|02-04-2006, 11:27 AM||#1|
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I am: James G
Join Date: Jul 2004
Location: Brampton, ontario
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There seems to be more and more people using Lipo's more and more these days, and with the growing popularity they have become more safe, but you still have to be very careful how you handle them and your application.
For starters, if you are using a 3 cell lipo you must and I mean must make sure your speed controller has a voltage cut off, if not and the battery drains below 3.1 volts per cell, the batter will discharge and may over heat, and permanently discharge. And never let the battery temp exceed 140F
Lithium-Polymer ( abbreviation : LiPo) batteries require particularly careful handling. Mishandling these batteries may lead to explosions, fire, smoke and a risk of poisoning.
Don’t series or parallel connect battery packs since the cell capacities and the charging condition may be too different.
Charging voltage :
These batteries should charged with a charger that is specifically designed for LiPo cells, charging at above 4.25V per cell , which is the absolute maximum voltage. It must be strictly prohibited as higher voltage causes permanent damage to the cells and causes fires. Charging current:
LiPo batteries can be charged at a rate of max. 1.5C (1C corresponds to the cell capacity). Charging with higher current than recommended may cause damage to cell performance and safety features deeply, and can lead to heat generation or leakage.
(To caculate C = C x 1.05Amps = __ amps)
These batteries shall be charged within a range of temperature 0C to 50C. If these batteries are charged at the temperature out of the specified range, leakage, heat generation or other damage may be caused.
Discharging current :
LiPo batteries can be discharged at continuous currents of around 7C (with 70~80% capacity). High discharging current may reduce the discharging capacity remarkably or cause over heating.
Discharging temperature :
These batteries shall be discharged within a range of -10 degree C to 60 degree C.
At a temperature of -10 degree C or less, the battery will show a significant decrease in discharge capacity. The battery temperature during the discharging should not exceed 70 degree C.
Normally, LiPo batteries start to discharge at 4.2V and terminate at a cut-off voltage of 3.0V. Discharging these batteries to a point below 2.5V per cell causes permanent damage to the cells, and this must be avoided.
Lithium cells and batteries must be shipped in 30% charged state for safety reasons.
Appogee has a great artical about Lipos, break in, discharge, and storage do's and don'ts (PDF)
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