Battery and charge controller advise before commisioning.

[jmarc]

I recently installed a 24v off grid system with 8 L16H-AC 6v batteries. Prior to connecting the batteries, the voltage reading indicates at the batteries were about 70% SOC.  Not sure the proper steps with the batteries and charge controller. I tested the system and it works. Just want to get the battery issue situated before go live. Thanks for your help.

[Vic]

jmarc,

Do you have a Hydrometer?   This is the State Of Charge (SOC) Golf Standard.

Resting voltage can also be good,   BUT,  the measured battery voltage must be temperature compensated,  and of course,  a known-good DMM must be used.

Search for that battery model number for recommended charge parameters ...   that looks to be a Trojan model number.

Later,  back to work,  here,   Vic

[mike90045]

Fire up the gear and get the batteries charged, even if you just use defaults.   The longer the cells sit <80%, the more they sulphate.
In the AM, the sun comes up slowly, and the panels/controller start charging slowly, you won't hit the batteries with full array power all at once.
So switch the gear on tonight, and tomorrow by 9am, you should be seeing some charging going on.

[ClassicCrazy]

I agree with Mike ,
If you have the batteries manufacturers Absorb and Float setting  - turn it on and let those batteries start charging.
If you have the Whizbang you can set up the AH capacity and battery efficiency for the SOC
Then after you use them  you can see how many AH you have taken out of them at night . If you want to set up Ending Amps you will need to get an idea of what that should be from your battery manufacturer . Then you watch the SOC count up towards 100% , and watch the system amps via Whizbang ( what is actually going into batteries) . Take the specific gravity reading during this process a few times and when the SG gets to what battery manufacturer says is 100% then you see if that is at the same  system amps that would correspond with Ending amps. Once that  you confirm this a few times you can set the number into Ending Amps and let that terminate the Absorb instead of using time.

Not sure how you have your batteries wired up  but you may want to take a look at this for best battery life.
http://www.smartgauge.co.uk/batt_con.html

Larry

[Vic]

Hi jmarc,

The Trojan Data Sheet says;  Absorb voltage = about 29.7 V,  Float V = 27.0 V,  EQ V = 32.4 V.

Here is the Data Sheet:
http://www.trojanbattery.com/pdf/datasheets/L16HAC_Trojan_Data_Sheets.pdf

The Temperature Compensation should be -- 5 mV/C/Cell.   If it is available in your CC,  the EQ voltage should be Temperature Compensated (IMO).

The Absorb time needed for a full-charge will depending upon the Depth Of Discharge that the batteries experienced in the previous discharge.

The Battery Temperature Sensor (BTS) should placed,  midway down the side of a battery in the center of the battery bank.  If there are multiple BTSes,  they should all be on the same battery,  next to the any others.

Will try to see which CC you have,  from your previous Posts.

Initially,  why not set your Absorb time to 4 - 5 hours.

It is often good to do a full battery charge,  and then a Commissioning Equalize,  for about two hours.

You will want to number each battery,  and letter each cell of each battery,  ie,  1,  A - B - C.  2,  A - B - C,  etc,  with a felt-tipped pen.

Then you should really set up your Battery Logbook,  in which will want to record charge settings in the  CC,  SG readings,  Dates of EQs,  with SG readings druing/after EQ.   Amount of water consumption,  and date that Distilled Water was added,  and other observations about the battery bank,  changes to charge settings and other observations about the battery and its performance.

You will want a good Hydrometer.  My favorite is the type with a glass outer tube,  and glass float,  without colored bands  --  just the SG numbers,  if possible.

The Target SG for a fully-charged battery is 1.277.  SG readings might need to be temperature compensated,  if the electrolyte temperature varies much from the Trojan Reference Temperature of 80 F  --  about 27 C.

FWIW,   Vic

[jmarc]

Hi,

Thanks for all the replies! I'm new to batteries. The charge controller is installed is a conext mmpt 60 150.  I'm just getting familiar with the 3 stage charging process. Comparing the charge controller defaults and battery manufacturer's recommended settings is a little different. Should I apply the settings now or wait till the battery is completely charged?

