krleas
FPV Freak
4120 Axis are 5-8S motors, if u want to have perfect combo then u need at least 6s and 17x6 xoar props as i have.
Aeronavics / Droidworx Skyjib V2 Battery Options
- Thread starter benbigdude
- Start date
4120 Axis are 5-8S motors, if u want to have perfect combo then u need at least 6s and 17x6 xoar props as i have.
iseeit
Day or Night...
I have a SkyJib 8 with 4120, 2x Zippy 8000 (6s) batteries, 15x7 Xoar, 360 gimbal and GH3 for a total TTW of 9.5kg
If this was yours, how far down would you normally fly each cell's voltage?
I just completed my longest flight of 9 minutes yesterday and ended up (right at shutdown) with 23% on the batteries and 3.7(ish) on average for each cell.
After a bit of a cool down it went up to 33% and about 3.8(ish).
Carapau
Tek care, lambs ont road, MRF Moderator
First up, changing from 5s to 6s is as simple as plugging in the 6s battery. In BECS you generally do not need to change the input voltage, just the output voltage you require thus a change from 5s to 6s is as simple as plugging in the 6s battery. Just check beforehand what the spec of your equipment is ie if you motors which get a direct feed are specced at 5s only then you will need to change these. Another thing to bear in mind is that by moving to 6s the motor rpm will increase.
As for batteries, I think that using voltage to judge the amount of flight time left is completely the wrong way to do it. The best way to do it is by judging how much you need to put back into the battery. The golden rule with lipos if you wish to maximise life of the battery is the 80% rule. So, if you have a 10,000mAh battery you should not be putting anything more than 8,000mAhs in when re-charging. To work out your flight times, conduct let's say a 5 min flight, recharge and note how many mAhs went back in, divide by 5 to get your mAh per minute and then divide that into the capacity of the battery. Simples. This is what you then set the timer to on your TX. The other advantage to this is that you know that when the timer goes off on your TX you still have sufficient power left to immediately return to base. For those guys running down to 3.2 v per cell, I think this is quite dangerous as you are now getting into the zone where ESCs may start to automatically shut down (be it sudden or a gradual reduction in power). One thing is for sure, you are shortening your battery's life when going to 3.2v per cell.
As for batteries, I think that using voltage to judge the amount of flight time left is completely the wrong way to do it. The best way to do it is by judging how much you need to put back into the battery. The golden rule with lipos if you wish to maximise life of the battery is the 80% rule. So, if you have a 10,000mAh battery you should not be putting anything more than 8,000mAhs in when re-charging. To work out your flight times, conduct let's say a 5 min flight, recharge and note how many mAhs went back in, divide by 5 to get your mAh per minute and then divide that into the capacity of the battery. Simples. This is what you then set the timer to on your TX. The other advantage to this is that you know that when the timer goes off on your TX you still have sufficient power left to immediately return to base. For those guys running down to 3.2 v per cell, I think this is quite dangerous as you are now getting into the zone where ESCs may start to automatically shut down (be it sudden or a gradual reduction in power). One thing is for sure, you are shortening your battery's life when going to 3.2v per cell.
SMP
Member
Hi Carapau,
Still very new so just wanted to clarify something. We've always used the mah per minute method you described above. Here's my question. When using two batteries in parallel does this change the equation? In other words lets say I have a single 10,000mah battery. I fly for 1 minute, go recharge and put in 1000mah. So 1000mah per minute. Ignoring the 80% rule and flying it out to dead this means I have 10 minute flight time. Now... If I add a 2nd battery in parallel (and ignoring the weight/80% etc) Did I just gain another 10 minutes of flight time due to the extra battery or do I need to calculate this at now 2000mah per minute (1000mah per Battery).
I think its kinda like MPG. You get 10mpg and you have a 10 gallon tank. Add another battery and you still get 10 mpg but now have a 20 gallon tank?
Still very new so just wanted to clarify something. We've always used the mah per minute method you described above. Here's my question. When using two batteries in parallel does this change the equation? In other words lets say I have a single 10,000mah battery. I fly for 1 minute, go recharge and put in 1000mah. So 1000mah per minute. Ignoring the 80% rule and flying it out to dead this means I have 10 minute flight time. Now... If I add a 2nd battery in parallel (and ignoring the weight/80% etc) Did I just gain another 10 minutes of flight time due to the extra battery or do I need to calculate this at now 2000mah per minute (1000mah per Battery).
I think its kinda like MPG. You get 10mpg and you have a 10 gallon tank. Add another battery and you still get 10 mpg but now have a 20 gallon tank?
Without nitpicking any other portion of your analogy above, I can tell you that you MUST take into consideration the weight of the extra battery since if it was weightless than you should disconnect the battery and send it to me right away, along with any spare batteries of the same kind!! hahaha
no...but to answer your question, (someone please correct me if I'm mistaken), in THEORY, yes, like your gas tank analogy, for paralleled batteries you add the capacities while maintaining the voltages -- so your analogy holds true. (1 batt 3S 2000mAh + 1 batt 3S 2000mAh =~ 3S 4000mAh, when added in parallel), while (3S 2200 mAh + 3S 2000mAh ＝~ 1 batt 6S 2200mAh, when added in series).
no...but to answer your question, (someone please correct me if I'm mistaken), in THEORY, yes, like your gas tank analogy, for paralleled batteries you add the capacities while maintaining the voltages -- so your analogy holds true. (1 batt 3S 2000mAh + 1 batt 3S 2000mAh =~ 3S 4000mAh, when added in parallel), while (3S 2200 mAh + 3S 2000mAh ＝~ 1 batt 6S 2200mAh, when added in series).
SMP
Member
Ahh thats good! Since the Zippy 8000's I'm flying are like bricks pretty sure your mailbox is safe. 
(Add Batts= Weight/Time/75-80%Margins = Diminished Returns)
OK the gas tank part sounds good. Now my question is figuring out the mileage... Two batteries, in parallel. Fly 5 minutes. Recharge puts in 1000mah in battery 1 and 1000mah in battery 2. I know I need to divide by 5 (flight time) but do I use 1000mah or 2000mah?
(Add Batts= Weight/Time/75-80%Margins = Diminished Returns)OK the gas tank part sounds good. Now my question is figuring out the mileage... Two batteries, in parallel. Fly 5 minutes. Recharge puts in 1000mah in battery 1 and 1000mah in battery 2. I know I need to divide by 5 (flight time) but do I use 1000mah or 2000mah?
Carapau
Tek care, lambs ont road, MRF Moderator
It will not give you twice the capacity although in theory you are correct. What you need to do when adding the 2nd pack in parallel is go through the timing process again. As a rull of thumb, if you double the capacity you will get about 150% of the flight time.