Can't get my battery charged

ColoradoSolar

I have not been able to bring the SG up to full charge on my new Solar-One HUP 1375ah 48v battery bank. My lowest cell is at 1.250 and has been holding there even though my systems says it is getting to 100% full.

A little about my system:
Conext XW+6848
3 MPPT60-150 charge controllers with 12kw of panels

Here are my settings:

Boost Voltage (used for the 1st hour of absorb): 59.2

Absorb Voltage: 58.6

Absorb Time: 6hrs

Equalize Voltage: 62

Float Voltage: 54

Temperature Coefficient: -108 mV/C

End Amps: 27.5

I never get to the absorb time limit because the charge amps always go below the End Amps. For instance yesterday I started with an indicated SOC of 91%, went into bulk at about 8:15 (wasn't until about 8:30 that the panels started really producing good power), went into absorb about 9:50 and then into float about 10:05.

It seems that if the charge current goes below End Amps that the battery should be pretty well charged but that doesn't seem to be the case. What setting should I change to get the charger to stay in bulk/absorb for longer. Raise the voltages, lower the end amps, ...

Also should I get a deeper discharge before recharging? My system has been running for a week and the lowest it has gone is to 91% SOC

Thanks,
Eric

Estragon

What is the range in SGs from lowest to highest cells?

ColoradoSolar

1.270 - 1.250

Photowhit

So this is a new installed system?

Did you do a commissioning equalizing of the battery bank? You might ask if they recommend this, it's normal, though battery banks take a while to 'season' and fully form their plates, when first starting out.

Photowhit

Initial Charge Page 4 of the manual;
http://www.hupsolar.com/pdf/HUP-Installation-Manual-Users-Manual.pdf

ColoradoSolar

Yes it is a new system with brand new batteries. I did a commissioning charge but may have not charged it long enough. I went all the way through EQ but Schneider (for some reason) will only do a 1hr EQ.

While the plates are 'seasoning' would the SG remain low?

westbranch

While the plates are 'seasoning' would the SG remain low?

Possibly,  you could move the Absorb up incrementally, in 2 / 10 's of a Volt towards  the Commissioning Voltage and watch it carefully.
Did you notice vigorous gassing off when you did the first EQ?  No bubbles = no EQ.
Do you have temp compensation turned ON?

ColoradoSolar

Temp compensation is turned on and yes there was bubbling when doing EQ.

I know the only real way to tell SOC is by measuring SG but why would the charging go down to End Amps if the battery wasn't close to fully charged?

myocardia

ColoradoSolar said:

I know the only real way to tell SOC is by measuring SG but why would the charging go down to End Amps if the battery wasn't close to fully charged?

The sole purpose of equalizing any battery bank is to equalize the SG between the cells. If your SG has not equalized, then you are not finished equalizing your battery. Equalizing can take as long as 12 hours, although 2-4 hours is much more normal, no matter what any ill-informed charge controller engineer may have at one point thought. If you do not have equalized cells, reset the charge controller, and do 60 more minutes of EQing. Repeat this last step until your cells have equalized, ie they have the same (or at least very close) SGs.

edit: I forgot to answer the question. Your battery bank is fully charged. Your other cells are a tiny bit overcharged, making up for the lower SG in your lowest one or two cells. Equalizing is a controlled overcharge, forcing the lazy cells to get back to work, so to speak.

Estragon

I don't entirely agree with saying the bank is fully charged, for 2 reasons:
- a bank is never truly 100% full. We consider it full when the current drops below an arbitrary, low but non-zero value, at an arbitrary constant voltage. Holding a given voltage, current will decline on a curve approaching but never reaching zero. Raising the voltage takes current back above end-amps current, so was the battery really "full", or was the constant voltage too low?
- more importantly, anything other than a single cell will have varying states of charge between cells, which is why I asked about the range. We don't want to let low cells end up with hardened sulfate because the higher ones fooled us into thinking the bank was "full". 1.25-1.27 isn't terrible, but I'd work on getting it as close as possible, especially on a new bank.

1hr EQ sessions isn't a problem. I have mine set for 1.5hrs, which I repeat as many times as needed, over a period of days if need be. After each session I check water in better cells, and SG in weaker ones. When the weakest stop rising in SG, that ends the EQ series.

