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Very interesting...!
Would be great to hear your results and how many batteries you need to run the tube motor.
Thanks for sharing this.
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[#0000FF]I'm all in favor of light weight. But I am more in favor of having plenty of surplus power behind me if I need it.
I have a concern about the voltage being adequate. I top off my AGM series 27 battery before a trip and start out with a bit in excess of 13 V. After a long day and a lot of motor useage I am down to about 12.2 volts...still showing about 60-70% charge. However, as the voltage drops, so does the output. I can really tell the difference in thrust at the end of a trip vs the beginning.
My concern...some motors simply will not perform when voltage drops below about 11 volts. Have you checked your motor for any such specs?
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[quote MasterDaad]It's time to replace my tube battery. I also want some new RC airplane batteries so I'm going to go back to some previous experiments using Lithium-Ion Polymer batteries for my float tube.
My average tube trip consumes 20mAh of battery capacity. So to achieve that and a little extra, I'll be carrying 6 of these:
[url "http://www.valuehobby.com/power-systems/batteries/3s-lipo/25c-5000mah-3s-trx.html"]http://www.valuehobby.com/...-5000mah-3s-trx.html[/url]
3S lithium Ion batteries have very similar voltage ranges as a 12V Lead Acid battery (12.6V fully charged, 9V dead).
They don't have "memory", are suitable to full discharge but are vulnerable to damage if over-discharged.
A big advantage is the weight of the 30Ahr Lithium battery will be about 5lbs.
Handling any current lithium ion technology requires proper safety measures (so do Lead Acids). Samsung demonstrated this in spectacular fashion. I will post pictures of my set up and safety measures I use.[/quote]
MD,
Very interesting project, keep us posted.
I take the lazy way out and use existing high capacity lithium batteries and chargers meant for cordless lawn tools on some of my high power requirement projects. There are other advantages to doing it that way besides getting to be lazy.
The battery usually includes thermal, overload, over discharge and over recharge chips for safety plus a fuel guage which lets you know how much power you have left. Also, a satisfaction warranty (90 days at HD & Lowes) helps if they fail too soon and they can be exchanged quickly at these stores which are everywhere. The lithium battery pack voltages on high power lawn equipment are usually above the typical 12v for troll motors though, so I have to use other ways to make it work.
I think TD does have a good point, especially about the lower voltage. The 12.6v full charge on the lithium paks I use very quickly drops to rated 11.1v where it remains fairly flat for maybe 60% of its capacity. That means considerably less thrust than you would get with a standard 12v battery. You can solve this by going up to the next pack size which adds one more cell.
Hope this helps.
PM
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For someone without the dual use I have (my airplanes run on either 3S or 6S packs) I'd certainly go the 14.8V power/garden tool battery route too. Much simpler with an added safety factor.
My system will be the lightest weight (because airplane batteries are built that way) with the downside of some additional monitoring during use. My tube's fish finder has a voltage display option I always use for a fuel gauge anyway.
And I already have the proper chargers for the airplanes too.
I have some ideas to experiment with much lighter weight brushless DC motors that should dramatically improve range with greater efficiency.
Where there is an option to use a boat ramp near the fishing hole, the heavier equipment has the clear advantages.
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[quote MasterDaad]For someone without the dual use I have (my airplanes run on either 3S or 6S packs) I'd certainly go the 14.8V power/garden tool battery route too. Much simpler with an added safety factor.
My system will be the lightest weight (because airplane batteries are built that way) with the downside of some additional monitoring during use. My tube's fish finder has a voltage display option I always use for a fuel gauge anyway.
And I already have the proper chargers for the airplanes too.
I have some ideas to experiment with much lighter weight brushless DC motors that should dramatically improve range with greater efficiency.
Where there is an option to use a boat ramp near the fishing hole, the heavier equipment has the clear advantages.[/quote]
MD,
I can see your advantage of having the cells available for multiple applications. I also can use in multiple apps, from cordless tools to electric bikes, skate boards, mowers, etc. , but not RC aircraft. One thing to watch out for is not to let your lithium batteries get submersed or soaked from rain or splashes.
The only present advantage of heavier electric propulsion equipment is $$ cost that I can see, if everything else is the same. I think lightweight electric tube propulsion of proper design can do some things that heavier electric cannot, but not the opposite. Also one can go to gas motors which have greater range and are faster but have other issues, plus cost more.
Troll motors are built for moving heavy bass boats and are very inefficient for powering tubes, is what I have learned. Brushless motors will help, but are not as important as hydrodynamics, according to what I have learned from monitoring the boat design forums over many years.
Hope this helps.
PM
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Hi PM,
Yes it't helpful.
First, water + any lithium = Bad day. The batteries are sealed, but mitigating water exposure is important
If and when I get to the motor design, I recall seeing some work done with different prop options to improve efficiency.
I received my batteries today!
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