Switchgear Redundant DC Battery System

[Knoll149]

I have a customer wanting a fully redundant battery system, their design is each battery feeds and ATS which then feeds a DC distribution panel out to the switchgear loads. I'm looking for thoughts or white papers on their design vs. paralleling two batteries directly to the DC panel & having each charger connect to a branch circuit in the DC panel.

 

[davidbeach]

What's the matter, you forgot to include the cost of the ATS your bid?

Why do we get this constant stream of "my customer wants ______, but I want to do ______ instead, how do I talk them into it" questions?

If the customer wants something, why not just provide it? They're the one's paying the bills. If you left something on the table at bid time just suck it up and be a big boy. A contractor's favorite way of doing things is just the contractor's favorite, but it is the owner who gets to make the decisions and they get to have it their favorite way.

 

[Knoll149]

We are currently working on bids and have no issue providing the ATS, I'm just trying to educate myself so if a customer asks my recommendation I have an opinion. Also, the customer put the responsibility of designing the DC system on the switchgear manufacturer.

 

[dpc]

The disadvantage to in the alternate approach you propose is increasing the probability of a common-mode failure taking down the entire system. Also, you probably don't want the batteries and chargers all tied to a common bus - one failed or dead battery will take all of the charging current from both chargers, as well as drain the good battery. The batteries need to be isolated from each other.

 

[cranky108]

Two batteries, two chargers, two Dc panels. One feeds trip one, the other feeds trip two. That is what I would have specified, and then I would have had to had to hear how excessive that is.

The ATS seems to be a common mode problem. However this is distribution so maybe it dosen't matter to them.

 

[dpc]

I agree that the original design also has some common mode failure issues. Two completely separate systems would be more reliable. The most common thing I see fail on dc systems is the battery charger.