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A Main Hobbies . Boca Bearings . Modefo's RC Helicopters

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e-Electric General Discussion > Battery question and general shame
 
 
tricid
Heliman
Location: Sherman, TX USA

I'll start with my question on lipos.

The 80% rule, is that recommended as a rule of thumb to be the safe limit, just to give a buffer?. In other words, if I discharge a 2200mah battery, charge it and put 85% back in to it, have I done it harm? Or do I actually need to go over 100% of 2200mah before I do it harm?

Between timers and my ESC's auto protection I aim for 75-80%, but as I play with different things like heat sinks, weight, balance, blades, etc, my flight times can be longer (my ESC won't shut down), but I am going a little over the 80% rule. I was curious if this is damaging my battery.

Also where does voltage under load come in to play here. My ESC's auto protection is voltage based, so if it's allowing me to go beyond 80% I assume that's just because my voltage on my pack isn't dropping until after that point. If it were to drop before 80%, does that mean I'm doing it harm? I only ask this because I wonder if I should use both my ESC's protection and a timer, or if it is safe to only use a timer and watch out for the 80% rule ignoring the voltage drop protection that the ESC tries to provide.

I apologize, I have read/searched this info, but I'm still a little confused and I want to avoid buying batteries more than I have to.

Also has anyone gone from big'ish(.50+) nitros to a mini electric (450) and fallen in love with the little birds ;x. I find myself wanting to fly my little mini titan more than my others lately lol, I almost feel ashamed
06-25-2008 04:41 PM
 
 
Pistol_Pete
Elite Veteran
Location: Tampa Bay non-Buccaneer

to my understanding it was a rule of thumb given when lipos hit the RC scene in order to protect batts from overdischarging.

Fast forward to today...we now have lipos that can be completely discharged and charged as much as 3C.

We also have programmable Rx such as the Berg7 from CC

I use both a timer and the backup is the cut off in my Rx. This gives me a buffer for landing attempts (planker) and for helis I rather have a planned auto than a forced one.

As for the Rx cut off...its under load at all times when flying so in my case I use 9.6V.


You will not harm a lipo by discharging more than 80%. Worst case scenario is that yoo might decrease its life cycle...but once again...given the latest out there...doubtful.

Edited:
Finally you will notice when you are reaching "empty" given the performance of heli.

<><>...the lunatic is in my head...<><>
06-25-2008 04:51 PM
HOMEPAGE  
 
 
tricid
Heliman
Location: Sherman, TX USA

Before I put a heat sink on my ESC, I definitely noticed the charge protection, it'd drop power and kind of pulse, for a lack of a better way to explain it.

After throwing a heat sink on my ESC from suspecting heat issues, I can hardly tell the performance loss when it drops (if it's dropping at all), yet my last few charges I've gone as high as 85-90%.

I didn't know some Rx's had some voltage protection built in, I assume they keep power to the servo's/gyro and cut power to the engine when they detect you're too low? Know if one is out that is both PCM, and has dials to change the crystal frequency (like my futaba 9chp radio can)?

I'm just using a standard cheapo non-pcm fm reciever right now.

Thank you very much for the reply on the percent.
06-25-2008 04:59 PM
 
 
Pistol_Pete
Elite Veteran
Location: Tampa Bay non-Buccaneer

Quote 
I didn't know some Rx's had some voltage protection built in

its the voltage cut off setting for batts...some offer auto or preselected according to batt used while Berg7 can be customized.


Quote 
I assume they keep power to the servo's/gyro and cut power to the engine when they detect you're too low?

yes...part of the BEC function.

Quote 
Know if one is out that is both PCM, and has dials to change the crystal frequency (like my futaba 9chp radio can)?

no clue on this one...but try the futaba web site.

Quote 
I'm just using a standard cheapo non-pcm fm reciever right now.

I used PCM until a bad crash and never replaced since 2.4 were around the corner. (and still have not upgrade radio) as Im sold with the CC Berg line...so far.

<><>...the lunatic is in my head...<><>
06-25-2008 05:09 PM
HOMEPAGE  
 
 
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e-Electric General Discussion > Battery question and general shame
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