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Thread: Boom there goes the batteries

  1. #1
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    Boom there goes the batteries

    It finally happened... after years of dealing with batteries i have never actually seen the damage a battery is capable of until yesterday.

    They went boom (batteries are 5 years old ...so was sort of expecting to replace them soon)... the first sign of the what was to come was the smell ...like 6 month old rotten eggs... then they heat increases until battery acid everywhere... from 5 years of normal operation to suddenly with 2 hours everything went wrong.

    My advise to anyone who has an inverter big or small... beware ...it is not a pretty sight.

    2 things i learnt from this experience... ISOLATION ISOLATION ISOLATION ...VENTILATION VENTILATION VENTILATION.

    A means to disconnect your batteries from the system without the use of a tool...i see so many installations with the batteries directly below the inverter...with a fuse attached to the battery terminal...connected directly to the inverter DONT DO IT... make sure your battery has a pull out fuse system or a plug in battery.

    Make sure ALL the disconnection devices are accessible and clearly labeled.

    The first thing i noticed was the "blueing" (what happens when you overload a cable and it looses its conductivity) of the cables... i thought it was due to a massive overload as a result of this incident... i disconnected and removed some of the wires and noticed the clean copper and the insulation wasnt melted... I took a rag and wiped the cables clean ...back to shiney bright copper.

    The next question is how dangerous are these fumes from the battery when they blow out... is it wise to leave an inverter in your lounge...we are know the batteries give off a highly flammable gas while charging but just how dangerous ...this is the big question... at what point do you need to pay attention.

    IF you have battery banks in a room ...when does it become a concern...do you monitor the gasses in the room.

    There are thousands if not millions of small mobile inverters in homes around the world... some way older than 5 years ...that gas they start releasing when they become a problem...how bad is that gas for humans...after seeing the damage to the cable ...it made me pay attention.
    Comments are based on opinion...not always facts....that's why people use an alias.

  2. #2
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    Some info i found...


    "Ventilation
    Charging batteries in living quarters should be safe, and this also applies to lead acid. Ventilate the area regularly as you would a kitchen when cooking. Lead acid produces some hydrogen gas but the amount is minimal when charged correctly. Hydrogen gas becomes explosive at a concentration of 4 percent. This would only be achieved if large lead acid batteries were charged in a sealed room.

    Over-charging a lead acid battery can produce hydrogen sulfide. The gas is colorless, very poisonous, flammable and has the odor of rotten eggs. Hydrogen sulfide also occurs naturally during the breakdown of organic matter in swamps and sewers; it is present in volcanic gases, natural gas and some well waters. Being heavier than air, the gas accumulates at the bottom of poorly ventilated spaces. Although noticeable at first, the sense of smell deadens the sensation with time and potential victims may be unaware of its presence.

    As a simple guideline, hydrogen sulfide becomes harmful to human life if the odor is noticeable. Turn off the charger, vent the facility and stay outside until the odor disappears. Other gases that can develop during charging and the operations of lead acid batteries are arsine (arsenic hydride, AsH3) and (antimony hydride, SbH3). Although the levels of these metal hydrides stay well below the occupational exposure limits, they are a reminder to provide adequate ventilation."
    Comments are based on opinion...not always facts....that's why people use an alias.

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    We have been involved in a few arguments over the placement of batteries with regards to inverters and UPS - The latest being last week where 37 batteries where going into a sealed server room.

    When positioning multiply batteries you need to check the calculations in SANS for hazardous locations - Have pasted a letter below that I use to send out when I feel the argument is about to start - I just change the figures to suit the installation.

    We are also finding that so called inverter experts have no idea of the calculations needed to ensure that he batteries are not over worked - Sans 10142 also has a statement that you have to automatically disconnect any load that will go over the rating.The house owner always want the full installation on a couple of batteries which starts the problem.
    We are certified installers for Tesla Power Wall and the struggle to explain what loading you can run on an inverter is real.It is mind boggling the amount of incorrect information out there

    7.12.2.4 Where the alternative supply is intended to provide a supply to an
    installation that is not connected to the main supply, or to provide a supply
    as a switched alternative to the main supply, the capacity and operating
    characteristics of the alternative supply shall be such that danger or damage
    to equipment does not arise after the connection or disconnection of any
    intended load as a result of the deviation of the voltage or frequency from the
    standard range. Means shall be provided to automatically disconnect such
    parts of the installation, as may be necessary if the capacity of the
    alternative supply is exceeded
    .


    As discussed previously with regards to hydrogen build up from batteries on charge.

    Our electrical standards are SANS10142 which contains a clause 7.14.3 which deals with battery charging locations and directs us to SANS10108

    – I have pasted the relevant sections below.

    The Qty of hydrogen can be calculated and compensated for with mechanical ventilation which then defeats your Aircon unit for the servers – At the end of the calculation it is recommended that levels are tested during operation to ensure compliance. At that stage it is generally too late to start changing rooms and walls around , which is why we recommend that a separate battery room gets allocated from the start with natural ventilation and rather leave out all electrics in the room.
    When using forced ventilation, generally everybody forgets to service the unit until there is a problem.

