Battery Cutoff Voltage
05-07-2003, 01:28 AM
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Battery Cutoff Voltage
I'm just curious, and perhaps maybe a little over cautious, but I was wondering what most people think is a safe voltage to fly their 4 cell reciever packs on? 5.3V, 5.2V, etc... A dead battery seems like such a silly reason to crash, I can crash all by myself, I don't need a battery failing to help me... 
Mike
Mike
05-07-2003, 01:57 AM
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Battery Cutoff Voltage
4.8 V is where the bulk of the capacity is.
The answer partly depends on how many flights you get from a charge. If one charge lasts many flights, then you can go to a lower voltage since you use a lower percentage of the packs capacity each time. This is because the voltage test is an indication of the remaining capacity measured as a percentage of the battery's capacity.
E.g. if you get four flights before the pack is completely flat, you want at least 25% of the capacity available before you would fly.
If you get ten flights on a pack, then you only need to see at least 10% available at the start of a flight.
In the first example, the safe to fly voltage will be higher than the second example.
If you discharge the battery using your ESV, and note the voltage every 10 minutes, then draw a graph of voltage vs. time you will see how the voltage varies with time. The battery is unsafe to fly just before the voltages decreases sharply after the long, flat interval at 4.8 V. You want to be sure that you won't run off the end of the flat section during a flight.
Run the discharge test once after a day's flying (i.e. you have decided that the battery should be charged), before you recharge, and once just after charging. Line up the end-points (where the battery goes dead flat) and you'll see how much capacity your day's worth of flying took out of the battery.
The answer partly depends on how many flights you get from a charge. If one charge lasts many flights, then you can go to a lower voltage since you use a lower percentage of the packs capacity each time. This is because the voltage test is an indication of the remaining capacity measured as a percentage of the battery's capacity.
E.g. if you get four flights before the pack is completely flat, you want at least 25% of the capacity available before you would fly.
If you get ten flights on a pack, then you only need to see at least 10% available at the start of a flight.
In the first example, the safe to fly voltage will be higher than the second example.
If you discharge the battery using your ESV, and note the voltage every 10 minutes, then draw a graph of voltage vs. time you will see how the voltage varies with time. The battery is unsafe to fly just before the voltages decreases sharply after the long, flat interval at 4.8 V. You want to be sure that you won't run off the end of the flat section during a flight.
Run the discharge test once after a day's flying (i.e. you have decided that the battery should be charged), before you recharge, and once just after charging. Line up the end-points (where the battery goes dead flat) and you'll see how much capacity your day's worth of flying took out of the battery.
05-07-2003, 03:24 PM
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Phil - it's nice to see some people still know how to perform this test using low-tech equipment. Nowadays everyone uses automatic cyclers to perform the discharge, but they aren't always calibrated correctly. I still prefer the low-tech method, as I have more control and higher (perceived) accuracy.
05-07-2003, 05:12 PM
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Battery Cutoff Voltage
Hi,
Here's a link that gives most everything you need to know about batteries.
http://www.rcbatteryclinic.com/
HTH
Jerry
Here's a link that gives most everything you need to know about batteries.
http://www.rcbatteryclinic.com/
HTH
Jerry
