15nov08 - OK - so I’m new at RC helicopters, and I really don’t know a whole lot, but I thought that sharing what I've learned might help you.
Using Google a lot, I found people throwing around battery names, sizes and times like there was no tomorrow, all a bit overwhelming and totally unintelligible.
- LiPo (Lithium Polymer) is *really* cool! it seems to be a really big step forward in battery technology, and apparently, even
tho they’re *really* expensive, if well cared for, they seem to last a long time.
- The darn things will catch fire and even explode if you treat them wrong - so read on!
- See advice in the “what to buy section” - but the simple words are - getting a good charger is a *good thing* - so do it!
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Things I think, but don’t really have any experience to back up yet:
- if, when you’re done flying, your battery is *not* really hot, this is a good thing (relative to the longevity of the battery).
I think this is because when your battery is really hot, this indicates that you are draining amps from it at near it’s design limits,
and operating near limits is generally a bad thing - I always try to be in a less aggresive position - somewhere about 50%-80% of the way
between 0 stress and maximum stress.
- don’t charge or start using the battery when it’s hot.
I don’t really know what to say about this, it just seems to come out of what I read online. The batteries tend to explode or
catch fire when they’re charged incorrectly, and catching fire is about being too hot.
I don’t know if one would actually catch fire from being taxed too heavily, but laptop batteries have been known to catch fire,
so why not these? Err on the side of caution; the battery can be a relatively big investment, so take your time.
Consensus: things that many folks seem to converge to, but I haven’t been flying long enough to agree with myself:
- When you notice that the battery is weakening, *stop* immediately.
This falls under the guidelines of not discharging your battery below the magic 3 - 3.3 V limits. I try to religiously practice this, and my
one battery is still going strong after (as of 10Dec08) 31 recharges.
Apparently going below these limits will destroy your battery.
- Wait to recharge your battery until it has cooled down (this is pretty vague I know - sorry)
- Don’t be afraid to be anal and keep track of relevant info - as in - keep a log of *each* battery charge.
For cripes sakes! - my battery cost $300. It's the single most expensive part of the whole machine - I’m *extremely*
interested in knowing exactly how that sucker is doing. Here is my little spreadsheet I’ve setup to keep track of each cycle of my (one) battery.
- It seems like the operating ranges for LiPo batteries are from around 3-3.3 to 4-4.2 V, and apparently if you exceed especially the low range
(meaning allow your battery to drain below 3V or 3.3V)) then you’ve probably ruined your battery - goodbye $300.
- Another rule of thumb I found is that if you’re charging your battery less than 85% of it’s capacity, then you're not destroying it.
I just havent found a way to discover how discharged my battery is, other than the voltage reading on the charger when I start recharging it.
- It seems that there are several different styles of connectors on batteries. Most of the ones I’ve seen in stores, the main power
leads have no connector on them, and there is some sort of other connector used for balancing and charging. This is important because
“balancing” the battery during charging seems to be pretty important, and if you have charger brand X with style Y connectors, but
that last $250 battery you bought is a different style connector - well, there are adapters to be found, but probably there is some
kind of wait involved.
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9 Feb 09 ** IMportant note** In late January, I grew concerned about cell #5 in the battery, it was consistently lower than
the rest, so I emailed ThunderPower with a screenshot of my charge log and my question.
The answer was that I've been consistently depleting the battery too much. It's a 5000 mAh battery, and I've consistently been charging
it at very close to 5K. He was quite clear - draining it to the point that it requires more than 4000 mA means I've over-discharged the battery,
and if I keep it up the battery will be gone soon.
I didn't realize the meaning of the mA number that my charger produces, but now I do.
9 Feb 09 So with the new info from the tech guy at Thunder power, I started out with shorter flights using a countdown
timer in my cellphone. This allowed me to discover that about 13 minutes of sustained hover training would generally keep the re-charge to under 4000 mA.
I'd sure encourage you to get a charger that will tell you how many mA your battery took to recharge.
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4 Sept 09 ** Useful Information** In late July, the battery suddenly was substantially hotter after a 13 minute flight, so I
emailed FlightPower who informed me that Hobbico was now supporting the battery.
My questions were:
How hot is too hot?
Is overheating an indicator that the battery is dying?
Why wouldn't the charger want to rechsarge the battery?
The answer was:
About 120 degrees is too hot. The battery can warm up during charging and discharge. But if it heats up to over about 120, that's not good.
He didn't directly answer this question. But, reading between the lines, it appears that it's an indicator that at least one cell has dropped
seriously below the minimum voltage threshhold and that cell is being damaged.
Most modern chargers will have a builtin charging requirement that all of the cells of the LiPo are at least 2.5V. Mine was at 2.4V.
Here's my perspective on this info.
First of all, my battery has been severly mistreated over sometimes extended periods, and it's still working, so while it can be damaged, it seems
to need to take some *extremely* serious mis-treatment to actually cause it to catastrophically fail.
The short history of my battery use is:initially fly til the heli fell out of the air, charging really close to 5Kma (did this for about 3 months, about 55 flights).
Then I cut the flight time to 13 minutes, and was routinely charging right around 4Kma - did this late Jan thru early May09, about 140 flights.
Then suddenly in early May, the battery was quite a bit hotter than usual, so I reduced the flight time to 10 minutes - now charging routinely around 3Kma. for the last 130 flights.
I've got about 320 flights on the battery - a total of 4130 minutes. This even with the early mis-treatment.
The tech said that batteries tend to last "a few hundred runs", and when it poops out that's it. I'm happy that I've got my
costs down to < $1/flight, about $0.07/minute, and I'm totally OK with flying for 10 minutes at-a-time. Gonna try to keep nursing the battery along until
it just really rolls over and dies. And I think that'll likely be an extremely hot battery.
I've discovered that how I fly affects how depleted the battery is. For instance, if I spend a lot of time much higher than usual,
the battery will be more discharged (makes sense). If I am more jerky, or let the machine zoom here and there, also more discharged.
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When you buy your charger, you will also need a power supply for it. I've seen chargers come in 2 basic styles, the simple plain charger, or the integrated charger.
I've seen them also referred to as DC or AC/DC chargers, w/ the DC only being the simple charger.
A simple charger will require a 12v power source - as in, your car battery (and chargers typically seem to come with battery clips), or one of those "bricks"
that plugs into the wall somehow and has a little connector on it that feeds 12V to your charger.
| Simple charger w/ radio shack 1200 mA transformer
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Integrated Charger
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The one thing you need to understand, is that unless you're charging rather small batteries - as in under 1000 mAh or so, you'll need a substantial
12V power source. The typical bricks you can get at radio shack for $10-15 or so are usually not much bigger than 1 amp, and so are just barely enough for
your 1000 mAh battery (1000 mA = 1A). My battery is a 5000 mAh battery, so I had to spend rather more than I wanted to get a > 5A 12V power source.
Of course, I could lug the car battery in the house, but my wife would object I expect. But, even if I did that, then I'd still need a reasonable charger
for the car battery.
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9 Feb 09 This business about over-discharging your battery is important (read the full story here)
and I just wanted to re-emphasize that here - as in, one other thing that seems to be useful is if your charger will tell you how many mA it had
to pour into your battery to recharge it.
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It seems that lack of standardization is rampant in this industry too.
You've probably seen the typical LiPo battery, with the one heavy power connector and the small "charging" connector. They are also called "balance taps".
These darn things come in several varieties, so you just need to be aware of this.
The Hyperion charger, for instance has a nice collection of balancing tap adapters, and there are 4 varieties:
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This is my little spreadsheet to keep track of battery info and I have a second one to keep track of my operating costs as well.
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