came with my 550)


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[moonpie57108]

I think this isn't what you meant, as 3S vs 4S you cannot typically use the same motor/prop, as RPM would be ~25% higher - so would be like trying to pull away in 3rd gear - you can do it, but its not efficient and will not give best service life.

3S packs are nominal 11.1v, 4S are 14.8v so for the 920kv motor the unloaded RPM would vary from 10,212rpm to 13,616rpm (voltage x kv is unloaded rpm), so would need different props to run efficiently.

Typically the 920kv motors (which were used on Phantom1+2/F450/F550) would run 9x45 - 10x47 props for 3S, for 4S you would run smaller props (8"?) as RPM will be higher

Within reason you can use the same prop and aren't necessarily over propping anything. Just know what your equipment is rated for to start with. Many motor prop tables overlap significantly between 3s and 4s.

At the 900ish kv range you can run a standard 9x4.5 DJI prop with a 2312 on 3s or 4s depending on what you want to do/need and craft weight. The 3s system will be about 12 amp per motor with 4s being about 20 amp per motor and the esc should handle either assuming a 20 amp from the DJI kit.

Particularly if your running a docile 3s and your equipment is rated 4s, your not going to normally have any problems.

Regarding hover rpm, if your using the same prop you are going to hover at a lower throttle percent on 4s because of the rpm scaling but the same rpm to make x thrust.

 

[jamesb72]

what range of Motors are ok to use with 30A esc (came with my 550)

Any motor/prop combination drawing up to about 24Amps is fine, you want to stick to 80% of capacity for motors/escs/lipos so you are not pushing your luck.

For a Hex 30A ESCs should be enough for a pretty big multirotor, as you would have to draw 144Amps to start hitting that limit (24Amps x 6 which is 1600w on 3S) , which is something like 8Kg take off weight, which is a pretty massive Hex with huge batteries !!

 

[CGO89]

I hope I did the right thing, I have ordered a P3 battery https://goo.gl/KY0MPT at a discounted price. I have my doubts that it may actually not be genuine but couldn't resist the price difference. In local shops (also from now on called thieves) a P3 battery goes as highs as a whooping 170-180 euro ! Also most local shops don't agree to fulfill warranty as they consider this a consumable part

The one posted above is cheaper than on site as I have used a coupon that works "RC18OFF" so only paid 127.66$ for it (around 110 euro). As for warranty the seller although slow it has honored my previous problems with other stuff like phones and tablets. So when I get this first thing I will do is to update it's firmware, to be sure it passes this and use the latest available go app to see if the battery is validated. Any other thoughts about this, or how to check if it's the real deal ? I know it may be a risk but maybe it's genuine after all ?!

 

[Delwin]

Better not...

Enviado desde mi D5103 mediante Tapatalk

 

[Delwin]

sorry...

Enviado desde mi D5103 mediante Tapatalk

Enviado desde mi D5103 mediante Tapatalk