|04-18-2008, 06:14 PM||#1|
RCC Senior Contributor
I am: Travis H
Join Date: Mar 2007
Location: Muenster, Saskatchewan
Feedback: 9 / 100%
Total Props: 13
Am I killing my Lipos?
Remove this ad - become a site supporter!
I am wondering what is the rule of thumb when it comes to running lipos? I am usng E-flite 7.4v 800mah lipo's in my Blade CX2. I stop flying and change packs when I notice a loss in power. If it takes more throtle to maintain a hover or does not lift as quickly I land as soon as possible. Is this an acceptable way of judjing a packs voltage/capacity or should I be landing before a power decrease is noticed? I am noticing a decrease in performance of the two packs that I have been using in this manner. The packs are only about four months old, but have quite a few flights on them. This leads to the question, am I killing my Lipos?
I normally charge the packs with the supplied balancing charger, but I have checked the mah replaced after a flight with my Accuclcle Elite charger.
Here is an example of the two packs before and after a flight.
Pack "A" - After a complete charge I get a reading of 8.34V.
After a flight a reading of 7.31V.
After charging with the Accucycle 8.37V and replaced 661mah.
Pack "B"- After a complete charge 8.82V.
After flight 7.5V.
After charging 8.83V, replaced 523mah.
I need to figure out how to properly use lipos without damaging them before I can move onto bigger projects.
Thanks in advance for any advice offered.
Pie tastes better with Cool Whip.
|04-18-2008, 06:34 PM||#2|
I am: Boolean21
Join Date: Sep 2002
Feedback: 0 / 0%
Total Props: 56
Re: Am I killing my Lipos?
To get the most out of a lipo the following should apply,
minimum open circuit resting voltage after pack has cooled = 3.7 v/cell
maximum 80% of capacity discharged.
No more than 60C temperature
Try to avoid dropping the pack below 3.2-3.3 v/cell under load in flight, to check this you need a micrologger or equivalent way of monitoring pack voltage real time in flight.
As you use the pack and it ages you have to discharge it less to meet the 80% rule, this is where measuring the voltage after a flight becomes important.
If you follow the above you are not abusing your packs, and a decent pack should give you at least 100-200 cycles before you lose 20% of its capacity. If you can't get this out of them, the pack has crappy cells. There are high quality low cost packs, and low quality high cost packs! Choose wisely!
Lipos also have a shelf life, don't buy them if they are going to sit. Try and cycle them out before winter hits so they don't sit and you will get more time out of them.
On my big 10s packs (10s 5000 mah), after the second season of flying (going into a third year) they pretty much fail regardless of how many cycles I have on them.
|Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)|