A complicated question about LiFePO4 batteries, - and switching.

Talking about backup batteries, I sometimes carry a portable USB "power bank" as a backup power source for my flight computer (Nook), in case of problems with the main glider battery, 12v-5V converter, or the associated cabling. I found one of the rare models with a real (slide) on-off switch - the far more common ones with a pushbutton seem to turn themselves off whenever the Nook isn't drawing enough current.

So, unlike the LiFePO4 batteries discussed in this thread, this is a lithium-polymer battery, a less stable chemistry, albeit a lot smaller (about 2-3AH at 5V). Is it safe enough to carry in the cockpit? Before you reflexively say "no", remember that you are (probably) carrying at least one such battery, in your cellphone. There's also one inside the Nook, and any other tablets people use in the cockpit. And inside some varios, Portable powerFlarm, who knows what else - almost anything that is rechargeable these days.

I use a cheap android phone with xcsoar, kept in the side pocket, fully charged. Powered off it can be going in a minute, and using its own GPS.
I have a mechanical Winter as vario backup. You dont get to go solo here without the ability to do a circuit and land with all instruments covered.
Losing power would little to no inconvenience.
A truly independent backup that costs less than $100.

On Friday, July 27, 2018 at 4:21:41 AM UTC-4, Charlie Quebec wrote:
I use a cheap android phone with xcsoar, kept in the side pocket, fully charged. Powered off it can be going in a minute, and using its own GPS.
I have a mechanical Winter as vario backup. You dont get to go solo here without the ability to do a circuit and land with all instruments covered.
Losing power would little to no inconvenience.
A truly independent backup that costs less than $100.

I have a mechanical variometer and a chart. They have gotten me home when needed for more than 40 years. I expect they would again albeit without a flight log.
That said the only power issue I've had was due to a very low primary battery and a backup that wasn't charged as I thought. I turned everything off except the ClearNav and got around OK.
FWIW
UH

On Friday, July 27, 2018 at 1:21:41 AM UTC-7, Charlie Quebec wrote:
I use a cheap android phone with xcsoar, kept in the side pocket, fully charged. Powered off it can be going in a minute, and using its own GPS.
I have a mechanical Winter as vario backup. You dont get to go solo here without the ability to do a circuit and land with all instruments covered.
Losing power would little to no inconvenience.
A truly independent backup that costs less than $100.

I have a LxNav S3 with the UPS battery pack, which according to specs should give me 8 hours of vario with audio should I lose ship's main bus, and all those pretty glass instruments. Coupled with a JSW, Super Class, wiz wheel it is just like my first 300 hours of xc flying before I purchased the most modern flight computer made, at the time, the B100. I also have a real sectional(s) for the area I fly, and iGlide loaded on a phone zipped into my pants on flight mode.

On Friday, July 27, 2018 at 8:24:30 AM UTC-7, Jonathan St. Cloud wrote:
On Friday, July 27, 2018 at 1:21:41 AM UTC-7, Charlie Quebec wrote:
I use a cheap android phone with xcsoar, kept in the side pocket, fully charged. Powered off it can be going in a minute, and using its own GPS.
I have a mechanical Winter as vario backup. You dont get to go solo here without the ability to do a circuit and land with all instruments covered..
Losing power would little to no inconvenience.
A truly independent backup that costs less than $100.

I have a LxNav S3 with the UPS battery pack, which according to specs should give me 8 hours of vario with audio should I lose ship's main bus, and all those pretty glass instruments. Coupled with a JSW, Super Class, wiz wheel it is just like my first 300 hours of xc flying before I purchased the most modern flight computer made, at the time, the B100. I also have a real sectional(s) for the area I fly, and iGlide loaded on a phone zipped into my pants on flight mode.

I'm using an iPhone X with iGlide as the primary tactical display. If the avionics battery and everything connected to it fries, iGlide simply switches to internal GPS, barometer and battery. It will give a warning about the charge power going out, if you miss that it is seamless enough that you may fly the rest of the day without noticing. The main thing I notice is no more Flarm targets to leech from.

On the other hand, with a well done installation the chances of the whole panel failing should be quite remote. I'v got two independent batteries with two independent supply paths to the power bus - which is the single point of failure but being a solid piece of copper fairly reliable.