Solo Battery_Capacity and affect on Low Battery RTH

[Rich_Adams]

I have a question regarding how battery remaining is calculated by Solo, and whether Battery_Capacity is used in the calculation.

I'm running Open Solo, and have been playing with the default battery RTH parameters in mission planner. One thing that I've noticed is that when I connect to Solo (via UDP), the Battery Capacity is not set at the Solo battery capacity of 5200 maH. When i set the battery capacity to 5200, then go fly and re-connect after flying, a value less than 5200 is shown on the advanced parameter list Battery_Capacity (on the order of 2800-3300). Does the smart battery change the default or is there a calculation that overrides the input value and sets the battery capacity based on calculated RTH current?

Also, in general, can someone provide a quick overview of the RTH triggers (capacity remaining, low voltage, etc and which takes precedence). I understand that distance-based RTH is based on an assumption of battery current that can be adjusted by the user in mission planner (i've set mine at 26). is battery remaining related at all to the distance-based low battery RTH calculation?

Thanks for the help!

 

[Pedals2Paddles]

Battery capacity is updated by the smart battery on boot to the battery's actual live current capacity. Changing it to 5200 manually would be lying to yourself.

The smart battery reports it's own mAh remaining, throughout the flight. ArduCopter calculates the % remaining based on that information, which is what you see on the screen.

The battery failsafe kicks when the mAh remaining drops below the value in parameter FS_BATT_MAH. The default is 520 mAh. The battery failsafe will also kick in when the voltage drops below the value in parameter FS_BATT_VOLTAGE. The default there is 14 volts.

Now if you have open solo on the stock cube, you also have that distance based battery failsafe enhancement. That actually overrides the FS_BATT_MAH parameter, using the mathematical calculation of power required to get home. That FS_BATT_CURR_RTL parameter is a fairly crude multiplier. Testing shows that a multiplier of 22 will get the solo on the ground at about 10% capacity remaining. Jacking it up to 26 will probably get you on the ground more like 15-20% remaining.

 

[Rich_Adams]

P2P,
Thanks so much for the information. Your description is exactly what I was looking for.

Given that the smart battery reports actual battery capacity, is the battery's calculated battery capacity an indicator of battery health?

Thank you again!!

 

[Pedals2Paddles]

It can be. Expect it to get lower and lower over its lifespan like any other battery. But monitoring how fast the cell voltages drop off is a sure fire way to monitor the health. You'll usually fine one of the 4 cells starts to drop much faster than the others in flight. You can see the cell voltages in Solex if you have a green cube.

 

[hobo solo]

In a similar vein. I had a quick peek at my battery capacity in parameters on Tower and it showed that Batt_Capacity was at 5200 though Batt2_Capacity was 3300. Now I'm assuming that Batt_2 refers to a copter on ardupilot running a second battery but would just like confirmation and if so why is it showing any value at all?

 

[Pedals2Paddles]

Yes, that's correct. BAT2 is for a second battery monitor, which the solo does not have. The 3300 value is the default.

 

[hobo solo]

Thought so. Cheers.