Battery power

[mark03]

Also (important to know for anyone that tries this), the system will *not* automatically shut down when the battery is low, because it has no battery-management circuitry built in! That means you need to disconnect the Li-ion cell before it reaches levels that will permanently damage it. (Or better, build a little subsystem with a charge/discharge controller. I will probably put this on my daughterboard.) Depending on the cell, there may be a "protection PCB" inside the battery wrapper to prevent overcurrent and overdischarge. But if it is a hobby (RC) LiPo, there is no protection circuit at all...

Note that the limiting factor in low-voltage running is the 3.3-volt linear regulator's dropout voltage. At reasonable current this is spec'ed at still less than 100 mV, so, referring to Li-ion discharge curves, you would have to be running outside in very cold weather for this to be an issue.

[tverrbjelke]

http://rc.runryder.com/helicopter/t438903p1/ showing some nice graphs on Voltage vs discharge curves, at various temperatures and discharge currents. OK the discharge current in that tables are high (for racing cars) - paralella boards will suck at the lower boundary (maybe 0.5 - 2CmA with 2000mAh battery ?)

So what I read from that:

* I am a bit surprised HOW dependant the discharge process is to temperature! at 30°C/86°F feels good, you dramatically get lower values at even 55°C/131°F.

* Battery age, so maybe the first carges we may use >80%, but then quickly come to only be able to use lot less of its capacity.

* I am currently not sure what dropout the cuircuit of our parallella boards actually has - so asuming 3.6V would be the lower bound. Question : How is it actually?

What i like to have is a likewise graph for the paralella usecase:
"Sucking x mA we can expect with LiPo of y mAh an in-duty uptime of z Minutes/Hours for our paralella board."
(So when someone is planning for outdoor action with given weather/temperature expectations, maybe with autonomeaus drones/robots, or field-sensory experiment he can forecast some uptime for the computational side)