[Warning this is a long read but it is fun if you like these sort of projects. I am listing my plans in detail before the questions, skip to the bottom if you just want to see them. And please use constructive advice and don't rant about how wrong everything is.. its just a geek project I wanted to do ]
STORY
So my company moved buildings and the new building is LEED certified so they outlawed personal electronics including coffee makers. Problem is, what they do serve in the break rooms is really crappy. It's free I know.. but it's also terrible.
Soooo I built a solar powered coffee maker on some basic numbers and through testing it I have a few <ahem> challenges . It's been about 15 years since I worked with power conversion and circuits like this so I'm novice but rusty.
PLANNING
Ok here is what I have.
I like the Keurig systems.. the coffee selection is awesome and the brew consistent. Plus one cup at a time would save on over all power and Ah needed. (for those concerned about recycling k-cups, I found a way to recycle.)
So I got the Keurig B140 k-cup
http://www.keurig.com/brewers/b140
I saw that it was rated at 700w.
The time it takes to brew 10 cups [not all for me ] came out to around 30 minutes a day (I'm just assuming constant 700w but it is not 100% of the time)
So I think that would be 70 watt hours needed for 10 cups so I purchased a 10watt solar panel which could charge 14 watt hours per hour at 100% or 7 watt hours per hour at 50%.
http://www.amazon.com/Solar-Battery-Charger-Charge-Controller/dp/B006RE2KL0
Ok for the inverter I saw that they have a .5amp constant draw with a percentage of efficiency with power inversion. 12*.5 = 6 watt draw (I have it switched so not to constantly drain) so to add all that up for the total watts 6 watts + (700 watt load / 0.85 inverter efficiency) = 830.5 watts total
830.5watts / 12 volts = 69.2 amps draw from the battery.
69.2 amps * .5 hrs = 34.6 Ah / 10 cups of coffee = 3.46 Ah per cup. So I figured I could get by with these.
http://www.amazon.com/gp/product/B001TE0IMG/ref=oh_details_o03_s00_i01
http://www.amazon.com/gp/product/B006LO7LV0/ref=oh_details_o01_s00_i00
CHALLENGES
1. The battery will be fully charged and show about 15 volts 14.5 rested. I start the coffee maker and the heating element turns on. The inverter and fan kick on and drop the voltage to about 12.5 and the fault light on the inverter turns on and the unit resets cutting power to the coffee maker. Click click click click.. that sort of thing.
2. The sun that I get at the window is indirect and it stays between 11 - 15.5 volts throughout the day.
3. I think that although I was going for 10 cups with my specs, I would be lucky to get 3 cups with some of the testing I've done over the week.
QUESTIONS
1. How bad off was I?
2. I think I am going to get another panel and battery.Would another panel wired in series to help keep the voltage up and wire the controller it comes with a good idea? Or would I want to look to get more wattage in a paralell configuration for the duration of the day it is above 12 volts.
3. Would getting another battery help sustain constant load to the inverter while the heating element is on so that it wouldn't fault? One other thing is the 8 gauge wire I have on it gets pretty hot, not melting but hot to the touch.
4. I have considered a super capacitor as probably my best option to get the inverter working but still not sure I could get all the cups of coffee I want throughout the day.
Let me know if there are any details I left out or could be helpful. Any insight is greatly appreciated!!
STORY
So my company moved buildings and the new building is LEED certified so they outlawed personal electronics including coffee makers. Problem is, what they do serve in the break rooms is really crappy. It's free I know.. but it's also terrible.
Soooo I built a solar powered coffee maker on some basic numbers and through testing it I have a few <ahem> challenges . It's been about 15 years since I worked with power conversion and circuits like this so I'm novice but rusty.
PLANNING
Ok here is what I have.
I like the Keurig systems.. the coffee selection is awesome and the brew consistent. Plus one cup at a time would save on over all power and Ah needed. (for those concerned about recycling k-cups, I found a way to recycle.)
So I got the Keurig B140 k-cup
http://www.keurig.com/brewers/b140
I saw that it was rated at 700w.
The time it takes to brew 10 cups [not all for me ] came out to around 30 minutes a day (I'm just assuming constant 700w but it is not 100% of the time)
So I think that would be 70 watt hours needed for 10 cups so I purchased a 10watt solar panel which could charge 14 watt hours per hour at 100% or 7 watt hours per hour at 50%.
http://www.amazon.com/Solar-Battery-Charger-Charge-Controller/dp/B006RE2KL0
Ok for the inverter I saw that they have a .5amp constant draw with a percentage of efficiency with power inversion. 12*.5 = 6 watt draw (I have it switched so not to constantly drain) so to add all that up for the total watts 6 watts + (700 watt load / 0.85 inverter efficiency) = 830.5 watts total
830.5watts / 12 volts = 69.2 amps draw from the battery.
69.2 amps * .5 hrs = 34.6 Ah / 10 cups of coffee = 3.46 Ah per cup. So I figured I could get by with these.
http://www.amazon.com/gp/product/B001TE0IMG/ref=oh_details_o03_s00_i01
http://www.amazon.com/gp/product/B006LO7LV0/ref=oh_details_o01_s00_i00
CHALLENGES
1. The battery will be fully charged and show about 15 volts 14.5 rested. I start the coffee maker and the heating element turns on. The inverter and fan kick on and drop the voltage to about 12.5 and the fault light on the inverter turns on and the unit resets cutting power to the coffee maker. Click click click click.. that sort of thing.
2. The sun that I get at the window is indirect and it stays between 11 - 15.5 volts throughout the day.
3. I think that although I was going for 10 cups with my specs, I would be lucky to get 3 cups with some of the testing I've done over the week.
QUESTIONS
1. How bad off was I?
2. I think I am going to get another panel and battery.Would another panel wired in series to help keep the voltage up and wire the controller it comes with a good idea? Or would I want to look to get more wattage in a paralell configuration for the duration of the day it is above 12 volts.
3. Would getting another battery help sustain constant load to the inverter while the heating element is on so that it wouldn't fault? One other thing is the 8 gauge wire I have on it gets pretty hot, not melting but hot to the touch.
4. I have considered a super capacitor as probably my best option to get the inverter working but still not sure I could get all the cups of coffee I want throughout the day.
Let me know if there are any details I left out or could be helpful. Any insight is greatly appreciated!!