Safety for the user  is not as big a deal - batteries at around the KV level can be made to be no more dangerous than a fuel tank. What is needed is isolation mechanisms to chop the pack into isolated shorter strings if there is a fault condition or a serious crash. The other aspect is current limiting. Current car battery pack designs however  are something to behold -

The Tesla S as a 'high performance' example has a battery built up from many many small cells....

each cell is an 18650 of about 3 amp-hours capacity.

(that part no means  an 18mm diameter cylinder, 65mm long, so to visualise it has a  similar aspect ration to  a stick of two  C cells  )

Each cell is 4.1 to 4.2V when fully charged, and more like 3.5 when run down.

Now a car has 7104 of these cells

arranged as 96 series by 74  parallel cell s (to make ~ 402 volts at full charge ) .

( so a single module is 3.5 to 4V or so  but 220 AMP-HOURS !!!)

The economy 60-kWh battery option uses fewer of the same 74 cell parallel modules (to make "just" 352 volts, needing 'only' 6216 cells)

Other car makers vary quite a bit, but the basic requirement for large numbers of small cells in series parallel stacks is always the same.

The 'gaps' between the cylindrical cells in the modules are not wasted by the way but used to circulate cooling fluids (forced air  or liquid depends)


connectors are something else and need pilot contacts  and interlocking to ensure dead or at least no more than exposed ELV when unmated.

And 3 phase is better than DC for arcing and power density for a given weight of copper.

personally I see something near to an AC supply of  690/1k2 as a possible future sweet spot in terms of the cross-over between sensible connector pin sizes at lower current, and the level of insulation needed at higher voltages.


M.

Safety for the user  is not as big a deal - batteries at around the KV level can be made to be no more dangerous than a fuel tank. What is needed is isolation mechanisms to chop the pack into isolated shorter strings if there is a fault condition or a serious crash. The other aspect is current limiting. Current car battery pack designs however  are something to behold -

The Tesla S as a 'high performance' example has a battery built up from many many small cells....

each cell is an 18650 of about 3 amp-hours capacity.

(that part no means  an 18mm diameter cylinder, 65mm long, so to visualise it has a  similar aspect ration to  a stick of two  C cells  )

Each cell is 4.1 to 4.2V when fully charged, and more like 3.5 when run down.

Now a car has 7104 of these cells

arranged as 96 series by 74  parallel cell s (to make ~ 402 volts at full charge ) .

( so a single module is 3.5 to 4V or so  but 220 AMP-HOURS !!!)

The economy 60-kWh battery option uses fewer of the same 74 cell parallel modules (to make "just" 352 volts, needing 'only' 6216 cells)

Other car makers vary quite a bit, but the basic requirement for large numbers of small cells in series parallel stacks is always the same.

The 'gaps' between the cylindrical cells in the modules are not wasted by the way but used to circulate cooling fluids (forced air  or liquid depends)


connectors are something else and need pilot contacts  and interlocking to ensure dead or at least no more than exposed ELV when unmated.

And 3 phase is better than DC for arcing and power density for a given weight of copper.

personally I see something near to an AC supply of  690/1k2 as a possible future sweet spot in terms of the cross-over between sensible connector pin sizes at lower current, and the level of insulation needed at higher voltages.


M.