24V
Trojan recommended settings.
Bulk: 29.64
Absorption: 28.20-29.40
Float: 27.00

Conext MMPT 60 CC defaults
Bulk: 28.8
Absorption: 28.8
Float: 27.0

After some research, i read that I need to check to make sure that the water level is above the plates before I start to charge. Then after charging add water to fill line once charge is complete. Is this correct?

[Vic]

jmarc,

With the Conext MPPT 60 150 CC,  you would probably want to set the Bulk and Absorb voltages the same.  Personally,  would use the recommended Charge and EQ voltages from the Data Sheet table,  and would do that now.

So,  IF the SOC is about 70%,  then would set the Absorb time to 4 hours,  for now.   If you can get the battery fully charged in one day,  you could start the Commissioning EQ on that day.

Once that the battery has been fully-charged,  and with no loads on the battery,  if the EQ could not be started at the end of Absorb,  you could allow the Absorb to finish on the following day.   This Absorb would be very short.   You could then do the Commissioning EQ,  at the Trojan-recommended Veq,  and the EQ voltage should be Temperature Compensated,  if your CC allows this.

The Conext CC  will end Absorb either by the time setting,  OR,  when the output current from the CC diminishes to 2% or the battery Ah Capacity setting.   This 2%  is hard-wired,  necessitating the user to potentially LIE about the Ah Capacity of the battery to make the CC Ending Amps function work.   AND,  of course the Schneider CC does not have the nifty  WBjr function (if one buys enough Schneider widgets and gizmos,  perhaps a moderately accurate measured battery current might be inferred by their system).

Initially,  Ending Amps will probably be a bit of a moving target,  as most batteries will need about 30 - 75 discharge/charge cycles before they settle in,  develop full Capacity,  and become much more repeatable.

You will want to watch the Absorb stage,  and look for the plateau in CC output current (ideally with no loads on the system).  This will suggest an EA value for now.   With little or no loads (not even an inverter)  Absorb will not take long,  if your batteries are charged daily.

Be sure to use the Battery Temperature Sensor (BTS).

Later,   IMO,  etc,   Vic

[ClassicCrazy]

Vic ,
Are you saying that the Conext Charge controller will quit Absorb on any one of those three criteria , which ever comes first ?

2%, time, or battery capacity ? So it has shunt and will count what is taken out ?

Glad I have the Midnite !

Larry

[Vic]

Hi Larry,

NO,   probably did not word that part well ...

The  Schneider 150 - 60 CC (aka SCC) (or whatever they are calling it this month),  Will end an Absorb  based upon the time setting,  OR   when it feels that 2% of the battery Capacity SETTING has been reached.

SO,  if one wishes to change the percentage,  one must lie,  and change value of the Ah Capacity.   That is,  if one wanted to try 1% of Capacity as an end-point,  one would just need to change the Ah Capacity setting to half the actual Capacity.   (IMO,  the Schneider CC  is not that bright)

Also,  I should have mentioned,  that the Temp Compensation of the charge voltages is not handled in  a user-friendly manner.

The user needs to multiply the number of battery cells by the compensation value (in the of the OP,  this should be 5 mV X 12 cells = 60,   IIRC,

I,  too,  and very happy to have MidNite CCs!!   The range of Aux functions is quite limited in the Schneider CCs.   No Aux 2,  no PWM Waste-Not functions,  not even the Aux function of "Aux active on CC reaching Float"

BUT,  for those with brand S inverters,  perhaps it can make sense to try to have all of hardware boxes in a dull shade of grey.

The SCC does have a Shunt,  but it is in the negative lead of the PV input.   The output current is inferred from the input current and the battery voltage (would guess).   This requires that the user land the PV negative cable inside the CC,  only,  and not on the common negative buss. (the KID does this also)/

Guess that I should not rag so much on Schneider  ...   Sure am glad that MidNite really strives to excel in every thing that they do.

Doubt that any of the above,  regarding the Ending Amps or the way the Temp Comp is set has changed in any FW revisions,  since I last looked at it.

Thanks MidNite !!   Cranky Vic

[mike90045]

Beware, that as batteries age, their finishing amps will gradually increase, and the "2%" will become 4% and 6% as time goes on.  And that any loads you have, may confuse the calculation.   

