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Old 02-22-2009, 04:26 PM   #1
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Default lipo 101

can someone tell me where I can find out information about lipo's, I run a stock slash and want to put in a 7.4 2s at least 3600 lipo is, I have a onyx 240 charger...am I good to go?
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Old 02-22-2009, 04:31 PM   #2
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You are good to go. Just know that there is no low voltage cutoff on that stock xl-5 esc so just be aware of your battery voltage.
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Old 02-22-2009, 04:36 PM   #3
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Default what do you mean cut off

sorry, really new to lipo so what is a cut off or what does it do, or what does it.
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Old 02-22-2009, 04:55 PM   #4
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Quote:
Originally Posted by slicksterone View Post
sorry, really new to lipo so what is a cut off or what does it do, or what does it.
Its prevents the battery from dropping below a certain voltage (I think its 3.0v per cell). The esc, if equipped with a Li-Po cutoff, would shut down all power to the car (or most power in some cases) to prevent the battery level from dropping. This is all done internally and electronically through the esc. I believe that Novak makes a Li-Po cutoff that you can plug into your receiver and it prevents the battery from over discharging.
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Old 02-22-2009, 05:07 PM   #5
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Is google broken or something?

http://www.google.com/search?hl=en&r...ipo+batteries+

The first site is a good one.
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Old 02-22-2009, 05:15 PM   #6
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Default I've looked alot of places

but as a dumby on lipo I have read lots of sites, and still looking for better information...so thanks for the reference.
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Old 02-22-2009, 05:21 PM   #7
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There are many small things about Lipos, but the basic rule of thumb is drain .5 volts per cell from full charge. This may depend on the quality of the battery you have. Read the label on the battery and the charger manual.

I've had many brands of lipos and few different chargers. The best thing is to follow the manual. Lipos in my opinion is not governed by voltages but capacitance or charge. So, what this means is you should watch how much you charge, how fast you charge and how much you discharge. Usually the charge rate is 1c, there are others that you can charge 2c or more but that will shorten the life of the lipo, so is discharging. if you drain it close to some ESC's lipo cutoff, you may be damaging the lipo. This also depends on the quality of your lipo. to be safe, do not discharge below 3.5 or so volts. (it's normally 3.7)
so charge at 1c (your total capacitance) to 4.2 volts per cell and discharge to 3.5 or higher. Use the balance charger to be safe.

I opinion is that car guys seems to be less careful about lipos than plane or heli people.
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Old 02-22-2009, 06:15 PM   #8
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Lipo cells have both a minimum and maximum voltage you need to stay within. Going below the min voltage can damage the cell and lead to swelling where the cell literally swells up like its filled with air. At that stage, the cell is damaged and beyond repair and your lipo is pretty much finished as its unsafe to charge or run in the swollen (usually called puffed) condition.

Min voltage is actually 2.7v/c. We typically have a low voltage cutoff (lvc) in the speed control to shut down or pulse the power to let us know voltage is getting low at anywhere from 3 v/c and up. I personally have mine set at either 3.1 or 3.2v/cell to give me a little safety margin. Max cell voltage is handled by your charger and should not exceed 4.2v/cell. Lipo requires a lipo charging protocol. CC/CV, where in the initial part of charge, lipo is charged at constant current (CC) until the max cell voltage of 4.2v/cell is reached, then the charger changes to constant voltage where the current decreases while the lipo is topped off.

There is a diff in tolerance of overdischarge based on cell quality. Higher quality cells will tolerate mild overdischarge better than lower quality cells will - overdischarging a high quality cell and a lower quality cell to the same extent and you'll usually see the lower quality cell fail (puff) while the higher quality cell can or will recover. The higher quality cell will also be damaged, but the damage will show up as a decrease in life (number of discharge/charge cycles) rather than puffing. Higher quality cells will also have less tendency for the cells to become unbalanced (cell voltages not equal) while lower quality cells will show more of a tendency to get out of balance.

This will give you a little background - read the lipo parts

http://www.batteryuniversity.com/partone.htm
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Old 02-22-2009, 07:53 PM   #9
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Just so you know, the Onyx 240 doesnt charge lipos. The 230 does however.
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