Disconnecting a String on Large Solar Bank
ForeverHomestead
Registered Users Posts: 27 ✭✭
I have a 48 volt battery bank consisting of two strings of 24 S-1450 batteries. I fear a few of my batteries have been damaged. I am wondering about taking one of the strings offline to do a full change on the good string to see if the string with possible damage is dragging my other string down.
What is involved is taking 24 S-1450 off my system for a few days? Just want to ensure I dont miss anything.
I am assuming I need to adjuct the total Ah that my mate 3 sees
Do my Charge controllers stay the same if removing a parallel string. still 48 volts.
What is involved is taking 24 S-1450 off my system for a few days? Just want to ensure I dont miss anything.
I am assuming I need to adjuct the total Ah that my mate 3 sees
Do my Charge controllers stay the same if removing a parallel string. still 48 volts.
My system:
Radion 8000w Inverter, Load Center, Mate3, FNDC, Hub 10, Midnight Classic Controller x3, 10 Kw Array, Generac Ecogen, PV Combiner Box x2, Midnight Solar Birdhouse
Comments
As for your solar, it depends on how your configured to go to float? If it is end amps then divide by 2. Not a big deal for this problem though.
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I am having some major issues right now as my backup generator died and man using a smaller 6500 watt inverter until the parts come in for my 15kwh ecogen. I decided today to disconnect one string and get to 100 percent and then do a 2-3 hr eco. then I can do the same to the other side.
The batteries are only about 4 years old, I would be surprised if any are bad. Just hard to get to max voltage with either solar or generator alone.
I did not know much about off grid living when I installed the system. I feel like the company that designed it undersized the solar part of things and oversized the battery bank. I worry that the batteries are being damaged and at over 15 thousand in batteries it really turns my stomach.
Why is it hard to get 62VDC or more out of the Radian inv/chg with a genset?
You should be able to correct the Surrettes. Post your SG here! You have to do this now! 4 years can be the point where you fix them or loose them!
You are the boss offgrid, if you use more energy than the design allows, it really is on you to cut back the usage or add more charge capacity. And that is also where the saying, "two kinds of people, those who want solar, and those who want more".
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https://www.solar-electric.com/basw1300amp.html
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I can get 62V on the batteries. My batteries say to eq around 64VDC my bulk is around 60VDC
Tonight with one string 1 did a 2 hour eq. between 64-65 VDC The eq does not show as complete, but that is because it needs 2 hours at 65.
Our house uses about approx 17ah an hour overnight. so 136ah a night. However lately I am walking up to batteries at around 47-48 volt. with 48 s-1459 I should be much higher than that in the am.
Oh and I hear you with "two kinds of people, those who want solar, and those who want more". I am currently working on adding a a water turbine in the spring. I think I should be able to do 400 watt continuous from the stream running through our property.
I appreciate your help. I have been losing allot of sleep over this lately. Winter off grid living is not my favorite.
Always use make before break for this!!!
Most people are afraid of over charge and it really is the opposite. At this point be very liberal with time and voltage!!!!
Since you did not install this, I need to know you are safe with this? 4/0 is really what I would use for everything here!!!
Where is home?
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...comes into play. Basic suggestion is to monitor your Specific Gravity (SG) every hour until it no longer increase over 2-3 hours. This will likely require you to run your generator in the morning to give you a long enough period to get a meaningful equalizing done.
I know I have a tiny system compared to some homes, but dang that's a large load! Almost a kWh each hour! I guess a furnace fan is the big 'sucker of electric'? Might look at your loads. If you are using an electric blanket, switching to an electric mattress heater might save you 2/3rds the electric.
You are in Great hands with Dave, I just wanted to interject about differences in 'maintenance equalizing' vs 'corrective equalizing' I think Rolls Surrette is one of the few battery manufacturers which makes this distinction in their manuals.
I never saw what the SG was after your EQ? Never saw what your SG is after a normal charge. I would be guessing without the data.
For this, here, just an average or some pilot cells that show what the big picture is. What is the delta in SG?
Mark the bad cells with a number so you can just use their data. Makes it alot easier.
Not many better than Photowhit at the offgrid life! He works tirelessly and I do bill often but no worries here. I am sure you could find me and make this private.
Your usage is high for offgrid but you do have the battery for it. I think you just have had too low of absorb time and guessing not enough corrective EQ. This part now could take some time. In Summer one would just set float for EQ voltage and do this every day until it got into the normal range.
Can you see the system and look at charge and EQ like my Schneider screen below? Alot of times, big systems are pulling down the setpoints! You can see the clouds doing that in the second screen.
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I will list my setpoints later today, I have them written on a white board in the power house. Think something like Float at 54, bulk at 60 and eq at 64.9
I did read http://www.reps.fi/datasheetsandmanuals/rolls-battery-user-manual_reps.pdf yesterday and saw that a 4-6 hour eq may be needed. My generator is supposed to be fixed tomorrow, it has been out of commission for 3 weeks and I have been relying on my backup.
As far as loads, there is not allot. fridge, freezer, well pump occasionally if RO water being made. In the winter, there is a fish tank heater. The downfall for sure. I have come up with a way to hook that to a heat exchanger to use the wood furnace, but have not implemented it yet. Our heat is radiant, so the draw there is pumps, but that it not large. We do have a barn and pump house running but not much draw there.
