Disconnecting a String on Large Solar Bank

ForeverHomestead

Thanks BB that is great.  I took my notes on a few things.  I have two strings at 1120 aH, so based on what you said, my charge amps need to be around 112 amps.  That is tough for the charger in the Radeon for sure.  but if I charge battery bank full, then disconnect a string and run the eq for 5-6 hours one day, then do the same fore the other string the next day the charger should have a better chance at getting all cells equal if I am understanding this correctly.

You are correct with the type of batteries I have.  I used the recommended charging voltages and such from the batteries but I think it is not enough.  

I have had the generator running for 5 hours now.  It is putting 4.3kw into the load

ForeverHomestead

Ok so I ran the small generator for about 11 hours today.  Checked batteries every hour...ish.  Temps got up to about 78f.  SG pretty much accross the board are at 1.025.  There were a couple that were at 1.26 - 1.265.  The water was a bit lower in those so I topped it up and am letting the generator run for 1 more hour.  I will head out after diner and check all. 

I am going to run the house on this string alone tonight, then connect the other string first thing in the am and give the whole bank a couple hours charge then disconnect the other side and do the same thing tomorrow with the 2nd string.

I know ideally the batteries should be closer to 1.27 but I think this will be a bit of a process to get them all there.  it will be a bit easier when the big generator is back up because I can only set the charger to 27 amps while on the little generator.  So max voltage reached was between 62to63 ish volts.

I will check the SG tomorrow morning on this bank and then I can give the delta.

ForeverHomestead

So my half battery bank did well overnight.  I only had one half connected all night) when I woke up this am it was as 48.1 volts.  I check the SG on a few cells and they were at 1.2  So the delta then would be 1.5 to 1.2.

So assuming I get the 2nd half to be the same, what should I have my charge voltages and times set for?  I would like to keep these in much better shape now that I am learning more and more about them.

I am doing a long EQ on the 2nd string today, will run on just that string all night then tomorrow I want to do a good charge on both together,

Looks like we may have a day of Sun on Saturday so may attempt to EQ the whole string together that day as well.

mcgivor

ForeverHomestead said:

Ok so I ran the small generator for about 11 hours today.  Checked batteries every hour...ish.  Temps got up to about 78f.  SG pretty much accross the board are at 1.025.  There were a couple that were at 1.26 - 1.265.  The water was a bit lower in those so I topped it up and am letting the generator run for 1 more hour.  I will head out after diner and check all. 

Hopefully this is a typo, a SG of 1.025 represents a completely discharged cell, the trouble having some cells at normal SG in series with others of low values is the good cells gas excessively due to over voltage, which translates into water loss.

When attempting a corrective equalization it's imperative to not cycle the battery during the process, not ideal in offgrid applications, especially during times of low solar production. The process can take weeks, because the cells are individual  2 V,  I would be inclined to connect all the lowest SG ones in series so as not to punish the good ones in the process. Should this be done and there is little to no current flowing, it is possible that recovery is not possible without more drastic measures such as water treatment, a last resort.

Having such a high capacity bank only adds to the problem of recovery, my problems with FLA were minor in comparison, I did manage to recover a dead cell but I had both the luxury of a second bank and endless sun. Having now abandoned LA entirely my focus is on LFP, however the memories linger of all the needless time spent on a bad choice, mostly made in ignorance of alternative technology which would better suit my personal situation, environmentally speaking.

Hopefully everything will work out, I do wish the best of luck to you, hopefully it was a typo and  you are in fact in a better position.than suspected.

littleharbor2

ForeverHomestead said:

Thanks BB that is great.  I took my notes on a few things.  I have two strings at 1120 aH, so based on what you said, my charge amps need to be around 112 amps.  

112 amps PER STRING. More like 224 amps for the entire bank.

ForeverHomestead

Oh yes Mcivor.  That was a typo.  Meant to be1.25... NOT 1.025