1)you can make your own lead acid battery. If a battery is totally dead you can reuse the case and terminals, but you have to fully take it apart and insert the items required.
2) thats fine, ofcourse if anyone is near me either via public transport or location and want to donate their dead batteries feel free. I'll also be taking some materials for recycling for my battery project as well.
3) Dead batteries cant, but repaired dead batteries can. you can use them for jump start if you get the CCA right but capacity wise nope.
4) Simply that some of the thickness of the metal anode/cathode will be gone. Since you can scrape some of the material away and some material is lost to the whole reactions over time, this is why the lifespan will be a lot less and why the performance will only be a bit less. remember the CCA testing tool is your friend here in checking if its ok to buy and irregardless recond or new, price is the main factor. To me the risk of recond batteries makes them only worth half of a new battery. If the metals are too thin and you discharge the battery too much at one time, could be permanently dead. Also rust is a factor here.
5) Yes but its mostly computing, i do intend to update the information layout and add more content soon but my next few articles are going to be on IT related stuff as thats the most recent stuff i'm writing. I'll definitely do a youtube on the battery and write up but theres a queue. Just search for my forum name, its a well known alias in some places.
For instance system-error-message.com . I'm still working on my site as i migrated it out of shared hosting (being broke) and onto my own clustered low powered hardware. Still got a few things to work out for the site to be working well other than just working.
6). as long as theres metal and electrolytes, the battery lives. The thicker the metal, the longer before the metal disappears or becomes completely unusable. You can replenish the electrolyte easy but the metals require full disassembly. The thinner the metal, the faster it dissolves, the faster battery dies.
7) battery being in the boot, away from heat does help its lifespan. Lead acid is acid, it dissolves metal slowly, heat helps speed up the process.
8) They do, heck even i did manage to repair the old AGM battery, but because of corrosion and shorted cells it achieved 8V which is its new fully charged state due to it now being 4 cells only (4x2V is 8V), 6x2v is 12V. I do not intend to create a business of repairing batteries, the charger is cheap enough that you can do it yourself. foxsfur (not sure of exact spelling) is one inexpensive brand that you can buy that supports charging different 12v/24v batteries and repairing lead acid ones as well. If the pulsing doesn't work, after the process finishes, you proceed to replenish electrolyte then charge. Many youtuber testing did find repairing to work half the time. Good quality batteries work well with this because all it does is clear the metal plates from the crystalisation from the sulphur bonding to the plates and covering them, breaking the circuit. But sulphur does have its place in the voltage chart so the right voltage does cause it to become an ion again.

That seller is unscrupulous. A recond/repaired battery will never be as good as new. My car has space for 2 batteries and new batteries can be cheap as well. It was never the intended purpose but the metal you put the battery on is big, only the side metal holding the battery broke away. Duct tape does a good job here though. you can use recond battery as backup batteries, UPS, emergencies, etc. For instance theres a lead acid based starter instead of the lithium ones. Those are bulky and what breakdown services use when you're stranded because you left the lights on and use lead acid batteries. Recond/repaired batteries fit fine here, or in your boot as an emergency, or even as a UPS battery if your old one dies. Thats why i said their value is half, They're no good anymore for use in the  car because even with the CCA rating the capacity isn't there for the design of the car to operate a certain amount of time if the alternator fails. Battery size choice for cars is based on the engine CCA needed, starter motor used and how long to run the car in event of alt fail. If alt fail + battery fail, then car dies which is why the accident is due to both battery run out of juice and alternator fail first. A lot of times an alternator failure is not shown on the car (battery light doesn't turn on). Also a rush job and not properly connecting terminals and isolating them can cause said accident where car dies. Happened to me after a bad pot hole, some streets later the battery slit forward and shorted against the hood. Car totally died but it was some inroad and i stopped just right infront of a TNB substation. Ironic to stop infront of TNB for an electrical issue. There was an explosion at the battery terminal, the battery still had some juice but it was completely useless in starting the car. I had a powerbank starter so after i got the connector off the hood, i started the car and drove off, went to mechanic next day and got another incoe battery. These incoe batteries are tough but only for the see through ones, they can con you with the non see through ones.