    The argument often comes up that the qty of batteries is small and therefore irrelevant – In a sealed room with no outlet for the hydrogen it can become a problem quickly during a power outage and restart which is when the majority of hydrogen is produced.

    There is a calculation example on page 25 of SANS10108 using 120cells ( 20 Batteries ) in a 8sqm room which shows the hydrogen produced being over the limit.
    The spec sheet sent through on the UPS shows 60 batteries .
    To be accurate I would need to find out how many batteries and what the charging current is but my gut feel is that we would be over , especially since it is a sealed room.



    D.1 Calculation of hydrogen emission rate
    D.1.1 To ensure that the hydrogen concentration in battery rooms and cabinets or cubicles is always
    within acceptable limits, it is necessary to calculate the minimum ventilation requirements, which are
    dependent on the rate of evolution of hydrogen from the cells, particularly in the event of overcharging.
    D.1.2 Hydrogen evolution under overcharge operation can be calculated, using the following equation:
    V = N I 0,00045
    where
    V is the volume, in cubic metres (m3), at standard atmospheric pressure of hydrogen,
    liberated per hour;
    N is the number of cells in the battery;
    I is the overcharge current, in amperes (A);
    0,00045 is the constant value, in cubic metres per ampere (m3A−1).
    NOTE 1 In the case of vented (flooded) cells, the current, I, should be that value declared by the manufacturer at
    the maximum boost voltage to be used across the battery.
    NOTE 2 In the case of valve-regulated cells, the current, I, should be that value declared by the manufacturer as
    IE, which is determined from an overcharge gas emission test at 2,4 V/cell.
    NOTE 3 If a valve-regulated cell has not been subjected to a gas emission test, the current, I, should be that value
    declared by the manufacturer at an overcharge voltage of 2,4 V/cell.
    D.1.3 The volume of hydrogen obtained can be expressed as a percentage of the total volume of the
    room or cabinet or cubicle, and this can be used to calculate the number of air changes per hour
    necessary to keep the hydrogen concentration below the recommended maximum of a volume fraction
    of 0,8 %.
    D.2 Example of the calculation of hydrogen concentration
    A battery of 120 cells, that has an overcharge current, I, equal to 17 A, in a room of dimensions
    4,0 m 2,0 m 3,0 m, on a stand where the battery and stand are occupying approximately 3,0 m3.
    The volume of hydrogen liberated per hour can be calculated using the following equation:
    V = 120 17 0,00045
    = 0,92 m3
    The volume of the room is 24 m3.
    The volume of the battery and stand is 3,0 m3.
    The volume of air is equal to the volume of the room minus the volume of the battery and stand, which
    is 21 m3.
    Therefore, the percentage concentration of hydrogen gas in the room after 1 h of charging would be
    0,92/21 100
    = 4,4 %
    D.3 Calculation of air changes
    In order to keep the concentration of hydrogen gas below a volume fraction of 0,8 %, the air should be
    changed at a rate of at least 5,5 times/hour. To allow for the inevitable variations and contingencies, a
    ventilation rate of six times the volume of air in the room per hour would be the recommended practice.
    NOTE 1 The effectiveness of a ventilation system can only be assessed by sampling the gas concentration under
    operational conditions.
    NOTE 2 Some batteries are made up of monoblocks, each containing a number of cells. The number of cells
    should be used in the calculation, and not the number of monoblocks

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    ians (08-Feb-20)

  5. #4
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    Now to decide which batteries to use instead of lead acid

    The price is a huge factor.

    lead acid 105 amp/hr ...R1800.00 ex vat

    AGM 80 amp/hr ...R2000.00 ex vat

    AGM 100 amp/hr ...R2400.0 ex vat

    lithium 100 amp/hr ... R12000.00 ex vat

    I believe the most cost effect way to go right now is the 80 amp/hr AMG for 4 batteries just to get the system up and running...i have removed the entire installation from the cupboard (I didnt install it in the cupboard ...the installtion was done by a solar expert) and we have plans to move it to and outside courtyard.

    I know lithium would be the best route but just not within the budget.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Hi Ians

    There is such a hype around lithium but like normal, not all lithium batteries are the same and when you start looking at DOD and cycles the cheaper lithium are no better than AGM.

    If you take the AGM 100 , 4 off, at least you will have a 1 440 watt hours and should get 4 years - Problem is that you now need to size the load on 4 hours use so you only have 360watt/hr .

    Most people are still sizing for 2 hours and installing 720watts/hr which is why batteries are failing early on there life.

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    Diamond Member Justloadit's Avatar
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    My personal experience with lead acid and solar systems.

    If you use the Lead acid every day for back up, then I recommend that you only use 30% of the battery capacity if you want to get over 700 cycles out of them.
    If you discharge to 50% of capacity daily, then you will only get 200 cycles! then you need to replce.

