Even if you don’t get the same rate you might get more altitude before the batteries die. It will be interesting to see the results. Not only do you have more weight and a big slow wing but aren’t you using different props too? Do you have an amp meter?
I’m using the wood props again, the carbon fiber wouldn’t stay on. Yes have a power meter to see the amps. I might not be able to test for a week or so.
My son weighs 30 pounds less than I do and he flew my motor and wing this morning. He held the throttle at 65 amps for 15 minutes and gained 3400 ft. When I do the same thing I only gain 2800 ft. Hopefully I can gain that extra 600 ft with a new and larger wing. I’m 30 pounds over the certified weight of my wing when I use 6 batteries.
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I’ve been collecting data for climb rate with different amp draws. I find it interesting how linear the data is even when I include zero amps, which is my descent rate (-278 ft/min), and 36 amps which is level flight:
I combined the equation above with battery capacity to chart how high I can climb with 6 batteries as well as how long I can fly. I didn’t test above 75 amps but I extrapolated to create the last 3 rows (I don’t ever go above 80 amps for an extended period). The flight time calculation includes the descent and matches pretty close to what I see in calm conditions with batteries that are well used and starting to puff. I should be getting new batteries next week and I hope to see longer flight times with them:
Here is a graph of the maximum altitude:
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Approximately what thrust does that correspond to to maintain level flight @36A per motor?
GliderPilot averages 27.8 minutes with 12S 66000 mAh :
Current[A] = Capacity[Ah] / time[hrs]
So 66000 mAH = 66 Ah
27.8 minutes converted to hrs : (27.8/60)[min] / 60[min/hr] = 0.463
Current = 66Ah/0.463hrs = 142.55 A
Average Amps in a flight is 142.55 A
Run_time(min) = Capacity(Ah) / Current(A) x 60min/hr
Capacity: 66 Ah
Current: 142.55A
Run_time = 66/142.55 x 60 = 27.8 min.
Batch4 use KV150 motors and 14S batteries (~15% more capacity)/
KV150 / 14S 66000 mAh setup should reach 32 minutes…
You just reversed my math to get amps. The data I collected was amps per motor which is 36 x 4 motors = 144 amps. I calculated runtime to be 27.8 minutes based on a 66AH capacity. Then as a sanity check compared it to flight times and that is about what I get. But I think I will get more with new batteries but that’s where the math doesn’t quite add up because I would expect the manufacture to exaggerate capacity rather than underestimate.
Then add 15% for batch 4 like you said.
New Bonka’s which have full capacity or something different?
There are new safer Lipo’s coming out… but expensive:
Any thoughts how we can ever achieve 2 hour flight time?
There are a lot of variables like weight/size and sink rate of your glider etc. for determining flight time.
From data I read from the Paracell eppg it needs on average 100 A for pilots over 85 kg and
90 A for lighter pilots.
Actually from this thread here I think we are somewhere around 120 A with 12s
100 A average with 14s = 5180 watt
120 A average with 12s= 5328 watt
Not a huge difference and to fly for 1 hour you will need over 105000 mAh batteries…
I do think it is possible with the perfect combination to save 15-20% power consumption.
Those tattu batteries are heavy too. Nearly six kilos each. The bonkas are 10lbs a pair which is less than 5 kilos.
I would guess the Tattus will have truer capacity (better manufacturer) than the Bonkas.
Has anyone done a full charge/discharge cycle to see capacity of the Bonkas?
This battery is a new generation lipo with BMS!
Tattu 22000mAh 12S 44.4V Battery Features:
- Communication protocol
- Communication protection
- Fuel gauge
- Self-inspection
- Using time log
- Current detection
- Ultra-Low power consumption
- Abnormal log
- Local after-sales service (Located in Dublin, CA)
Tattu 22000mAh 12S 44.4V Battery Specifications:
- Minimum Capacity: 22000mAh
- Configuration: 12S1P / 44.4V / 12 Cells
- Discharge Rate: 25C
- Max Burst Discharge Rate: 50C
- Net Weight(±20g): 5800g
- Dimensions: 235.5mm Length x 172mm Width x 116mm Height
- Charge Plug: micro USB+JST-XHR
- Discharge Plug: AS150U-F
Tattu Plus , a smart battery specially designed for UAV. Protective casing give these batteries extra safety during the flight. Power lead is also longer then normal tattu batteries. Indication LED lights of the batteries can let you know how full of the capacity the batteries have when charging. Warning lights to give you indications of the temperature, over/under the charge and cells balance healthy level. These lipo batteries will also go into an intelligent storage mode when you fully charge the batteries and decided to store away. The batteries itself will discharge in the storage mode to keep the voltage at a certain level for storage. The amazing battery management system(BMS) will smartly manage your battery and extend your battery life. This BMS is a trend of Lipo batteries, it’s the new generation of UAV batteries.
Amazingly I get full capacity from the batteries when I run them down to 3.2V per cell. Twice I’ve had to run them down to 3.0V in an emergency situation and got nearly 23Ah out of them. Usually I land at 3.5V and use ~20Ah per pack.
P.S. This is calculated from my watt meter, and verified from a quality charger, the HT700 does not give accurate Ah when charging.
Nice! Is this new, or after how many cycles?
That little bit of energy is nice to have in an emergency but have you noticed how fast the voltage drops once they get that low? Once they hit 3.5V there is very little capacity left. We are talking seconds worth of power at partial throttle. I’ve learned to cut my flights 1 minute short so that I actually have an emergency reserve rather than risk damaging my batteries.
I also fly with a mindset that my motor could fail at any moment and I stay within gliding range of a safe landing area. However, I admit that sometimes my bailout option is too small and I find myself thinking “it would sure suck if my motor were to fail right now!”
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I have about 50 cycles, and the numbers seems to be holding.
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8 Bonkas would be a useful option for aircraft with wheels