How do I check the voltage of my Lipoly? (Full Version)

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Flyboy1958 -> How do I check the voltage of my Lipoly? (4/11/2008 8:32:26 PM)

I'm new to electric and just bought an electric plane with an 11.1 volt, 3 cell 2100 mAh Li-Po battery. Now I do have a Hobbico charger that will charge a lipo battery, but do I just fly until it starts to die or what? I am used to checking my NiCads and NiMH batterys with my volt meter, but what about the Li-po battery?



Swift427 -> RE: How do I check the voltage of my Lipoly? (4/11/2008 10:05:06 PM)

Your plane's RX/ESC should have a built-in 9v cut-off. It's always a good idea to read the planes instruction manual at least a couple times.[;)]

Your Hobbico charger should have built-in jacks for external battery voltage monitoring with a voltmeter. It's a good idea to charge your lipo at .5C (2100mAh = 2.1 amps x .5 = 1.1 amps) instead of 1C to get the most life/performance from the battery. It's a good idea to balance a lipo before charging and check it again after charging.

Condition cycle your lipo the first 3-5 flights with a conservative flying pattern at half throttle, using a full throttle burst just for the initial launch. Then after 5 flights you can start flying more aggressively as by then you will have a better handle on your own skill level and the planes aerodynamic speed potential.



Flyboy1958 -> RE: How do I check the voltage of my Lipoly? (4/13/2008 1:28:49 AM)

Thanks, I'll dig into it a little more as far as reading the Manual for my charger and the instructions that came with the ESC. I can tell this electric flight experience is going to be another big learning curve.



jdetray -> RE: How do I check the voltage of my Lipoly? (4/14/2008 6:37:48 AM)

Flyboy -

Welcome to e-flight.

One important thing to know about lipo batteries is that they are sensitive to being over-discharged. If a lipo is discharged below 3V per cell, permanent damage can occur. That means a 3-cell lipo should not be discharged below 9V, and a 2-cell lipo should not be discharged below 6V.

A good tool for checking any type of e-flight batteries is wattmeter. It's much more than a battery checker, though it can be used for that. This device plugs inline between the battery and the ESC and displays volts, amps, watts, and often other parameters. It's meant to be used on the ground (not in flight) to check the performance of e-flight power systems. Here is one of many models on the market. (I selected this one only because it is a nice picture of a typical wattmeter display.)

Most modern ESCs will have a low voltage cutoff (LVC) feature. When operating correctly, the LVC monitors the battery pack voltage and protects the pack from being over-discharge. It does this by reducing or cutting off power to the motor while maintaining power to the receiver and servos. This gives you a chance to land the plane while protecting the battery from damage. Some ESCs will "pulse" the motor as a way of signaling you that it's time to land. The instructions for your ESC should explain how it behaves when the cutoff voltage is reached.

Of course, it's better not to fly until the battery is all the way down to the LVC level. You can use your wattmeter after a flight to check the battery voltage and learn how close to cutoff you have flown. Pretty soon, you'll know how long you can fly without hitting the cutoff point or risking battery damage.

Have fun!

- Jeff



Flyboy1958 -> RE: How do I check the voltage of my Lipoly? (4/15/2008 11:42:55 AM)

Great answers guys. I feel I understand much better already. Now in real life, does one usually bring an extra battery pack to the field with them so they can swap out batterys while the other one is recharging or what? My thought is that if you go out to have a good time and fly for maybe 10 minutes, run the battery down, then would you normally have to let the battery cool for twenty minutes or so before you can recharge it? Sounds like a lot of down time between flights,



jdetray -> RE: How do I check the voltage of my Lipoly? (4/15/2008 4:42:35 PM)

You will definitely want more than one battery. It takes a little over an hour to charge any size lipo if you charge it at the recommended 1C rate. If it's only partly discharged, it will take less time to charge.

I think three batteries is a good number. If you arrive at your flying site with three fully-charged batteries, you''ll be able to fly continuously for 30-45 minutes. After that, if you maintain a steady pattern of charging, cooling, and flying, you won''t have long to wait between flights. There will still be some down time. If you fly with others, that down time gives a chance to socialize, watch other pilots, help newcomers, etc.

- Jeff



Flyboy1958 -> RE: How do I check the voltage of my Lipoly? (4/15/2008 6:47:36 PM)

Good point, thanks



wickman11 -> RE: How do I check the voltage of my Lipoly? (5/7/2008 7:07:31 PM)

Great thread guys. I am new as well.

On the "number of batteries" thing: how do you charge at the field? Is it through the car battery?



jdetray -> RE: How do I check the voltage of my Lipoly? (5/7/2008 7:28:06 PM)


quote:

ORIGINAL: wickman11
On the "number of batteries" thing: how do you charge at the field? Is it through the car battery?

Most R/C battery chargers are designed to work on a 12V power supply. A car battery works fine. Note that if you are using large R/C batteries and charge them many times, you may eventually drain your car battery enough that your car won't start at the end of the day.

For this reason - and for the convenience - many people prefer a portable "power pack" similar to this one.

[image]http://ecx.images-amazon.com/images/I/51lHOF4v6RL._SS400_.jpg[/image]

You charge up the power pack at home, then bring it with you to the field, where it can be used to power your R/C battery charger and other electronic gear.

- Jeff



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