I think I can share my opticsre login with you if you think that may help you understand better. usually between .7 and .8 overnight. Not sure what would make the loads the high. The system was designed around 21 KW a day if I remember correctly
FWIW, Vic
I have my charge controllers set to absorb time of 3 hours and currently have eq set to 2 hours.
two strings 1124ah for a total of 2248 aH
The quote was from the Linked switch. And this max VDC rating is about the highest that one will find for that switching style.
IMO, Vic
If this is for long term and not just an aid to get you though the EQ corrective, you can use 2 of the Midnite or Outback 250amp breakers that your radian has. They sell them in the store here also. Mount them in a metal box.
No time for me today maybe someone can find something out there. Or, just do a manual cable disconnect without load. Good Luck!
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|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Cut me slack me if I missed that. I do not remember if you ever stated that. The reason I showed the graphs was to hit home that you need to make sure the setpoints are holding and not being pulled down by loads or clouds.
This may sound easy to many here, but a bank this size really needs more than a single radian can output with it's 125 adc charger.
Also, hitting 48.0 vdc in the am is not so bad. Batteries like to be cycled and you really are not at 50% Soc, unless there is no load at 48vdc for hours. Probably higher Soc than you think. Cheers and good luck !
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So my generator was not repaired today. Turns out, the motor blowing was not the problem. The main rotor bolt came loose and snapped, causing the rotor to bash around inside the stator and eventually jam causing the motor to stop dead, blowing through the side.... More parts being ordered from Generac. So another week waiting on parts.
By Delta SG do you just mean my SG reading? I will do this once my generator is rebuilt, or the sun comes out.
I think I would go to Costco and buy a 9KW genset. Pretty expensive batteries that may be savable.
Some blended canadian whiskey and I will join you! Cheers
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So by Delta do you mean the high and low of the same battery or the sg of the highest cell and the lowest cell?
I noticed that the battery had better storage that night. Usually the batteries were 47.4 or so in the am, but the next morning they were 48.2. Much better. I will get the delta this week.
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On the bright side it makes for good content on the youtube channel. lol
Since they are all connected together (series/parallel), you are looking for all cells (and cells or batteries) voltages/SG/Amp charging/amp discharging to be the "same".
Same is "relative"... More or less, when the SG between cells is something like 0.015 to 0.030 difference between the high and low cells--Then it is time to EQ... Raising charging voltage to something in the range of 15.0 to 16.x volts (12 volts--or 30-32 volts for 24 volt bank, 60-64 volts for 48 volt bank) and looking for charging current in the range of 5% of AH capacity (i.e., 200 AH * 5% = 10 amps)--(or at least >~2.5% rate of charge).
You want all the cells and all the cell/battery voltages to be pretty much "in sync" with each other. If you see one (or several) cells/batteries that are very high or very low relative to the rest--Then is time to investigate (may need EQ, may need terminals cleaned, may be failing cells/batteries, etc.).
Note: Cells are individual 2 Volt (lead acid chemistry) cells. A battery is composed of multiple cells (3x cells in series is 12 volts, 6 cells in series is 12 volts, etc.). So when we talk about batteries--It could be multi-cell batteries (i.e., 6 volt battery with 3x 2 volt cells in series)--Or whatever.
Older batteries (and many "forklift" batteries), you can measure the voltage of each cell... However, modern batteries, you cannot get at the per cell connections and can only measure the overall battery voltage (i.e., 6 volts, 12 volts, etc.). The "sealed" top of batteries does help to reduce terminal corrosion and such.
You can occasionally find some batteries with different configurations... For example there are a few 2 volt batteries that actually have 3x 2 volt cells in parallel. And a few batteries that have 3 cell caps--But it is actually one big interconnected 2 volt cell. Both of these types are not real common--But they are out there (Trojan and other brands?).
Note that elevated EQ charging is only done for Flooded Cell Lead Acid Batteries (elevated charging voltage)....
EQ for AGM/Sealed Lead Acid batteries is (typically) holding the Absorb voltage (i.e., something like 14.4 volts for AGM) for >6-8 hours or so... AGM batteries can overheat the catalysts and/or vent Hydrogen+Oxygen (loss of water) if over charged/High EQ voltage...
Note: Always refer back to the manufacturer's manual. For example, Concorde AGM batteries recommend a very high corrective EQ voltage if trying to recover capacity for older/mistreated AGM batteries.
Li Ion--Never EQ (battery cell balancing is achieved by charging/discharging individual cells--Many times with a BMS--Battery Management System). In general, EQing Li Ion cells will ruin them (at the very least).
Sorry for the long post--I think this is your battery (really a single 2 volt cell)?
https://www.rollsbattery.com/wp-content/uploads/batteries/S-1450.pdf
So, in each case, your cell voltage will be in the range of 2.10 to 1.75 volts (basically resting voltage from "full to dead").
And if you are charging at 62 volts (for example), each cell should be around 62v/24 series cells = ~2.583 volts (under full absorb/possibly EQ charging). More or less, ideally the differences between cells should be around 0.030 volts maximum (over that, check specific gravity and possibly needing EQ).
-Bill