In an older bank, the weak cells might stop rising well below the SG of the stronger cells. Mine isn't that old, but I do have a few like that. I put a 6v charger on those (L16s so can't do individual cells) periodically. With a new bank though, you should be able to get them pretty close with a series of EQ sessions, and should do so.

ColoradoSolar

Thanks for everyones help.

It was cloudy yesterday so the batteries got a deeper discharge. So today I am running the generator to hit them hard with a charge. I am going to continue running EQs until I can get the SG up. Over the weekend I am going to turn off all the loads and see if I can't get all the SG higher.

@myocardia
Your edit about the battery bank being "fully" charged makes complete sense when taken as a whole.

mike95490

if you can, charge the single low cell, and spare the rest of the bank from excess charging.

was there any sign of spilled electrolyte  when you got the cells?   maybe 1 cell was "low on acid" and was made up with water, in that case, it will never recover.

ColoradoSolar

I don't have another charger that I can use on the cell. What type of charger would I need to charge one 2v cell?

It did not look like any spills when I got the batteries.

Estragon

If you have a charger that does 6v, you could do the three lowest, but that's a PITA to rewire. Has running EQs on the bank as a whole improved things?

ColoradoSolar

Running EQs have helped some. I have not checked all the cells but most of the ones I checked were 1.275-1.280. The lowest cell is still only 1.260 at the highest and it was back down to 1.255 today once I got into float. I was going to do more EQ today but it was cloudy, tomorrow is suppose to be sunny so I will see what I can do.

mcgivor

There are two excellent comments in this thread, which I believe give the information needed, @westbranch and @Estragon  said the same thing, which I have to agree with, but in different words, a battery is only fully charged according to the voltage programmed, if too low then it will be satisfied by the end amps at a given voltage. Up the voltage which  will prolong the charge, thereby delaying the end amp termination, which will in turn raise the SG to levels that are acceptable. For example setting boost charge to 60V and absorbtion to 59.2V, will over time rise the SG perhaps to perhaps 1.300 across all cells, then back off the voltage to where the systems discharge/recharge ballance is found, SG ~1.270 - 1.280 depending on manufacturers recommendations. There is in my opinion, no set figure which applies to all situations, but often the conservative approach is what leads to undercharging, with the SG readings posted, it would appear you are pretty close, the boost, or mini EQ if you like, every day , may very well be all that is needed, it will however take a few weeks, that was my experience anyway.Hope you find your ballance point, keep the updates flowing, because all will benifit from information supplied.

mcgivor

An additional point to the above, the SG will rise as water is consumed, if the SG is high and the electrolyte has dropped, add water to the appropriate level, then check again after a few days when everything is mixed, it took 9 months in my case, SG were at 1.300, adding water for the first time brought them down to 1.280, it's a dynamic situation which takes time to become confortable with.

ColoradoSolar

The SG is coming up. The lowest cell is now reading about 1.260. I am going to tweak the bulk/boost and the absorb voltages a bit higher to try and get it the rest of the way to 1.275-1.280. Once I get it balanced out I am going to reduce the voltages back down a bit and see if it stabilizes.

ColoradoSolar

Just a quick update. I checked the SG today after the batteries got to float and they were in the range of 1.265-1.270. I'm going to keep the voltage up for a while longer and see if I can't get closer to 1.280

mcgivor

Good to hear, it will probably  take a week or so due to cycling, what voltages are you using? 

ColoradoSolar

My voltages are currently:
Bulk/Boost = 61
Absorb = 59
Float = 54
EQ = 62

Unfortunately it is cloudy and snowy here today so I won't be getting a full charge. But tomorrow is suppose to be sunny so I can catch up then.

Vic

Hi ColoradoSolar,

Agree that you really need to CYCLE these new batteries.   At least down to 80-ish percent SOC  for,   at least several cycles per week.   These batteries are essentially Fork Lift type batteries,   and DO need cycling.

Have you contacted HUP Tech regarding charger settings for RE (Renewable Energy)-charged systems?  HUP  is a bit picky about their long Warranty,   so please DO make sure that you contact them about RE charging parameters.

Their  EQ procedure,   is really a Constant-Current charge approach.   On our Solar-charged systems,   this is a bit difficult to manage.

