Thorp Air Command - T18.net

Guys,

I was out flying on Sunday and after about 0.8 hrs, I could smell smoke and then my GPS started to act up. I noticed it seemed to be coming from my GPS unit. It's an iFly 720 with a portable lithium battery taped to the back. The power from the plane goes to charge the battery and then a wire goes from the battery output port to the GPS. The battery was so hot, I almost couldn't touch it. I peeled if off the back of the GPS and set it on a small towel I had available and headed back to the airport. I was flipping the battery frequently on the towel to prevent it from burning. Once I landed I was able to slide the canopy back and throw it out.

I have a Delco Remi 12S alternator that is putting out 14.2 volts. It turns out that the T Power, lithium battery is limited to exactly 14 volts when charging. This got me to thinking that if I would have been further away and the battery got much hotter, I would have had a situation here. I haven't been able to slide the canopy back when in flight to be able to throw it out.

I guess the alternative is to see if the voltage can be dialed down or to not have the battery charging while in the plane.

Anyway, just a heads up to others that are using these types of batteries.

Best regards,

Jim

Jim: I have the iFly 720 also ,but I do not use the battery pack in flight unless I were to lose all ships power (it is a back up only) . I power the 720 from 12 volts thru a plug in the dash . I assume you are using the battery pack that you can buy from I FLY ? Sounds like the alternator may be putting out a tad much at 14.2 ?

RB

14.2 volts is just fine for the lead acid battery in the airplane. A special charger should be used for the newer battery types like lithium or NMHi even NiCad.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Like Bruce said, 14.2v on your main buss is common & OK. Depending on the exact type of your main ship's battery, something between that & 14.6v will be optimal (for lead acid types). Just feeding a 3 or 4 cell lithium battery pack those voltages without some kind of battery management system - BMS (built into the pack, or external) is a recipe for disaster, as you found out. A 3 cell pack can be fully "stuffed" at 12.6 v., but individual cell voltage must be monitored & controlled. For something simpler & perhaps a little safer you could use a Ni-MH, or even a NiCad pack, which would be heavier, etc. Lithium batteries are a rather complex discussion, & I would recommend some serious research before even considering their use.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Yes, I was running the GPS from the portable battery and charging it with a power plug from the plane at the same time. It was the one offered by iFly. It seemed like a good idea at the time with the thought that if the plane power pooped the transition to the lithium battery would be seamless.

Jim

Jim : Might be worth a call to iFly to see what they have to say about the battery and the prolonged charging . I would be interested also . I have the battery pack and charge it at home and it does get a little warm to the touch .

RB

me too. I use the 720 as well and have thought about buying the battery pack

The new iFly 740 has a built-in Li back-up battery, and I am assuming it has a BMS to keep it properly & safely charged. I too would be interested in what they say about your experience, and also would like to know if the 740 is "safe", as I am considering one for my new project.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

John : As a side note I have the iFLY 520 that I use as a back up should my 720 poop the bed . It has the built in battery which is why I bought it for a stby GPS . During charging it does get warm to the touch on the back of the case . I do not charge it in flight , only on the ground . I have not looked at the 740 , but I assume you can hardwire it to the panel like I did the 720 ?

RB

Yes, you can power it the same way. Dimensionally it is a little thicker, but pretty much the same in height & width I believe. A lot of nice improvements - much brighter, faster processor, etc.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Jim, for what it's worth, I have a Mophie 6,000 milli-amp hour backup battery that I use on occasion for my cellphone and tablet. The instructions on that device say that it should never be charging while powering a device. Check your's as well to see if this is supported. My guess is that it isn't.

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John Twigg N12055 SN.79 Pittsburgh, PA (KFWQ)