Battery Location, "Master Switchs"mn and Vortex Generators.

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Battery Location, "Master Switchs"mn and Vortex Generators.

Postby jjacky » Mon Jul 17, 2017 4:28 pm

Ok I'm going out on a limb again for a sanity check. I'm thinking of locating a light lithium battery , probably Shorai, in a box directly behind the passenger seat. Next to it will be the master switch, a 200 amp (1000 surge) keyed marine battery switch and, finally, 14 gauge wire to and from the starter. I think this configuration has these advantages:

No hot Master relay sucking an continuous 1 amp out of the Rotax's miserly 16 max amp alternator;
In a forced landing turning the "master" off will completely isolate ships power.
A battery that weights 1/6th of a regular battery;
A short run to the starter motor;
Easy access to the battery;
Plenty of current to crank the Rotax 912. Rumor has it that low starting current causes kickbacks.

I'm worried about the weight and balance aspects of loosing that battery weight behind the aft bulkhead and anything else I may have overlooked.

And one more item. Do you think Vortex generators are effective?

Thanks for your time....jbird.
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Re: Battery Location, "Master Switchs"mn and Vortex Generato

Postby kenryan » Mon Jul 17, 2017 5:05 pm

Regarding W&B I wouldn't worry about being nose heavy. You can always add the necessary amount of cargo to the way back. Here in Alaska that would be cold weather survival gear. In desert country, it might be water. Anybody could benefit from a tool kit. With the generous baggage area of our airplanes, if you start out a little bit nose heavy it should be pretty easy to get it "just right." Steve Henry has said one of the reasons for his large header tanks (located in aft baggage) is to help counter the weight of the heavier 914 (style) engines that he was using. Put the battery on the firewall and have an even shorter run to the starter. I hope you meant to say "4 gauge" and not "14 gauge" to the starter. 14 gauge would be severely undersized. With the battery on the firewall, 8 gauge would probably work, but with the starter circuit there are advantages to sizing things up a notch. One thing is that hard starting will wear out your gearbox. Are you certain the battery contactor consumes 1 amp? Even if it does, what's your total maximum load? Do you really need all 16 amps or, like most, is your total load considerably less?

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Re: Battery Location, "Master Switchs"mn and Vortex Generato

Postby av8rps » Mon Jul 17, 2017 6:05 pm

I've heard lithium batteries can overheat and burst into flames, which is the same reason the airlines no longer want laptops and the Samsung 7 had issues. Ok, just what I heard.

I personally would build it with a Oddysey battery. Ive had really good luck with that battery in a couple different planes. They seem to make a lot of reliable long term power from a very small battery.

My totally stock Highlander is a rocketship, but built relatively light at 680 lbs with larger than average 8.50 tires. Not that making it even lighter wouldn't be even better, especially considering that I like to fly with amphibs so a light airplane is extra important to me. But with that said, if I really wanted to reduce empty weight (besides starting with reducing my own weight) I would look to save weight in other areas. Areas that didn't have me thinking about a cabin fire in flight. Just my two cents worth...
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Re: Battery Location, "Master Switchs" and Vortex Generators

Postby jjacky » Mon Jul 17, 2017 8:12 pm

Thanks guys and yes I did mean 4 gauge rather than 14 and yep, I have the the same concerns about a lithium battery fire..I'll check out the Oddysey...Thanks!
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Re: Battery Location, "Master Switchs"mn and Vortex Generato

Postby kenryan » Mon Jul 17, 2017 8:22 pm

Check out EarthX lithium batteries. They have built in circuitry to minimize possible dangers. Everyone that I personally know who flies Experimental has gone to lithium battery. Thousands (maybe even millions) are in use in motorcycles, snowmachines, etc. There are many, many different types of lithium batteries. The type people are using in aircraft (and motorcycles, etc.) are LiFePO which are inherently safer than other types, and with EarthX there is circuitry built in (BMS) to prevent problems. Nothing is 100% safe, including lead acid batteries. Do the research and decide for yourself.

