IEC defines SELV (Safety Extra Low Voltage) at 48V. That's enough to hurt, but unlikely to kill you. Over that, all bets are off.
A 48V battery is not lethal in terms of electrocution. There is other risk involved (dropping metal or creating a short), and those risk are not dependent on the electrically being 48v, but also apply to 36v, 12v or 6v. You need to take care when headlining a 12v battery or a 48v battery.
Up to 48V is considered a 'safe' voltage, but you can definitely feel it and DC is far more dangerous than AC (because with DC your muscles contract and stay contracted so it can be very difficult to disengage from the source).
A touch voltage of 50 V AC (1-1000 Hz) or 120 V DC for long shock duration (> 3 s) should not be exceeded in healthy adults otherwise a life-threatening condition may occur. For children and livestock the touch voltage is limited to 25 V AC or 60 V DC.
Low voltage is defined as 50 volts (V) or less. Common low voltages are 12V, 24V, and 48V. Low voltage is normally used for doorbells, garage door opener controls, heating and cooling thermostats, alarm system sensors and controls, outdoor ground lighting, household and automobile batteries.
Electric shock
A voltage as low as 50 volts applied between two parts of the human body causes a current to flow that can block the electrical signals between the brain and the muscles. This may have a number of effects including: Stopping the heart beating properly. Preventing the person from breathing.
48V systems have the benefit of increasing power to components without raising the current – minimising copper, which requires expensive cabling and a loss in transmission. 48V is competent enough in handling EV components without compromising fuel-economising strategies.
This low power level is the reason why low-voltage (<50V) shocks have never been fatal — there is not enough electrical energy available to disrupt bodily functions.
To achieve this safe current level the voltage across the human body must not exceed 100 volts.
It is sometimes suggested that human lethality is most common with alternating current at 100–250 volts; however, death has occurred below this range, with supplies as low as 42 volts.
Negative 48VDC (-48V), or positive grounded, was selected for use by Bell when it was found to be superior to positive voltage. It prevents electrochemical reactions from destroying buried copper cables and rendering them useless if they happen to get wet.
Because 48V systems run at higher efficiency while using fewer amps, they can operate appliances more safely than lower voltage systems. A 48V system will not have to increase its amperage regularly to provide the same power level as a 12V or 24V system.
The advantage of 48V over 24V is that only half as much current is required to get the same power. Assuming 95% converter efficiency, for 3kW output at 24V your battery wiring has to handle 132A! At 48V it drops to a more reasonable 66A.
People can be electrocuted by coming into contact with 100-200 volts and there have been reports of injuries or death resulting from being shocked with as little as 42 volts.
You point out in your letter that some consensus standards consider live parts operating between 50 and 60 volts, DC, to be non-hazardous under certain circumstances. However, OSHA considers all voltages of 50 volts or above to be hazardous.
The human body has an inherent high resistance to electric current, which means without sufficient voltage a dangerous amount of current cannot flow through the body and cause injury or death. As a rough rule of thumb, more than fifty volts is sufficient to drive a potentially lethal current through the body.
Call 911 if a person experiences a high voltage shock, which is one of 500 V or more. These voltages can cause deep burns that require immediate attention. Go to the emergency department following a low voltage shock that results in a burn. It is important not to try to treat the burn at home.
Voltages greater than 450V a.c. are especially dangerous. At this point the resistance of the skin can break down which significantly reduces the body's overall resistance thereby causing a substantial increase in current.
Similarly, if the voltage is very low (say, 10 V) and the current rate is high, still the shock will be harmless. Thus, a voltage greater than 50 volts is sufficient to drive a lethal current through the body if sufficient current is provided.
12V isn't a shock hazard, but it IS a burn hazard.
Even without a short circuit, if you make or break an electrical connection that has a lot of current going through it, the point at which the connection is made can get very hot very quickly and can burn your fingers.
You could be killed if you touched the 7KV source with one hand and ground with the other. After that, one might wonder if a 7000-volt electric fence will kill you. It will hurt for about 10 minutes, but it won't debilitate them, leave a burn mark, or kill them.
At 600 volts, the current through the body may be as great as 4 amps, causing damage to internal organs, such as the heart. High voltages also produce burns. In addition, internal blood vessels may clot. Nerves in the area of the contact point may be damaged.
48V system - most efficient and safe system when operating, when holding the same power (3000w) in the circuit, compared with 12V or 24V system, the high voltage makes it just lose very few energy during transmission, and no risk of big current.
The peak charging voltage for Gel batteries is 2.3 to 2.36 volts per cell, and for a 48 volt charger this works out to 55.2 to 56.6 volts, which is lower than a wet or AGM type battery needs for a full charge.
48V is a telecommunications industry-standard operating voltage. It is considered a “compromise voltage” by being high enough to enable relatively low signal loss transmissions over large distances, and yet low enough to be a “safe low voltage”.