Battery Voltage working optimum?

adas
adas Solar Expert Posts: 136 ✭✭✭✭✭
Aloha, since i want to get the most out of my batteries, I have a couple of questions:

1: We work our system a lot during the day and the 2 FX80's are mostly on Bulk and almost never absorb or float. So absorb voltage is set at 28.8 and most of the day I am at 28-28.6, etc. Is it OK to charge this high continually as it never drops down the whole day. Should I set my bulk to 28.2 or less or so?

2: Related question is how much lead (leeeed) voltage can I use and not boil out the water. Batteries are not getting warm.

3: At the end of day and batteries at rest and no inverter, my voltage goes to 25.4 -- 25.6 or so. Turning on the inverter with a little load the voltage drops to 24.8 right away and even after using a lot of power for 3-5 hours the voltage still is around 24.7 or so. In the morning (I turned the invertor off at night) the voltage shows 25.3 or so. Is this "working voltage range" for the batteries and is normal?
Thanks
Frank

frank

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Battery Voltage working optimum?

    Frank,

    I think, in the end, using a hydrometer and/or a battery monitor is way you will answer this question... If the batteries are above 75-80% state of charge most of the time--then they will not be sulfating.

    And, as long as they are not "boiling" them hard during the day, just light bubbling (except when you equalize)--you should be fine.

    ... From what little I have read, fork lift batteries are OK to even overcharge to a degree (lots of bubbling)--just as long as you keep them relatively topped off with water (not overfilled) or get them overheated.

    28.0-28.6 volts at the battery does not sound high at all.

    Presumably, on weekends (or at least Sundays), they get a full "normal" charge cycle?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Battery Voltage working optimum?
    adas wrote: »
    Aloha, since i want to get the most out of my batteries, I have a couple of questions:

    1: We work our system a lot during the day and the 2 FX80's are mostly on Bulk and almost never absorb or float.

    Sounds like deficit charging - you not getting above 80% charged. At about 80%, is when the charger throttles back to let the last 20% trickle into the batteries.

    Can you run a generator for an hour or so in the AM, till the sun is up enough to get some good amps out of the PV's ? This will give you a head start, and maybe get a full charge on days you run generator.

    The more time the batteries spend below 100%, the shorter their life, depending on the depth of discharge, you might get 7 years at 98%, 2 years at 80%, and 6 months at 30%, all depends on how the batteries are made.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery Voltage working optimum?

    Aloha, Yesterday I was able to EQ all four batteries individually for 1 hour each. @ 31V. All bubbling cheerfully. One of the batteries has a bad cell that is not getting any better. Until I get another battery of the same cell to pull out the cell and replace it, should I still run this battery? The one cell is 1.2V and all the other 11 cells are charging to 2.2 V each. Will this battery bring down the other 3 batteries overtime or soon. Should i take it off line until I replace the cell, or OK to run it until replacement?
    Frank
  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery Voltage working optimum?
    mike90045 wrote: »
    Sounds like deficit charging - you not getting above 80% charged. At about 80%, is when the charger throttles back to let the last 20% trickle into the batteries.

    Can you run a generator for an hour or so in the AM, till the sun is up enough to get some good amps out of the PV's ? This will give you a head start, and maybe get a full charge on days you run generator.

    Aloha, when charging at 28+ or so the batteries are already bubbling, although I do not throttle down to absorb/float. If I disconnect the PV the batteries will go to 27.5, 27, 26,5, etc. and after a while come to rest at 25.6~25.4. Is this not full charge?
    My concern is that use of my electrical equipment and periodic cloud keeps the batteries from going into float mode and makes them charge at 28~28.7 all day, whereas a "normal charge" would do the bulk/absorb/float. Panels are putting out 3500/4000W most of the day, resulting in 150A 24v charging.
    Frank
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Battery Voltage working optimum?
    adas wrote: »
    Aloha, when charging at 28+ or so the batteries are already bubbling, although I do not throttle down to absorb/float. If I disconnect the PV the batteries will go to 27.5, 27, 26,5, etc. and after a while come to rest at 25.6~25.4. Is this not full charge?
    My concern is that use of my electrical equipment and periodic cloud keeps the batteries from going into float mode and makes them charge at 28~28.7 all day, whereas a "normal charge" would do the bulk/absorb/float. Panels are putting out 3500/4000W most of the day, resulting in 150A 24v charging.
    Frank

    If the charger is not throttling back on it's own, something is not configured right. You should not have to disconnect the PV's.
    25.4V at rest should be a full charge, so that's good news. Does your charge controller have a voltage/time graph of how it decides you have reached the end of bulk, and to begin the timer for absorb?

