New Rolls 445 Ah Batteries, 6.35 OCV with LOW Sp. Gr.

Rob7

Hello Folks ..  I have register to the forum becuz I have a battery situation that I need help understanding.  Thought I'd bring it to the experts.  Thx in Advance.   Just bought eight Rolls S6 L16-HC 445 Ah 6v … to incorporate into existing, whole house solar system.

 

I made two mistakes, right off the bat .. #1 ... Didn't check the SG (at delivery) or before charging and #2 ... added 1/4" of H2O to top off ... Then did a 24 hr < 20 amp 12v charge to a pair of the 6v in series.  Final open voltage is 6.35V … with a SG of about 1.215 after temp correction for a 60* battery temp.  … WHAT ?  I said .. Why is the SP so low, with a good OCV?  Figured, prolly cuz of adding H2O when I shouldn't have. So I did a Equalization on these two 6v, one hour with a little 20A Xantrex charger. … The SG came up .015 to 1.230 .  But …  There's a long way to go to get to 1.270 .. Which is why I'm here to get some expert advice, before doing anything else .. PLEASE advise :-) !!

 

Is this a normal occurrence with LA Batts?  Is there a problem with these Rolls batts, or just with me :-) ?  How do you all think I should proceed to get SP.Gr. to a new battery level ?  Thanks in advance :-)

BB.

Welcome to the forum Rob.

And while I am not a battery expert... Some observations.

Adding distilled water to cells is not a huge issue... The "problem" with adding water to a "cold bank"--Charging causes heating (water expansion) and gassing (hydrogen+oxygen) -- The electrolyte can rise and flood out the caps making a mess and losing electrolyte. As long as that did not happen, you are fine. Generally, check to ensure plates are covered, then charge, and when charging is completed top off cells (near full, not 100% full--To allow room in the future for expansion). Adding a bit of water is not going to dramatically affect the SG readings of the battery bank--And adding to "new batteries" is no "worse" than adding it a few days down the road after a "commissioning charge". In may drop the "100% State of Charge" SG by a couple points when water is added--Not 0.040 units.

Not checking/logging battery resting voltages and specific gravity... You learned. If you have low SG/voltages (say less than 75% SoC), low electrolyte levels due to spilling--Then you may have shipping damage (cracked case, batteries dumped off pallet).

So lets look at today's questions. Always follow the manual as a starting point:

https://www.solar-electric.com/lib/wind-sun/surrette-manual.pdf

Ideally, the batteries should have 10% rate of charge of 445 AH capacity... 5% minimum, around 13% to 20% maximum rate of charge (watch battery temperatures as batteries on even 2.5 to 5% rate of charge can overheat if left on for "many hours to days" of charging (gassing/EQing).

For your 20 Amp charger (bit less than 5% rate of charge)--What was the charging voltage set point? The Rolls batteries tend to "like" higher charging voltages--Or starting at 15 volts @ 77F for absorb charging.

Did you measure the charging current (initial, during, and end of charging cycle)? More or less, your charger should be outputting around 20 Amps (full output current) until ~80%+ State of Charge, and less than 1% (4.45 amps in your case) current as the batteries approach 100% SoC.

And to be a pest... You need to know that your volt meter is accurate (more than a few problems here when DMMs had "dead batteries") and your hydrometer is also calibrated. It sounds like you have an existing solar system with FLA batteries--So I would guess you are seeing expected values when doing maintenance on your home power system (DMM readings close to solar charger/other meter readings, battery bank SG reach ~1.255 to 12.75 1.275 SG (fixed. -BB) units--Rolls specs)?

When your battery bank reached ~15.0 Volts--That would be the transition from Bulk (max current from charger) to Absorb (voltage set point charging). And timed absorb would be around 2-6 hours (2 hours if shallow discharge, 6+ hours if deep cycled).

EQing battery... 2.5 to 5% rate of charge--That is fine for EQ. For Rolls, they tend to need higher EQ voltages than other brands/models--Maybe in the range of 15.6 to 15.9 volts or so... During EQ you should see "fizzing" (not rolling boil) from gassing. Watch battery temperatures (not over 115F. If battery bank is cold, you will probably need higher EQ (and charging) voltages... With EQ, the "correct" voltage should give you around 5% to 2.5% rate of charge.

If you do not have one, an AC+DC Current Clamp DMM can be a great help in understanding and debugging your system. Note there are AC and AC+DC current clamp DMMs... For our needs with battery systems, need the AC+DC CC DMM (there are AC only CC meters, and they are great units--Just not for our needs. Also an AC only CC meter will measure DC voltage--So don't confuse specificaitons).

Here is a good (moderately priced~$130 USD) AC+DC CC DMM... You can find units down under $60 too, or >$300.

https://www.amazon.com/gp/product/B019CY4FB4

Other questions... You have other new batteries--Have you charged them yet? What is the specific gravity range of the cells on your new batteries... 0.015 SG or less from "high to low cells"---Good. >~0.030 from high to low is not great and at the very least, need EQ charging.