Where did you get your Temp Compensation value of -108 mV?

In  the early versions of the Xantrex  SCC 60-150,   the Ah entered as the battery Capacity  was the only way that End Amps (EA) was determined  --  it was fixed at 2% of the Capacity entered.   Perhaps with added Schneider gizmos and thingies,   you can now actually set the desired EA.

Most of this has already been mentioned ...   Good Luck,   VIc

ColoradoSolar

The temp comp is the default set in the MPPT60-150. You still can't change the 2% except by changing the battery size.

I am getting all the charge settings from the SolarOne manual except that I am raising the boost voltage up a bit while I'm getting the SG up.

As it gets colder here I will definitely be getting the SOC down a bit more overnight because my pellet stoves will be running more. And if it is still not getting low enough I will, on occasion, throw in a few more loads.

Horsefly

Vic said:

...

In the early versions of the Xantrex  SCC 60-150,   the Ah entered as the battery Capacity  was the only way that End Amps (EA) was determined  --  it was fixed at 2% of the Capacity entered.   Perhaps with added Schneider gizmos and thingies,   you can now actually set the desired EA.

Nope. On my XW-MPPT60-150 (which I assume is the newer version) it is still fixed at 2%.

Steve
(A different Solar guy in Colorado  )

Solar2

We have similar Battery banks.
They are excellent Batteries.
The first set I bought is still in service 11 years later with no noticeable back off of capacity.

An asorb time of 6 hr is too long for a 27.5 amp end point.
And in general, I would not be comfortable with the high voltages you specify. 

It takes a while for new batteries to settle out.
Generally the voltage will increase over the first year.

Things usually go well during the summer when you can bring the bat up to full charge daily.
But things seem to go to pot in winter for those of us in north climates
when the bats can go for several days at less than full charge.
Charge monitors tend to get out of sync with the bats.

How are you measuring sg?
I préfère the refractometer.
They only take a drop of electrolyte and seem to get a more consistent result.
Measured sg can be quite different depending upon where you measure.
Using a dropper with a long thin end you can reach down between the plates and usually find the sg to be different there.
Sg is the way to determine charge but the problem is to get a good, representative sg reading.
So in general do not loose any sleep over small deviations in sg, particularly with new bats. 

ColoradoSolar

I don’t think I will ever get close to 6 hours of absorb. As long as I have good sun I will get to the end amps long before the 6 hours.

I am going to reduce the voltages some once I get the SG a bit higher.

Currently I am using a hydrovolt hydrometer and it seems pretty good but I did just get a refractometer that I am going to give a try

Dave Angelini

The deeper you discharge, the end amps will tend to not be reached, and the absorb time will be the driver in this algorithm.
You will see this one day and with winter coming. It is not a bad thing to do while breaking in a new battery and a new user

ColoradoSolar

It seems like the absorb cycle should not be a timed event anyway. If the batteries have not reached the end amps then they are not done charging. I would likely run out of sunlight before I hit the time limit.

Vic

ColoradoSolar said:

It seems like the absorb cycle should not be a timed event anyway. If the batteries have not reached the end amps then they are not done charging. I would likely run out of sunlight before I hit the time limit.

EA is very sensitive to the Vabs (Absorb voltage).   Increase Vabs,   and battery charge current increases,  reduce it and charge current decreases.   SO,  when changing Vabs,  be prepared for the probable need to change EA,   and this adjustment will probably need a few days of observation to get correct.

For now,   CYCLE,   CYCLE ...   cycle those batteries.

Also  be certain to RINSE,  RINSE  ... rinse that Hydrometer three or four times with Distilled Water.  Not doing so will cause sticky residue to build up on the Hydro,  causing false readings.

Have you asked HUP for charge voltage settings for their batteries that are charged from Solar CCs?   This is important.   Good Luck,   Vic

ColoradoSolar

Unfortunately with Schneider equipment you can't change EA unless you change the setting for the size of the battery bank.

I always rinse my hydrometer, I had seen that mentioned on this forum.

Yes I have been communicating with my HUP dealer to make sure I had the settings good.

ColoradoSolar

When everyone is talking about cycling the batteries. How deep of a discharge are you talking about?