Inrush from 48V battery into 9mF of power supply output capacitance

Hi
We are developing a 12kW , 48Vout Power supply with 9mF of output capacitance.

It is for a customer load which also has a 72Ah lithium battery connected in parallel with the load. (there is no inrush circuit on the load).

So we designed an inrush limiter to staunch inrush from the customer’s battery into the power supply’s output caps upon connection…however, the customer has requested we remove this, and that we simply make the connection, and tolerate the contact sparking as their battery inrush’s into the power supply output capacitors.

How long do you think the connector will last even if its highly rated up for such treatment?

Anyones guess but I would imagine a long time.
Exactly how long would depend on many factors, not only the connection material but how quickly the connection is made. A very rapid connection will create very little spark, a slower and maybe intermittent for a while connection would do far more damage.

Brian.

treez said:

Hi
We are developing a 12kW , 48Vout Power supply with 9mF of output capacitance.

It is for a customer load which also has a 72Ah lithium battery connected in parallel with the load. (there is no inrush circuit on the load).

So we designed an inrush limiter to staunch inrush from the customer’s battery into the power supply’s output caps upon connection…however, the customer has requested we remove this, and that we simply make the connection, and tolerate the contact sparking as their battery inrush’s into the power supply output capacitors.

How long do you think the connector will last even if its highly rated up for such treatment?

Click to expand...

I remember to have used some motor controllers for EV where the input capacitance is similar to the value you have used in your converter. The input battery voltage was 48V .So it is similar to your application.

The controller was a very rugged one (Manufacturer claims one or two failures in 1 million pieces)!!!!! These controllers have in-built inrush protection.

We have seen some failures in discharging contactors(Contactor welding issue) due to inrush at the starting(key-on condition) in above applications. Then we included inrush protection on the battery side as well to limit the inrush.

I suggest to include inrush protection at least on one side for your application.

Hi,

, the customer has requested we remove this, and that we simply make the connection, and tolerate the contact sparking as their battery inrush’s into the power supply output capacitors.

Click to expand...

I see no benefit in the "requirement", all I see is uncreased stress to several parts, not only the contactor.

Thus - if the customer wants this - you may/will design it, but beforehand you should clarify with the customer, that you don't support his idea ... and that he is responsible for the resulting (and expectable) problems.

It's easy for a customer to make "unusual" requirements .... and he tries to give the responsibility to the designer.
But some customers seem to not start thinking until they become responsible for their ideas.

Klaus

Eventually the contacts are going to either spot weld to each other, or get so much pitting that their resistance increases severely, or they break. If you fulfill their request, make sure they know the risks and that they're responsible.