Battery State of Charge

Thanks Dave,
That link has immensely improved my knowledge indeed on the misery of battery stage of charge.
Once again, Thank you.

Usman Kazaure

Bottom line is that you need another way to remove the load.  A VCS (voltage controlled switch) will meet your needs.  The VCS can be wired to a relay which turns off the inverter when the battery voltage reaches a specific state of discharge. (You set the voltage value).   The second setting on the VCS is the voltage at which the inverter is once again be reconnected.  I have mine set up to reconnect the inverter ONLY when the batteries are nearly fully charged.  By doing that, I am avoinding damage that would occur by chronically undercharging my battery bank.  You can find the details here: 

http://solarjohn.blogspot.com/2008/02/ive-automated-my-off-grid-pv-system.html

I hope that helps.  And, thank you Dave for the kind words.

SJ

I respect your extensive off-grid experience Thomas, but the solution you suggest requires the user to constantly monitor battery voltage.  This may be a good strategy for those with big battery banks, but not so good for those of us with smaller ones.  I work away from home, and therefore don't monitor my batteries during the day.  I also needed to avoid sleep interruptions caused by Low-Voltage-Alarms.  For me, the voltage controlled switch (VCS) not only solved these problems, it allowed me to get more energy from my system, and it reduced my electric bill.  I suspect that Usman's system is also smaller than it should be, considering his loads, and that he might benefit from the solution I've suggested. He could, of course, buy bigger batteries, but not all of us can afford to do that.     

Thanks Thomas, your posts have helped me understand some of the fine points of off-grid living.  However, my situation is much different, and I believe that is why we have different priorities where equipment is concerned.  Unlike you, I am grid-connected.  My goals are to get as much from my system as possible, reducing my carbon footprint and my electric bill, and to have a backup source of electricity to serve in the event of a grid failure. 

My VCS helps me to accomplish these goals by cutting and reconnecting the load at precise setpoints.  Before I installed the VCS, I had to disconnect and reconnect loads manually.  In doing so, I was not using my system to its full potential.  On several occasions (when I was away from home or sleeping), battery voltage dropped to unacceptable levels.  To avoid low battery conditions late at night, I found myself disconnecting loads at bedtime.  According to my calculations, I am getting about 50% more energy from my system than I did before installing the VCS.

How much PV do you have?  What do you use for refrigeration, heat, and cooling?  You must be doing a lot of things right to get by on 1600 amphours of battery capacity.

John

I'm reading the posts for sure. i do not chimed in because im still learnig from your experiences, for you as an off gridder while John as on grid person like my self.
You need to understand that i fully relyed on utility power to charge my battery. therefore, John idea for CVS is also very imfortant cos i may not available always to monitor the battery myself.

My dedicated loads are my refrigerator and a chest freezer.  I've been adding solar panels, and I've upgraded my battery bank a couple of times, as my budget permits.  I look forward to the day when I'll have enough capacity to run these loads entirely off of solar power. 

When I need to conserve, as in the case of a grid power failure, I don't run the refrigerator.  I keep the freezer going in order to protect frozen food, and I use an ice-chest for items needing refrigeration.  By doing this, I have enough capacity to run a few lights, and other household items.

I like PV because it's reliable, and requires little maintenance.  I would like to eventually eliminate my use of all fossil-fuels, but that is a long-range goal.  I've already installed a bio-fueled stove and made many energy-efficiency improvements.  Check my Gallery on this website, and my Blog for more info.  http://solarjohn.blogspot.com

John

Oh, diffidently.
Battery energy storage is a luxury and not an all together inexpensive one, especially with todays metal prices. But then, to me, electricity is a luxury that I learned to live without. During that time I learned to live without electricity, there was time to reflect on how the human race as a whole lived without electricity. For thousands of years. Time to reflect on how we, the human race (having utilized electricity for only about the past one hundred years) could now, it would seem, not live without it. Very strange from my perspective.

Obviously the entire 6.5 billion people of the planet Earth cannot live as I do. Just look at the history of the East coast of the North American continent from the time of the first settlers up to now. Much has been lost forever in the way of flora and fauna from those earlier times. Did you know that the entire east coast was once blanketed with White Pines? Some that could rival the Giant Sequoias of California. Today there are only very small patch's of what could be considered virgin White Pine forrest left anywhere on the East coast. Most are just old growth that folks believe to be virgin growth from pre-colonial times.
 Anyway, Elk was once found in vast herds nearly as large as a county all up and down the East coast in pre-colonial times. The only Elk found here today were brought in by truck and are repopulating in restricted areas.

Progress, it would seem, can be measured in many different ways. There was a bit fiction I read once. Fantasy fiction actually. In these stories were a people who had evolved to learn the "magic" of the Land. There were those that could "forge" stone to their will and those that could "forge" wood and so on, the "magic" was limitless. There were the wise ones of old that also knew that if this "magic" was used wrongly it could destroy he Land forever. So, because of this, a University of sorts was created so that as these "magics" were discovered they were kept put away and closely scrutinized for hundreds if not thousands of years before they were allowed if ever to be utilized.

One could take this and apply it to mankind and what has been happening right here on the planet Earth. The human race has, over the centuries discovered new "energies" and have utilized them with blind abandoned and with devastating results. I wanted to believe that RE was going to create a new beginning out of that, sort of Phoenix from the Ashes as it were but there is something elusive about it all now. Something about RE that reminds of the same people that would go about it all with blind abandoned, all for the sake of money, bottom line. Not all people in the RE industry mind you but enough have been corrupted by greed as to yield to the will of the usurpers and they would blind all they could to all but their truths. They are after all, promoting the use of "energy." A rather broad term, don't you think? Kind of like "magics."

Oh! In case you were wondering the stories I refer to are of Stepphen R. Donaldsons, The Chronicles of Thomas Covenant the Unbeliever. A bit reminiscent of The Lord of the Rings but far enough away as to be entertaining in its own right.