Rolls batteries are known for sometimes needing multiple discharge/charge/EQ cycles to bring up "low SG readings". Once you have verified the charging voltages/currents and (possibly) spoke with Rolls (or you battery distributor) customer support--Placing them into service and cycling them with (tending towards the high end) charging set point voltage and EQ a few times over the weeks/month--Then see what happens.

More or less--The long term absorb voltage set point can be "adjusted" by monitoring your water usage... Typically, you would need to top off with distilled water every 1-3 months. If you are using a "lot of water" every month (or more often), back down on charging voltage. If you are only needing to add water every 6+ months, crank up the charging voltage.

Also, if you are adding parallel strings of batteries/cells--This website does a good job of explaining of how to do that "correctly" so that batteries share charging/discharging current equally:

http://www.smartgauge.co.uk/batt_con.html

Again--I am not a battery expert. And I am not the person to talk with about Warranty Claims... Just trying to help set expectations and understanding what may be happening.

-Bill

Photowhit

Well I would contact Rolls.

Adding distilled water is no sin! if it needed it it may indicate batteries sitting for a long time. Ask Rolls abut the age of your batteries.

Where do you live? In hot climates they may use lower SG than in cold climates. 

If you bought 8 then charged 2 in series, I need to ask what is your system voltage? I would assume for that large a battery bank in a home system it should be 48 volts. Do you have an inverter/charger to charge them? How are you charging them in 12 volt strings?

Rob7 said:
Final open voltage is 6.35V … with a SG of about 1.215 after temp correction for a 60* battery temp.  

Are you doing your temperature correction for temperature correctly? check C vs F values.

Rob7

@ BB  

Wow !! It's been a few weeks since I posted my problem ... Let me bring Y'all up to date, concerning my 8 x New Rolls. S6 - L16 - HC ( 445 Ah ) in a string = 48V .  They are connected to a Magnum Energy 4448 Inverter / Charge, connected to the grid only, using my garage as a load = 20 - 30 A. for 5-6 hrs.  I use a fluke DMM and a tube / float hydrometer ( refractometer on order ).  

 I've talked to Rolls Tech Support, Steve Higgins, who said that the Rolls batts, manufactured in July '21, will need to be cycled  20-30 times to "develop the plates" to be able to get a 1.265 SG / 100% charge state.  He directed me to set the bulk & absorb to 60.4V / 60.5V and absorb time to 4hrs.  He advised to change the remotes "battery Ah" setting from the 400 Ah, that I had set, ( for these 445Ah batts ) to 325Ah. ) 

  ...  I couldn't follow his explanation for this, somethin' to do with Magnum doesn't stay in absorb long enuf at the 400 Ah setting. (?)   I've cycles the string 10 times, and still seeing the Sp.Gr. range of 1.225 - 1.250 ( temp comped) @ full charge.  When Batts are @ about 48V inverter discharge ( approx 1.210 1.200 )  is when I start charging again = a cycle. .. The charge cycle starts with the Bulk @ 56V / 63A ..

 QUESTION ; Rolls recommends a bulk / absorb .. of 60.4 / 60.6V  ... my bulk starts off at 56V @ 63 A , doesn't go above this, then at absorb it starts in at 60.4V …  ? Shouldn't the bulk be @ 60V also?  Can't find anywhere in remote control settings to enter "bulk" value …  Seems like I need to see the bulk at 60.4 V

 Thanks for you help in advance :-)

littleharbor2

At the beginning of the charge cycle (bulk) the battery voltage dictates the number you are seeing. Bulk is simply, all available current charges the battery until the Bulk/Absorb voltage setting is reached.  The voltage rises up to the Absorb voltage setting and holds there as the battery finishes absorbing a slowly decreasing amount of current.

Photowhit

Rob7 said:
QUESTION ; Rolls recommends a bulk / absorb .. of 60.4 / 60.6V  ... my bulk starts off at 56V @ 63 A , doesn't go above this, then at absorb it starts in at 60.4V …  ? Shouldn't the bulk be @ 60V also?  Can't find anywhere in remote control settings to enter "bulk" value …  Seems like I need to see the bulk at 60.4 v

A charge controller or in this case the inverter charger, primarily controls the 'run away' voltage as the battery reaches about 80% full.

Until that point the batteries electro-chemical nature determines the system voltage. 

Rob7

Thanks guys ..  What you said makes sense ... I'll spend the next couple week, cycling this bank, then let y'all know how these Rolls look... My 16 x 6v, 430 Ah 6 yr old Crowns 48V bank is resting now :-) and should benefit from what I've learned recently, once I switch back to using them and change their charging / EQ parameters.  
Thank You