Battery shenanigans

[Karolyiboys]

Hello there! I have purchased and built an Ft Mini Corsair, and for it Flitetest has reccomended a Tattu 75 C 850 mAh battery. Now COVID was kind enough to come along and prevent me from being able to order the battery. I could not find the same battery where I live (Hungary), and so again I was left without a battery. I know that the amount of electricity that I can draw from the battery is 63,75 A (C x A). But all of the other batteries I found that could deliver that many amps were too big for my compartment. How would it affect my flight if the battery would deliver somewhat less amps? Say 40 instead of 63,75. Thanks ahead.

 

[JasonK]

what motor/ESC do you have? because that will determine the max draw that will be done.

 

[Merv]

I agree with @JasonK, if your setup draws 40 amps or less, then the battery will work.

 

[BATTLEAXE]

Hello there! I have purchased and built an Ft Mini Corsair, and for it Flitetest has reccomended a Tattu 75 C 850 mAh battery. Now COVID was kind enough to come along and prevent me from being able to order the battery. I could not find the same battery where I live (Hungary), and so again I was left without a battery. I know that the amount of electricity that I can draw from the battery is 63,75 A (C x A). But all of the other batteries I found that could deliver that many amps were too big for my compartment. How would it affect my flight if the battery would deliver somewhat less amps? Say 40 instead of 63,75. Thanks ahead.

As far as flight characteristics with the choice of battery will come down to the weight and positioning of the battery for balance. As for the performance of the power system on a lesser battery (less mah) is just flight time. As long as it has the same cell count it will deliver relatively the same power. Just a smaller battery won't last as long.

That being said you will get better performance with a higher C rating (30C vs 75C). But the problem with the C rating is its highly subjective. There is no standard the C rating follows. A 45C in a Tattu compared to a Venom wont be the same battery. They either underestimate or over exaggerate the real performance of the battery as far as power delivery.

For the average novice you wont notice the difference in slow trainer style flying. I would say go with whats economical and available to you. As long as you are in the air, thats the real goal. Batteries will be a trial and error thing just like half of everything else in the hobby. Good Luck

 

[Mikej]

If you are able to get stuff from HobbyKing, their 3S Nanotech 850s are very good. I have both Tattu and Nanotech and they are very similar

Sorry - just checked and they are Out of Stock in Global, EU and UK warehouses https://hobbyking.com/en_us/turnigy-nano-tech-850mah-3s-30c-lipo-pack-jst.html?wrh_pdp=7

I've also heard very good things about SLS lipos in Germany https://www.stefansliposhop.de/index.php?cPath=173&filterMM=18f1

 

[Karolyiboys]

The ESC is the Flitetest 20 A ESC with an XT-30 connector. Would 20 Amps be enough to keep a Mini corsair up? And preferrably not all too sluggish?

 

[BATTLEAXE]

The ESC is the Flitetest 20 A ESC with an XT-30 connector. Would 20 Amps be enough to keep a Mini corsair up? And preferrably not all too sluggish?

What is the motor size and prop you are going to use? The ESC shouldn't make the plane to sluggish really, they should have a linear throttle range to the top end just like any ESC. The 20 amp rating doesn't cut your throttle at 20 amps, thats what it will handle. The more amp draw (bigger motor) will run through a 20 amp ESC till it burns out. If your motor is a 2205 or smaller in the 1700-2300kv spectrum then you should be fine with a 6x3-6x4 props or smaller. The larger diameter or higher pitch of the prop will strain the motor more to cause it to draw more amps. Its the motor/battery/prop combo that will decide the size rating of your ESC. Most motors come with a chart that refers to different voltages and prop sizes to give you amp draw/thrust/watts. These charts need to be reviewed if you are to select the right gear for your airframe.

So if you would like help with the selection for a given airframe, we will need all the information on your gear. Do you have any gear yet?

 

[Mikej]

I use a 18 amp ESC on my Mini Sportster with a 2204 2300kV and 6 x 3 x 3 prop - it's a little powerhouse and runs fine on the 18 amp - the amp spec for ESCs is generally continuous output, max output is higher.

 

[GremlinRC]

A mini like the corsair is not going to draw anything like 40 amps. If it did, your 20A ESC would be dead anyway. A battery which CAN deliver 40A will be just fine.

 

[burbigo3]

I was going to suggest the same thing, a 40A battery is enough.
TweakBox Tutuapp

 

[bwarz]

Agree on all statements of the battery being able to deliver enough even at 20A, want to reiterate to be sure to review size.

I ended up using the 650mah and just roll with the shorter time. I've got a larger motor so the cg balances out for the slightly lighter battery. That compartment is tight so be sure not to deviate much in the dimensions, especially don't go wider than the 850. I find the thinner battery (is my 650) better as the skewer to hold the hatch shut ends up right where the back of my battery is...

FYI I'm running a 2204 1350kv, 20A ESC, 7x4 prop. Lots of power, near 8 minute flight time. Although I'll be switching to a 6x4 prop as I'm having low speed torque issues with the bigger motor and 7" prop...

 

[quorneng]

People seem to forget a LiPo can deliver almost an unlimited current which is why they are so dangerous if accidentally sort circuited.
For flight what is important is the maximum continuous amps that can be sustained without suffering long term damage.