Equalizing batteries and thinking they are getting to hot!

Options
Fe-Wood
Fe-Wood Solar Expert Posts: 96 ✭✭
I decided to equalize my batteries today and the ambient temp is about 88 Deg. F. The batteries very about .002 points of SG between cells at this point. I'm wondering if I should stop because the batteries are approaching 98 deg.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    They sound "close enough" (usually difficult to measure closer than 0.005). And you are below the 0.015 to 0.030 range for equalization.

    Normally, the recommendation is if all the cells' specific gravity stop rising after 30-60 minutes of charging, then the battery bank is fully charged/equalized.

    You certainly don't want to go much above the 100-120oF range.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Hi Fe..,

    I agree with BB Bill. STOP! Dunno hot is "hot", but heat it not good for your fairly new battery bank.

    Looked through your past posts, and found this, "I have a 4024PAE with 8 batteries @6VDC with a combined 790Amp Hrs"

    So you have two strings of batts on a 24 V system. Just to make certain, do you have BTS/RTS (temp sensor) on all charge sources?

    How are you measuring the SGs? Glass Hydrometer, Refractomerer, or ... ?
    What is the SG that you measured when you were seeing that 2 point variation? AND, just to be clear you are seeing a variation of, 1.265 on one cell, and 1.267 on an other? ... just as an example.

    In another thread you mentioned using a generator for charging, do you have some PVs? And, what brand/model are the batts? Just curious.
    At some point if you could create a signature this would help some. Thanks. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Fe-Wood
    Fe-Wood Solar Expert Posts: 96 ✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Thanks for the replies!!! I waited a bit hoping someone would jump in with a quick recommendation.... Not seeing that, I did stop.

    I'm using a Hydrometer with the thermometer built in. Purchased through our host. I'm wondering about its accuracy and my ability to read/understand it. Sadly I did not have it until long into the batteries service life. Today, when I took my first reading I was getting 1.75 plus 2 of the intermediate lines. In my mind this should equal 1.185. Then add the .004 temp adjustment for 89 deg. and I get 1.189. On the battery monitor, I was showing Float Charge @ 100% Charge. The above mentioned was a low cell. The high cell was 1.204. So the difference was 0.015 between cells. After Equalizing for about 1.5 hrs the difference is about 0.005 between cells or 1.223 and 1.228. My battery monitor said I was at 97% of charge. The Volt read on the batteries is 6.191 to 6.205 at 96% of charge. Its looking like I am vastly undercharging! I should read about 7.056 Am I right? I had the charger set at 100% recharge rate. I just changed it to 85%.... This is SOOO confusing! I think I need some BIG help here...

    I have Crown Batteries, model CR395 6 Volt. The magnum 4024PAE with battery monitor and temp sensor. I am charging off the Generator with the Magnum. No Panels as of yet... On the list....
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Measuring voltage on a battery is a bit of guess work... If they are charging/resting/discharging, the numbers are all different. And other than resting voltage, have only a weak relationship to state of charge.

    The Hydrometer (properly calibrated and used) is going to give you the most accurate numbers. Using this Crown Battery Manual (PDF):
    Specific Gravity
    State of Charge Level
    
    100% 1.265 or Greater
    75%  1.225 - 1.230
    50%  1.185 - 1.190
    25%  1.140 - 1.175
    0%   1.125 or Less
    

    And they also list battery voltages too (after a 15 second load test--to take of the "surface charge"?)...

    Note that your batteries should read about 6.3 volts fully charged (room temperature, resting voltage).

    And about 7.3 volts (~29.2 volts) voltage set point for absorb charging.

    There are lots of theories about how best to charge your battery bank... Pick one that works for your charging setup and then monitor the bank... If the bank is "undercharged", then add time and/or voltage. If the bank is overcharged, drop time or voltage a bit...

    Depending on how your charge controllers can be programmed... One method is to measure the time to Bulk Charge (from below ~29 volts to absorb point at ~29.2 volts) if that took 2 hours, then add two more hours for the absorb time (holding at ~29.2 volts). Then turn off or drop back to float (if you have a genset, you will pick turning off the generator).

    Another method is to set Absorb to ~29.2 volts and set the Absorb Timer to 2-4 hours... 2 hours if the bank is lightly cycled and ~4 hours if the bank is deeply cycled.

    Watch the specific gravity and water usage... If you have to add water about every 2 months to a cell--you are probably OK. If you have to add water more often that once per month, you may be charging a bit too much (excessive charging/"boiling"/equalizing is not good for a battery bank). If you are not adding water, you probably are undercharging.

    A 4kW inverter/charger is pretty good sized... Your ~790 AH at 24 volt battery should be charged around ~5% to 13% rate of charge (at 20 Hour rating--these are typical numbers, always refer to mfg. instructions to confirm):
    • 790 AH * 0.05 = 39.5 amps minimum
    • 790 AH * 0.10 = 79 amps "nominal"
    • 790 AH * 0.13 = 103 amps "healthy maximum"

    Depending on the programming/capabilities of your inverter/charger, and the capacity of your genset--hopefully your numbers fall somewhere in the ~80-100 amp range for charging this batteries.