    As to the bubbles, some, like in a champagne glass, are normal, furiously boiling bubbles are a sign of overcharging, but as long as there is water, and batteries stay cool, no damage, except from the acid mist getting on everything.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery Voltage working optimum?
    mike90045 wrote: »
    If the charger is not throttling back on it's own, something is not configured right. You should not have to disconnect the PV's.
    25.4V at rest should be a full charge, so that's good news. Does your charge controller have a voltage/time graph of how it decides you have reached the end of bulk, and to begin the timer for absorb?

    Aloha, it does not reach 28.8

    (CORRECTION--it does) I go into absorb but with electrical usage I jump back into Bulk, so the unit is working bulk absorb, bulk absorb, and not going to float unless I do not use much inverter power.

    because I keep robbing the power during the day, keep knocking it back to 27.8, then building back to 28.6, etc. (and variations of the above). but the point is that it hangs out in the 28~28.7V range and when it is ready to go to 28.8/absorb, along comes a cloud!! So that is why it never gets to be "officially" charged via bulk/absorb/float, but stays in the 28 range for a good part of the day.
    To refine my question, is it ok to be in the 28v+ range for a good part of the day, rather than a typical charge scenerio of maybe 1-2 hrs at 28?

    Also maybe to clarify, the batterys/inverter/charge controler are all connected together. If the sun drops below 25.4, then I rob power from the batteries, if over 25.4, the batteries get charged and I use power from the PV.

    frank
  • al128
    al128 Solar Expert Posts: 65 ✭✭✭✭
    Re: Battery Voltage working optimum?
    adas wrote: »
    If the sun drops below 25.4, then I rob power from the batteries, if over 25.4, the batteries get charged and I use power from the PV.

    frank


    hi frank,

    if you dont mind me asking ... how is your setup that allows you to use power from the PV above 25.4? ... or do you go through the batteries here as well?

    I am debating something like this, for running shorter but higher loads (500w clothes washing machine) for 1 hr. during the peak time around 11.00am

    Would this situation allow me to use the washer, but not have to take "previsions" for it when sizing the bat.bank? .... (assuming I have some wiggle-room to push a washing cycle back a day or 2)

    cheers & thx
    al
  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery Voltage working optimum?
    al128 wrote: »
    hi frank,

    if you dont mind me asking ... how is your setup that allows you to use power from the PV above 25.4? ... or do you go through the batteries here as well?

    I am debating something like this, for running shorter but higher loads (500w clothes washing machine) for 1 hr. during the peak time around 11.00am

    Would this situation allow me to use the washer, but not have to take "previsions" for it when sizing the bat.bank? .... (assuming I have some wiggle-room to push a washing cycle back a day or 2)

    cheers & thx
    al

    Aloha, You can use whatever voltage is provided as long as the inverter is capable of it. My inverter uses 20-29V DC. It is good to time your energy intensive loads when you have the most sun, as you say. But if you do not have enough of a buffer=(battery bank), if you are washing and you get a cloud cover, you will have nothing to draw on.
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Battery Voltage working optimum?

    Frank,
    1. 28.8 V (ref 77 F) may be a low absorption target for your batteries. ~29.5 V to 31.0 V is more common for true deep cycle flooded cell lead acid batteries. What brand are your batteries?
    2. Not sure I understand your question… but, the lower the voltage used to fully recharge your batteries, the better, although recharge time may be longer. Ref: http://www.rollsbattery.com/files/BU-RS-614.pdf
    3. ~25.4 V to 25.6 V at rest (several hours of no charging and no loads) would typically indicate a fully charged 24 V battery bank. The voltage drop you see when applying a load is normal, as is the voltage increase when the load is removed.
    HTH,
    Jim / crewzer
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery Voltage working optimum?
    adas wrote: »
    Aloha, Yesterday I was able to EQ all four batteries individually for 1 hour each. @ 31V. All bubbling cheerfully. One of the batteries has a bad cell that is not getting any better. Until I get another battery of the same cell to pull out the cell and replace it, should I still run this battery? The one cell is 1.2V and all the other 11 cells are charging to 2.2 V each. Will this battery bring down the other 3 batteries overtime or soon. Should i take it off line until I replace the cell, or OK to run it until replacement?
    Frank
    it seems this point of a bad cell in one of your batteries was overlooked. this will strain the entire system and drag down your other batteries. do take it out of line and replace it asap as the loads to the remaining batteries will also stress the system.
  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery Voltage working optimum?

    Aloha, Jim. very interesting voltages on the Rolls battery. I do not know the brand of batteries as they are renamed with a third party name. I think I will adjust my voltages down (as they recommend) and still get a full charge, say by 2pm. Keeping in mind the need for power during the day.

