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Understanding Batteries 101

stay-fun

Helicopter addict
#41
LiFe batteries are quite a bit different from LiPo batteries. Fully charged is 3.6V per cell, and when in use it drops quickly to 3.3V. It stays there throughout the cycle (as opposed to LiPo, which has a decreasing voltage), and then starts to drop. Typical LVC in ESCs are set at 2.8V per cell.

LiFe batteries are generally more robust than LiPos: more resistant to overcharging, they don't burst into flames as easy (doesn't mean it can't happen!!). They don't suffer from deep discharges as much - although a 20 cycle break-in of the battery is recommended, before deep-cycling. They're best stored between 20 and 100% charge - I keep mine always charged. Perfect for transmitter/receiver batteries :) which is what I'm using them for ;)
 
#42
I just got a taranis and a 1500mah LiFe. What should I use for the low voltage alarm? 9.7? Thanks for the info. I figured this would be a good place to have LiFe info posted!
 

stay-fun

Helicopter addict
#43
Well that's a little bit of an issue... You can't reliably set a low voltage alarm, because as soon as it's tripped, the battery will be almost depleted. Better to just charge it often, there is absolutely no harm in discharging a LiFe battery only 20% and then recharge to full. That's what I do (2100 mAh 3s LiFe battery for my transmitter)

I fly a little during the week, and in the weekend I fly at my club. I charge at the beginning and end of the weekends ;).
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#45
"Safe" is never below 3.2v/cell loaded. Always a bad Idea to go below that.

I try to never go this low, however. My target discharge is typically 3.7v/cell unloaded -- depending on the powersystem, this could mean 3.6v/cell loaded, or 3.2v/cell loaded . . . all depends on how much current they draw and how much current the pack can source. If a battery comes back, and after 30s or so is sitting at 3.7v/cell, I've hit my target. It might be the half-way point between 4.2 and 3.2 volts, but at that voltage there's not much charge left on the pack -- it's down to about 10-20%. At that point the voltage drops RAPIDLY, which is a hint the chemestry is changing from "reversable reactions" (AKA, Recharge) to "irreversable reactions" (AKA, Damage).

How do I know when to land? timers are popular, and I have a few lightweight/space constrained models that I use this on, but typically I use a voltage alarm:

3ffa7cff49342e1d7d756395861f86e1.image.689x550.JPG

Cheap and effective. Get one with a loud alarm and a adjustable alarm voltage. You'll need to set the voltage for the power system you have. typicaly, on an untested airframe, I'll mount the battery alarm and set the voltage point higher than I'd expect. Fly until it sounds in a cruise, and come in for a calm landing. I'll wait 30s, then check the voltage. If it's over 3.7v/cell, I push the alarm down one or two steps and fly some more. repeat until I hit or cross 3.7v/cell after restign 30s or so, *Never* going below 3.3v/cell (you need time to land after it alarms).
 

Balu

Moderator
Staff member
Admin
Moderator
#47
Below 3.2 is actually the safest a LiPo can be. Because about no energy left also means, it will not burst into flames violently ;)

Only problem is that - if you compare it to a car - you've now been locked out of your LiPo and there's usually no way of getting back in.
 

Balu

Moderator
Staff member
Admin
Moderator
#49
Just to make sure you got that right, rchead7. I was paraphrasing the best way to kill a LiPo besides throwing it into a fire. :)

If you deplete a LiPo completely, you will not be able to put energy back in.
 
#50
OHH

oh, i was thinking that really contradicted all the other posts, but now it makes more sense any way my charger has a discharge setting to retire a battery.
 

Balu

Moderator
Staff member
Admin
Moderator
#51
Yeah, I thought you might have got me wrong there, so I'd better clear that before you have a lot of dead batteries :)
 
#53
which charger should I get for the Turnigy 2200mAh 3S 20C Lipo Pack?
I'm a beginner and I have no idea. please help me and possibly send a link of a charger. thanks
 

pressalltheknobs

Posted a thousand or more times
#55
which charger should I get for the Turnigy 2200mAh 3S 20C Lipo Pack?
I'm a beginner and I have no idea. please help me and possibly send a link of a charger. thanks
First read this http://flitetest.com/articles/lipo-battery-bunker
and this
http://flitetest.com/articles/beginner-series-batteries-and-safety

If you are just want something that works and you don't want to worry, get a balance port only charger like this and a Lipo Charging Bag


If you are reasonably technical and responsible get a 4 button charger like this...
http://www.hobbyking.com/hobbyking/..._Professional_Balance_Charger_Discharger.html

or this...
http://www.hobbyking.com/hobbyking/..._6_80W_10A_Balancer_Charger_LiHV_Capable.html
You will need a separate power supply for this one. Something like this http://www.hobbyking.com/hobbyking/...ng_105W_15V_7A_Switching_DC_Power_Supply.html

4 button chargers will charge you battery faster and more reliably if you use them properly but they are fairly complex to use. Most lipo fires happen due to charging errors. If you get one make sure you understand how to use it safely,

In any case, always balance charge, use a Lipo charging bag or better, charge away from flammable material (ie not in a bedroom) and never leave a lipo battery charging unattended,
 

ttelutz

Junior Member
#56
I'm new and i don't know i got a 1200kv motor whit a 20a speed controller and i bought a 1200mah on 25c using on plane single motor what battery you recommend ?
 

Balu

Moderator
Staff member
Admin
Moderator
#57
Hello ttelutz,

welcome to the forum.

I'm not sure what you are asking. You have a 1200mAh 25C battery (how many cells?) and still want suggestions for another battery?

That requires a lot more input. It depends on the size and weight of your aircraft, the prop size, the exact motor type (manufacturer, size, ...), etc. Everything else would just be guessing.