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Lipo safety
#16
I should be clearer with my statement. It's "myth" and not practically proven. By this I mean, people may have seen FPS drop when they switch to a longer barrel but unproven it's caused by a backdraft/suck-back or if it's caused by some other means.

As for going too fast for the piston to break, I want to ensure people understand the dynamics of how the mechbox works. It's not true that high RoF guarantees a piston break. On AirsoftMechanics, modders there have -successfully- built a full 16-tooth 40rps mechbox with no piston breakages. Naturally the stresses there are high and it depends on the the kind of piston, gear ratio, motor, and battery capacity+voltage.

See my post on Swiss Cheesing a piston. By making it lighter, it can return faster, thereby reducing the chance of piston break for higher RoF.
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#17
Sorry, what I meant is that, to have the piston already re-set and released right after a shot, while the BB is still in the barrel, you would need to have the main gear spinning so fast that it wouldn't give the time to the piston to fully reset, thus giving piston breakage or gear block.

It's very easy to check through math though. What does 40rps translate to in terms of BB per second? 40?
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#18
40rps = 40 rounds per second

Also that's why you short stroke your piston and sector gear so you don't have that problem.
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#19
Yeah these days I tend to say "rps" 'cos that translates to how many revolutions your sector gear completes (and if done properly, translates to # of full piston strokes).

But that doesn't mean you'll get 40xBB's/sec. That depends on how well your mags feed.

YCare, yes I understood what you meant. But what I wanted to clarify is that just because you have high RoF, doesn't mean you're always going to have a piston break. It depends on how high the RoF is, and depends on how light the piston for return. And was quoting that members in AirsoftMechanics members have managed to tune so well that you could have 40rps with full piston teeth (no short stroking) without piston break.
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#20
Absolutely, and actually scrap what I said, I got my stuff mixed up.

You can have suction if you time your gearbox to the millisecond, but you'd need a barrel way too long to actually have the BB losing power/stopping because of it. But if you do end up with a barrel ~>1.5m, with an AEG shooting 40 rps and on Japanese power limit with 0.2g BBs, then yes, your global power output will probably decrease dramatically.

(it takes 0.025 second for a round to be shot,so one full cycle of gearbox, and within that time the BB will have traveled 2.45m. But a full gearbox cycle means the piston will also be pushed back, so I kinda made an approximation based on feeling Wink )

But let's remember that 40rps is definitely NOT the usual... and 98m/s is one of the lowest legal limit power output you can find.
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#21
I think we are veering off topic. Still related, but let's focus on the lipo aspect.
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#22
So no one is impressed by my crazy M@th P0w3rZ?

Ok then, back on topic :p
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#23
i have busted 4 lipo batteries recently and the 2 were brand new. ive never liked lipo batts its because its just too complicated i think. so where did i go wrong? ive set my charger on lipo charge 2amps 11.1v. 3s. and plugged it in the normal socket. i was charging my madbull ultimate lipo in my advanced charger that can charge almost anything.
normally, people use the balance charger and set it at 1amp.
normally, i understand that lipos can be charged even if its not discharged. or might be mistaken.
now i'm just too afraid to charge the next ones. any insights? ive always used huge nicads.
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#24
Are you depleting the Lipo before you charge?
I have been told that you shouldn't let a Lipo run to zero.

A little google bird tells me...

OVER DISCHARGING - THE NUMBER ONE KILLER OF LIPO'S!!!

A very good rule to follow here is the "80% rule". This simply means that you should never discharge a LiPo pack down past 80% of it's capacity to be safe. For example, if you have a 2000 mAh LiPo pack, you should never draw more than 1600 mAh out of the pack (80% x 2000). This is assuming a healthy pack as well that has the full 2000 mAh capacity (as packs age, their capacity drops).

This again is where computerized chargers pay for themselves many times over so you can see how much capacity the battery takes allowing you to adjust your flight times accordingly to stay within that 80% rule to get the most life out of your pack.

If you don't have a computerized charger to confirm the amount of capacity, another good indicator is to measure the open circuit voltage (no load voltage) of the pack or individual cells after a flight/drive with a digital volt meter or other similar digital device. An 80% discharged LiPo cell, will give an approximate open circuit voltage of 3.75 volts. A 3S LiPo pack therefore would show about 11.25 volts after a flight when it's 80% discharge, a 6S pack would be about 22.5 volts.

I am often guilty of going past that 80% (3.75V per cell) number down to 90% (about 3.7 volts per cell) while flying, and on most decent quality packs if they are not being worked that hard - this is usually ok - at least in my experiences.

http://www.rchelicopterfun.com/rc-lipo-batteries.html
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#25
thanks, i have a computerized charger with everything in it, how do you guys charge yours?
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#26
Now you guys are scarring me. What exactly happens to your LiPo when they are "busted"? How can you tell they are 'busted"?

Personally, all the LiPo I received upon purchasing were completely depleted and I had to charge them to even test fire, so I'm pretty sure to have a depleted LiPo, well, an almost unused one that is. But like my other batteries, I regularly charge them, like once a month when I don't play for example.

Besides that old Echigoya battery which short circuited by itself, I had no problem at all... so far.
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#27
first time i charged it was upto 340 mah which i thought would be 1000. so i tried using it to drain but not fully drain. i charged it again but not using the balance charger just regular charge because it usually alarms anyway, then my lipo batts just decreased it mah to almost zero (85mah). surpising that it was brand new then i i found out i should be charging it at 1amp not two. but when i checked youtube it seems fine.
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#28
Personally have been using ET-1 LiPos with a UFC Super Multi Charger and haven't had any issues. I always switch batteries at lunch-time, regardless of how much I've been shooting (just to be safe), and when charging at home, always use the balance method.

http://www.et-1.com/product-list/2

http://ufc-web.com/products/parts/by/ufcbc01ufc.html
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#29
I use a couple Et-1 and a few enRoute batteries. All 4 that I own have been, but I don't charge them all together as they charge at different A settings.
I have the L4 charger from EnRoute, and you can find the Japanese manual here.
http://www.enroute.co.jp/manual/docs/L4Manual.pdf

The manual says that you should set you A based on the mAh of the battery.
It also warns to never drain you battery past 90% of charge. (The second star at the bottom)

After a game I simply set the switch and plug in my battery. Never had a problem.
Could your charger be damaged wezley?
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