Thread: Telemetry?
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Old 01-06-2017, 09:04 PM   #21 (permalink)
extrapilot
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Join Date: Aug 2010
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Quote:
Originally Posted by mkovalcson View Post
mah is the best most accurate way to measure the power you've pulled from a battery.

Batteries sag differently depending on how new they are and their C rating.

A new high C rating battery won't sag much in the beginning. An old lower C rating battery will sag a lot and consistently read a lower voltage when it has more juice left in it.
Yea, but who cares, if the use of that metric is to determine when to land? You have what amounts to a fuel totalizer- a device which tells you have many gallons you have burned, but not how many were in the tank to begin with; you cant determine how much remains.

You want to kill a pack- run on an mAh sensor, with that pack at 3.8v on departure, or with too high a capacity defined for it. Heck, just a real change in temperature has significant effect on battery capacity, and that requires some testing.

It probably works OK for people who fly all the same packs on a given machine, at a consistent temperature, and who check their pack voltage before departing. But what do you do if you find a pack in the bag that shows 4.05v/cell? What do you set your mAh limiter at? There are a slew of ways to get in trouble here. If you use pack voltage- there are no ways you can get in trouble, so long as you fly a given cell count on a given model.
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