Hi Guys, 

I'm in the midst of designing my first ever quad (250mm) and it's reached the point where I need to choose a battery. I've waded through the mound of available information and I think I understand the process fairly well, but I've still got a little bit of confusion and uncertainty and just want to verify I'm going about this the right way.


I've picked out x4 Emax 2205s kv2300 as the motors. I plan on running with a tri-blade, looking at the specs, each motor draws up to 36A when running with a Dal T5045 at 16V. Does this mean I need to choose a Battery that can handle 144A? From my research into existing builds I feel like this is a very high current draw. It's been suggested I just buy a 4S lipo, so i'll only be getting 14.8V from it, does this mean I can anticipate slightly lower peak current? 

I've found a Tattu R-Line 1550mAh 4S 95C that I think satisfies the requirements. I've also selected Emax bullet 30A ESC's which I think will handle the motors fine as the 30< current draws will only be bursts. Is this correct?

I've been reading webpages and forum posts all evening but still don't feel confident in my understanding of the subject, thanks for any help.

Hey Hrob243,

144A would be the max amp draw if all 4 motors ran at 100%, your average amp draw would be much less and you would only pull these high amps for short bursts.
The Tattu R-Line batteries can provide a continuous current of 147A with burst's up to 294A for a few seconds. Therefore your setup wouldn't really stress these batteries at all.

You can work out the continuous and max discharge rates using, C rating x Capacity. So in your case:
1.55A (1550mah) x 95c = 147.25 Continuous
1.55A (1550mah) x 190c = 294.5 Burst

Oscar's article at https://oscarliang.com/lipo-battery-guide/ was a huge help to me when trying to understand the different battery types.

All math aside, I am currently running Emax RS2205S 2300kv with 5051 tri-blades and 30A ESCs off of Tattu 1300mAh 75c packs. Motors and ESCs barely get warm and the Tattus I have only had them get really hot, but not overheated or puffy, when filming some high speed, long full throttle passes recently.
The R-line Tattus will be the next packs I buy probably

Hey Hrob243, welcome to the forum!

To supplement what DoP says above, all of my batteries are rated to be able to handle my quad but I have had problems with some lumeniers. The R-Lines however have yet to puff on me. Not even when abused and over discharged. I managed to pull one of the R-Lines down into the 11-12v range, literally to a point where the quad sagged and fell out of the sky... and while it was hot after the flight, with proper time to let it cool and recharging the batter still works great and the internal resistance on all cells is still less than 10.

These batteries are a few grams heavier, and a couple of bucks more expensive but at this point they're easily my favorites!

Static thrust tests are nothing like it in real flight. You are more likely to get 20%-30% less current draw in forward flights as the props are moving forward really fast and they have an easier time spinning and thus draws less current.

To be honest C Rating is quite meaningless these days... just get some brand name lipo and you should be fine.
I personally have tried Acehe Formula, VCanz 95C and they are both great options for high current builds.

(04-Jul-2017, 12:06 PM)Oscar Wrote: Static thrust tests are nothing like it in real flight. You are more likely to get 20%-30% less current draw in forward flights as the props are moving forward really fast and they have an easier time spinning and thus draws less current.

To add to this also, full throttle doesn't necessarily mean full thrust on all 4 motors. For example in the attached blackbox screenshot I am at full throttle and applying a little bit of negative pitch on my quad. You can see that motor 1 (bottom right) is at about 90%, motor 2 (top right) is at about 85%, motor 3 (bottom left) is at 100%, and motor 4 (top left) is at about 80%. (1 and 4 are applying more thrust because of the negative pitch to the throttle)

Thanks for all the help guys, I was reasonably sure I'd spec'ed it correctly but it's great to get all your knowledge and insight. Feel a lot happier about pulling the trigger on the build now and feel like I understand motors and batteries a lot better.

Going to hijack this with another question if possible. I plan on using a Betaflight F3 with an integrated PDB, the specs I've seen for it say it can handle 100A continuous and 140A-160A burst. Based on what you've told me regarding the current draws I take it this will be fine as I won't be reaching those currents too often?

I'm also just picking out the extra bits I'll need to complete the build. I need to grab some silicone wire to connect the battery to the F3, most charts I've looked at indicate I'll need 10 gauge to best handle the higher current flows, the Tattu battery I intend to purchase has 12 gauge wire. Does this mean I'm ok to use 12 gauge wire also or should I just stick to 10? I read that the only drawback of higher gauge wire is weight but just want to see what you more experienced people would use more than anything.

Based on Oscar's post in this thread

Quote:Basically there is no overkill when choosing AWG of a wire. You can use thicker wires than you need. Thicker wires give you less resistance in the system. Less resistance means less heat, better safety and higher efficiency. However thicker wires come with extra weight, so if you want to build a light weight quad, you should properly choose the AWG of electrical wires.

So what you say above is correct... weight is the drawback. On my first and my second build weight was only a minor factor for me. As long as it was lighter than my tank of a ImmersionRC Vortex then I would be happy and in general I have been

I've referenced the quoted post above a couple of times, it's definitely a quick and easy one.

BTW, these are great questions! We get a lot of questions around here, and many times they're the same, very specific to one product or another type questions. I really like seeing general overall theory questions because I can learn more from them.

(05-Jul-2017, 03:28 AM)Carl.Vegas Wrote: Based on Oscar's post in this thread

So what you say above is correct... weight is the drawback. On my first and my second build weight was only a minor factor for me. As long as it was lighter than my tank of a ImmersionRC Vortex then I would be happy and in general I have been

I've referenced the quoted post above a couple of times, it's definitely a quick and easy one.

BTW, these are great questions! We get a lot of questions around here, and many times they're the same, very specific to one product or another type questions. I really like seeing general overall theory questions because I can learn more from them.

Also keep in mind the diameter of the wire trying to fit into the small frames and tight flight-stacks nowadays. I follow the rule of thumb where I use the same AWG wire as the component comes with. If the battery lead is 12awg I would use 12 on the XT60 going to my PDB. Same for motors and ESCs. If the motor uses 18 and my ESCs come with 20 I would change the ESCs power wires to 18.

I haven't tried for an all out ultralight build yet though either

Awesome, thanks for the response guys. I'd read Oscar's article and knew 10awg would be fine but wanted to see what your opinions on going down to 12awg would be. It's a first build so I'll just be happy if it flies hahah, but I've been trying to learn as much of the theory as possible as this is definitely something I want to get into.

sounds like the way to do it to me!

A+ on your homework

FWIW, I've only ever used 12awg. The only exception is on my Tarot, but it uses a 6S 10,000 mah