    So far I might have it.... The last few days the batteries charge up quicker and we are putting more equipment on line (such as the more powerful electric leaf blower to dry units instead of the gas one), installing timers for the toolroom lights, having employees turn off unnecessary items, but not skimping on power if they need. So far the 5KW Diesel Genny has not been started for 2 weeks

    FRank.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Battery Voltage working optimum?

    Some tips for industrial batteries from Crown:
    Today’s industrial battery is designed and built to give anywhere from 1000 to 2000 operation / charge cycles, depending on the application and the operating environment. If such a battery were to complete on cycle per workday, the life expectance would be 4 to 8 years. Exactly how much life a battery will provide depends to a great extent on how well you take care of your battery. The following maintenance procedures, properly carried out at the proper time, will go a long way toward prolonging the life of the battery and making it more efficient.
    Routine battery maintenance consists of three functions:
    1. Properly charging the battery
    2. Adding water as needed
    3. Cleaning as required
    Instruments for Inspecting Batteries
    Three testing instruments are required to check batteries accurately and efficiently: a voltmeter, hydrometer, and thermometer. The specific gravity and open circuit voltage readings are normally in direct proportion to each other; therefore, a voltmeter or hydrometer can be used to check the battery. The use of the voltmeter is a faster method of approximating the individual cell state of charge, and can reduce dramatically the time required for routine battery checking. When using the voltmeter method of battery checking, take specific gravity readings on the two cells having the highest and lowest voltage readings. This will confirm both cells’ state of charge and accurately pinpoint the difference in the state of charge between them. The voltmeter is used when on–charge or on–discharge voltage readings are needed.
    A battery thermometer is read like a normal thermometer. A proper thermometer should have specific gravity correction marked on its scale.
    The hydrometer has an extra–long scale to make readings more accurate. For ease of correcting for temperature, the specific gravity corrections are marked on the scale of the thermometer. The cell tester (voltmeter) has a 1.5 to 3.0 volt scale, and an easy–to–handle, one–piece terminal probe.
    By far, the most important part of routine maintenance is the proper charging of the batteries. Generally speaking, lead–acid batteries may be charged at any rate of current which does not cause excessive “gassing” of the electrolyte, and does not produce temperatures in excess of 115 degrees F. (125 degrees F. is acceptable for infrequent, short periods). Fortunately, today’s automatic voltage controlled chargers take the guess–work out of charging. Providing the battery is well maintained, all that is necessary for routine charging is knowledge that the charger is functioning properly. This is accomplished be periodic inspection and adjustment of the equipment. Periodic inspection and adjustment of the charging equipment can be performed by an outside professional charger repairman. However, a basic knowledge of what is involved in the charging operation, plus a brief description of the more important types of charging and when they should be used, should provide valuable information in the event of automatic charger malfunction, or for charging operations not using fully automatic equipment.

    And here for more charging details.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery Voltage working optimum?

    Aloha and thanks for all the info on Charging, Bill. It seems my batteries are getting more and more efficient, they are reaching back to full charge by 8:30 am, even though we start using power at 6:00 am. By 11am one FX80 is showing charged and during the rest of the day the other FX80 is running the shop off the PV. The PV is easily keeping up with the 2 10A 120V grainger-type box fans and also the turning on and off of the hand tools and welders, etc. Only once in a while will the second FX80 wakeup if we are using a lot of power and we hit a very cloudy cover. It really seems that it takes very little to bring the batteries back up to full charge, whereas when I just got the batteries, they seemed they were much more of a power hog to charge. (maybe I shud sell some of the excess power to my neighbor <g>)


    frank
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery Voltage working optimum?

    more efficient is questionable. it can be viewed as reaching full charge earlier as a loss of capacity too.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Battery Voltage working optimum?

    What Neil Said,

    Failing batterys come up very fast to absorb voltage, means NOTHING about the total charge in aH they might contain. I have a battery with a bad cell that comes upto absorb in minutes ( 110 ah ) and probably has maybe 1/100th the rated capacity

    Since you have old, used and abused forklift batterys, most likey you have minimal storage.

    The ONLY way to know the battery condition is a load test and measuring the specific gravity, everything else is meaningless.
  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery Voltage working optimum?
    What Neil Said,

    Failing batterys come up very fast to absorb voltage, means NOTHING about the total charge in aH they might contain. I have a battery with a bad cell that comes upto absorb in minutes ( 110 ah ) and probably has maybe 1/100th the rated capacity

    Since you have old, used and abused forklift batterys, most likey you have minimal storage.

    The ONLY way to know the battery condition is a load test and measuring the specific gravity, everything else is meaningless.

    Aloha, thanks for the advice, so I guess I will try and learn and apply as much from the posts here and Battery sites and hope for the best. And contain my euphoria a bit. I do not have a lot to loose in the Battery investment.
    But happy to have saved $425.00 in July on Diesel. Almost pays for 1 of the 24 panels!
    frank