[ClassicCrazy]

Beware, that as batteries age, their finishing amps will gradually increase, and the "2%" will become 4% and 6% as time goes on.  And that any loads you have, may confuse the calculation.

yeah - I have recently found that out on my lead acid batteries .  Good idea like Vic says to keep log book and make scheduled checkups . I had neglected that and was under charging for awhile.

Mike, do you also think that batteries end amps would need a tweak for seasons if like mine they are located in an unheated space ? I thought it may have been due the cold but could also have been due to aging. Or probably a bit of both.

Larry

[Vic]

Beware, that as batteries age, their finishing amps will gradually increase, and the "2%" will become 4% and 6% as time goes on.  And that any loads you have, may confuse the calculation.

Have always used End Amps to end Absorb,  and sure have not seen this dramatic a change.

Have  increased Vabs somewhat on each of the main battery banks here,  about 0.4 V  increase.   This has resulted in an increase of the EA value from about 1%,  to about 1.45% of Rated 20-hour Capacity.   Although,  perhaps these batteries are  no yet old,  as they are only in their 12th-year.

Have  not noticed any change in the EA value verses temperature.  The Surrette-recommended Temp Compensation value of --5 mV/Cell/C  seems correct.

The only effect of loads on the operation of EA,  is the effect of a large load (like a conventional A/C unit),  resulting in  a small change in battery current,  due to voltage drop in the cable and circuit breaker between the Classic output and the battery.

Due to the Classic's WBjr accessory actually MEASURING the current into the battery via a Shunt (rather than trying to deduce it from other devices,  like the inverter),  the battery current data it uses is quite accurate.

Believe that the primary reason that the proper EA value has increased,  is that the Vabs did need to be increased.  in order to fully-charge the battery (probably due to battery age).

We are using a Skip Day charge routine  --  Skip three days,  and fully-charge on the fourth.

Just my observations,  although  probably my batteries are not yet "old" ...
FWIW,  Vic

[ClassicCrazy]

Good point Vic - instead of changing ending amps increasing the absorb voltage sort of does the same thing . They do give a range in the battery specs of my batteries.

Maybe part of the problem I had was that the batteries sat floating for long time . I think part of the solution for that might to use equalize function at absorb voltage - or slightly higher every ten days to get help get the electrolyte mixed up so it doesn't stratify.

I just invested in some crystal lead batteries - pretty much like gel batteries but they have no sulfuric acid in them so are not ever supposed to sulphate up even if they are left sitting in low SOC for periods of time . They are supposed to perform better in the cold than flooded batteries too . So hoping that all this is correct and I am also looking forward to not having to deal with adding water to them and dealing with splattering acid , etc.  Time will tell if they live up to their reputation. I have not put them online yet but soon.

Larry

[Vic]

Hi Larry,

Yes,   the EA did need to be increased,  probably mostly due to the need to  increase the Absorb voltage.   This is on situation where Flooded batteries are good,  as the SOC can actually be directly measured.

Will be  interested to hear your experiences with the Lead crystal batteries.    You are a bit adventuresome!

73,  HNY,   GL.   Vic

[Westbranch]

Larry, I just looked at their FAQs and saw this...
They sound as good as LiFePo4 batteries except that they can somehow sulphate...?

9. Do Lead Crystal® batteries sulphate?

Due to the construction and chemical reaction inside a Lead Crystal® battery, sulfation hardly ever occurs. Lead Crystal® batteries contain less sulphuric acid. They do not contain toxins such as cadmium or antimony either.

3. What is the lifespan of a Lead Crystal® battery?

Lead Crystal® batteries have a design life of 18 years.

10. Can Lead Crystal® batteries achieve a 100% Depth of Discharge?

Yes, Lead Crystal® batteries can be discharged in full frequently, even to 0 Volt. This makes Lead Crystal® batteries extremely resilient for deep discharging.

11. Can Lead Crystal® batteries be partially charged?

Yes, Lead Crystal® batteries can be partially charged i.e. you don’t have to charge them fully to be able to use them.