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Dec 23, 2012, 07:09 PM
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pitchp's Avatar
Quote:
Originally Posted by perdification
EDIT: Heheh, I did all 5 batteries back to back with no rest, not only are my batteries now all flat, I'm flat out too..
Don't forget the 80% lipo rule
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Dec 23, 2012, 07:14 PM
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Quote:
Originally Posted by pitchp
Don't forget the 80% lipo rule
Oh, I just hovered for 5 mins on each battery just to be safe. 5 mins shouldn't take up more than 80%, or else the battery is faulty. My balanced charger isn't here yet. My training gear isn't here yet too! Luckily I haven't had any crashes with this thing. Gonna burn another 5 batteries on just plain hovering later.
Dec 23, 2012, 07:43 PM
Yes, I know it's upside down.
Quote:
Originally Posted by perdification
Oh, I just hovered for 5 mins on each battery just to be safe. 5 mins shouldn't take up more than 80%, or else the battery is faulty. My balanced charger isn't here yet. My training gear isn't here yet too! Luckily I haven't had any crashes with this thing. Gonna burn another 5 batteries on just plain hovering later.
Perdi, do yourself a big favour and buy yourself one of these. So easy to carry in your pocket, and it will stop you from taking off with a used battery, and also will stop you discharging your battery too low. (Don't go below 3.7v/cell).

http://dx.com/p/digital-multi-cell-l...c-models-20024
Dec 23, 2012, 07:50 PM
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mhills51's Avatar
I agree with Harrow but those can be confusing. One of these is much better.
http://www.hyperion-world.com/produc...HP-EOS07SENTRY

It even has a fuel bar that tells you in a glimpse what your pack is at so you don't need to to calculations in your head. Yes you can remember what the volts need to be on the other type, but if you use different packs it get confusing really fast.
Dec 23, 2012, 07:52 PM
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Quote:
Originally Posted by Harrow
Perdi, do yourself a big favour and buy yourself one of these. So easy to carry in your pocket, and it will stop you from taking off with a used battery, and also will stop you discharging your battery too low. (Don't go below 3.7v/cell).

http://dx.com/p/digital-multi-cell-l...c-models-20024
I have a digital multimeter with me in my toolbox all the time. But I prefer to use the 80% rule, but that is if my charger arrives. Yesterday I stopped the moment my cells hit 3.8V, because I heard that judging by the voltage isn't very accurate. That's why Lipo alarms don't work. I'll stick to the 80% rule.
Dec 23, 2012, 07:54 PM
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Quote:
Originally Posted by mhills51
I agree with Harrow but those can be confusing. One of these is much better.
http://www.hyperion-world.com/produc...HP-EOS07SENTRY

It even has a fuel bar that tells you in a glimpse what your pack is at so you don't need to to calculations in your head. Yes you can remember what the volts need to be on the other type, but if you use different packs it get confusing really fast.
Isn't this just a nicer version of a digital multimeter if you're sure about what type of cells you're using and the voltage range for them?
Dec 23, 2012, 07:54 PM
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ahamay's Avatar
Quote:
Originally Posted by perdification
I have a digital multimeter with me in my toolbox all the time. But I prefer to use the 80% rule, but that is if my charger arrives. Yesterday I stopped the moment my cells hit 3.8V, because I heard that judging by the voltage isn't very accurate. That's why Lipo alarms don't work. I'll stick to the 80% rule.
I personally think voltage alarms work very well, providing you have set your voltage alarm levels correctly. The voltage alarm is measuring the voltage under load which will be different to what the pack reads once you've landed and checked it.
Dec 23, 2012, 07:57 PM
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Quote:
Originally Posted by ahamay
I personally think voltage alarms work very well, providing you have set your voltage alarm levels correctly. The voltage alarm is measuring the voltage under load which will be different to what the pack reads once you've landed and checked it.
Yeah, I understand that there's voltage sag under load. But I remember reading somewhere that Lipo alarms aren't an accurate measure, and the 80% rule is. I have a Lipo alarm that I bought that triggers off at 3.3v and it's not adjustable. I think it's way too low a voltage there. I'll find the source and post the link here.
Dec 23, 2012, 08:03 PM
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ahamay's Avatar
Quote:
Originally Posted by perdification
Yeah, I understand that there's voltage sag under load. But I remember reading somewhere that Lipo alarms aren't an accurate measure, and the 80% rule is. I'll find the source and post the link here.
80% rule and checking voltage etc is great when you start to learn to fly and it will give you a safety net over destroying your packs.

