Solar/Battery/Inverter plan

[cmreumund]

Ok, heres the plan:

My goal is to have an inverter that can run 1500w coffee maker (10 minutes only), computer, and other smaller electrical needs.

Componants: 8D battery, xantrex 1800 inverter, 120 solar panel + controller.

I can put the 8D (weight 150lbs) inside the compartment behind the hitch, this is actually under the queen bed in my 27 Safari FB SE. I do not keep anything else in there so I think the extra weight will be ok. I also do not store anything in the bedroom storage areas.

The inverter can go in the night stand next to the bed, within 4 ft of the battery but ion a separate compartment. I can run the AC wire to the galley area outlet for small appliances.

The solar can be standard mounted by Airstream dealer, but go to the new 8D instead of the A/S battery.

What input do you guys have for this set up? It is self contained. It would be completely isolated from the A/S standard electrical system.

Craig

[ArtStream]

Do yourself a favor and get a classic gas fired peculator.

While I do like the 1800 Zantrex, if you are just getting it for the electric coffee maker... with the gas model coffee maker you drop your wattage needs to 500W you can just install a few 12 V plugs and plug in a small inverter for the items you mention.

[Druupy]

With the "Coolness Factor" of 9.5 out of 10
for a dedicated solar coffee system, oh yeaaaaaa.

My quick figures are that you could brew 7 pots of coffee on a cloudy week, without damage to the system.

Battery placement sounds good, inverter location sounds good, the only question, and I assume you grind your own beans, How dark a roast?

Nicely dark brown, or more of an asphalt-ic tint of black?

[FLYNCLD]

The first thing you will want to do is get yourself a "Kill A Watt" meter. Radio Shack sells them for around $25.00. Then you will want to measure the number of AMPS each piece of equipment draws. You will then multiply this by the number of hours you will run each appliance each day. This will give you the numbers you need to determine the battery size, the panel size and the inverter size. I know it sounds complicated, but here is how it works.

Let's say your coffee maker draws around 75 amps while it's brewing, and 1 amp when it is just keeping the coffee warm (I just tested mine and that is what it does). If you figure 5 minutes to brew and then an additional 30 minutes on warm, you will need approx 6.5 amps hours per day to run that appliance. You will definitely need the meter to measure your computer. A average laptop uses only about 4-5 amps, while a desktop will pull anywhere from 10-25 amps. Same math here, once you know how many amps you are pulling, multiply it by the number of hours you will use it each day. (FYI, when you measure 120V amps, you need to multiply them by 10 to get 12V amps) Other small devices such as phone chargers run a very small load, around 1 amp, so just throw on a couple of extra amp hours per day for these and other phantom loads.

So let's assume you are using a laptop for 4 hrs a day. 5 amps x 4 hr= 20 amp hours per day. Coffee maker 6.5 amp hrs + Computer 20 amp hrs = 26.5 amp hrs per day.

OK, so now you know your load. A single 120W solar panel will give you an average of 25-30 amps per day to charge your batteries. You should never run your battery down more than 30-50%. So, if you are using a laptop, a coffee maker, and a few other small loads, the setup you are describing will do the job, although you will be running right at the edge of the panels ability to recharge the batteries. On some days or in some situations, you may not get a full recharge. If you are planning on using a desktop computer, or any other power hogs like a microwave (150 amps!) or TV, you will need much more power and storage. Once again you will have to know the exact load, and then use the calculation of 25-30 amps per panel, and never use more than 30-50% of your battery in amp hours.

Now, as to your inverter. Now you need to switch back to watts, and determine how many watts you will draw at peak power. You can usually get this from the owners manuals of the devices, but the meter can measure this as well. Based on the devices you are talking about, your wattage demand will be pretty minimal. You could probably get easily with a 300W converter and save yourself a heck of a lot of money (which I would spend on another panel and 2-6 volt batteries instead). If you don't want to wire into your AS system, there are some small portable inverter available to do this. However you may want to consider wiring into your system as it is quite easily done.

Anyway, I hope this helps. You don't have to be a rocket scientist, but it sure helps!!!

