So i flew my new 7'' over the weekend for the first time in an area where i could push range/flight time, and nearly lost it due to the amps/MAH reading being so far off.

I fly a 1500 6s, and the OSD told me i had used ~700mah, so i figured i was fine. Im just upgrading from 4s so im not used to the way 6s lipos sag less at the end of the pack, so i didnt notice an issue until i was going down. in hindsight, i should have realized that my heavy 7'' quad carrying a gopro probably isnt drawing only 12 amps at like 70kph either.

I used Oscar Liangs post, here , to attempt to adjust the scale to a better range, and tested the past few days. Using his equation, i went from the 490 scale given by speedybee (the 50a blheli32 one thats in the f7 stack), down to 366. His equation for anyone who doesnt want to click over there is new_scale = old_scale x (OSD_mAh_consumed / mAh_charged) .

I had drawn 543mah and my charger listed 726mah going back in, multiplied by 490 to get 366.



Today, i flew for 698mah drawn, but still put in 960, which apparently should be a 266 scale. Does this seem wrong to anyone else, that speedybees stock scale could be off so far, and that it would need two corrections that large back to back? 

I'm going to pick up some alligator clips in order to test with a multimeter tomorrow, as i don't trust this method anymore. In the meantime, does anyone see something im doing obviously wrong? Thanks in advance for the help

The problem I can see there, is with a multiplier of 490 in betaflight, you have 0.049A per V. Presumably you use a modern flight control that tops out when the adc pin hits 3.3V. So with 490, you get pegged at 67.3A. Even if it was a 5V pin (not likely), it would max out at 102A (136A using 366). As a data point, my 7" rig with 6s1400 pulls 200A WOT, 10A hover, and about 20A at 70kmh... similar with 6s2200. If yours comes even close, even if it is calibrated you'll be loosing those mAh everytime you go past 67A... which should be often on a 7" when flown vigorously.

You should get a clamp meter really. You aren't going to pull enough amps on an MM to get accurate out to ~200A, where that thing should max out. I had a similar issue with a HB Tekko32 metal. It came with a scaling of 180 from the factory, which was accurate according to my spendy BK precision clamp meter, and topped out at 182A on my 3v3 fc (bad, but not as bad as yours probably). On a 60A 4in1 with 70A peak, it should read to at least 240A right? The logs and osd won't help here, since the pin is over volted and the mcu has no idea what to think of that. I had to add a voltage divider to the current sense line to get the range to cover what I fly. The good 0.1% resistors I had on hand made it go to ~300A max, with a scaling of 109. I could buy resistors that are spot on for 280A, but whatever the resolution is fine.

The thing that bugs me about this on high powered quads is the sense pin is getting overvolted. So it's important I think to observe early on, and get a volt divider on there soon... not just for landing time awareness, but also to not overvolt an mcu pin. IMHO, a 4in1 curr pin should output 3.3v or less at it's max rating. That prevents this kind of issue, and avoids ugly addon resistors.

This was a way more in depth answer than i was expecting and hoping for lol. I was praying for a 'flip this setting in betaflight, dummy"

that being said i do understand the concept. Im running the pretty new speedybee f7 v3 stack so i assume all that was said applies to my setup regarding the sense pin. If i understand correctly as well, if i were to hover at low power for lets say 500mah on my OSD, it would recharge at 500mah on my charger (or close enough, not 30% off like i am now). And actually flying the quad like normal is where the sense pin gets overloaded and i 'lose' MAH readings?

Its mind blowing to me that such a weird limitation occurs when i can purchase a 50A rated ESC(per motor obviously) and only read 67amps total in betaflight, or is it speedybee who i should be upset with?

I could add a resistor inline on the connector between the ESC and the FC to try to correct this problem though? I have no problem doing so.

thanks for your response truglodite, either way, im just glad to know im not crazy and cant read basic numbers correctly lol

so after some more googling, i see a video by joshua bardwell about adding shunt resistors on top of the existing ones to increase the range the FC can 'see', but the speedybee ESC has a heatsink on it covering basically everything, so i think that is out of the question for me. I don't know if i can just splice in a 'regular' resistor into the current wire between my ESC and FC either, but i do see matek makes an external hall effect current sensor that i could use: https://www.getfpv.com/mateksys-hall-eff...-150a.html . Its rated for 150 amps, which is less than the theoretical 200+ i could pull through my ESC, but my plan is more cruising/long range than freestyle so i think this could give me enough accuracy to be able to trust my quad more than LOS/walking distance.

While unlikely, does anyone have any experience with these? i imagine this is more used on ardupilot style builds than in our freestyle/racing quads that are more common on this forum.