    There is a specification that every one seems to miss for lead acid batteries, they require a 24 hour charge cycle for full charge if completely discharged, and are limited to a maximum amps per hour charging rate. How ever if you have an erratic charge cycle, as is the case with solar and clouds affecting the current available for charge, the batteries never fully charge for the next cycle of work. Another issue is that there is really only 6 hours of solar charge available, and this must be factored into your system.

    Now the good Lithium batteries can be charged in 2 hours and will give you between 1500 and 3000 cycles if you discharge them to no less than 20% daily. If if you discharge a little less your cycles increase, and if you size your PV array correctly, then even on cloudy days, you will be able to charge the batteries to maximum.

    There is a new breed of Lead Carbon, which can be charged faster and have better cycles, but this is new technology and I have no experience with them. There are some suppliers locally offering this new technology and are supposedly reasonably priced. A simple google search will bring them up.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za

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    Yip the battery shop was talking about them (lead carbon) yesterday ...however the were all sold out.

    I am just looking for 4 batteries to keep the computer and a few lights working for the next 2 months...while we wait for the room to be completed... i have am using 1 of the 3 inverters as a temp. backup ...then i will be relocating the whole system to an outside room with a door which has a vent low down etc etc.

    The full system is made up of the following items:

    A 60 amp manual changeover.

    3 x 5 kva RCT inverters in parallel (48 VDC)

    3 x banks of 4 12 volt batteries.

    no solar panels...just using the inverters as pure sine wave backups units.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    It seems to be common for installers to fit an inverter/s in a cupboard in the house and stack the batteries close to each other or sealed in a box...at floor level (the gas released during the charging stage is heavier than air and highly explosive).

    I took my thermal imager with to site...to get an idea of the temp profile while batteries are charging... I also noticed that the inverters if connected in parallel they have have a min spacing between units ...top bottom and sides.

    Now that we have had a first hand experience with batteries popping ...it turns out i am not the only one who has experienced this problem... there is an investigation going on with another company.

    That saying ...but it has worked for all these years why now "suddenly" ...that is the same question i am asking.

    What caused the batteries to pop (we have an idea that it was overcharging) but why...is it the inverter at fault or just old batteries...what are the signs to look out for and how do you monitor the batteries SOC.

    Why didnt the 100 amp fuse blow ... and if a fuse is not the solution to prevent this happening again ...what is the solution... gas detection units... temp probes to monitor the battery temp.

    How to handle a situation like this... what precaution to take to prevent injury to the customer ...family ...and staff working on the premises ...what precautions are required for the cleanup operation...gloves...masks etc.

    I need someone in the know to explain to us what actually happened...what causes the batteries to pop ///overcharge or what ever it is that created this dangerous situation.

    Something that concerns me about the way this parallel inverter system was connected...

    3 inverters connected in parallel

    4 x 12 VDC batteries connected in series to make up 48 volts (1 bank)

    then the 3 banks all connected to 1 bussbar which has tails feeding a positive and negative to each inverter.

    my thoughts and i could be wrong ...would it not be better 1 bank to inverter 1 ...bank 2 connected to inverter 2 and bank 3 connected to inverter 3.

    no solar connected ...we are using the inverter as a pure sine wave backup.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    According to the instruction manual ... all 3 banks must be connected in parallel to 1 bussbar and 3 tails ...one to each inverter.
    Comments are based on opinion...not always facts....that's why people use an alias.

  11. #10
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    The first issue is the connection of 4 batteries in series. This has been so since the beginning of battery circuits.
    Under no circumstances during manufacture or battery use, will all 4 cells charge and discharge by the exact same amount.
    If you take a volt meter you can see for yourself.
    Measure the voltage of each cell and write it down on a piece of paper.
    Now the specifications say that each battery will be charged to 14.8V for a full charge cycle.
    During the battery lifespan, the chemistry each each battery will be affected individually, meaning that not all cells will charge to 14.8V, what you will find is that some batterries will take longer to charge than others, so if you measure each battery you may get say 12V, 12.2V, 12.5V and 11.5V. Add them all up, and the charger sees a total of 48.2V. No probelem it will continue pushing current into the bank of batteries at the same rate to achieve 59.2V.

    Can you see where i am going with this. By the time the charger sees 59.2V, it does not mean that each battery will be 14.8V each. It may mean that the slower charging battery may be at 13.8V, and the battery that charged faster will now be over 15V. Continue this for a few hours and a few more times, and you have a problem in which the Higher voltage battery now fails completely, but the charger does not see this, it only sees 59.2V!. So one of the batteries will probably go way above its specifications, and start boiling and poof you have your bang.

    This is exacerbated by banks of batteries which are connected to the bus bar, and not isolated from each other. This is one reason why my customers complain that my chargers are too expensive, the reason? I monitor each battery and adjust the charge accordingly for each battery. This is why it is expensive. This also means that the batteries have a much longer lifespan, as each battery is always charged with in the specifications.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za

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