Not sure what the H@*& is going on!

Rngr275

Installed 16 new Crown RE 350AH batteries last Tuesday. Set my charge controllers per the documentation. Absorb/Bulk 58.1V, Float 54V.
It says "Suggested starting or initial timer setting for the absorption phase is 2 hours per parallel string. Suggest no more than 2 parallel strings within the battery bank". So I set the absorb time to 4 hrs. The past three days have been sunny and the system went through the absorb and into float. I did a spot check of SG the day they were installed and they were fully charged (SG at 1.270-1.275). I checked them today (same cells and they are sitting low at around 1.255. So I checked all of the batteries. SG ranges from 1.265 to 1.248. I've got 4Kw of panels and looking at my Mate it says DC today was 194AH and 10.7wH in today with 127Ah and 6.4wH out and 68Ah and 4.4wH Batteries. Charge controllers are saying I got 16.9KwH in to day. I've been off grid for 9 years so I'm not a rookie but definitely no expert and I could use some help.

McD 

Photowhit

I've not used the Outback system, Wonder if it's doing the math for you saying your batteries received 10.7 kWhs and you used 6.4 kWhs Which would pretty much jive with your charge controllers saying you generated 16.9 kWhs from your array?

FWIW - I doubt I pulled 3 kWhs today during the rainy day in Missouri.

Dave Angelini

You have new batteries ! Right? You probabaly are not calibrated yet. There are 2 kinds of people in solar offgrid. Those who want solar, and BTW, those who want more. You probably have bad data from the clouds and really did not fully charge.

 It does not matter how long you have been doing this if clouds and bad data are your problem. That is, my friend the reason for excess solar offgrid!

 4 KW is a starting point with those loads! Clouds or loads can interupt charging as in screen below.  Blue voltage should be a straight line for absorb time. Or, if that is not it, you need to add abs time to get SG up to spec.  Or, your abs voltage is low.    Good Luck!

Rngr275

Update from Crown: "

Start up amperage on bulk for 700AH of Battery should be 91.0 DC Amps.

 For every 100 ah of battery the DC Amps should be 12 to 15 amp.

7 X 13 dc amps= 91.0 dc amp start up.

 If you can not get the amperage up to 91.0, you will have to increase the time on

The Bulk /Absorption phase of the charge."

 My understanding on the way my Midnight controllers work is to dump as much amperage to the batteries as possible during bulk until the Absorption Voltage is reached then hold the voltage and decrease amperage as the absorption does its thing stopping when timed out or end amps id achieved. 

So today , sunny< I watch the amperage slowly climb as the sun continues to rise, from a few amps up to about 46 amps coming in at around 10:30-11:00 this morning. AT that time the 58.1 Volts crown recommends was achieved and then absorb started and did it's thing for 4 hours. Check SG and the batteries were NOT fully charge per my initial post.

So I'm not sure what to do! Per Crown I need more amperage but I can only put in what's available and I don't know how to extend the Bulk phase to get more amperage (increase voltage?). There is no way I can put 90 amps to the battery when the sun hasn't even reached it's peak. Is there a way to stop the controller (MidNite 200 Classics) from going to absorb and wait till the amperage goes up?

I don't think I can get that amount of amperage out of my panels! How do I calculate max amperage I could expect from my panels? I have 16 255 watt solar world panels 8 feeding one controler and 8 feeding the other controller. 

Maximum power Pmax                255WP

Open circuit voltage Voc             37.8V

Maximum power point voltage Vmpp    31.4V

Short circuit current I sc     8.66A

 Maximum power point current I mpp 8.15A

48V system

Open to all suggestions.

Mark

Vic

Hi Mark,

Most battery manufacturers spec charging from the Grid  --  where Bulk,   is Constant Current.   We off-gridders simply cannot charge that way (without the genset).

Some battery manufacturers spec a Commissioning EQ (Surrette) for a new bank.

In your earlier post,  it did seem,  that 58.1 Asorb was too low.   Would suggest that you increase this,  to at least 59 V,  and see how things go.   And,  try EQing when you have the batteries as fully charged in Absorb as you can get them.   You may need to reduce the discharge,  on the night before your EQ.

Think that you have a genset,  which can help you reduce the discharge of the batts before EQ,  get a jump on Absorb,  and help during the EQ,  too.

Are the low SG batts all in one string?  Do the date codes match for all batts in both strings.

Later,   Vic

mcgivor

The array is insufficient to fully charge the bank, by rough calculation 255W ×16 × 75% ÷ 58.1V = 52.6A, the lower 46A is likely due to less than perfect alignment, this will occur only for a short window of opportunity, near noon. The bulk  of the chaging occurs during the absorption stage which coincides with the reduction of output past noon, decreasing as time progresses.

Being the array is undersized to recoup the overnight withdrawals, there options are to A: Reduce the overnight consumption B: Increase the array capacity, or C: Supplement the charging using a generator.

