Recommendations for an intermediate type solar book?

softdown

Read four introductory type solar books over the winter.Such as the Solar Electricity Handbook and Photovoltaic Design and Installation for Dummies. Had a simply 12 volt system for four years prior the current 48. My knowledge feels inadequate for the constant challenges and questions that pop up.

For example....when batteries reach a deep discharge overnight....say to 49 volts. Why does it only do Bulk for about an hour...then Absorb....then Float in spite of the fact that the batteries are still deeply discharged. My system still says the batteries are discharging and I am in Float mode. Shouldn't it still be in Bulk?

I put a lot of room temp food....about 70 pounds... in an empty freezer today. The system is working very hard for that reason.

I am preparing to fire up the generator. It is a very sunny day. The panels should handle this.

I keep chickening out and putting my Outback system back in Default mode. Yes....I am being a chicken. Afraid I've pushed some wrong numbers when I DIY. Only been using it for a few months...

Today I have had 87 Ah out and 27 Ah in....

softdown

Currently 109 Ah out....35 Ah in. Batteries continue to discharge under very sunny conditions. Seems to only be able to do an ~ 1 hour bulk once a day.

I did buy the communications hub. It could have been hacked? Well....I get hacked a lot. Long story you do not want to hear.

softdown

I'm confused by the readings. Both banks read 54.6 volts....though they are receiving 54.8 volts at a low rate. Yet the system says my batteries are low....are discharging...and their state of charge is currently at 54%. The SOC has been steadily dropping throughout the day.

What makes today different? The freezer has run non-stop since about 9am....8 1/2 hours ago. Uses 200 watts. Also used small electric chainsaw for about 20 minutes.

Why didn't my system simply Bulk until the batteries were at 99%? That is what normally happens.

I can't find a book that focuses on how bulk...absorb....float are supposed to work. I thought I knew how they worked. They didn't work today....a very sunny day.

Desert Rat

What is your current battery setup? Age of batteries? Have you checked SG? What are your Absorption and Float setpoints?

softdown

Two strings of four 12 volt 8Ds...approx. 170 Ah/battery @ 12 volts. So....two 48 volt strings. Age....average is about a year. Just replaced a bad one after finding a SG of 1.00...water. Currently everything is at default levels on the Outback FM80. Float voltage is ~54.4. Absorb voltage is ~57.6.

Ahha....manual says absorb time is 1 hour. Float time is 1 hour. Seems that bulk takes an hour as well.

Perhaps the default settings are just horrible?

My batteries were good last month according to my solar guru. He looks at the history on the CC/inverter.

Every time I mess with my batteries....about once/week...I get holes in my clothes. Every time.

softdown

Fired up the genset for one hour of charging. I'll see what that does.

EDIT: System is charging at 2 amps with a 6000 watt genset. So.....about nothing. Seems the batteries are ok.....just the charge controllers readings are weird. Still says my batteries are low....now at 53% state of charge.

softdown

Voltage down to 51 volts. Disconnected freezer. I'll check SG in the morning I think. Could be...yet another bad battery.

Then again...steady drain of over 300 watts all day. We'll see. Voltage will bounce back a bit with much lower power drain.

BB.

softdown wrote: »

Fired up the genset for one hour of charging. I'll see what that does.

EDIT: System is charging at 2 amps with a 6000 watt genset. So.....about nothing. Seems the batteries are ok.....just the charge controllers readings are weird. Still says my batteries are low....now at 53% state of charge.

What voltage at the battery bank terminals during the 2 amp charge rate? 58 volts would be (my guess) the minimum I would want to see with Flooded Cell batteries--Held for 2-4 hours.

What type/brand of batteries (flooded cell, agm, AH/Voltage rating of bank)?

If your hydrometer is showing low specific gravity--Going to 60-62 volts (perhaps in 0.5 volt increments) would be worth trying. Some Rolls/Surrette see to take those much higher charging voltages (watch gassing, battery temperature--Don't overheat the batteries as they finish charging--Basically enter equalization).

