Greenhouse growing in Arizona?

[littlefrog]

Mine is at least 8 years old and I don't think is made anymore. It is a Trace 2512 I think. Actually it is on its way out, it is starting to kick out when it gets too warm in the greenhouse. Will be replacing it if I ever manage to move.

I haven't done research on the replacement yet. There are more models and more options now. It is important to determine what you are using it for (battery backup or solar power, are you tieing it to the grid or is it stand-alone... all sorts of things). And to determine your maximum load. The more watts you want to pass through the inverter, the more expensive it is. If you only need 1000W, then don't pay extra for 4000W. There are very nice ones that give a very 'clean' output if you are using them for running your expensive stereo equipment or medical devices, probably don't need anything like that for running some evaporative coolers.

One nice thing about solar panels in Arizona is that the times that you need electricity the most are the times it is the sunniest. If you use electricity primarily for cooling, and the sun is doing the heating... well... you do the math. Of course it can get cold in Arizona in the winter too, so it isn't exactly a perfect solution. Living in Michigan, I don't have the same problems, although solar can be a good solution even here. Germany is effectively the same climate (a bit warmer, I think), and they use solar extensively with good results.

[keithrs]

I was wondering if you are using 6,8, or 12v batteries?

You can get trickle chargers(which is the best way to charge deep cycle batts) for about $300-1200 depending on how many amps you need. If you need more capacity you can get solar batteries which most are 2v, or run series-parallel with 6v deep cycle batts.

[keithrs]

Clarify... By trickle charger I mean solar trickle charger.

[Ray]

Thanks Rob. I did some searching, and you're right about the choices - and price range.

I have a query in to the manufacturer of my heater on the necessity of a "pure" versus "modified" sine wave for the solid-state controller.

Keith - I would think that your choice of battery voltage would be - to some degree - based upon your inverter. Most I've seen so far are either 12V or 24V, but of course, how you have them wired will also play a role.

[littlefrog]

You can choose from almost any battery. There are a bewildering array of types and prices. The inverter will have a DC input voltage, and you need to match the voltage of the battery bank to the input. So mine was 24V in, so 4 6V golf cart batteries in series. My inverter has settings for different kinds of batteries.

For my estimated load, I decided that the 4 golf cart batteries were the way to go. It was less than $200. If I was trying to get more than a few days worth of power out of the battery bank, I would have used more batteries and wired them differently (still needs to be 24V in for my inverter). There are all sorts of websites that will give you great information on that.

[Ray]

Forgive my ignorance, but does a battery capacity (amp-hours) translate to AC current directly? For example, if I have 100 amp-hours of storage capacity in my 24V battery bank, does that invert to being able to power 20 amps of 120VAC for one hour?

[keithrs]

Wet lead/acid batt prices went though the roof for any decent battery..... One Trojan t105 is going for $160 each.... Us2200 is about $140 each. Those are the only lead/acid 6v batteries at are worth anything in my book. Costco and napa batteries are cheap but you get what you pay for. I like AGM batteries, less maintains but you need a charger for AGM batteries...... You guys are right on the inverters. I have seen them as high as 48v but most will be 12 or 24v. Efficiency is important when buying a converter. Wal-mart special will be around 50% while a high end one will be up in the 95% range. Not sure what a evapcooler will pull wattage wise, but I bet it's pretty high.

[keithrs]

Originally Posted by Ray

Forgive my ignorance, but does a battery capacity (amp-hours) translate to AC current directly? For example, if I have 100 amp-hours of storage capacity in my 24V battery bank, does that invert to being able to power 20 amps of 120VAC for one hour?

Not exactly.... Depends on how efficient your converter is as to how long you can go. No converter that I know of is 100% efficient.

[Ray]

So is my figurin' OK, if I allow for losses?

[littlefrog]

Originally Posted by keithrs

Not exactly.... Depends on how efficient your converter is as to how long you can go. No converter that I know of is 100% efficient.

And you probably don't want to completely drain your batteries, either. No anything is 100% efficient! *grin* It isn't just _a_ law, it is _the_ law. (2nd law of thermodynamics, to be precise).

20A of power is a lot... I don't think you'd need that much. Most equipment draws heavy at the beginning and then tapers off. The power required to start a fan is less than that required to run the fan. Not an electrician, but I think the amperage reported for a device represents the maximum current draw, not necessarily the operating current. That is one thing. And another thing is to decide where you are trying to go. If you want to run everything off of backup that you would run normally, you are going to spend a lot of money. If you focus on mission critical systems, much easier.

Something that I never bought but should have... A meter to figure out actual power use. Might be more than one brand, I know one called 'Kill-A-Watt'. Armed with one of these you can make some very precise calculations of demand, and then add 10 or 20% margin (or more!).