circuit over view and help with extras

[shortcircuit2]

hi all so i am wanting some comfermation that what i have done (as a rugh idea) will work fine and safly but also i would like to know how i would beable to tell if any of the contactors would be welded closed
i soulw like the welded contact system to run off the controle 12v system (not shown) but if not possable i understand (just trying to isolate HV and LV best i can)
so the long and short is my project will oparate ate aprox 110v dc but will charge are 220v dc (aprox)
to do this i am useing a set of contactors to reconfiger how the 2 battery packs are aranged
see atached pic
but the idea is as follows
befor any configeration a full welded contact test is performed
if one of the 2 series contacters (eg contactor 1 and contactor 15) is welded closed it will throw/show a error of wich contactor if welded closed
if both contactors in a series pair(eg contactor 1 and contactor 15) is welded closed performs an emergancy shutdown and prevents any contactor being activated

for series oparation
cantactors 1,2,15,17,9,13,14,12,3,4,18,19,5,6,22,23 are energised one at a time (indervidualy to minimise inrush current)
for parallel
contactors 1,2,15,17,27,26,7,8,20,21,25,24,3,4,18,19 are energised one at a time (indervidualy to minimise inrush current)


HVLC (high voltage low current (both battery packs in series))
LVHC (low voltage high current (both battery packs in parallel))

i know i shown contactors as switches it was just easyest and closest thing i could find for a quck mock up
sorry nubering all over the place

TLDR: need to check if each contactor is welded closed for safty

orry for spelling and grammer issues due to suffering with dislexia

[jwet]

Putting a bunch of contactors in series won't prevent welded contacts.  The last switch to close will take the same surge current.

In high current apps like electrical vehicles, they use techniques like pre-charge resistors.  You first turn on a relay with a series resistor in its path that keeps currents below your contact rating.  This might 0.1 ohm.  After some time period, you short this resistor with a relay that gives you the final current without any surges.

Usually these things have a little bit of intelligence to measure voltages before closing switches. 

Be careful, batteries can produce huge currents and melt wires, etc.

[shortcircuit2]

Putting a bunch of contactors in series won't prevent welded contacts.  The last switch to close will take the same surge current.

ho that is done for safty as i stated so just in case one dose weld closed the power can still be diconected

In high current apps like electrical vehicles, they use techniques like pre-charge resistors.  You first turn on a relay with a series resistor in its path that keeps currents below your contact rating.  This might 0.1 ohm.  After some time period, you short this resistor with a relay that gives you the final current without any surges.

thank you for the tip there

Usually these things have a little bit of intelligence to measure voltages before closing switches. 

there will be constent voltage, temp and curretn measurements taken place and if anything falls out of line it will shut down

Be careful, batteries can produce huge currents and melt wires, etc.

and i understand that i takeing all safty percotions needed even haveing special fire exstinglisher at hand that is made to deal with lithium based fiers


and i was just mostly asking about how sound my idea is honestly