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sealed lead acid to flooded lead acid battery

Discussion in 'Power Electronics' started by roltex_rohit123, Apr 29, 2010.

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  1. roltex_rohit123

    roltex_rohit123

    92
    0
    Oct 12, 2009
    I have a sealed lead acid battery of 7.5 Ah from my computer UPS. it shows diminished performance but charges to 13.2 volts. I think the liquid inside it has evaporated. I am thinking of converting it to a flooded lead acid battery and use it for my emergency lantern. can I convert the sealed lead acid battery to a flooded one by pouring battery acid in it? then i could maintain it by adding water from time to time. is there any risk? will the battery work? I have build a charger to give unrectified 17volts to batery which is maintained at 14.6 volts.
     
  2. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    DO NOT DO IT. It is not going to work and will be extremely dangerous. Sealed lead acid batteries use immobilized gel rather than a liquid so it is normal for them to appear dry.

    Giving 17V to a 12V battery is equally dangerous. That is not the way to charge a lead acid battery. And that assumes that you mean "rectified" 17V.

    ---55p
     
    Last edited: Apr 29, 2010
  3. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    While I do not share 55p's perception that everything in life is extremely dangerous, I acknowledge that there are several reasons it probably won't work.
    1st is that there are more failure modes to a battery than just drying out.
    2nd is that even if it only has gone dry the plates will likely have suffered sulphation.
    3rd is that by really flooding it you will get serious problems with gas burping spilling acid all over the place as the vents are not designed to separate the acid from the gas.
    These batteries usually has fiberglass mats that acts as separators and acid storage. Gelled batteries also exists but are not as common.
    There are rubber capped vents underneath the (circular) lid(s) in the top. The lid(s) can be pried off to gain access to the caps - which can then be removed for interior axess.
    When a battery dries out it's only the water being lost, not the acid, so refilling should only be done with distilled water, and only so much as to replace what has been lost.
    After filling the guesstimated amount the battery should be turned upside-down and allowed to drain any excess acid. Fill small portions because if a lot comes out again then the remaining acid will be too weak and you will be challenged in restoring it to the correct strength. Replace the caps and glue the lid(s) in place.
    Charging of course takes place with a regulated supply of 14.6V with no more than 2.3A available.
    There is only a low likelyhood that the battery will perform well after this procedure.
    If economy forces you to do this you should be aware that acid has a surprising ability to find it's way onto your clothes - which will ruin them..
     
  4. roltex_rohit123

    roltex_rohit123

    92
    0
    Oct 12, 2009
    I will plug nylon cotton like material in the vents instead of rubber caps or make pin holes in the caps to let gas escape and minimise water losses. I dont thing the seperators would affect the battery performance since they are insulation materials. I could then desulphate the batteries. also i can lower the voltage to 14.2 volts and float to 13.9 volts. what do you say?
     
  5. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Plugging the vents like that won't help. The nylon fabric will saturate with acid and start to produce bubbles & droplets itself. I'd rather put clear plastic tubes onto the vents, stretching up at least 4 inches / 10cm - if you insist on flooding & boiling the battery.

    The original rubber caps does let gas escape the way they are designed. They open at a certain pressure and then immediately reseals themselves.
    You can boil-/overcharge these batteries pretty hard w/o the vents venting. The puffs can be heard.

    But sulphating is not the only problem with SLA batteries. The grid is quite thin and after years of service the lead in the grid itself will have turned into active material all the way through. This material is brittle and the grid will break up, effectively disconnecting large areas of the cell. This can't be remedied.
    I don't know why you mention the separators in your last reply.

    For cyclic use (as you intend?) 14-15V initial charge is recommended, and float is said to be 13.5-13.8V. Temperature dictates wether you should be high or low.

    Be certain to work with the battery in a containment vessel to protect your surroundings from any acid spills, but don't enclose it so much that gas can gather.
     
  6. roltex_rohit123

    roltex_rohit123

    92
    0
    Oct 12, 2009
    yes I'l take your advice seriously. I just added 5 ml of water in each of the cells of the battery and it got hot and one of its cell swelled a little. i got scared that the battery would now n ran from there. but now i'l go to take a second look offcourse wearing my rubber raincoat. pray for me
     
  7. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    So a chemical reaction took place in the cells and it got hot all by itself? Interesting..
    I've seen these batteries swell from just getting old & dry. I don't know what's happening in the cells that makes them swell.

    It's good that you're taking precautions, sometimes reactions can take you by surprise. Using glasses or goggles of some kind is also a good idea around chemicals.

    On a couple of occations I've lost track of time while manually fast-charging Ni-Cad's. One I had to pitch out the window into the snow as it started smoking and glowing red, the other I had to put out on a window ledge where it kept smoking & popping & hopping for like 15 minutes..
     
  8. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Many unexplained things happen around this poster. In fact, he claims exemption from the laws of physics and chemistry as the rest of the world knows them. Posting history is your friend!

    There are many things that are not a good idea in general, but considering the individual asking the question, they become "DO NOT DO IT" in big red letters.

