Recommendations for an intermediate type solar book?

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)?

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,

GC2s are a much better learning battery.

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