    If you are having problems getting the batteries above ~1.260 specific gravity and you have a "big genset", you can try running longer with a smaller genset and battery charger to save fuel (a Honda eu2000i and ~30 amp, or a bit less, AC charger or if the inverter/charger can be programmed for lower charging current to finish the charging).

    You do not know what the initial "fill" S.G. was... So you don't know if you can reach ~1.265 or not. And if absorb charging (and some deeper cycling--exercising) does not bring the S.G. back up--Then you may have started to sulfate the battery bank (unrecoverable early aging).

    Battery Monitors usually have some sort of "reset to 100% full"--Like if they see 29.0 volts for >1-3 hours or something). If you do not reach those conditions, the Battery Monitors will "drift" from "true" 100%. Also, sulfation will reduce battery capacity--which the Battery Monitor cannot detect.

    Anyway--My guesses from behind a keyboard.

    Good Luck!
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Fe-Wood
    Fe-Wood Solar Expert Posts: 96 ✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Wow! Thanks BB!
    I'm going have to re-read this again in the morning.... Lots of good info! Testing to be done. All the numbers you are talking about are good with what I've been doing. Looks like I'm going to have to dig deeper. I'm thinking I may have set up/initialized the monitoring part of the charger without a full charge. Thoughts on that?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    I really do not have anything I can add... Be do'in the same thing as you reading the manuals for setting up / configuring the monitoring system.

    In the end, figuring out the present state of your battery bank and how, if needed, you will need to get it back to full/proper state of change. Hopefully, getting the battery monitor sync'ed will fall out at the end.

    Depending on size of of genset and such--If you have a large genset and this is your only charging source--you may end up really needing a smaller genset (and possible mating AC to DC battery charger) to finish the charging. Bulk usually ends at around 80-90% state of charge, and "absorb" (tapering towards zero charging current) takes place over the next 2-4 hours. Using a "large" genset that can drink 0.5-1+ gallon per hour vs a smaller genset that may take 1/4 to 1/9th gallon per hour for those last "4 hours" may save you a bunch of fuel costs over the long haul.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Hydrometers can be very tricky to use properly. Most installers I know use cheap ($50) refractometers. They have no moving parts and temp compensation is built in. You can buy them online or at an auto parts store. Search this forum for 'refractometer'.

    There have been at least a few threads like yours on this forum that were ultimately resolved by learning that the hydrometer was wrong (or used improperly).

    One more thing... this affects both hydrometers and refractometers: stratification of electrolyte. When charging you are concentrating the dilute sulfuric acid. The heavy, concentrated sulfuric acid sinks to the bottom of the battery. What you may be measuring is the dilute acid at the top. Industrial batteries often have electrolyte circulation systems. The way most of us deal with stratification is by charging far enough into absorb stage that bubbling (gassing) occurs. The bubbling stirs up the electrolyte.

    Do you routinely achieve gassing? If not, you certainly have been undercharging your batteries. In addition to sulfation being a problem, the concentrated acid in a stratified battery really corrodes the bottom parts of the battery.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Fe-Wood
    Fe-Wood Solar Expert Posts: 96 ✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    I put these batteries online back in November and I haven't had to add any water. Or maybe I did add some once. I'm not positive on that. I do get the water bubbling so the electrolyte should be well mixed.

    Here is the recommended profile for my batteries. These settings don’t correspond to any of the setting on my controller.

    I currently have the Charge Rate setting on my controller set at 100% This allows me to charge at 97 to 100 amps during bulk charge.
    I am currently running the absorb cycle 3.5 hours after the bulk stage has finished. From my understanding the bulk phase is an un specified length of time and is done to bring the batteries to a Specific Gravity or Voltage. Then the Absorb phase starts.

    What does charge factor mean?

    Recommended Charge Profile:
    Following discharge, constant current charge the CR-395 battery at 40 to 50 amperes until the battery voltage measures
    2.42 volts per cell (7.26 volts open circuit voltage).
    The constant voltage charge phase begins after the gassing point (2.42) is achieved. During the constant voltage phase,
    the charger voltage limit is regulated to the gassing point of 2.42 volts per cell, while the input current is allowed to
    gradually fall off. When the input current drops to the finish rate setting of 15 amperes, the charging phase will change
    from constant voltage to a sustained 15 ampere constant current mode. The charging cycle will be terminated 3.5 to 5
    hours from the gassing point, with factors such as ambient temperature, battery condition and depth of discharge
    affecting the charge completion time.
    The CR-395 battery should receive a full recharge following the completion of each discharge, along with a weekly
    equalization service charge. During the equalization charge cycle the finish rate charge time is extended by 3 hours (6.5
    to 8 hours from the gassing point).
    The charge factor of the standard recharge should be equal to or greater than 1.07 (107%). The charge factor of the
    equalizing cycle should be equal to or greater than 1.15 (115%).

