AstroCoder123

So I'm new to LiPo Batteries and I have some questions regarding their setup/maintenance/usage

Discharging is the process of lowering the cells 'charge' right?
So what effect does this have and why would you do it? Does that decrease the 'voltage' or the 'mAH'?

Am I right in thinking that as you are using the battery in an RC vehicle, you are effectively discharging it by decreasing the voltage?
And if the voltage is decreasing the performance is decreasing because you have less volts?

Wait...If you are 'discharing' a battery, are you are decreasing the mAH left on the battery or are you decreasing the voltage..or both..? What? Because I read 'capacity determines how long you can run before you have to recharge' but does that mean recharge the 'mAH' or the 'voltage'?

Thanks

aymodeler

My Feedback: (3)

Discharging is simply the process of using the battery by drawing current from it. It lowers both the amount of charge left in the battery (typical expressed as milliampere-hours or mAh) and the voltage. The charge rating is the amount of current that the battery could produce over a period of time. So a 3200 mHa 3S battery at 100% capacity can supply 3200 millamperes (which is the same as 3.2 amperes) of current for 1 hour, at which point it would be completely discharged. Of course, higher current will discharge the battery in a shorter time.

The "S" after the number in 3S represents the number of cells wired in series. A LiPo cell has a nominal voltage of 3.7 volts, and when fully charged, it will typically be closer to 4.1+ volts. So a 3S pack will have a nominal voltage of 11.1v (3 x 3.7) and will typically be at around 12 v or so when fully charged. The peak voltage will tend to drop off quickly when you first start to draw power from the battery, but will stabilize around 3.8-3.9 volts. BUT it is critical to never over discharge a LiPo battery. If the voltage drops below 3.1 - 3.2 volts per cell, then you will ruin the battery (and risk fire if you try to re-charge the battery again). Most chargers will not even let you charge a LiPo battery that is below 2.9-3.0 volts per cell. I never let my batteries run below 30% charge (which typically keeps them at or above their nominal voltage of 3.7 volts per cell).

The "C" rating is an indication of the max current capacity for a battery. So back to our 3200 mHa example, if the battery had a 20C rating, it could theoretically discharge at up to 20 times it capacity limit, or 64 amps for 1/20th of an hour (3 minutes). A 3S battery has a nominal voltage of 11.1v total, so in this example, the battery could (in theory anyway) supply 64 amps x 11.1 v, or 710 watts of power for 3 minutes before running completely dry.

Sometimes you will hear people talking about discharging a battery outside of its intended use. Most chargers support a "discharge" function. There are only two reasons I know of for doing this. One is if you have a fully charged battery that you do not intend to use for a long time (1 month or so). LiPo batteries should be stored for long periods at somewhere around half capacity. So before putting your batteries away for the season, it is best to apply a "storage charge" with your charger which will raise or lower the amount of charge in the battery to get a level that is comfortable for long term storage.

The other reason is to dispose of an old LiPo. What some will do is hook up the battery to a 12V (again assuming a 3S) car light bulb and let the battery drain completely dry over an extended period (I would do this out doors!). After discharging via the light bulb, then you soak the battery overnight in a salt water solution (which should discharge any residual charge left). When completely drained, the battery is inert and no longer can be charged. It is also no longer a fire hazard and can be disposed of in regular trash. Disclaimer, I have not attempted this myself.

ghostofpf1

suggested reading for all first time lipo users....http://www.tjinguytech.com/charging-how-tos
have fun and be careful
ghost

AstroCoder123

Thanks a lot!