Increasing the absorption time and relying on end amps would reveal wether the absorption is actually completed, my assumption are that this is not the case.

As a means of confirming this theroy, I suggest charging with a generator until absorption is reached before the PV has reached its peak output then monitor what happens noting how long it takes for the current to drop to 2% of rated capacity, 14A in the case of  700Ah nominal. Bare in mind that as the afternoon progresses the array potential is diminished and the 14A represents 30% of the 46A peak output as noted.

Failure to address undercharging will manifest over time until it's impossible to recover the capacity that will be undoubtedly become lost due to sulfation. 

Noticing this in the early days of battery life is good, in that it allows remediation before failure.

Photowhit

Lots of little things others might want to expand on....

During the first 60-90 cycles the battery is still getting formed, not sure I'd worry a bunch before that...

Did you do a commissioning equalizing charge? Generally once you setup a new battery bank, you would do a commissioning equalizing charge, then read/record the SG from each cell.

Rngr275 said:
My understanding on the way my Midnight controllers work is to dump as much amperage to the batteries as possible during bulk until the Absorption Voltage is reached then hold the voltage and decrease amperage as the absorption does its thing stopping when timed out or end amps id achieved.

Well that's how all charge controllers work... Charge controller basically limit voltage. Some, like Midnite, can regulate the max current, but during bulk the current flows as much as the battery will absorb, once the battery reaches 80% or so full the voltage will rise to the absorb point and the charge controller will limit the voltage to the set absorb point.

Opinion;

I would do a commissioning equalizing. I saw at some point Crown was suggesting equalizing as often as once a week for their commercial batteries, gosh I hope they didn't do this for RE batteries! Not sure how with what you have, I'm sure you can extend the absorb time, and perhaps raise the absorb voltage, but I'd prefer staying with the recommended absorb voltage and increase the time by running a generator in the morning or just increase the time.

I would shoot for an array that 'can' provide 10-13% of the battery bank capacity, So more like a 7,000 watt array for a system that is cycled daily. While I understand Crowns comment, it will be rare, in a properly designed system to ever reach maximum delivery. A system should be setup for you to use 20-25% of capacity overnight and you should see a lot of the overnight lose returned before the array can even reach full capacity. I suspec you watching the current level you can understand this.

Ralph Day

I think you just have to increase the absorb voltage and time.Here's the equation to figure absorb time from Surrette...I'm sure the physics is the same.

.42 x Ah 20hr / charging amps capacity

For my 420ah L16's, 2.1kw pv the equation works thus:  .42 x 420 / 30amps = 5.88 hours

I've observed this time to be true after a 15 - 20% discharge overnight.  I could use more pv.

Rngr275

Thanks for all the inputs. A few points for clarification. I do have a genset so there is no issue there. I did not nor was it recommended to do a commissioning EQ. The low SG is spread out in the battery back (some in each parallel string). While I understand the 4kW of my array is undersized, I used this array for 9 years with 740Ah of Trojan L16 batteries (of course maybe that's why I lost a couple cells last spring), but I'm not getting why a larger array will help me given that the controllers are dumping all the amperage they can into the batteries during bulk until a specific voltage (currently 58.1) then go into absorb. Since my system goes into absorb before my array is even able to put out max Amperage (it hits 58.1 before 11:00 am and the amperage output is at about 46A) and finishes absorb before the sun goes down. Won't putting more amps in earlier from the expanded array just make it go to absorb earlier? And at some point during absorb the amperage goes so low that extending the absorb time doesn't help?

So today I have upped my Absorb voltage to 59.2 with a time of 4.5 hrs. after that I will fire the genset charge with that voltage until the amps go down as far as they can then do an equalize. I will spot check the SG as I go through all of this.

BTW, I have all ready started the planning to add an additional ~2.6Kw of panels on a ground mount. I have been planning this to help out in the winter but it will help now. I am planning on doing a fixed angle for winter. I only have about that much room on my current 2 Midnite classic 200's.


Thanks all
Mark

wellbuilt

Hmmmm I’m no expert for shore , my bank is430 amp hours and I use cheep GC battery’s . 

 I tried the 58volt absorb setting for a few months and it was not working out at all .
 I changed my adsorb voltage to 59.2 and 2 to 21/2 absorb time and every thing got real good .
  I do up the absorb time to 31/2 hours and will lower the voltage voltage to 59 volts so the battery charges longer thru out the day . 

In winter or when it’s cold I use 59.5 for some extra zip , I don’t get good sun in the winter .
 I’m not sure if this setting is to high but it seams to bring my lower cells SG up to the rest .
  Starting now I turn off some solar strings 1 or 2 out of 5 and this keeps me charging all day and absorbing up till late after noon . 

 This keeps all the battery’s above 12.8  

UpNorthMan

One possible item to check is if the cc voltage has been calibrated with a reliable dmm. From what I've read, many cheaper priced dmm don't read dc voltage accurately. This could also cause some charging issues.

Ed