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G-Shark MKII
08-20-2005, 03:20 AM
Just bought a BP-21 motor witha BP-30 amp ESC The instructions on the ESC shows a jumper for cut-off that is left in for 2/3 cells and disconnected for 3 cells.
If left in cut-off will be 5 volts if taken out cut-off will be 7.5 volts.
I thought you should never let Lipoly's get below 3 volts per cell. If that is true this ESC is taking 2 cells to 5 volts and they should not get below 6 volts and 3 cells to 7.5 volts and they shouldn't be below 9 volts.
What am I missing or is this ESC no good for Lipoly batterys?

fdix
08-20-2005, 01:18 PM
You shouldn't let the voltage drop under 3V under no load, but under load it isn't a problem if the voltage drops temporarily to 2.5V per cell. So your ESC is fine for LiPos

G-Shark MKII
08-22-2005, 03:53 PM
Thanks for your answer,I'm new to this electric flying so thanks for taking the time.

GeraldRosebery
08-29-2005, 09:31 PM
Fdix gave you the answer you need! Right on the money. I always set my ESC's for less than 3V per cell otherwise you often get premature cutoff with a powerful motor.

rcers
08-29-2005, 10:15 PM
Better than that - time your flights, land with plenty left in the battery and forget about LVC!

Mike

Unbalanced prop
08-30-2005, 04:01 AM
Better than that - time your flights, land with plenty left in the battery and forget about LVC!

Mike

Ditto what Mike said. Much easier on your packs flying by time. Also if your LVC is kicking while flying and the LVC is set to 3 volts per cell, then the batteries are losing their power. Any lithium cell that can not maintain 3 volts at its C rating is dying or isn't very good to start with. Of course if flying above the cells ratings, then anything can happen.

Doug

Plane_freak
08-30-2005, 05:58 PM
you don't really need a lithium polymer esc to use lithium. I don't even own one even though they are recommended over the normal esc. Just fly around untill the battery fells like it is going dead and throttle up every once in a while. My 2 cell lipo has been brought down to like 4.8 volts it didn't do anything.

rcers
08-30-2005, 06:22 PM
Just fly around untill the battery fells like it is going dead and throttle up every once in a while. My 2 cell lipo has been brought down to like 4.8 volts it didn't do anything.

No you need to time it, measure how much you put back into the battery to be safe.

If you have a 2s pack that has been down to 4.8v you have significantly decreased it's life span. All the cell manufactures say 2.5v/cell is when damage will occur.

Mike

HoboDog
09-04-2005, 06:15 PM
i just bought 2 JETI brushed controllers from Hobby Lobby. They say "LiPo Friendly" on them and on the web site.
The cutoff for 2 cells is 5.2 volts and 3 cells is 8 volts.
Is this "Friendly" enough? I would be happier if it were 3 volts per cell.

fdix
09-04-2005, 11:34 PM
If you really want to be "firendly" to your lipos do what Mike and Doug suggested: time your flights. First time you fly land with plenty of capacity to spare so you have an idea of how long you'll be able to fly in the future.
Of course it is important to maintain a constant flying style.

rcers
09-05-2005, 12:40 AM
The cutoff for 2 cells is 5.2 volts and 3 cells is 8 volts.
Is this "Friendly" enough? I would be happier if it were 3 volts per cell.

Nope that is too low 3v/cell is what I use. But TIME YOUR FLIGHTS! That is the ticket. I have 3-4 planes with LiPoly with ESC's that don't have proper cutoff. So you will be fine, just use the timer.

Mike