Checking voltage on my LiPo battery

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1

Hi

I’m trying to build a quadcopter based on Gadgeteer (yes, yes, I know, it’s hard, almost impossible, we’re talking interpreter here, the speeds are low, yada yada yada),
There are several voltage checkers in the market that buzz when dropping below 3 or 2 vols (like this one http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=18987, but there are many others).
I am interested in such a voltage checker that can talk to the Hydra.

Ideas?
Thanks

2

Connect your battery voltage to resistor divider (2 resistors) to scale the voltage below 3.3V then use any of the analog inputs.

3

Yup.
That should do it.

thanks.

4

Keep in mind that LiPo’s keep the voltage quite constant over time, so I don’t think it’s a good measure to monitor your battery capacity.

5

There’s a lot of talk on rcgroups about voltage dividers and measuring pack discharge/warnings, so it’s not that unusual; however as Eric says, they have a very flat discharge curve that ends in a steep cliff, so you do need to be pretty careful with divider ratios and how quickly the rate of change is detected - one common ratio I see mentioned is ~1:6.5, but of course it totally depends on how many cells your battery is (ie the starting voltage)

6

Also remember that you probably don’t want to leave the voltage divider hooked up constantly, as it’ll reduce your battery life as it heats the resistors.