HELP ME PLEASE.. After 1 flight , both my battery 5400mah yuneec is drained . I'm using 0riginal charger from the box to charge, but it error. Both my new battery show solid red light (error) when i want charge.
Its a common mistake with newcomers to the hobby you never want to let the battery drop below 3.5 volts per cell under load @ 10.6 volts you should be landing, this will prolong the longevity of your battery's and protect them from permanent damage.
However in your case it may be possible to save the battery with low volts, by changing your charger settings temporary to select NiMH for battery type and select 0.5 amps just to bring the voltage back to 3.6 volts, DONT LEAVE IT ON THESE SETTINGS FOR NO LONGER best if carried out outside in case of battery malfunction fire, and watch it closely as the voltage climbs and if the battery starts getting hot or puffing stop charging immediately, once the battery is back to 10.6 volts you can stop the charger and re select lipo battery settings as normal and continue to charge.
As long as you observe what I have said your battery may possibly be saved.
There a loads of video's on youtube regarding charging low volts lipos this is just a couple I found for you.
Glad it worked out for you just remember you cant always bring them back to working condition, it pays not to discharge them to low, there are loads of youtube video's to give guidance particularly to newcomers to the hobby regarding looking after your lipo batterys for longevity and understanding of the battery workings.