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FPV on lipo balance lead

#1
I’ve been running my FPV system off the balance lead on my 3 cell lipo, the same battery running the airframe. Is this an “acceptable” practice and is it detrimental at all to the battery/fpv system. It’s been working great and it saves space/weight by not having to carry another battery.
 

Merv

Well-known member
#2
I’ve been running my FPV system off the balance lead on my 3 cell lipo, …..
I tap the balance lead to run my FPV system also. Just make sure all the components are happy running the voltage of the flight pack. Some have trouble with lines across the screen. If your like me and don't have that problem, great. If at sometime you do run into a problem, capacitors and chokes can help smoth out the interferance.
 

Boberticus

Active member
#3
Id say if you are only plugging into one Cell of a 3 cell, you could be discharging one cell slightly more than the others, which is bad for batteries, but it depend on the final voltage of the batteries after youve discharged them. If you were only using the camera, you could be discharging one cell so much you cause it to be more worn out than the others, but if you are discharging the other two cells as well you should be ok over the course of the lifetime of the battery, as long as you are relying on a balance charger to get them back to a balanced charge every time you recharge.

the VTX i always buy has input voltage of 7-36V, and a output of 5v for the camera, so i just splice directly into the ESC leads. When i plug in the battery, i plug in the VTX too, directly to the full voltage of the battery across all cells, with one connection, seems to work for me. if your VTX is rated for at least 12v, you could probably get away with it under full voltage of a 3S Lipo(12.6-9.0V), it really depends on what you are using, a 3.3V tiny whoop VTX wont like that at all.

this is sorta a non answer, but in 2020 with modern charging equipment charging modern batteries, you should be OK, to the point of never noticing a difference, but you might get a few more charge cycles (like 250 cycles vs 225)of charging and discharging if you baby your batteries a bit more. That being said, a few hundred miliamps wont make that much of a difference.
 

Merv

Well-known member
#4
Id say if you are only plugging into one Cell of a 3 cell, you could be discharging one cell slightly more than the others, which is bad for batteries,....
If you only draw from 1 or 2 cells, I agree, that could be a problem. That is not what I do, perhaps I misunderstood the original question. I run 3S and tap the balance lead to get the full 12V from all 3 cells in the battery. All my FPV equipment is happy running on 12V. The balance lead is just a convenient place to get the power from.
 
#7
If you only draw from 1 or 2 cells, I agree, that could be a problem. That is not what I do, perhaps I misunderstood the original question. I run 3S and tap the balance lead to get the full 12V from all 3 cells in the battery. All my FPV equipment is happy running on 12V. The balance lead is just a convenient place to get the power from.
I tap the balance lead to run my FPV system also. Just make sure all the components are happy running the voltage of the flight pack. Some have trouble with lines across the screen. If your like me and don't have that problem, great. If at sometime you do run into a problem, capacitors and chokes can help smoth out the interferance.
That’s how I run mine too. The balance lead runs to each cell to balance them during the charging process so it shouldn’t be pulling from only one cell.
 
#9
Ah i didnt even know that was a thing, i never thought to get a jst-xh adapter, that's actually sorta brilliant, no splicing and resodering a ESC, and you can do the same for a 4S too, as long as you've got the right adaptor for the leads... might be picking up a bunch of these,
this is what your talking about, right?[/QUOTE
Yes! Exactly except instead of buying it I just used the last two pins on the outside and removed all the ones in between then soldered and applied shrink tubing because the hobby shop didn’t have those connectors you’re looking at.
 

Attachments

#10
Also if you notice on mine I have the male end of the JST connected to the balance lead adapter, shouldn’t matter just a heads up, make sure you get the corresponding jst to hook everything up.
 

Hondo76251

Well-known member
#11
I've had some old cameras that didn't like more than 5 volts that I ran off of single cells (through the balance lead) and, although it does discharge one cell more than the others in a pack, I never had an issue with it. As long as you recharge them with a good balance charger its usually fine.

In larger, more complex builds I'll almost always put in the appropriate BEC and/or filter to run whatever FPV gear I need (helps keep interference down) but I still run a lot of my smaller stuff off the balance lead. A lot of my favorite cameras (like the runcam swift) will actually display the voltage on screen while you're flying which is very handy. Because those cameras are usually something like 5-24 volts, I'll wire them to the balance lead but use all of the cells (negative wire for negative and farthest (+) wire for posative) so that that camera can give me a good idea of what voltage I have left in the battery while flying...