-Bill

softdown

BB....the 8Ds are FLA. My guess on the Ah is close to 170 at 12 volts. They are not ideal batteries. That is why I continue to look.

Voltage was 49.5 this morning after the usual night loads.....fridge etc.

softdown

Now I don't know what to think. The CC switched to Absorb at 9:30am...MST. The battery SOC was "40%...critically low".

At 10:00am, I was preparing to switch on the genset and do an Equalization at 60 volts. Looked at the CC first:
Float mode....batteries at 99%....fully charged.

I do have low SG in some cells. Equalization concerns me because I killed a couple batteries a few months ago with an overly aggressive charge rate from the genset. Was 12 volt at the time. As I recall....I charged at ~15.2 volts for ~2.5 hours....at ~50 amps....charging four 8Ds. The two batteries connected directly to the charger were killed. The interior batteries were mildly injured. Partially protected because the interconnects were ~#4 AWG wire. All of these numbers are my approximations of the deadly event.

zoneblue

Sounds like you are in the deep end. The major cause of batteries going to absorb and float early is battery failure. Basically the internal resistance rises as the batterys deteriate, and the extra cell reistance raises the terminal voltage, telling your chargers to slow down. Which is kind of the opposite of whats needed.

But i dont think you should be relying on the controllers default settings. Get the right voltage setpoints from the battery manufacturer, and get the absorb time from an "average discharge, charge cycle", monitoring it with a hydrometer.

You have if i get this right 4 x 12v FLA batterys in series. Thus, you can check the terminal voltage of each battery, to see if you have a oddball. If they are all high, then check all the sgs. If they are low, you need to get some serious EQ on them. You dont need a generator, solar will do fine, because it doesnt need amps, just volts. If its sulphation you are dealing with and its not set in concrete, extended EQ is the only way you can reverse that.

And, you also need to find out how the batteries got this way. Have they been at low SOC for long periods? Have they acheived a proper float regularly (target SG)?

softdown

Thanks for the thoughtful reply. The big new challenge for the batteries? 1) Charging up a forklift battery. This consumes a steady 8 amps....at ~14-15 volts. Using another steady 2 amps charging up another set of batteries. Put almost 100 pounds of warm meat and bone in an empty freezer. It is for the dogs. Took a lot of energy to freeze all of that. System has been cruising after everything got properly frozen.

Vic

As zoneblue noted,  Default settings can be DEATH for Flooded batteries,  in particular.  Usually Absorb V too low,  and Absorb time often far too short.

We have asked before,  here and on that other Forum what was the manufacturer of your batteries,  recall,  that you do not know.

A real EQ,  at a reasonable Veq should be done,  when the batteries are as reasonably fully-charged as possible.  We could guess about a nominal Absorb voltage,  and probably a good EQ voltage.

For now,  would suggest Vabs of about 58.5 V or even more,  until you know more about the state of these batteries.  Usually,  the Veq would need to be above 61 V.  Both of these voltages MUST be temperature compensated.  The FM80 CC  does not compensate EQ voltage,  so you should do that manually.

Also,  you need to Limit the charge current into the batteries as the EQ voltage is approached.  Even with two strings of 8Ds,  running 50 Amps into them is probably excessive at any temperature compensated voltage much above 60 or 60.5 volts.

And,  have mentioned this before;  Trying to use voltage readings to infer SOC can be a problem,  as loads at the time,  loads in the previous few hours,  AND battery temperature all affect the accuracy of voltage verses SOC guesses.

How is it that you are determining the SOC percentages that you are noting ...  you do not have the OB FNDC with a Mate 3,  do you??

Or,  are you using another Battery monitor?  Is so,  what is it?  Do you have a Shunt in the negative lead of the battery?  Being able to read the current that the battery is accepting is a very good thing to have.  This part of a Battery Monitor (to me) is its most important function.

Your Hydrometer is the only real indicator of real SOC of each cell of your battery,  but it is not known just what is the correct SG reading for full charge,  as there is no data from the unknown battery manufacturer.   What is your personal Target SG for a fully-charged cell?