EAA Webinar on lithium batteries:
http://www.eaavideo.org/video.aspx?v=5456130349001&mkt_tok=eyJpIjoiWldNM1lqazFOVGN3TVRCaiIsInQiOiJibk4rVERxbHViSlYxSzlmSm1lVGpuWU1TbjUyUk13MnhqdjBcL2krNUZzMXQwWFFGcEZQcHdoZ2NydUZGRjJmbE5Lb3hHUEY2enJKc1ZNWlMzbFNRSVpPOThxTnZpYWZzQ1NuaFJ2cmFUbGJUKytpcjNXeDFMalM2T2MzdSs4RUQifQ%3D%3D
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Re: Battery Location, "Master Switchs"mn and Vortex Generato

Postby Winston » Mon Jul 17, 2017 9:37 pm

I have been using a Shorai battery mounted under the passenger seat for 800 hours and still no explosions or flames, but I'm keeping my fingers crossed. I think some lithium battery chemistries are more hazardous than others and the type used by Shorai and EarthX are of the more benign variety. Holding a lithium battery compared to a similiar size lead/acid is like holding an empty battery case.

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Re: Battery Location, "Master Switchs" and Vortex Generators

Postby jjacky » Tue Jul 18, 2017 10:34 am

Thanks Again Guys...I feel better about lithium batteries now. Kenryan you're right about the current demands but due to: some physical fit problem with my legs ( a Wiley Coyotie dirt bike accident) I'm using a lot of electrical stuff...trim, flaps, avionics, Autopilot (someday), 10 KW stereo ;>); and a minor obsession with keeping the weight off I'm trying to keep the electrical load to a minimum. Hey did ya'll see the Levil wind powered BOM...kinda cool..j.
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Re: Battery Location, "Master Switchs"mn and Vortex Generato

Postby FredHoffman » Wed Jul 19, 2017 10:18 am

Earthx on firewall, I did put it over the passengers feet though ! I thought if it melted the pax could move their seat back and left seat pilot landed asap. Very short run to starter from this position. No master relay in my build, using an ExpBus as a master relay with a short cable going to it that is well supported and has a thick clear plastic tube around it as extra armor. Earthx also has a nice battery holder so that's one less fabrication task.
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Re: Battery Location, "Master Switchs"mn and Vortex Generato

Postby kenryan » Wed Jul 19, 2017 11:04 am

As Bob Nuckolls (Aerolectric fame) has said hundreds of times, the first step to crafting your electrical system is to do a load analysis. Write down every piece of equipment and its current load. Then add them all up. Until you have this number, you are only guessing. Remember, loads like electric trim and flaps and radio transmission don't really count. Loads like that are intermittent, and regardless of your charging capacity, the battery will take up the slack, and the charging device will quickly replenish the battery when the intermittent load is disconnected. One other thing to think about is that the Ducati regulators don't have the greatest reputation for reliability, and they seem to fail more frequently when they are working harder. Personally I would not want to run it at max current all the time. It's important to mount the regulator in a location where it has air flowing over it. There is a huge difference in cooling depending on whether it is mounted in airflow or stagnant air. And if you need more juice there are other options. Rotax makes a 40 amp belt driven alternator and B&C makes a gear driven one that mounts to the back of the propeller gearbox. Of course the penalties are expense and weight. But you can't know whether or not you need more juice until you add up all of your loads.
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Re: Battery Location, "Master Switchs"mn and Vortex Generato

Postby jjacky » Wed Jul 19, 2017 2:39 pm

Ya Kenryan..wise words, Thanks. I've heard about the Ducati Regulator problem and therefor got an additional wad-o-heatsink to mount it on . Is any one familiar with the replacement unit from Silent Hektik? And why does Rotax use this minor part that has proven to be so troublesome.
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Re: Battery Location, "Master Switchs"mn and Vortex Generato

Postby rmullins » Sat Aug 05, 2017 12:54 pm

I put my Odyssey battery on the firewall. Easier access, shorter lighter cables, and more baggage weight capacity. Empty I am slightly forward of the front of the CG range but throw the Claw in the back and I'm back in. The downside is the plane is faster with an aft CG but we didn't buy these planes for speed anyway. I went to a lithium for a while. On my plane I don't have a master relay either, but a manual switch made for RV's to disconnect the battery for extended storage. I turned off the panel but not the master and drained the battery (all Rotax will do that unless the battery is disconnected) and ruined the battery, ....twice. Lithium won't tolerate being completely drained. The EarthX batteries have a circuit to prevent that from happening but they are quite a bit more expensive.. After the second expensive battery was ruined i decided to go back. The difference in weight between the Odyssey and lithium was a bit more than a gallon of gas. Unless you are doing STOL contests, the expense and intolerance of being drained was the deciding factors for me.

As for vortex generators, I flew my plane for 6 months before i put them on. Wow, what a difference. Dropped the stall maybe 8 mph and now it wants to mush rather than dropping off on a wing before I installed them. You DEFINITELY want to install them. Also install a strip over the flap gap, another big improvement in slow speed performance.
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