Solo battery analog readout (Attopilot-like)

May 12, 2017
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Good ol' Europe
Hi, guys!
Have you ever considered to forget the SMbus and just using the Pixhawk2 analog inputs for reading battery voltage and current? It's pin 47 and 49 on the 80pin connector. Mission Planner allows you to modify the battery data readout method from SMbus to analog... But I'm not sure if the original Solo firmware actually will read those pins :( If not, we can try the Solo Master alternative firmware.
I get to this conclusion because I bought Solo+controller bargain on Ebay (without batteries...) and now I am trying to get them in the air. Everything works fine, the single issue is that the arming must be done with external application (Mission Planner, Tower, etc). After that, the controller seems to acknowledge that the Solo is already armed and responds to stick commands. Till then it reads 0V from battery via telemetry and doesn't want to send the "Arm"signal. But if we can fool it by making the Solo read the analog inputs, then I'm convinced it can be used for arming, too. Any thoughts, suggestions?
I'm sure you checked the green and white wire coming off the battery connector, just to make sure its plugged into the solo main board?
I just want to forget those fancy (in fact very low C-rated) "smart" batteries and use "dumb" ones. The wires you are talking about are the SMbus wires - I don't need them for analog readout. In fact dumb batteries have only the power wires. I usually buy 5800mah 4S batteries for my Tarot 680 at 40 bucks, so I don't wanna pay double for smart ones. But obviously, I want battery telemetry to remain via analog readout.
Those pins on the DF connector require a pretty serious soldering rig. They are tiny and very close together.

You can do it and there's no reason it won't work. You can change that parameter and it should work fine on solo firmware or master.

But TBH IMO, it's not worth the effort. You're not going to gain anything other probably screwing up the connectors...
Thanks for the replies!
Regarding the soldering, I'm not so worried. I'm a hardware engineer and reworked hundreds of notebooks and phones ;). I have several Solo-sized "dumb" batteries, even slightly larger capacities and higher C-rating, thus increased flight time. Like I said I purchased my Solos without the smart batteries, so this is the most logical step for me. Also, one day the Solo batteries will be discontinued and this solution will be a good alternative, if it works ;).
But Pedals2Paddles - You are right - if you don't have the right background, equipment and skill, don't even think about this mod. So for everybody reading this: Don't try this at home! :)
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Also note, simply putting in a higher capacity battery doesn't give you a linear increase in flight time. A higher capacity battery also weighs more, which undercuts the flight time increase and negatively impacts performance. Many people have tried adding battery capacity (myself included). You really can't squeeze more than another 2-3 minutes out of it before the impact on performance becomes too great. And beyond that, the flight time goes down due to weight. You will need larger motors and larger props to do better.
Well, I don't expect much longer flight times, these are the batteries I own (5800mAh, 4S 30C continuous) - even a little bit less heavy than the original ;)
On the other hand, my only concern regarding the original batteries is the 20A nominal rating - at 5200mAH it means about 4C rating (according to Not sure if it's a typo, too much caution from 3dR regarding ratings, low C-rating due to the additional MOSFETs in the smart battery structure (leading to voltage snags) or just weak cells. But to actual standards it is toooo low and can trigger battery failsafe too soon on aggressive maneuvers, if it's true. Anyway, as a HW engineer I don't like any additional connectors, switches (MOSFETs) or any other device that can make additional voltage drop between the battery and ESCs. Just Keep It Stupid Simple. :). Yes, it can be dangerous in inexperienced hands, but this gives you the best performance.
Regarding the weight, I have no concern. I used heavily in building bigger birds already and I already have several "visions" about the Solos - making them bigger (hardware already in drawer). I bought several Solo kits on Ebay (drone+controller, without batteries) at 150USD (with shipping+taxes) so even taking the guts to bigger copters make it worth. Till now every kit seems to work very well (after a few childhood diseases...). When my time allows, i will do this mod (from the firs post).
I will keep you updated.
I don't recall the number but I'm pretty sure it's more than 4C. The documentation sucks though. But anyway, I agree with you. I miss slapping whatever battery was best for the mission on my Y6. But I do like the simplicity of the smart battery when it comes to daily use.

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