Dennis M's posts

Hi Tony,
The lower over all temperature that you work in the more efficient the system will be. You will have less heat loss and the higher the temperature the panels run at, the less efficient they are. Also you may run into problems with super heating your exchange media on good collection days. I would parallel your panels. Best of luck!
Regards,
Dennis

Usually code requires that the ground wire be as big as or bigger than the largest conductor in the system usually a #6 is what they will want to see. It also has to do with the voltage of the system. If the system exceeds 50 volts (125% of the open circuit voltage of the PV array) then the negative conductor has to be grounded. On a roof mounted system ground fault protection is required. If you post your Email address I will send you a PDF of the NEC.

Hi Thomas Allen Schmidt,
 I really enjoy your blog posts and admire the fact that you have been off grid for as long as you have. I also have a scenario where I have a subpanel that I have wired to my inverter (Xantrex SW 4024). Currently I have the outlets in my home office (Computer) my freezer, refrigerator,lights and heating system (Radiant floor with solar hot water assist) tied to the PV system. See Dennis M Gallery. I am in Wyoming so we have good sun most of the time. I think that I save more energy staying tied to the grid but I have no way of knowing for sure. I think cycling the batteries consumes more power than staying grid tied. Any feedback would be appreciated.
Regards,
Dennis

Evergreen blems perform as good as any other for a lot less.
http://sunelec.com/index.php?main_page=product_info&cPath=5&products_id=61
Regards,Dennis

Having batteries to back up your heating system and a few essentials can be very handy.
Regards,
Dennis

My Xantrex SW inverter will do what you are wanting and I am sure there are probably others. The new XW series are probably even better.

Dennis

If the DC motor is not a permanant magnet motor then they may be to the field. Usually the red and black are to the armature so the other two would be to the field.
Regards,
Dennis

My PV bank is 16 Kyocera KC158 G with a Vmp rating at 23.2 volts. That is hooked to a Xantrex SW 4024 the system is grid tied and I have 5 Rolls 4CS 17PS batteries that make up a 20 volt battery bank. I have the inverter set to maintain the batteries at 22.1 volts but I don't have a separate charge controller. I am just using the inverter.
Should I have a separate charge controller and do any of them work properly at 20 volts?
Thanks,
Dennis

Hi Keith,
Call the manufacturer and ask them, and let us know what they tell you. I had some in my garage, and when I did an equalizing charge on them they would stink up the garage to the point that it worried me. After the first time I did that I always made sure I had all of the garage doors open first.
Regards,
Dennis

Hi Steve,

Most deep cycle batteries are rated at a 20 hour draw. So... 550ah/20 hours =27.5 amps at 12 volts. To get 120 volts divide by 10 you get 2.75 amps at 120 volts for about 20 hours. That is 330 watts. The faster you draw on the batteries the less you will get. So the short answer is no it is not enough battery. To do what you are saying you would need about a 12,000 amp hour battery bank and need to be able pull 600 amps. The wire would have to be huge. You can figure this yourself 12 volts at 10 amps is 1 amp at 120 volts a 550 ah battery bank gives 10 amps at 12 volt for 55 hours and that equals 1 amp at 120 volts for 55 hours. This does not include any inefficiencies, but you get the idea.
Regards,
Dennis

Hi Keith,
The batteries do vent. The probability of them exploding is directly proportional to how badly you overcharge them. All batteries should be kept in a battery box of some sort that is vented to the outdoors. The vent should be placed at a high point as hydrogen gas is lighter than air and rises. If your batteries are in a shed just build a plywood box with a hinged lid and vent it outside with a dryer vent. It also protects your electronics from being corroded by hydrogen sulfide gas.
Regards,
Dennis

Keith,
Double check and make sure your inverter is good for 24 volts before you commit to everything else at 24 volts.
Regards,
Dennis

Keith,
I was assuming that you were going to go up to 24 volts on the battery also. I would go to a 24 volt battery bank. Just series two 12 volt batteries. This accomplishes two things. It makes the draw on the batteries half as much which will make the batteries last substantially longer and it gives you more reserve power. The point I was trying to make on the charging was to have high enough volts at load out of the panel to maintain the batteries properly. To maintain the batteries properly you should be able to do a bulk charge at 2.37 to 2.45 volts per cell or 28.9 volts to recharge the battery. When the battery is fully charged you will want to fall back to a float charge of 2.2 to 2.23 volts per cell or 26.58 volts. Then on a regular basis several times a year you will need to do an equalization charge on the batteries at 2.58 to 2.67 volts per cell or about 31.5 volts. This prevents sulfation of the batteries and makes them last much longer.
Most charge controllers have these features built in and you just program the voltages, durations and how often the charge occurs. So for a 24 volt battery bank you will want a panel that is capable of doing an equalization charge to the batteries. Check the manufacturers charging recommendations for the specific batteries that you buy. The panel that you are looking at looks like a good choice to me. The Sharp panel will give you 35.86 volts at load so you should never have any trouble getting the voltage necessary to maintain a 24 volt battery bank and you will get efficient usage of the panel.
Regard,
Dennis

Hi Keith,

I would agree that more panel or battery would be money better spent than a tracker. I had checked your inverter and saw it was good for 24 volts, thats all I was thinking you may want to do. I tried to check the volts at load of the Sharp NT 180V1 panel and I could not find what it was. I made the mistake of thinking that a 24 volt panel was a 24 volt panel. I bought Kyocera KC158G panels and they have a volt at load rating of 23.2 volts. To keep a 24 volt battery bank charged you need 27 volts. I ended up with a 20 volt battery bank. Not ideal but it works. I like your battery choice and I think you will be happier with that choice. I hope you enjoy putting this together it is a great learning experience and it is fun to do.

Dennis

If you intend to expand the system you may want to target a higher voltage on your PV system. Ultimately you will end up using much smaller wire and running less amps on the low voltage side. If I had it to do over I would target a 48 volt system.