    As always Thanks for all the replies and help!!!!
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Fe,

    Thanks for the added info on your system.

    Regarding the Hot batteries during the EQ yesterday:

    EQ should be started when the batteries are fully charged. If the batts are not fully charged, there can be additional heat generated in the batteries. This is especailly true when using a generator or Grid power as the power source, as the average power delivered to the batts is usually considerably higher than charging/EQing from PV.

    Since you have a good Hydrometer, it should not be difficult to get reliable readings from it. I assume it is a Brady brand with red rubber bulb and snout.


    The hydrometer will help you calibrate your Battery Monitor, but it may take a bit of time to do this.

    Hydrometers have been used for over 150 years to measure the SOC of flooded batteries, they work well if one is careful. Just a quick note on using one:

    1. Fill and expell two samples from a cell, and measure the SG on the third fill. Be fairly gentle in filling and expelling the electrolyte -- it is cleaner, and does not blast debris on top of the Moss Guard into the guts of the battery.

    2. Keep the Hydro's fill tube in the vent well of the battery as you take the reading. A flashlight can help yor see the readings. Keep the Hydro level, and make certain that the flolt is floating, not hitting the top stopper of the Hydro, and not sticking to the sides of the outside tube.

    3. Record the readings in your battery notebook for future reference.

    EDIT: 4. RINSE the Hydrometer in Distilled twice after each use, AND on the Brady, rinse the entire tip. (forgot to note this important part).

    As BB Bill mentioned, having a genset as the only charge power source can be a bit tedious and expensive if the genset is fairly large -- a long run-time at light loads for finish charging.

    As you know, there are two important settings for the Asorb stage: Asorb voltage, and Asorb time -- the amount of time spent at this voltage. The deeper the discharge of the battery, the longer the required Asorb time. Until you get the batteries fully recharged, Asorb times of 2-6 hours might be required. Near the end of Asorb, you should notice vigorous bubbling of the electrolyte. Agree that about 29.2 V Asorb or a bit higher for now is a good set point.

    Flooded batteries are very forgiving. They do not llike to be run low on water, sit in a discharged state, and heat will shorten their lives. But am sure that you will get on top of the charging process. PV is a big help, as you know.

    Forgot to ask about your generators. What are you using? Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Fe-Wood
    Fe-Wood Solar Expert Posts: 96 ✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Thanks Vic-
    I think I'm using the hydrometer properly and as described in your post. It is a Brady. I wonder if the paper used for the measurement has slipped down a small amount. There is quite a bit of room above it and it was shipped. Seems like the friction of the paper wouldn't allow it but....

    I am currently using 2 different generators for charging, depending on the other power needs I have. one is a Lister Diesel STA3 15KW and the other is a Honda ME6500EX

    In watching my charge monitor today, I'm seeing my absorb voltage set at 28.6 I have looked in the manual and I can't find a way to change it. It seems that voltage is generated from the battery type and Amp Hour rating entered into the setting when setting up the system.

    Thanks for the help!
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Hi Fe,

    Forgot to note the all important item in the previous post, Rinse the Hydrometer twice with distilled water, and rinse the red tip thoroughly after each use.

    There has been some discussion here regarding the canned settings on the Magnum Inverters, but thought that the ability to chnage this standard setting came with the Remote that I believe you do have.

    Fine on the gensets. Well the charger in the 4024 can output about 105 Amps DC. So with some allowance for inefficiency, that is about 3500 Watts max, and in Asorb, you would probably average half of that or less, so will take a bit of fuel, even with the little genset.

    Thanks for the sig line, this should help, and save you quite a lot of typing over time.

    More later. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Fe-Wood
    Fe-Wood Solar Expert Posts: 96 ✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Vic-
    Thanks for the help!
    I do rinse with distilled water- Thanks for bringing it up!

    Believe me, I understand about the fuel, I always try to have something else that needs power going during my charge cycles. I am hoping to get some panels in the next year or so. That will help a bunch. For now I upped the absorb time to 5 hours. We'll see how that works.

    Funny question but would you think its OK to use the rinse water as the water I add to the batteries when they need it, assuming it is clean with only electrolyte in it?
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Options
    Re: Equalizing batteries and thinking they are getting to hot!

    Hi Fe,

    Agree that saved rinse water thould be fine as battery fill water, altho, I just toss the rinse water. The systems here use a bit of water -- about 3.5- 4 gallons in 6 - 8 weeks, so the rinse water is a small % on these systems.

    Fine on the 5 hour Asorb time. Hope that you can find the way to enter "custom Settings" into the Magnum, as it would be nice to see your Asorb voltage higher than the default value. And, using a generator, you might want to set the value above the 29.2 V value mentioned above. You could qualify as an "Opportunity Charge" person -- higher Asorb V for a shorter time to help on fuel costs.

    Good Luck, and please let us know how you are doing. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.