I made my comments because I don't want to see people get hurt assuming a car battery is a safe device. With nothing in the circuit to stop the action (like a fuse), all of the stored energy gets released at the arc (as heat) or when the battery comes apart as heat and explosive force. a typical one might start at a few ohms and generate a ten amps or so - then metal starts melting and the resistance drops and the battery supplies more current - tens of amps and metal starts off gassing, plasma forms and the resistance goes lower to hundreds of amps and continues until the conductors burn away or the battery explodes. What that means - is that the current coming out of a lead acid battery is usually limited only by the load - if the load is a short circuit - the current is very large and not limited by the battery. 12 volts at high potential current is not safe.Ī battery will deliver current to a load as ohms law prescribes - Lead acid batteries have very very low internal resistance and look very much like a perfect current source. We are not talking about electric shock here - we are talking about power - mostly heat. Power in a DC circuit is simply voltage times current - 12 volts x 10 amps is exactly the same power as 120 volts times 1 amp. The fact that the battery is 12 volts does not make it safe or not require fusing. I think that he understands that theīattery needs to have a good fuse that is properly rated.Įveryone needs to understand that large 12 volt lead acid batteries are inherently dangerous and can deliver massive current into a short circuit. The gentleman building this project seems to be aware of doing it safely. I would not use a circuit breaker if it were mine. Use the lowest value fuse that allows you to run your equipment. Jump starts don't have this type of built in protection. but it has very low internal impedance to limit current - where an AC power supply has high internal impedance.īottom line - Make sure that the big battery has a good fuse that is adequate to interrupt the highest fault current that a battery can deliver. The battery does not force current into the device. There is no limiting impedance in this type of fault.
#DEEP CYCLE BATTERY BOX PC#
With a large lead acid battery, you may get a 100 amp or more surge into the device - burning traces of PC board and destroying the device. Usually you can change the bad part or fix the problem and go on. The problem is that if your camera develops a problem that results in a short - a component touching the case or some other type of fault that might occur - if it is connected to a power supply - you get a 5-10 amp surge and things shut down. There are a few mechanics out there missing fingers when a high school ring got between the positive battery lead and ground. I think the fact that a 12 volt battery presents no electrical shock hazard is part of the problem. Hot sulphuric acid is not a pleasant material. They also will explode if the high current short does not burn itself open. They can't cause much trouble - even if they fail.Ī large lead acid battery if not PROPERLY fused can instantly melt wires and burn off fingers. They will go into current limit or will blow an internal fuse. Generally they cannot deliver much more than the rated current under a short. Small camera batteries or AC supplies are limited in how much energy then can deliver. 5000 watts is a lot of excess power when you need 60 watts or so. Jump starts are designed for starting - not low current loads. It is designed to instantly deliver 3-5 KWH of energy for a short period. The battery is made to deliver 250-300 amperes to start a vehicle.
The problem is that you need 5-10 amperes at 12 volts to run the whole show. If your dew heater, laptop, or mount were to catch on fire while plugged into the wall, how long would it take for the breaker in the garage to pop? I'm not saying 'not to fuse', I'm just trying to say.it's not the size of the battery.
#DEEP CYCLE BATTERY BOX TV#
From reading everything above, I'm trying to figure out how the commercial power/battery packs don't do the same thing as the DYI packs here? Most commercial packs will also start a car, and their fusing is suspect at best.not too many people have bothered to take one apart to see what is inside.Īnd none of them force too much electrical current to motors, cameras, or laptops.if there is an over current detected, it'll be the fault of the device being powered or the wiring to the items For instance, the TV in your home doesn't require a 15amp breaker.but I'm betting the breaker on that section of those wall plugs are rated pretty close to that.Ī battery does not force current/amps to anything.
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