Solar powered battery bank at tie down

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theRDWRER
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Solar powered battery bank at tie down

Post by theRDWRER »

Has anyone had any luck with such a set up/is it feasible? I was thinking it might run a battery minder and a remotely controlled preheat but have never seen one in the wild.

Edit: the numbers seem to work with a 100w panel, 100ah 12v battery, 1000w inverter. Mostly concerned about practical limitations beyond the numbers.
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Wasi_8ball
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Re: Solar powered battery bank at tie down

Post by Wasi_8ball »

Has anyone had any luck with such a set up/is it feasible? I was thinking it might run a battery minder and a remotely controlled preheat but have never seen one in the wild.

Edit: the numbers seem to work with a 100w panel, 100ah 12v battery, 1000w inverter. Mostly concerned about practical limitations beyond the numbers.

We make products with SLA batteries, solar panels, inverters and chargers. Here are my thoughts:
100W is a powerful panel so use a solar controller to prevent overcharging and over voltage of the lead acid battery which can damage it.
On the other end, undercharge for extended periods can permanently damage the SLA battery so monitor the voltage of the battery (disconnected voltage open circuit voltage) to make sure it is not dropping too low.
Dust on solar panel can reduce the efficiency so it may need weekly monitoring.
You can connect a voltage logger pen to the battery terminals to capture what happens over several for days. We use the EL-USB-3 and it works well.
Since the inverter+maintainer is always loading the battery down you want to watch the voltage curve to make sure it is not dipping below 10-10.5V which is usually bottom cutoff for the inverter.
Make sure the 1000W inverter is 1000W continuous and the heater is less than 1000W. Heating elements are some of the most inefficient use of battery+inverter power packs so it may not run for too long.
Lead acid (or SLA) battery technology cheaper and robust but old, prone to discharge damage and cannot discharge fully without risking damage.
Li-Ion is the way to go but it is more expensive.
What you are looking for is called a "solar generator" and is available already built in SLA or Li-Ion versions. Be very careful to buy only units with UL certified batteries. There is a lot of dangerous cheap crap out there.
I hope this helps.
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rwtucker
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Re: Solar powered battery bank at tie down

Post by rwtucker »

Wasi,

Interesting ideas. A question: wouldn't a 100W solar array be too large for the interior of the DA40's glare shield?

If you were only interested in maintaining your battery, you could do that with a simple 28V solar array (two 12 volt auto panels, ~250 square inches each). These usually come with discharge protection when their voltage drops below a specified level. If not, a $1.50 diode optimized for that function is widely available. Given that we only use our Tanner's just before flight (I think it is a bad idea to leave it warming your engine more than needed for a start), you could pack a fresh motorcycle battery (ideally a sealed battery optimized for deep discharge) and a small 150W inverter. The Tannis draws about 140 watts (I believe). With a good blanket and nose plugs, I can bring my DA40 into starting temps in 30 minutes or so, sometimes less.

If you want to get a little more complicated and add desulphation to your system, you could crack your BatteryMinder open and add terminals wired to the (+) and (-) junctions of the full wave bridge that the BatteryMinder uses to produce the 28-30VDC from 117VAC. This would void your warranty for sure but you now have a desulphator that works from AC and from your solar panel and you avoid the energy losses, discharge issues, and other issues introduced by an inverter.

When I am traveling, I don't worry too much about my battery. On a few occasions when it was very cold, I packed a small 900W gas generator to run my Tannis. It is not a great solution but one that I had at hand.

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Re: Solar powered battery bank at tie down

Post by Wasi_8ball »

The original post did not say if the items were designed to be placed inside or outside. Since we place a full canopy cover on our DA40 I was describing a system placed outside. Assuming an honest world or chaining it down.
The over-discharge caution (sulfation) was for the outside battery connected to the inverter and not the aircraft battery battery.

Solar panel inside to maintain the aircraft battery: The most important component here is the expensive and critical aircraft battery. If maintained from outside we prefer to use a microprocessor controlled 3-stage charger which lowers the voltage after full charge for "float" mode. This is important to prevent battery damage by keeping it at a high voltage for long periods. This can be achieved by a good wall charger with a microprocessor that can detect the proper type of battery in the airplane (AGM, SLA, Gel etc.) but it will not be available in a direct diode system. A charge controller may be able to offer this function but should be carefully considered. This is why I would prefer a battery and inverter in the middle so a good charger can be attached to the AC port.
If a small solar generator is used for an inside system then a 40W panel might work.
The product link below has 70W and 100W range panels that can be placed inside the aircraft and shows connections to solar generators. it also shows it connected to a battery through the solar controller but I would have to confirm that the controller has microprocessor controlled 3-stage charging.
The cells used in this panel are also the newer Sunpower cells with higher efficiency. Older cells were 15% range and these new generation cells are closer to 25%

https://www.amazon.com/ACOPOWER-Foldabl ... olar+panel
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Re: Solar powered battery bank at tie down

Post by rwtucker »

Sounds like a fun project Wasi. Good luck and let us know how it works.

As for precision charging, I think you would be pleased with the BatteryMinder line. They have specific models so finely graded that they differentiate between the manufacturer's recommendations for Gill and Concorde by type. Concorde's new AGM line recommends a slightly higher float voltage and a slightly different transition algorithm than most aviation batteries and, of course, aviation batteries generally have higher float recommendations than general purpose or automotive Pb batteries. BatteryMinder has a comparable line for 12V aviation and for non-aviation 12 and 24V batteries as well. I also found them to be customer-centered. They replaced my defunct system even though it was years out of warranty and needed upgraded to the new Concorde standards. Good guys.
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Re: Solar powered battery bank at tie down

Post by gyro3816 »

I stumbled upon this today so I’m adding to this older post.
Batteryminder sells a Concorde solar-powered charger/desulfator

https://www.batteryminders.com/SCC1224- ... esulfator/
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Re: Solar powered battery bank at tie down

Post by mhoran »

As we're about to overhaul the engine I'm considering getting a preheater for the upcoming season so I don't kill a brand new engine flying through the winter months. I came across this setup for a solar powered battery relay for preheating: https://www.instructables.com/Solar-Airplane-Preheater/. Funny enough at least two other people in the comments sections are based in the NY/NJ area and have the same setup.
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Re: Solar powered battery bank at tie down

Post by Thomas »

I using a solar powered battery minder for my car in the winter holiday home. It`s on for 6 to 8 month and works perfect. Should work also for an aircraft battery with the dedicated battery minder product. (Concorde 28V)
The DA40 is on a wired battery minder in the hangar when I am using this car :)
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