Amperage on a Quad and Battery voltage drops

Hardware Multirotors
1

Hi, I’m doing somewhat of a big project with a quad. We were able to do a hover test, but the battery voltage was just dropping fairly low. It dropped to around 30% from being full, which is close to what our failsafe is. We are using two 6S 14000mah Li-ion batteries in parallel. We are also using the KDE4215XF-465 as our motors, KDEXF-UAS55HVC as the ESC’s, and KDE-CF185-DP props. At 100% throttle these motors, combined with the esc and props, pull close to 70 Amps from what I see in the performance data. This should mean we need at least 280 continuous amp draw from the batteries, right?

What I’m wondering is if this is common for quads, or do I need a stronger battery. I found this guy on Amazon: https://www.getfpv.com/batteries/commercial-consumer-batteries/tattu-plus-22000mah-22-2v-25c-6s-lipo-smart-battery-pack.html
The max amp would be 22Ah * 25 = 550 cont. amp draw if I’m not mistaken. It has an unnecessarily high cont. amp draw but its the best one i can find on amazon(quickest too since its prime).
I re-checked our current batteries cont. amp draw and they max out at 40A so that’s not really good. So would this be the problem? If I were to replace them with this other battery on amazon would the voltage drop so drastically?

We’re doing another project with a small tethered drone. We were testing the performance today by tying a weight (about 5-10lbs) just to simulate the wire and added stuff to the drone for tether. This one also had the voltage dropping extremely low, to around 50% from full. For this one we were using a 4S 4500mah 35C LiPo battery. So the max cont. amp draw would be about 158 Amps. It should have been enough I think, but I’m not sure though.

Would both these problem be similar in that I need to get batteries with a higher capacity and/or higher C-rating?
Just for your information, we are using these batteries because we had them on hand.

Edit: So I’m thinking of getting one of these(whichever weighs less) and want others opinions on this before spending the $500 lol

2

As far as I’m aware using Li-ion batteries for a quad is quite tricky, most Li-ion batteries that are currently on the market do not have the proper discharge rating for quads especially one that is swinging such large props. I would also recommend that if you have the capability to go with a large battery such as 8S-12S would also help as well as a larger C rating. I am by no means an expert on batteries.

3

For the current draw you are talking about LiIo are out of the question.
LiIo are good for low current applications only, not the current draw typical of multi rotors unless you have a very light low amp setup.

The batteries you listed are good, we use them.
But don’t use a battery at its rated maximum, they will not last long if you do.
We size our batteries so the maximum full throttle amperage is no more than 50% to 75% of the rated maximum.
And we get good life from those batteries.