FLYNCLD

[bryanl]

The Kill-A-Watt is a good idea. It will measure watt-hours over a period of time and you can compare that to the available usable energy from your battery (about 1 kwH for an 8d) - or you can just 'ballpark' it and figure a quarter KwH per pot (1 kW for 15 minutes).

a 120 watt panel is a bit under optimum for an 8d - you should plan on 100 watts of panel for each kW max battery capacity (the 8d has about 2KwH max capacity, half of which is usable as a rule of thumb). - you might get perhaps a half KwH of energy from your panel in a day so that's good for 2 pots of coffee as a referent.

The inverter is marginal, I think, but it should handle the coffee maker. Make sure that the leads from the battery to the inverter are as short as possible, keep them matched in length, size, and type, keep them tracking together (impedance can be important with high current changes), and sized so that you don't have significant losses.

Once you brew the coffee, put it in a thermos and don't use the heating element to save on the battery.

Watch out for the "other small electrical needs" as they can add up if you aren't careful. A lot of folks seem to miss the fact that watching a DVD in the evening with some lights on will just about do in a standard 60# (group 27 or T105 sized) battery. Intermittent loads are better for the battery than continuous ones.

[cmreumund]

Thanks for the sage advice! I just ordered the gas coffee maker, I had no idea colman made such a thing.

I still plan on installing an inverter but the lighter loads will not require a larger solar panel than the 120.

CRaig

[bryanl]

I just ordered the gas coffee maker, I had no idea colman made such a thing.

Lot's of happy user reports on the forums and it isn't expensive. Biggest complaint seems to be that it is rather slow. A stove burner runs at about 1.5 kW max and the heat transfer efficiencies are not that great.

[Phoenix]

If you just want a really good cup of coffee, try a Bodum French press pot. There are several models with glass pots (not good for trailering) and one made out of some kind of plastic; but the one we have is stainless steel. The outside is polished to a mirror finish, so it looks right at home in an Airstream.

If you haven't used a French press before, you put the grinds in the bottom and pour in the hot water. After 4-5 minutes, you press the handle down, which pushes all the grinds to the bottom of the pot. Then, enjoy. Very simple, and it makes great coffee!

The stainless steel model is a little pricey, but it's well built and has lasted several camping seasons, so far. We grind our beans with a hand cranked contraption that looks like a giant pepper grinder, so no electricity required. Or, you can grind some at home to take on roadtrips. Just make sure to use a coarser grind, which works better in this type of pot. We get our whole beans at Costco, and about all of the brands taste great, but no Folgers! Starbucks, Seattle's Best and San Francisco brands will rival a cup from Starbucks, but be prepared for a few grinds in the bottom of the cup. It just puts a little grit in your craw!

Oh, roughing it in an Airstream... CAN'T WAIT!

[hampstead38]

If memory serves, epicureans seem to think the French press is the best way to brew coffee because it doesn't filter out the essential oils. It also does not continue to heat the coffee which can cause bitterness and acidity (as those of us who drank late night Navy coffee can attest).

[anami]

Originally Posted by FLYNCLD

The first thing you will want to do is get yourself a "Kill A Watt" meter. Radio Shack sells them for around $25.00. Then you

FLYNCLD

Just a note about this comment. Radioshack stores haven't sold kill a watts in years. When i was managing a RS (up until about 3-4 months ago) people would come in insisting we had to have these because one site or another or a forum said we did, we didn't. However, Radioshack.com still carries them as well as new egg and a couple other sites but no RS store has them. Hope this saves someone a trip or a little frustration

[FLYNCLD]

Originally Posted by anami

Just a note about this comment. Radioshack stores haven't sold kill a watts in years. When i was managing a RS (up until about 3-4 months ago) people would come in insisting we had to have these because one site or another or a forum said we did, we didn't. However, Radioshack.com still carries them as well as new egg and a couple other sites but no RS store has them. Hope this saves someone a trip or a little frustration

You are correct. The stores do not stock them, but I was able to order one through the store and they had it there in a couple of days without the shipping I would have paid online! Very good service.