Yes larger or more batteries would cause more damage than smaller or fewer batteries. All lead acid batteries have acid in them and can "explode" if shorted. The advantage is sealed batteries can sit in any orientation without leaking.



Batteries are optionally vented to release pressure of gases formed are hydrogen and oxygen -- specifically during charging. In the chemical reactions, sulphur only bonds to the lead and back to H2SO4. Sulphur is never vented because no other reactions are available with the chemicals Pb, H and O.



James, what would be helpful is details of ROOT CAUSES of these fires and stories you posted. Jump starting a car should not cause the battery to explode, so why does this happen? Some component failed and shorted and turned part of the circuit into a heater -- and the system supported huge currents and had NO FUSE. A battery in normal condition should also not produce enough O2 and H2 during charging, nor have enough volume inside the battery to support an explosion that blows the top off. Was the battery low on water or have other issues like being old and dead and thus having a very high internal resistance?



Was the cause only ignition of O2 and H2, or was there a short or thermal run away?



Short any car battery or sealed lead acid battery -- or almost any battery -- and you have a guaranteed fire.



Cars and equipment with large wires are so dangerous because it allows a large current and lots of power. Any system with smaller wires would (failing a fuse), quickly melt wires -- instead of heating giant wires into molten copper and boiling the battery until it explodes.



The most common fire during jump starting is from crossing the polarity. Be sure to hook plus to plus and minus to minus! A safe way to jump start is to hold on to one of the clips, then put another hand on the insulation of the wires to sense temperature. If something gets too hot, disconnect. Otherwise the insulation will melt and the bare wires will touch the car frame(s), shorting the battery. However if you cross polarity, you may have no time to disconnect -- it will start melting immediately!



Lastly, the large wires you talk about on cars and charging equipment is to support large current; large wires are NOT required and in-fact make a system SAFER. The reason car wires are large is because the voltage is so low, and the nature of electricity. If the voltage is doubled, the current is halved; likewise the gauge or thickness of the wires can be halved too. The efficiency of the transmission also increases and less energy is lost to heat. Wires should support the load. You don't have to charge a large battery at a large rate; the charger simply supplies any amount of electrons at 13 volts, and a thirsty battery will take it. It just takes longer, but no safety issues. Lead acid batteries last longer when charged slowly too. So charging slower will produce less potential oxygen and hydrogen.



When I was a child my dad worked at a large telcom office and data center (8 stories), where they had 6 backup generators in a separate building. However in the center of the main first floor (of the offices and data center) was a giant room full of large tractor-size lead acid batteries, hundreds of batteries. They were setting in shallow water trays with 1.5 inches of water. The batteries cover short power outages and gives time for diesel generators to startup. This has been common for data centers; with proper use, monitoring, fuses, disconnects and ability to dilute acid it has been safe.



We could freak out about all the lithium ion batteries in our pockets, in our headphones, laptops, etc. Any puncture is likely to start a fire that has its own oxidizer and literally cannot be put out with anything, including unlimited water. The only thing that can stop such a fire is a giant cryogenic dump or shower of liquid nitrogen.



You know lithium ion batteries can autocombust if their voltage is too high or too low, or if they are charged or discharged too quickly?



This project is on-target in the sense that using large lead acid batteries is traditionally the most efficient commercial option. Nowadays lithium ion batteries may be effective. However the logical option for consumers is to hack an existing UPS as done here.



We need more support, education and devices to support this type of hack. It might be that we can apply BMS or use a microcontroller to both control charging and discharging and safety, while also shutting the connected computers down. This way we can design our own safe and ideal system from the ground up and leave the UPS systems out of the loop.



All systems should have:

1. fuses

2. temperature sensors on key components: batteries, power supplies, hot / weak points

3. current and voltage sensors on key components

4. ability to shutdown or disconnect components if system shows thermal run away

5. placed away from people and nice things

6. tested before put into operation

