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Old Sep 02, 2012, 11:23 AM
Big Boats Rule!
boater_dave's Avatar
Wisconsin
Joined Jun 2007
2,051 Posts
I ran my big sailboat for the first time with a LiFe rx pack last night. No problems. I am using an old 72mhz Futaba radio with a Robot Zone geared Hitec servo. The LiFe pack I used is 2100 mah and came pre-wired with a pair of rx battery leads (for those dual rx systems) and a heavy wire deans plug lead for charging. I also plugged in an audible low voltage alarm. I figure in a sailboat an early warning is better than total system shut down.

Dave
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Old Sep 02, 2012, 06:47 PM
Registered User
Australia, TAS, Penguin
Joined Mar 2012
550 Posts
My personal preference for batteries for sailboat is the LSD NiMH range.

I have 6 volt boats and 12 volt transmitters.

For the transmitters I use 8 of these (US$1.59 each):
http://www.hobbyking.com/hobbyking/s...y_to_use_.html

And for the boat I use this 5xAA pack (US$7.49)
http://www.hobbyking.com/hobbyking/s...iver_Pack.html

This provide stacks of capacity - 8 hours sailing easy.
Weight is not an issue unless you are a top echelon RC sailor IMHO
.
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Old Sep 03, 2012, 09:15 PM
NORTHLAND NEW ZEALAND
D design's Avatar
New Zealand, Northland, Totara North
Joined Feb 2012
598 Posts
lipos are very powerful, very light, and do not need to be cycled. You gota do something very silly to cause a fire. If your concerned about fire, charge them in a metal amunition box or equv.
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Old Sep 03, 2012, 09:16 PM
NORTHLAND NEW ZEALAND
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New Zealand, Northland, Totara North
Joined Feb 2012
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I use lipo and gives me 10 hours of sailing time.
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Old Sep 03, 2012, 09:29 PM
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Australia, TAS, Penguin
Joined Mar 2012
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Videos like this put me off LiPo - use LiFe instead....

I realise this video shows extremes, but all you need is a short or a pinhole to get the fire started - and each cell burns separately and enthusiastically even underwater....

Lipo Explosion Montage (2 min 38 sec)
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Old Sep 03, 2012, 10:10 PM
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Barbados
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Any chemistry can explode,99% are caused by human error which is well depicted in the video to say the least.I run lipo's and happy with em.
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Old Sep 03, 2012, 10:12 PM
NORTHLAND NEW ZEALAND
D design's Avatar
New Zealand, Northland, Totara North
Joined Feb 2012
598 Posts
Going from nimh to life seems like a good decision but going from lipo to life is not such a smart idea. When cars first came out people were frightend the gas tanks could blow up so people stayed with low tech horses. Same story with batteries
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Old Sep 04, 2012, 09:16 AM
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Joined Jan 2006
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The only battery I have actually seen explode is a NIMH. With over 6 years sailing with Lipos in both the boat and TX, the fears about lipos are greatly overblown. Yes they can burn, but so can other types of batteries. Use what you feel is the best choice.
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Old Sep 04, 2012, 09:58 AM
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Barbados
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I use lipo simply because it's as close to 9v as i can get with a RMG winch and they love it,to a lesser extent fast charging and weight in the bilge.If you have proper charging equipment and do a bit of reading so you know what your doing there should be no problem,when a lipo starts to go bad there are at least two warning signs which the charger tells you,your eyes can see puffing and dissimilar cell voltages,if you have equipment you have to be able to use it.It's not very difficult at one time i did'nt know a dam thing either.The I Charger range are second to none at under a 100 bucks.
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Old Sep 04, 2012, 03:49 PM
NORTHLAND NEW ZEALAND
D design's Avatar
New Zealand, Northland, Totara North
Joined Feb 2012
598 Posts
I use turnihy accucel 6 charger. Very happy with it. Fully programable and can charge any type of battery. In an iom sometimes instead of putting corrector weights in, i just put two lipo batteries on each side of the fin case. This makes it possible to sail all day and just forget about the batteries in y our boat which makes a happier days sailing. And tug is 100% correct about voltage, the higher your voltage, the faster your winch will go. If using an rmg winch, higher voltage helps the internal regulater put out a much more reliable voltage and that will prevent brown outs due to low voltage when you operate your winch. However, higher voltages do tend to drain your capacity faser but you wont need to worry to much about that.
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Old Sep 05, 2012, 04:06 PM
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Quote:
Originally Posted by D design View Post
However, higher voltages do tend to drain your capacity faser but you wont need to worry to much about that.
This is simply not true.
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Old Sep 05, 2012, 04:27 PM
NORTHLAND NEW ZEALAND
D design's Avatar
New Zealand, Northland, Totara North
Joined Feb 2012
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I read that from a rc 4x4 guy. Maybe hes wrong but larger voltages require larger capacity therefor larger battery.
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Old Sep 05, 2012, 04:48 PM
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Quote:
Originally Posted by D design View Post
However, higher voltages do tend to drain your capacity faser but you wont need to worry to much about that. ... I read that from a rc 4x4 guy. Maybe hes wrong but larger voltages require larger capacity therefor larger battery.
The amount of work done by the servo is the same - the work will just be done more quickly.

Think of it in terms of watts, power, work.

Usually servos are strong enough that the voltage / kV / gear ratio is within spec for the application and you just end up with faster response and more holding power.

If you're using servos with really high gear ratios on low voltage, maybe consider changing gears with your voltage increase - but I doubt it!

I would love to see some metrics to dispel this myth.

My Victoria draws about 50-70mA per hour on 7.4v and my micro magic 65-70mA per hour on 2s LiPo regulated to 6v.

Go light, go HV, enjoy. My 350mAh cells let me run all day and I've got great control speed and power.
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Old Sep 05, 2012, 04:50 PM
Did you check the FAQ already?
SoloProFan's Avatar
The Netherlands
Joined Jul 2010
13,612 Posts
Quote:
Originally Posted by northernmike View Post
This is simply not true.
Well, in some cases it is. If the voltage increases, the rpm of a motor like the one in the servo for instance also increases, and with it the current. This is true for a simple resistor, but it turns out a motor behaves even different than a resistor. With a resistor, doubling the voltage will double the current, with a motor it will increase quadratically.

If however the voltage is reduced by a voltage regulator first, before it gets fed to receiver and servos there is no increased power consumption, as the regulator voltage is fixed. Depending on the type of regulator circuitry there might be a little more heat generation in that part, but that probably won't give a real power consumption increase.

Coming back to a small boat like the MM, the difference will be small. In normal conditions you will use less than 100 mAh (watch the "h" as we are talking used capacity here, and not simply current) and if the servos move a little faster due to higher voltage that won't affect power consumption much. Unlike a motor used to propel a boat, the motors are not constantly working. Should you take a motor propelled boat as example, the current running will noticably increase when voltage gets higher and run times will get shorter.
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Old Sep 05, 2012, 04:57 PM
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Another thing to consider is better quality batteries (LiPo) can have lower internal resistance - sagging less under load and providing current longer at a sustained voltage...

Solo thank you for the info on motor / power behaviour, was not aware of that.

Perhaps I have been too confident, enjoying my LiPos!
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