Miniquad and IRIS+ batteries


I’m the owner of an Iris+ and i recently build a mini quad, since I’ve bought six of the original Iris+ Lipo’s some time ago, i would like to use them on my mini quad as well.

But now I’m really confused about C-Ratings

If i understand this C-Rating correctly it calculates the Max current A coming from the battery. So in case of my Iris+ battery with the max of 8C with 5100MAh

it results in 5.1 * 8 = 40.8 A

does this means, the iris+ will never require more than 40A current ?

Some time ago, my original 4in1 ESC burned out on 1 channel and i’ve replaced it with 4 DYS-SN20A, so far so good.
For my mini quad, I’ve choosed the nighthawk EMAX frame and the same ESCs with the 2205 from T-Motor (2205)

Within the Set they are using ESCs with a max of 15A but i can’t find specs about the real max current of the Motors.

But know to my issue, as soon I’ve start flying, the quad land’s after short time and inspecting the logs showed it is related due to Battery Failsafe:

6: Battery failsafe
ECode 1: battery voltage dropped below LOW_VOLT or total battery capacity used exceeded BATT_CAPACITY

The battery dropped down to 9.8 V.

  • Is the battery with 8C to weak, or are their other possibilities which i should check first ?
  • If it is too weak, which batteries should i choose for ~15 min flight time ? (atm, the overall weight, with the Iris+ battery is 846g)
  • do the higher kv motors require higher C Ratings ?

Many thanks in advance for your help


You could probably use your Iris+ batteries with you miniquad but its probably gonna be abit heavy for your fpv quad to be super agile.

As for the C rating, the Iris+ does actually draw more than 40A at max throttle but all batteries have a continuous and burst C rating. Where most of them can handle upto the burst for around 30-60 seconds.

That said its best to find the exact specs of your motors, or use a watt meter to see how much current your setup is pullling as it is odd that your Flight Controller is reporting 9.8V. Does your battery get hot? Do you have other batteries to test?

I am also abit confused here, when you say you get that failsafe is that on your IRIS+ or your miniquad? Does your miniquad use an APM based flight controller. If that is the case then that failsafe is likely just due to a setting that is not quite right or a power module that is not correctly calibrated.

I know that it is possibly not as agile as it should, but as i mentioned, i have 6 of them and i would like to use them first if possible, in case it is not as good as expected, i will buy of course smaller batteries.

I don’t think the battery was hot, but i can’t tell since i didn’t touched the battery.

I’m using a APM based navio+ board on top of the miniquad, power module is an APM compatible Power Module which seems correctly calibrated, at least it shows nearly the same Voltage measurement as my Voltcraft Multimeter.

FS_BATT_MAH is set to 0.000000 and FS_BATT_VOLTAGE is set to 10.5

All my question are about the miniquad, IRIS+ works as expected!

Ok it does look like your battery failsafe has been set correctly and good to hear the power module is calibrated. So my guess is that your motors are pulling too much power causing the battery voltage to drop randomly. Could you check your logs to see how the voltage changes with throttle? So maybe if you want to use these batteries you will just have to either disable the battery failsafe, or limit Max throttle usage. But hopefully we can get to the bottom of this.

I’e already checked and it looks like it is in directly relation to throttle.
Is it save to disable FS_BATT_VOLTAGE ? i thought it is not so good for the batteries if i constantly get more energy from it as it can deliver ! and limiting throttle means i can just fly slowly ?

I think i will buy a new battery with a higher C-Rating and give it a try.

Many thanks

For a mini FPV quad I would say its ok as long as you have some sort of battery alarm so you know when to land to avoid discharging your Lipo too much. But its not realy solving the problem.

I have tried to find some thrust test data for your Air gear 200 motors and from what I can see some people are measuring 18A at max throttle so that could be the issue since the IRIS battery only outputs about 40A, so using a higher C rating battery will probably solve your problem. Let me know how you get on with the new battery.