If you wanna downsize your lead acid battery to start the car you can, but make sure you have another power pack to help run the accessories. starting the engine needs current, and CCA rating doesnt care about capacity, so you can make a battery with capacitor design for that current, but have little to no capacity to run stuff.  In my opinion a dual battery design would be a lot better, mixing a lead acid battery with another battery (not lithium) could pretty much do a lot of good for start stop engine feature and not having to keep the engine idling. Pulsing the battery restores the CCA rating, and maybe some of the capacity, and this is one way to keep your battery long lived if you do it every year while its still kicking. Pulsing is no myth, it does work but it can't do miracles. If a battery is fully dead, voltage won't help. If the metal plates are covered which does happen after enough usage, this helps. If you take care of your battery from things like heat, maintaining it and keeping it fully charged, pulsing it every year, it will last long. Not much you can do with maintenance on a sealed battery other than charging and pulsing. Pulsing too much is bad for the battery too as it does not like overcharging (or for lead acid, the electrolyte doesn't like high voltages). Once a year is the max i would do to keep it strong. Thats why its important to turn on your car engine every week at least to operating temperature for the engine, and for battery to fully charge. You can also get voltmeters to stick into your car's electrical sockets. If it can't go up to 14.2-14.5V you should check your alternator (it takes time to charge the battery but at full charge you should see said voltages).
As long as the electrolyte doesn't electrolyse away at 4V then it should work as intended, to have a battery that can be both safe and abused with half the materials reused.

1. Make a new battery as in video like Post's #29 Dead Old Battery Restoration by Young Boy ? If that was what you meant, then cannot because even if one is provided with a new terminals and case, one could still not make a lead-acid battery properly. And seriously it is not even worth it because the quality will never match that of a real battery produced in a state-of-the-art factory. Even batteries produced in shoplots can never match the technology used in such a factory. Like I had mentioned earlier there is a serious flaw between such batteries and those from state of the art battery factory. Has anyone found out what it is yet ?

8. I think I may have misunderstood something. I cannot remember the correct term as there was a huge disagreement in Battery University about this. When you mentioned Foxfur battery charger or any other battery charger, then yes I agree, in order to help maintain the health of battery continuously in a high state of charge. I cannot remember the term but I think is desulphator or something like that, which is used to breakaway crystals that have completely hardened to make it crystal free or very low resistance ohms. Of course, that did not happen, if it did, battery companies would have would up long ago. I believe charger can only do so much in breaking down the soft crystals only, not the tough hard ones.

Having said that, I believe that chargers are only applicable for batteries that are under charged. A battery that is regularly being charged up sufficiently, need not require to be place on an external charger whatsoever. Battery tests conducted regularly on my clients shows the same results. My client who drives daily even if its just short distances from Durian Daun to Ong Kim Wee will still be able to keep their batteries as a Good Battery status. Her retired mum that hardly uses her own car, i will need to re-charge her battery everytime it shows Good, Recharge status.

As for the alternator failure, that is why Century Battery advises motorists to get their battery and vehicle electrical charging system tested out regularly. That way, when an alternator is in failing period, a charging test will be able to detect it immediately and the owner must immediately address the situation. An alternator does not simply fail on the spot. It degrades gradually overtime and that is where good tester are able to accurate capture and show the results immediately after certain threshold had passed.

What ? Your battery shorted against the hood and it didn't catch fire ? That ain't supposed to happen. If both your terminals were exposed, the battery ought to catch fire already, when it came into contact with the hood.

1. Is the Red Terminal Plastic Cover over your positive terminal missing ? It is here for that reason.
2. The battery ought to be securely locked down. Ini mesti masalah mekanik. You cannot imagine the number of times I had come across cars with missing battery tie down or clamps. Crazy sial. Some mechanics thinks that those are a nuisance. It can be a pain in the ass to lock down in some models like Hyundai Matrix but it necessary to do the job properly for the safety of their clients. Gila sial some workshops with such lazy attitude.

TQ bro for sharing your experience about the pot hole, now I will advice clients without battery tie down about this.

Note : About other points that you have raised, yep I agree. 😊

Just out of curiousity where are you located if it is very far?
1) when i say make a new battery i mean using newly refined materials even if they are recycled. That means new lead, pure water, acid, etc. When you make your own battery the quality depends on the materials and process, and the only flaw a self made battery has is sealing it. The one thing that water based electrolytes are known for are electrolysis at 2V, so slowly the the electrolyte can turn into a gas. If it is air tight then this happens very slowly with very little gas escaping. Also many batteries no are made with vents so in the case of such a thing instead of bulging it will just vent the gasses. This is why you need to replenish the water in lead acid batteries. Also if you do not seal the battery, acid can spit out around. Really the major thing when making a lead acid battery is the lead, so good batteries have thicker lead used and car batteries care about CCA most which is surface area of the lead.

