do I have to discharge after use if only half used .they come new at about 11 volts,so why discharge?

No you dont have to discharge them and you want to make sure you don't run them down below 3v per cell or so. You want to put at most, 80 percent of the total capacity back in when you charge.

thanks barra

Why only but 80% back in when charging? Isn't that like driving a car with only 80% of the fuel? I have always charged my Lipos with the TRiton charger on Auto and it charges to 4.2 volts per cell. This seems to equal the current draw that I used during the previous flight.

Just looking for something I may have missed.

What BH was saying is that you don't want to drop the battery below 20% capacity. Well basically you don't want the cells to drop below 3V, and stopping when the battery has 20% charge remaining is a safe place to stop.

Therefor, since there's 20% left in the battery, you only have to add 80% to top it off.

-Dave

No, what was said was, "...You want to put at most, 80 percent of the total capacity back in when you charge". To me that means only charge to 80% capacity as he said.

Is there some reason NOT to CHARGE the LIPO fully?

That might be what it means to you but what he was trying to say is what dknovick said. The wording was kinda wierd but the point is full discharging is bad for lipos. It is fine to full charge them your charger/balancer should be designed to not overcharge past the safty point (4.2V per cell). When you do charge though you want to make sure your not needing to charge more then 80% of the total capacity of the pack because if it takes more then that then you discharged the battery to low and it can do perminate damage. My charger tells me exactly how many mAhs it is putting back in as it charges the pac. This made it very easy to figure out how long I can safely fly on a pac without risking damage. They do not need to be drained before you recharge them I usualy only fly half the capacity (3/4 max) of a pac before it hits the recharger.