12 or 24 volt sytem help please

Re: 12 or 24 volt sytem help please

DaveHaze wrote: »

Hi, what are the benefits of a 24volt system compared to 12volt? I realize there is less current drawn in a 24volt system allowing reduced wire size but does the reduced current draw also equate to longer battery capacity?

Not in and of itself. 2kwhr of battery storage is still 2kwhr.

However it will tend to reduce losses overall - and that will lead to longer battery runtimes.

I'm looking at building an off grid system that would be able to power a 37 inch lcd tv rated at 180 watts along with a dvd player, a desktop computer with satellite internet eqpt. and a small indoor dc water pump and a dc freezer (SunDanzer) that draws 40-80 watts and a small microwave, I think you can get them dc powered also.
Could I get by with a 1800 watt inverter?

Get a kill-a-watt meter and measure the microwave. They are typically around 1000 watts. If your loads are together less than 1800 watts then you're good.

Inverter? I'm leaning towards a Xantrex Prosine 1800.

I've used one and it worked well for me. Go with 24 volts unless you have a good reason not to (like 12V appliances you want to run.)

Batteries? This is really hard for me to choose. Flooded, Gel, AGM. Cost/benefit!

Flooded - cheaper. AGM - longer lasting, easier to keep indoors, less tolerant of abuse.

Re: 12 or 24 volt sytem help please

Cariboocoot wrote: »

A Prosine 1800 is a 12 Volt inverter, and perfectly capable of running the equipment you list. But depending on the total Watt hours you need to have on hand a 24 Volt system may make more sense. It usually does, btw.

Prosine can be 12 or 24 volt, Mine is 24 volt. ...adding to the confusion there is a Prowatt 2000, also a 1800 watt inverter though called a 2000( I think, only made in a 12 volt version) which is made by the same parent company, Xantrex/Schnieder. It is very inexpensive starting around $350, Prosine 1800 likely start around $1000-1200, come in 12 and 24 volt models and assorted outputs as well.

Re: 12 or 24 volt sytem help please

DaveHaze wrote: »

Not sure what the daily watts will be, my best estimate is 3680 watts.

I think (hope) you mean 3680 wattHours. I think you should ditch the DC only idea. Modern sine wave inverters are pretty efficient. You can buy one that includes a high quality battery charger and a transfer switch (for the generator input). DC wiring is inefficient and DC switches are hard to find and expensive. AC appliances are more efficient than ever and are much less expensive than comparable DC appliances. The money you save on an AC freezer will buy enough panels to more than make up the lesser efficiency (if it is less efficient) of the AC freezer.

DaveHaze wrote: »

Can the battery bank, charge controller and solar panels needed be determined from this?

Yes! By understanding your loads you are way ahead of most new forum participants. (btw, welcome to the forum). One more thing we need to know is your location so we can determine your solar insolation.

After determining your loads, the next step is to decide on battery voltage and capacity. That can be a difficult decision. The rest is easy... just buy enough panels and electronics to keep your batteries happy. Living off grid is all about keeping your batteries happy.

If your daily load is 3700 watthours, you want a battery with a capacity of about 10-15 kilowatthours. You never want to discharge your batteries below 50% SOC (state of charge), and it is much better to cycle them on a regular basis to about 80% SOC.

At 24 volts you would want a battery capacity of 400 - 600 amphours. Now which battery? The most important thing is to have just one series string of batteries. There are a number of choices. My personal preference (others will differ) is to use cheap mass produced batteries. That means golf cart batteries or L16 batteries. These batteries are 6 volt and you would need 4 in series. Unfortunately, to get the capacity you need, you would need 8 of these batteries (two parallel strings). Something to consider is going with a 48 volt system. Then you could have those same 8 cheap batteries in series. Of course you could stick with 24 volts and use higher capacity, more expensive batteries. One advantage of 24 volts (over 48 volts) is that you have only 12 (rather than 24) pools of sulfuric acid to maintain.

Anyway, the ball's in your court now... since you know your loads its time to pick your battery. Then we can talk about balance of system.

--vtMaps

Re: 12 or 24 volt sytem help please

Something else to consider... at 8 - L16 Your spending a pretty good chunk of change, and you might go back to a 24V forklift battery (I paid @$2550 delievered for a 24V 800Ah battery), there are reports of forklift batteries lasting as long as 20 years. L16's would average 5-7 maybe 7-10 for Trojans.

...but, for your first setup, I might well go with 4 L16 or 8 smaller golf cart sized batteries(In a 48 volt configuration) as the first time out often people misjudge usage or configuration of their system, or don't pay enough attention to their system(or understand what is happening) and end up killing off the batteries....