After you've been flying for a while you won't bother with the checks as you'll know exactly what time you can run your packs for your flying style. For me I know that I can get 5 mins per pack and never bother checking as I know that I'm in the 75-80% region.

Next you'll want to start parallel charging packs so getting a feel for the run-time before you do that is a good idea.
Dec 23, 2012, 08:11 PM
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Quote:
Originally Posted by ahamay
80% rule and checking voltage etc is great when you start to learn to fly and it will give you a safety net over destroying your packs.

After you've been flying for a while you won't bother with the checks as you'll know exactly what time you can run your packs for your flying style. For me I know that I can get 5 mins per pack and never bother checking as I know that I'm in the 75-80% region.

Next you'll want to start parallel charging packs so getting a feel for the run-time before you do that is a good idea.
The problem is that batteries will lose capacity over time, so the 80% of whatever max capacity in the battery will correspondingly drop, and so will flight times?
Dec 23, 2012, 08:18 PM
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ahamay's Avatar
Quote:
Originally Posted by perdification
The problem is that batteries will lose capacity over time, so the 80% of whatever max capacity in the battery will correspondingly drop, and so will flight times?
Yes that's correct, but you have to draw the line on how pedantic you get with monitoring these things. I'm getting around 150 flights using the 80% rule on a typical turnigy or nano-tech 2200mah pack before I will not fly with them due to capacity loss.

When your talking around $12-$15 for a pack then worrying about calculating runtime over the life of the pack is not worth the time. I'd rather be flying.

A draining pack that's nearly at it's end of life is quite noticeable, especially at the start of the pack when your head speed is not what it should be.
Dec 23, 2012, 08:38 PM
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Quote:
Originally Posted by ahamay
Yes that's correct, but you have to draw the line on how pedantic you get with monitoring these things. I'm getting around 150 flights using the 80% rule on a typical turnigy or nano-tech 2200mah pack before I will not fly with them due to capacity loss.

When your talking around $12-$15 for a pack then worrying about calculating runtime over the life of the pack is not worth the time. I'd rather be flying.

A draining pack that's nearly at it's end of life is quite noticeable, especially at the start of the pack when your head speed is not what it should be.
I think it's stated that nano-techs will degrade faster than normal turnigy packs, and last for fewer cycles.

Right, I learnt something new today, the "how to tell a pack nearing it's end". Thanks!

Oh yes, and I watched finless bob's maintenance vids, and he said to oil after every flight. So that means oil after every battery (which seems wayyy excessive) or oil after every flying session? For me, I'm going to fly six batteries in a single flying session now. I'd probably oil after flying all 6, which seems reasonable.
Last edited by perdification; Dec 23, 2012 at 08:44 PM.
Dec 23, 2012, 09:52 PM
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mhills51's Avatar
Quote:
Originally Posted by perdification
Isn't this just a nicer version of a digital multimeter if you're sure about what type of cells you're using and the voltage range for them?
You say that but then we all get lazy. Everyone at the field says the same until I show them that. The next question is Where the hell can I get one!!
Dec 23, 2012, 10:47 PM
Registered User
Quote:
Originally Posted by mhills51
You say that but then we all get lazy. Everyone at the field says the same until I show them that. The next question is Where the hell can I get one!!
Maybe I haven't been flying long enough to get lazy yet. I'll buy one when I do. Or maybe, if it's hard to find, make one myself by programming some AVRs or ARM chips. Will need help from the community again if I do. Just back from flying 7 packs of batteries in a row. I can feel myself being more and more connected to my heli now...
Dec 23, 2012, 11:54 PM
Yes, I know it's upside down.
Quote:
Originally Posted by perdification
I have a digital multimeter with me in my toolbox all the time. But I prefer to use the 80% rule, but that is if my charger arrives. Yesterday I stopped the moment my cells hit 3.8V, because I heard that judging by the voltage isn't very accurate. That's why Lipo alarms don't work. I'll stick to the 80% rule.
You will change your mind after the first time you destroy your heli due to flying with a used battery.

Low voltage is what kills your batteries, so that is the most accurate thing to measure. I agree, do not measure under load, that is no good, but after your flight is good, and gives direct feed back on your fight time and flight style. If your batteries are below their rated capacity, then measuring 80% capacity on your charger will not let you know if you are discharging them too much.


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