    ---55p
     
  9. roltex_rohit123

    roltex_rohit123

    92
    0
    Oct 12, 2009
    I have reason for the battery getting hot. its pure chemisry. many a times in our labs we have to prepare solutions of acids at particular strengths. there are two methods for it. either add acid to water ( correct way) or add water to acid. this is because very large energy is released in this process. many times our volumetric cylinders (0.5cm thick walls of borosil glass) also break when done by the second way. this is what happened in the battery. the swelling of cells in the battery may be because of the sulfation. but in my case the swelling was a deformity due to the heat produced. it was so hot that even water evporated that was there on my fingers when I touched the battery. now the battery is fully discharged and i have 4-5 such batteries. I am thinking of melting the lead in ceramic container and caste it as a hollow pipe 1 cm thick walls to make tubular battery. But I have no idea of how I could make other electrode. sometime back i had a similar battery and i broke open the plates. then i took two lead plates in acid and charged it very long of about a week and got a sort of brownish coating on the plates which holded good charge to light a 2 cell torch bulb for 1-2 hrs. I had no multimeter that time but now i think i should try it out.
     
  10. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Yes, that sounds like a plausible explanation, that it had run so dry that the remaining acid had become fully concentrated.
    It could be interesting to know if putting the battery in a freezer first could slow down the reaction enough to prevent a meltdown.
    Melting & casting lead requires careful considerations in how to deal with the toxic fumes, and also the risk of explosion if there is dampness in the casting container.
    But I'm wondering if not the cost of casting & all that would approach the cost of a new battery, and the result might not be satisfacory..
    Tubular electrodes are good for making long life - low current batteries. You'll have to make a paste of active material and fill in holes in the electrodes with it.
    The brown coating you observed is one of the active materials. Both electrodes can be made identical and simply be placed beside each other.
    I'm sure there are recipes on the net that describes the process. If you can't find it then I believe I have an old book somewhere that does.
     
  11. roltex_rohit123

    roltex_rohit123

    92
    0
    Oct 12, 2009
    this will crack the battery case and electrodes. never do that. if i could get the name of the chemical compound in the other electrode. I can make it at home. i have a simple assembl for Lead. even my solder machine can melt lead. I have 3-4 machines. but i am making a ceramic container to melt lead and a plaster of paris cylinder cut half vertically. i would cast the electrodes in it. the electrodes are meant to be just 3-4 cm long and about an inch in diameter. this will give me a good current density and a place to bore graphite rods from a AA sized battery in the lead electrodes. hop graphite sustains the acid. I dont have any chemical action for carbon and sulphuric acid. stil I will test it on concentrate and weak acid. also I have enough lead to make a 6 volt battery form a 12 volt battery. its abt one KG. its summer here so no dampness. n as there is slight wind all the time i will not have to inhale fumes of lead. the fumes of lead will be avoided by surgical mask and a lid on the melting container.
     
  12. roltex_rohit123

    roltex_rohit123

    92
    0
    Oct 12, 2009
    now trying a steel pot to melt the lead. I have a thermostat and an electric coil to melt the lead. once the lead melts the thermostat will be adjusted to just keep it melted until poured into ceramic mould to cast a cylindrical electrodes. The positive electrode I am not getting a solution. I am thinking of using a lead wire like soldering wire from the center and use a conical plastic electrode ( since experiment space is no problem) to retain the fallen material in the Plastic electrode case. how does it sound? will it work? steel can easily withstand the MP of lead abt 330 degree celcius. I would wear a oxygen mask and keep its pipe far behind and use cotton filter to trap lead particles if they get in the pipe at all.
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
    2,779
    Jan 21, 2010
    If you were to wear a mask with a long tube attached, you would quickly suffocate.

    That may be preferable to the damage you would do to yourself and your neighbours from the lead. A very good way of getting lead into your bloodstream is by absorption through the skin. Even if you can prevent breathing the stuff, you'll be quickly poisoned by alternate routes.

    In another post you suggest you're working from home. I know that India doesn't have the strictest observation of health and safety issues, but please don't take this as an indication that melting lead in your own back yard is safe.

    Please take note of my sig. It was designed for people who suggest things like this.
     
  14. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    A couple of cautions are in order here:
    Summer is no indicator for dryness of the casting form. It needs to be preheated sufficiently to evaporate all humidity in it - immediately prior to casting.
    Lead vapor is - a vapor, not particles.. A surgical mask or a cotton filter can't be relied upon to remove the lead content.
    Molten lead is very hot, and pouring it certainly requires skill and protective measures - like leather gloves, -shoes, and -aprons - in case of spillage.

    Do a Google on lead acid chemistry. You'll get a lot of hits. Wikipedia mentions the contents of the paste. I don't see what graphite rods have to do in your battery.
    Neither do I see the place of solder lead. That will introduce a lot of tin to the chemistry - with possible detrimental effects.
    While graphite & solder lead may work for a while, I'd use pure lead as leadouts to the battery poles, like all batteries do.
     
  15. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    There you go interfering with Darwin again.... Why rob the guy of his Darwin Award?

    ---55p
     
  16. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    So killing yourself is a goal of this exercise?

    ---55p
     
  17. roltex_rohit123

    roltex_rohit123

    92
    0
    Oct 12, 2009
    No offcourse not. If its so dangerous then I could skip this Idea...
     
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