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commalot

low voltage cutoff

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I joined this forum about a year ago and finally have a plane about ready to go with onboard video.

I'm running the Tx and camera (Black Widow A/V) on a 900Mah Lipo. I'm concerned about running the voltage too low on the Lipo. I could just keep track of the time transmitting. I have a servo/electric switch on channel 5.

A better solution would be some sort of low voltage cutoff set to 9 volts. I have a 3 cell Lipo.

Problem: I'm not an electronics whiz.

Is it fairly simple to rig up something like this?? :huh:

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This is a great question. I too use Lipos and am always concerned about draining them down to the fatal point. I assume there is a voltage at which the begin to refuse to take a charge - I am just accepting what Red Schroeder says. Red has been correct for 40 years. If anyone has run a Lipo pack to zero and then was able to rechage it to full capacity - please post. :rolleyes:

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I'm concerned about running the voltage too low on the Lipo.

There do not seem to be any LiPO battery disconnect/isolate products out there. Those that exist are designed to shut off the throttle signal. This is because with the typical R/C installation, shutting off the battery supply to protect it would mean the loss of an entire plane (rather than just possible battery damage).

Perhaps an audible alarm will work for you? For example: http://www.lightflightrc.com/HTML/products.../BattSignal.htm

If anyone has run a Lipo pack to zero and then was able to rechage it to full capacity - please post.

I doubt there are many satified customers in this camp. There is no expected recovery if the LiPO is discharge too low. Even if the cell took a adequate charge, it will never be the same. And it may even become dangerous to use.

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As another possible solution, the battey packs for cell phones have protective charge/discharge circuitry in them. Some include low voltage cutoff. Maybe one of these would be a good choice for powering the camera gear.

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If anyone has run a Lipo pack to zero and then was able to rechage it to full capacity - please post.    :rolleyes:

Have done that a few times, but with Li-ion batteries.

Once with a 2s 7.2V/5500mAh pack that was stored during 2 years, the voltage of both cells was 0V. I charged them individually and slowly, they recovered full capacity. The pack (was not mine at that time) was stored again during 6 months. When it was taken out it was at 0V again. Actually the pack was fitted with a circuit that might have been there for balancing the cells, but it was drawing current even if the battery was not used!

So I gave it another go (and removed the electronics!). It lost some capacity this time, but I've now been using it regularly for 1 year to power my DV camcodrer. It still has 3800mAh capacity. Apart from a relatively long charging time it works well.

I'm also using LiPos to power my camera systems. Most of the time I simply don't use them until they are empty, as I prefer to have video until the end of the flight!

Otherwise I land as soon as the video drops.

Edited by Kilrah

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Here's an update. I bought and installed the low voltage alarm suggested by Mr. RC-Cam (LightFlight). It works great and has several alarm features (lets you know the state of the battery each time you turn on the video and also starts alarming when battery gets low)

The only problem was the beeps were too quiet. I solved this by utilizing the audio channel on the transmitter which I wasn't going to use. I bought a very small microphone and intalled it by the beeper. Now I can here it thru the camcorder very clearly when transmitting video.

Just finished it today. Haven't flown it yet. :D

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