G'day DIY Drones,
I have a question about batteries, yes, I know this has been done to death, but I would like some real world experiences rather than the math.
I have used the search bar but I guess I am not using the right keywords, hence the reason for this post.
I am considering using 1 10000mah 4s instead of 2 5000mah 4s batteries to get more flight time from my 690mm photography rig.
A bigger battery of the same C rating or close to it.
Here is the math (feel free to correct me if I'm wrong)
2 x 5000mah 4s at 25 C = 125 max amp draw and has 10000mah. Weight, approx 1300g
1 x 10000mah 4s at 25 C = 250 max amp draw and has 10000mah. Weight, approx 800-850g
I only need about 115 max amps so both will do the job.
My question is about flight time and battery voltage sag.
I don't want theory but real world experience please.
Will the 10A, lighter battery give me more flight time because of the weight saving or will the voltage drop off sooner because it is only a single battery?
Another way to put it would be, would the 2 5A batteries hold the voltage longer than the 1 10A battery given the same flight situations?
Another way to put it is, are two batteries that equal the one in MAh, better?
I hope I am making sense here
Cheers
Aussie
Replies
Joe,
I agree that my failsafe values need to be adjusted down to avoid triggering the failsafe to soon. I am currently set for failsafe at 16v, after a flight ending in battery failsafe, with no load, the packs are usually around 18.5v, and that seems to high, OR, my 25C batterys are so shy of adequate current capacity that when under load the voltage is dropping from 18.5v to below 16v at 90-102A.
I have stated that I have been flying my drone for 3-4 months, I'm ready to fly farther and higher, but without confidence in the power, I need to stay close
The persons who made the statement that parallel packs do not increase the available current was from one of the more legit sounding websites, but as a vendor all advice given is suspect. I think the truth is that the 25C packs that I have produce a serious voltage lag when passing 50% of that C rating, and if you use packs with a much higher C rating than the calculated max load then the voltage lag should be minimized. I plan on upgrading to 60C packs, when the funds make that possible.
This leads to a different discussion of vendors and brand names that would probably be more appropriate for another site. I would be happy to copy all my communications with my battery supplier, but I believe this venue is more focused on the technical isues and is not meant for that type of conversation.
90 A to hover ?
I will be scared to use such high currents.
Your conclusion IMO is wrong, check your connections and cable size because currents are very high.
Beware, one of my customers, with his monster okto setup got solderings that melt due to high current and heat generated by current flow.
Luc:
I'm actually happy to hear you disagree with my conclusion. I'm heavily vested in the 3-pack parallel arrangement. I have the current issues under control with my power distribution, All 10ga wire and heavy distribution board. Any heat generated is in the esc's and the batterys. After a flight the batterys are always hot, and that concerns me. So I figure my biggest risk now is a failing battery from drawing near max current most of the time. Now that I made a parallel balance cable things look more stable. New "different" batterys are in my future
All you wrote is correct Harry, but if there is not a bottleneck in cable size or power transmission chain it is not possible that Ampere of the three parallel batteries do not add .
I might have not understood correctly your words since english is not my native language, if it is the case , I apologize for that.
The biggest factor for flight times is weight. So everything else being similar or good enough, the one with less weight will always win.
So really, there is a choice between redundancy and max flight time and a bit of a trade off.
1 battery (should) = more flight time due to weight saving
2 batteries (should) = slightly less flight time but redundancy in case of a cell failure
Yes?
Aussie
I've run both single and dual battery (Parallel) setup on 3 air frames. While weight is critical, I chose the dual for the redundancy factor much the way 2 of my 3 air frames have coaxial motor designs. Cost to rebuild or replace was becoming a big factor for me, so after testing batteries, I found 2x matching mAH batteries was the best way to go. The trick is to find the right mAH and C rated batteries for the amount of flight time you desire and performance demands (ie., hover, cruise, acro, or high speed) vs weight. With my copters, I built them with strong motor/propeller configurations to where the GW is at approximately 40-45% throttle, and cruises around 25-30 kph. Using 5A batteries rated around 35C, I found my sweet spot (12-14 minutes). I try to not push full throttle with these as they will cook the batteries, but my main objective it hover and cruise modes. As long as I do not push max throttle for too long, I will not destroy my batteries by puffing them.
Thank you for your perspective and reason. That's what I'm after
Cheers
Aussie
This discussion really sheds a light to me.
Currently i'm rebuilding my quad from a serious crash.
I'm using a 6000 mah 6s lipo and now considering of using 2 x 6000 mah 3s lipo in series.
Would it be better in term of amperage draw on each batteries as well?
The reason i'm asking is because things discussed is in parallel configuration and i want to apply a series configuration.
Thanks
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