8) Desulphate, this is what i mean by repair and yes i've tried it and it works. Given that the battery was at 4V and already shorted i got it up to 8V which is its supposed voltage (2V per cell). Since some cells shorted it became a 4 cell battery. It was a failure due to the short. The battery was physically damaged. Desulphation actually works. So we have batteries where it performs poorly because the surface is covered by sulpher crystals which reduces the capacity and CCA rating and this happens over time. A dead batter you can't repair/desulphate is one where the metal plates are already gone, if you want to see said effect, try the copper zinc salt water batter. The zinc disappears so it cannot be recharged and the copper is fully covered. Even if unused they will corrode away that even trying to recharge will barely work and you can't even charge at a high voltage. The distance between lead and lead oxide in a lead acid battery is > 2.1V. When you put 2 leads, add a charge 1 becomes oxidised. When you use the battery one terminal sulphates and thats why the cut off voltage is like 10.7V before charging gets difficult. You can provide a voltage but it won't accept any current, and this is where desulphation helps. I did test this as well with a bench PSU, i could see the amps it pulled. At high volts it started small then increased as the crystals broke free. Once the crystals broke free though then it decreased and you would be overvolting it. Desulphation should be left to computerised chargers than manually trying to do it (i tried a bit of manual to understand the volts and the rest i let the charger do it). The charger is cheap and has a desulphation mode but only works on 12V/24V batteries.

My car is old, it never had any terminal plastic cover. I bought it used. It did explode and i could see the insides. I'll post a picture later but it didn't catch fire. You see, electricity isn't fire, fire starts if you have something that can burn at the temperature produced by the short. Since its just metal thats not gonna burn and it throw the battery connector into the hood. My alternator was fine at the time, now dead (13 years old already so its right).

Much older cars had voltmeters so you could tell from there if your alternator fails. There are many signs as well so fool on you to ignore them and you can buy USB/extensions for your car sockets that show the voltage.

I am located in Melaka bro.

A dead short occurs when there is a direct connection from the positive to the negative and in such cases it will catch fire where the points meet. Since metal is not combustible so that is good, however wires and low quality insulation that is nearby has the potential of getting burnt. So that did not happen so it is most likely not a dead short.

Before I go further, how old was the battery that exploded ? Was it a Wet Cell or Dry Cell ? When was the last time the battery was checked and serviced ?

I teach all my clients how to interpret the voltage readings but not everyone will understand it fully. Over-charging happened to a client. Now that I have the evidence of an over-charged battery and how disastrous it can be, I used that damaged battery as a teaching tool to all my clients and now it is much more effective. 😊

Wet cell, approx 6 months old. Been fully discharged twice at least from new and even after it blew it was still able to turn the lights on but not start the car. Terminals are all pure metal so there are no plastics that will burn from that. As i said, the incoe batteries that are transparent seem well made, because you can actually see into them. It was not serviced for 6 months because i didn't really know much about the battery at that point as there was no info available. It was only after the incident that i asked my mechanic the details of the battery that he was able to give a few, however i find that these batteries lack specs because i suspect that there are many manufacturers/factories that make these batteries, so like any 3rd world factory, the transparent ones are good because you can see it directly, so the metal plates look small, same for the amount of fluids (giving them their lower CCA and capacity), but they seem sufficiently thick to last. However the non transparent incoe batteries have bad reviews because you cannot see into them. Incoe being indonesian as they were they cause behind the perodua and mercedes fuel pump issues (the indonesian factories were pumping out defective pumps).

Upon checking photos it seems that all that happened was that the terminal had melted itself. and could no longer be properly connected.

Overcharging is different from an external short. if you want to try repairing your batteries through desulphation sure, just get the charger with that mode, then after its been repaired add fluids then charge. The lifespan of a battery depends on its metal plate thickness. Most batteries for cars nowadays only need CCA (surface area) so use thin but large sheets. Batteries that deep cycle prefer smaller surface area but thicker plates.