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LI Po Voltage cut off

Old 01-12-2009, 06:56 PM
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DGUN
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Default LI Po Voltage cut off

I want to run a GWS 370 MOTOR (Brushed) in an old Crazy Max. I want to use a 7.4 volt Li Po battery for power. How do I insure that I don't run the battery down below 3 volts per cell (6 volts for the 2 cell 7.4 voly battery)? I have a 30 Amp speed control (overkill I think) but see no provision for voltage cut off. Looked around the various web sites and didn't see anything which talks about it.


Thanks.

Dave
Old 01-12-2009, 09:37 PM
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hugger-4641
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Default RE: LI Po Voltage cut off

Most programable controlers are for brushless motors. But here is a link to one for brushed motors that has a jumper you move to switch from nicad to lipo and I assume that this changes the cut off voltage as nicads usually take a lower cut off. I haven't tried it, but for the price, it might be worth a shot.


[link]http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6468[/link]
Old 01-13-2009, 09:16 AM
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Fliprob17
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Default RE: LI Po Voltage cut off

General LiPo Info - The best way to take good care of your packs, and avoid ever hitting the low voltage cutoff is to time your flights. Fly for a small amount of time, maybe 4 minutes (depending on the mah rating), and check the voltage of the pack. Then adjust your flight time as necessary, maybe in increments of 30 seconds to a minute, while continuing to monitor the voltage after each flight. When I land and check the voltage, I want the pack to be right around the manuf. rating. So on a 2cell 7.4volt LiPo, you want the voltage to be right around 7.4volts (3.7volts per cell). This is conservative, but will extend the life of your packs and if you run into a little trouble trying to land, you know that you have a little time to get it right before draining the pack too low. Hitting the low voltage cutoff on the ESC is not something you want to do on a regular basis, and not a device that you want to use to tell you when it is time to land. For what it's worth, I typically turn them off, or set them for a lower cell count then what I am actually flying to prevent the low voltage cutoff from chiming in and potentially losing a plane. After about 3 or so timed flights, you know about how long you can safely fly. Then you can set your timer and never have to worry about hitting the low voltage cutofff mark. Just my 2cents.
Old 01-13-2009, 09:49 AM
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DGUN
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Default RE: LI Po Voltage cut off

Thanks for the info. Looks like I need to put together a test rig to get the current draw from my set up. Was hoping to keep things simple.

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