Another Newbie trying to build his own system.....

Re: Another Newbie trying to build his own system.....

I fully agree with Mike on the batteries, but for different reasons, you don't want to add new batteries to old. I'd and many, often suggest using Golf cart batteries your first time out, the have a good cost per Amp stored, and maintaining them will add to your knowledge base.

The TR3624 is a MSW(modified sine wave) inverter, so if you have pumps and things with motors you want to run, MSW inverters will shorten their life and use more energy to run them. unless you need the 3600watts, a xantrex 1800watt prosine can be had in the same neighborhood.

As to the long wire runs, put your combiner box out at the panels and only run a single pair of wire(at higher voltage) to the charge controller. Looks like the Conergy P 180M is a true 24 volt panel with a VOC of 45V I don think you can run more than 2 in a string, so 4- 72volt strings to the combiner box then a single 72v for the run to the basement.

Re: Another Newbie trying to build his own system.....

For a 48v system the battery bank came out to about 1900ah, and at 24v this came out to about 7500ah.

The 24 v should be just double the 48 v system's capacity, or about 3800 ah. That's nonetheless a huge bank, as it sounds like you've figured out.

One possibility to think about: for my battery-based system at my (grid-connected) home, I went for only 16 hours of normal operation of the intended loads on the battery bank (to no more than 25% DOD). 16 hours is the overnight time between the start and end of meaningful power production from the PV in the winter at my location. Doing this considerably reduced the battery bank size and made the whole system more economical.

However, one advantage I have is that my inverter will automatically go to grid once the battery voltage falls below a certain setpoint, e.g., if it's cloudy and the panels aren't producing enough. So my system goes quickly to grid when solar production is low. Your Xantrex inverter can't switch to grid like this, but perhaps you could set something up for your lights so that they could switch to grid if battery voltage fell (they'd have to be briefly turned off first since you'd be going from MSW to grid, but presumably that would be acceptable to your plants). Maybe you could do this manually at first if you're home enough; get a battery meter with an LBCO that you set reasonably high to keep your batteries from cycling too deeply, and that alerts you if the cut off was hit; you then go switch the power to grid. Of course, with this kind of system design you'd have less power for a prolonged outage and would have to conserve, but you'd still have meaningful production from your panels and would hardly be without juice. And it would save you a lot of money while still allowing you to do what you want.

Simply put: try to look for ways to minimize the battery bank size and complexity, especially when you have the grid available. Over the long term, they are the most expensive, fragile, and maintenance intensive components of the system, and having a huge bank when you have the grid available is mildly insane (IMO, of course).

Re: Another Newbie trying to build his own system.....

Hamfast wrote: »

Still need to figure power consumption from the CC and inverter. I'm guessing the specs call this Tare Loss. The CC is 2.5W and the Inverter is 4W. Are these figures typically assumed to be Watts/hr?

Those are steady state numbers, not quantities per hour. You could look at them as Watt-hours per hour, I guess.