Know that you have been in a hurry to ruin some batteries,  to get that learning experience behind you,  but,  you acquired the current 8D set used,  with unknown history,  and you are denying yourself the learning experience that a good new set of batteries can provide,  where,  you have started with a known,  and what happens to the batteries is more easily diagnosed.

Also,  it is usually throwing good money after bad,  when one needs to replace individual batteries in a bank,  as customarily,  the remaining batteries do not know enough to not go bad,  soon after others have been replaced.  This is always dictated by economics,  but usually is a waste of time and money.

FWIW,   Good Luck,

softdown

The 8Ds are Energizers....by Johnson Controls. I have always known the manufacturer. I probably didn't know the Ah rating because....apparently none exists.  My CC is temperature compensated I think...there is a thermometer taped to the batteries and going to the Mate. The Mate tells me its estimated SOC....which I have found to be roughly 1/2 correct.

A trusted friend told me the 8Ds were, by far, the best buy in solar batteries. He enjoyed excellent experience with the ones he bought from Big R. He thought they performed as well as his Surrettes.

Would I buy them again? No. But I will ride them out until it no longer makes sense.

zoneblue

GC2s are a much better learning battery.

softdown

No kidding. I have bought over two tons of batteries over the past five years. All but three are still going strong.

What do these comments have to do with the search for a good intermediate solar book?

zoneblue said:

GC2s are a much better learning battery.

Vic

softdown said:

The 8Ds are Energizers....by Johnson Controls. I have always known the manufacturer. I probably didn't know the Ah rating because....apparently none exists.  My CC is temperature compensated I think...there is a thermometer taped to the batteries and going to the Mate. The Mate tells me its estimated SOC....which I have found to be roughly 1/2 correct.

A trusted friend told me the 8Ds were, by far, the best buy in solar batteries. He enjoyed excellent experience with the ones he bought from Big R. He thought they performed as well as his Surrettes.

Would I buy them again? No. But I will ride them out until it no longer makes sense.

OK soft ...

I stand corrected.   Was relying on defective memory from December '14.

BUT,  since you know the manufacturer,  and the brand,  then,  questions:

 1. Have you tried contacting the manufacturer to get the AH Capacity,  recommended Vabs,  Veq, Vfloat, Target SG for 100% SOC, temperature compensation coefficient for your chargers ??   Also,  would be good to know if these batteries are designed for cyclic use,  recommendations for EQ frequency,  and how else to know when your batteries need an EQ,  etc.

 2. Do you realize that your FM80 CC WILL temperature compensate the Absorption and Float voltages,  but will NOT compensate Veq?   This IS the case.  Place the Remote Temperature Sensor about half-way down the case of a battery in the center of the pack.

 3. What Mate model number are you using?

 The best intermediate books for answering your wonderments about things Solar,  at least initially,  are those that came with your OB equipment.  Just sit or stand in front of each piece of equipment,  and study each manual page,  while manipulating the controls on the equipment,  and then,  via the Mate.

More Later,   Vic

Vic

AND,  then,  there are all of the Links and discussions on this site that provide a lot of Intermediate/Advanced information:

http://forum.solar-electric.com/categories/solar-information-links-sources-event-announcements

Vic

softdown

This site is a fantastic source of information. Was thinking that a good book could provide more data at a faster clip. I wish that members had a designation for being a solar professional. That could impact a readers reaction to their advice...at times.

zoneblue

Soft, solar is pretty dynamic industry and given the pace of publishing, books are usually a generation behind. I wouldnt want to be following 10 year old advice in this industry. This forum contains all the knowledge youll ever need, and yes, you do need to be able to evaluate what you read, thats a given, and unavoidable. Batteries in particular are a blackbox, and hence difficult to assess their handling methodologies. The consensus is all we really have to go by. And that evolves over time. Some basic understanding of the cell chemistry may help a little there and for that can you use either "Lindens Handbook of Batteries", or  "Battery Technology Handbook", they are both good.