lithium batterys

Whats the story with li pol batterys, do i need to discharge them after every use, & what should i do to keep them in good condition, i have just brought a 2cell 1200mah batt & apache 2500 charger.

[dongle]

no - dont need to discharge them.

To keep them in good nick, dont go below 3v per cell under load (get a liposafe from HOTROD) dont charge them above 1C, and keep a carefull eye on them for going out of balance.

[reubenwilcock]

ehmm thats www.customidea.com for the lithium low voltage warning device (shameless eh [img]/ubbthreads/images/graemlins/wink.gif[/img])

[dongle]

LOL you terrible person [img]/ubbthreads/images/graemlins/tongue.gif[/img] really must remember you have a site to sell em through now!

A question for those of you that understand the black art of electricity [img]/ubbthreads/images/graemlins/blush.gif[/img]
I have Reubens low voltage warning device on my Pic and for an idiot like me it's a brilliant reminder - stop now!

But I've seen a proliferation of Lipolys being used in planks recently. Presumably designed to fly away from you at distances where the warning could not be seen / heard how does one stop the voltage drop from being exceeded?

I have been known to keep a plank in the air long enough for the BEC to cut the motor and I just glide home - presumably can't do that with Lipolys [img]/ubbthreads/images/graemlins/blush.gif[/img]

Confused of Cornwall [img]/ubbthreads/images/graemlins/crazy.gif[/img]

what I normally do is on the first few flights only fly a new pack for 5 minutes, then take it home and charge it. See how much juice goes back into the pack and make an eductaed guess at how long I could fly on a full charge and set the timers on the Tx up to alarm at that point.

so as an example if I have a 1500Mah pack and I fly for 5 minutes, take the pack home and charge it and it takes 500Mah so I know that I could fly for a maximum of 15 minutes. However i would set my timers for mor like 12 or 13 minutes to leave a bit of head room.

Obviously this doesnt test the voltage drop but has worked for me for ages now.

[reubenwilcock]

I will be addressing this problem soon.. Will post when its done.

[dongle]

Actually, on a plank I have been surprised by how far away you can be and here the buzzer anyway - though the man is obviously on the path to even greater things than that!

I'm glad it wasn't as daft a question as I thought [img]/ubbthreads/images/graemlins/grin.gif[/img]

And if I know Reuben his new gizmo will decide the battery's had enough - turn the plane on to short finals - lower the undercarrieage and land at your feet.
Either that or send 40,000 volts through your thumbs until YOU do it [img]/ubbthreads/images/graemlins/grin.gif[/img]

Most modern ESCs can set the BEC cutoff voltage to be suitable for liths - so they cut the motor at the 3V/cell limit but leave the radio gear working so you can land. That said, I still use the timer method but it's nice to have the BEC as a backup.