Connector sparking with multi kW equipment is just normal accepted practice?

[zenerbjt]

Dear Engineers,
I was being shown round a battery driven equipment of several kW power by a member of staff.
The equipment has multiple electric drive inverters and BLDCs.
Battery voltage is 14S LiPO , but sometimes 24S LiPO. The guy seemed worried. Then he said something which really concerned me. He said that when a newly charged battery is connected to the equipment, then if the battery is not very quickly and firmly slammed into the connector, then there is much sparking and the connector is so badly damaged that the connector has to be replaced, and that this takes much time, and is an awkward job. He told me that usually only special people are allowed to connect the battery, because it takes a “special touch” that most don’t have…….and otherwise, serious connector damage results.

So I take it that there is no inrush limitation on this circuit.
The inrush is obviousy into the bus capacitor banks.

To me this sounds very bad, as the connector could become high resistance and the equipment could possibly fail.
Can you describe…..i mean….maybe, just maybe, it is standard procedure, with high power items like this, to just save money and not use an inrush limiter?..... and just agree to replace the connector after every say five mating cycles?……I mean…is this the kind of thing which goes on with these kind of equipments?

 

[rjenkinsgb]

I'd say it is just bad / cheap design. There should ideally be some inrush protection or later switching so the connector makes and breaks with no load.

Or, is the equipment designed to be charged with the battery in place & the users are swapping batteries for their own reasons?

Some types of power equipment with connectors have special plugs with early-make pins and resistors from those to the main power connections, so the electronics can charge up before the main power pins connect.

 

[picbits]

Can they just not make a temporary "link loom" which charges up the caps through some resistance before swapping to the final connector ?

 

[gophert]

Try adding dielectric grease to the connector surfaces - then the arc distance is changed.