Sailplane Power Supply

Hello group,

I did a wiring overhaul in my cockpit recently. I learned a lot in the process and decided to document my research for various ways you can connect batteries to your electronics. Hopefully this will be helpful to folks like me half a year ago.

https://medium.com/taming-a-sailplan...y-479b6632fedd

For my ship I've chosen scheme I call "Commuted circuits". I must admit I was pretty amazed by elegance of the solution.

Any feedback, especially practical experience, is highly appreciated.

--
Andrey Lebedev
WU

Nice writeup and diagrams.
What I, and others, do is similar to one of yours.
Behind the panel, there is a single "common buss" for "+" and "-" that feeds all devices. Feeding that are 2 batteries, each with their own simple on/off master switch.
You then have 3 modes of operation:
-feed everything from battery 1
-feed everything from battery 2
-feed everything from both batteries at once. There is the previously stated issue regarding batteries at different states of charge, different ages, etc.

Plenty of our electronics can display battery voltage or add in a simple panel voltmeter to watch the "device side of the buss" to monitor battery/system voltage.
When voltage gets low, turn on the second battery and THEN turn off the first battery so everything remains powered.

I like to use screw type terminal strips to make it easier to add/remove devices.

These are nice since they've harder to short out.....
http://www.mouser.com/ProductDetail/...zIEaApPW8P8HAQ

These can be used with ring or fork terminals.....
http://www.mouser.com/ProductDetail/...NsEaAm_D8P8HAQ

I've concluded that this is the best solution, with one modification - each battery is connected through and ideal diode so there is no cross-charging.. Unlike Schottky diodes, which have on the order of a 0.5 volt drop at typical glider panel currents, ideal diodes have only a 0.03 volt drop up to about 10 amps.

9B

On Friday, January 27, 2017 at 12:38:59 PM UTC-8, Charlie M. (UH & 002 owner/pilot) wrote:
Nice writeup and diagrams.
What I, and others, do is similar to one of yours.
Behind the panel, there is a single "common buss" for "+" and "-" that feeds all devices. Feeding that are 2 batteries, each with their own simple on/off master switch.
You then have 3 modes of operation:
-feed everything from battery 1
-feed everything from battery 2
-feed everything from both batteries at once. There is the previously stated issue regarding batteries at different states of charge, different ages, etc.

Plenty of our electronics can display battery voltage or add in a simple panel voltmeter to watch the "device side of the buss" to monitor battery/system voltage.
When voltage gets low, turn on the second battery and THEN turn off the first battery so everything remains powered.

I like to use screw type terminal strips to make it easier to add/remove devices.

These are nice since they've harder to short out.....
http://www.mouser.com/ProductDetail/...zIEaApPW8P8HAQ

These can be used with ring or fork terminals.....
http://www.mouser.com/ProductDetail/...NsEaAm_D8P8HAQ

On Friday, January 27, 2017 at 9:58:39 PM UTC-6, Andy Blackburn wrote:
I've concluded that this is the best solution, with one modification - each battery is connected through and ideal diode so there is no cross-charging. Unlike Schottky diodes, which have on the order of a 0.5 volt drop at typical glider panel currents, ideal diodes have only a 0.03 volt drop up to about 10 amps.

9B

On Friday, January 27, 2017 at 12:38:59 PM UTC-8, Charlie M. (UH & 002 owner/pilot) wrote:
Nice writeup and diagrams.
What I, and others, do is similar to one of yours.
Behind the panel, there is a single "common buss" for "+" and "-" that feeds all devices. Feeding that are 2 batteries, each with their own simple on/off master switch.
You then have 3 modes of operation:
-feed everything from battery 1
-feed everything from battery 2
-feed everything from both batteries at once. There is the previously stated issue regarding batteries at different states of charge, different ages, etc.

Plenty of our electronics can display battery voltage or add in a simple panel voltmeter to watch the "device side of the buss" to monitor battery/system voltage.
When voltage gets low, turn on the second battery and THEN turn off the first battery so everything remains powered.

I like to use screw type terminal strips to make it easier to add/remove devices.

These are nice since they've harder to short out.....
http://www.mouser.com/ProductDetail/...zIEaApPW8P8HAQ

These can be used with ring or fork terminals.....
http://www.mouser.com/ProductDetail/...NsEaAm_D8P8HAQ

My (new to me) ClearNav has an excellent option for monitoring the battery in use. The voltage is displayed as soon as it drops below a level that can be set by the pilot. Now just switch to the secondary power source.
Herb

Charlie - Two comments on your comments.

1) These are nice since they've harder to short out.....
http://www.mouser.com/ProductDetail/...zIEaApPW8P8HAQ

OHM - When I use these I crimp on "pin" terminals rather than sticking the bare wire into each hole.

2) These can be used with ring or fork terminals.....
http://www.mouser.com/ProductDetail/...NsEaAm_D8P8HAQ

OHM - Use only ring lugs. After months of flying vibrations the screw holding the "Spade" (fork) terminals will back out slightly and the terminal will fall out.

Diodes - @9B - Yep. Watch out for those lost volts. Regular 1N4xxx series diodes commonly used are even worse than Schottky! And you can also loose volts by using too small of wire (14ga for the main run), or too small of breakers. Breakers? Yes, breakers. Stick with 5A breakers or larger as even 4A breakers loose 0.3V and 1A breakers are awful loosing 1.1V (Klixon spec max voltage drop)!! Who knew?

On Sunday, January 29, 2017 at 11:19:25 AM UTC-7, OHM Ω http://aviation.derosaweb.net wrote:
Diodes - @9B - Yep. Watch out for those lost volts. Regular 1N4xxx series diodes commonly used are even worse than Schottky! And you can also loose volts by using too small of wire (14ga for the main run), or too small of breakers. Breakers? Yes, breakers. Stick with 5A breakers or larger as even 4A breakers loose 0.3V and 1A breakers are awful loosing 1.1V (Klixon spec max voltage drop)!! Who knew?

Most new setups use Lithium batteries these days. Lithiums do a very good job of holding voltage until the bitter end. That makes the forward drop from a Schottky combiner pretty insignificant. Agree about the low amp breakers though.

I prefer to keep things simple, similar to Charlie M above. In my ship each battery has a 10 amp fuse and an on-off toggle switch. These toggle switches feed a single master on-off switch, which then feeds individual blade fuses for each instrument. Each instrument also has an on-off switch. Reliable, easy to control, and low voltage loss.

-John, Q3

Any glider Wiring Diagram should show a fuse located as close as possible to the battery. I put mine right on the battery using Automotive 5A blade style weather proof fuse holders. There is a lot of energy there, and there are a lot of bad stories out there about wiring shorts, and smoke filled cockpits when fuses were not installed right on the batteries.

I recommend using the automotive blade style fuses instead of circuit breakers. I can't imagine a situation where resetting a circuit breaker in a glider panel results in anything other than a second trip. Circuit breakers have a higher voltage drop, and are a lot less reliable than fuses.

I have always run my glider Batteries in parallel on a common 12V bus, and it's never been a problem. I always buy identical batteries at the same time, and retire them at the same time. The other wiring schemes depicted will work just fine.

SF

I believe everyone will agree to use a fuse close to/at each battery to give protection in case a wire is shorted somewhere along it's length, etc.
The OP (in his link) mentions this, but also indicated them being eliminated in his drawings to keep it simple.

As to a pin, ring terminal, fork terminal, soldering a boot at the open end can help with connectivity over time. Just don't wick solder up past the other end of the crimp to preclude making a stress point.

Wiring should also be fine stranded so it's flexible, solid wire can fatigue fail over time due to work hardening of copper with even minor bending.