Hoverfly Powering the board with 6s

[yeehaanow]

Maybe I read it wrong though, maybe he's considering powering the board from the balancing tap using only a few cells? The board probably uses a very small percentage of the overall power consumption thereby not putting the pack at risk of being flown out of balance by the end of the flight. So 6 cell power would be put through the ESC's and 3 of the 6 cells would power the board via the balancing tap? Is that what you had in mind yeehaanow? 3 cells being 11.1 volts and a low power condition of 9.9 on the OSC would be the signal to land.

Bart

That's what I want to do. Power the board from the balancing tap, and have it represent pack voltage. If possible, it eliminates a potential failure point. (bec dying mid-flight) an unlikely event but still can happen.

 

[Bartman]

That's what I want to do. Power the board from the balancing tap, and have it represent pack voltage. If possible, it eliminates a potential failure point. (bec dying mid-flight) an unlikely event but still can happen.

that's an awesome idea. a six cell balancing connector could be used to get a very sound connection then you just use whatever wire you want for the desired voltage to the FC. the only problem i could see is that the balancing connectors (especially cellpro plugs) can be subject to wear and have the potential to be loose even when snapped in place.

 

[Photo Elevate]

I like your thinking.

Just concerned that drawing power from just one cell of the battery to power the FC, could cause a very unbalanced battery condition.:nevreness:

 

[Bartman]

I like your thinking.

Just concerned that drawing power from just one cell of the battery to power the FC, could cause a very unbalanced battery condition.:nevreness:

P.E.

you wouldn't be using one cell, you'd be using three or four of the cells, three is probably optimum. spread over three cells the power consumption of the FC for one flight is nearly negligible compared to the motors. i'd be surprised if the FC used much more than a few hundred mah per hour. maybe one of the Hoverfly people can confirm this.

 

[Photo Elevate]

P.E.

you wouldn't be using one cell, you'd be using three or four of the cells, three is probably optimum. spread over three cells the power consumption of the FC for one flight is nearly negligible compared to the motors. i'd be surprised if the FC used much more than a few hundred mah per hour. maybe one of the Hoverfly people can confirm this.

Hi Bart

You are absolutely right silly me what ever was I thinking about one cell would be no good to power the board, three or four yes.
:shame:
From the manual. Battery source voltage 7.4v-16.8v. current consumption <200mA

I think it should be fine.

Go for it!!

 

[Bartman]

Hi Bart

You are absolutely right silly me what ever was I thinking about one cell would be no good to power the board, three or four yes.
:shame:
From the manual. Battery source voltage 7.4v-16.8v. current consumption <200mA

I think it should be fine.

Go for it!!

a good way to go about it might be to mount receptacles for the balancing taps to plug in to. i use dual batteries so i'd plug both taps into a harness and have parallel sources of 3s power going to the FC. what a brilliant idea!

i'm using 4S packs for power right now but this is a good feature to work into future builds.

thanks Yeehaanow for the idea.

 

[yeehaanow]

That would be even better to have two sources, and even if you lost a cell or had a drop, it would still power the board at > 7.4v if you tap the 3s.

I would still like to hear from the Hover Fly team to know if it's been tried, if it's advisable or not, and whether it would be better to tap 3s or 4s. I'm sure I saw this technique used elsewhere to power fpv gear, so I'm 95% sure it would not have any ill effects.

IMO- a heavy lifter on anything less than 6s is just silly. I have so much more power and flight time, and much less heat buildup since switching from 4s to 6s. Before I needed to cool down after every flight. Now I could comfortably go back-to-back flights all day. (If I had the batteries! ) So if more and more people see the light, this will certainly be an issue to have a simple safe way to power the board. I hate trusting my whole rig to a $20 bec that I've seen smoke before.

 

[Webheadfred]

I wonder if a voltage divider could be used such as this....


View attachment 6563

If you used two 10k resisters, you'd essentially divide the voltage in half.
The formula is V-out = (R2/(R1+R2)) x V-in.

So if you used 10k ohm as R2 and 3k ohm for R1, with a 6s battery it would be:

(10,000/(10,000+3,000)) x 22.2 = 17.07 volts from your full 6s battery. The regulators on the HFP would take care of the fluctuations as the battery depleted.

 

[S11D336B]

That's not a bad idea, but I think 10k would be problematic as I would plan for a maximum of 400mA. You would need a resistance no higher than 44 ohms to allow for this flow of current. Keep in mind that I make my living in computer science not electrical engineering, but I'm pretty sure your voltage would drop due to the current required by the HoverflyPro with 10k. I'd play with several values to see what voltage you get. Ideally, you want no lower than 9v with your flight battery completely depleted.

I would avoid tapping specific cells as this would un-balance your battery! Meaning you could potentially over discharge several cells during flight.

I wonder if a voltage divider could be used such as this....


View attachment 8607

If you used two 10k resisters, you'd essentially divide the voltage in half.
The formula is V-out = (R2/(R1+R2)) x V-in.

So if you used 10k ohm as R2 and 3k ohm for R1, with a 6s battery it would be:

(10,000/(10,000+3,000)) x 22.2 = 17.07 volts from your full 6s battery. The regulators on the HFP would take care of the fluctuations as the battery depleted.

 

[Bartman]

George,

You think the power consumption of the PRO would unbalance the cells during an 8 minute flight? It uses 200 mah per hour, right? Compared to the motor consumption the PRO's requirements would be negligible, besides if the PRO is being fed by a parallel harness to both batteries, the affect on the batteries is even less.

I"m an M.E. by degree so I know even less about electrons and such!

 

[S11D336B]

Practically speaking there probably is not a problem with this if you're balance charging your batteries every time... I would just carefully check your cell voltages over time to make sure there isn't a problem in the making. Lipos just make me nervous in general I guess and my instinct is not to mess with them too much.

George,

You think the power consumption of the PRO would unbalance the cells during an 8 minute flight? It uses 200 mah per hour, right? Compared to the motor consumption the PRO's requirements would be negligible, besides if the PRO is being fed by a parallel harness to both batteries, the affect on the batteries is even less.

I"m an M.E. by degree so I know even less about electrons and such!