Substation battery charger unit with dropping diode

[krisys]

In the substation battery charger (also called as DC UPS in some regions) in order to facilitate the boost charging of the battery, dropping diodes will be provided. This practice is being followed in many places.

Recently I have come across a team of electrical engineers in a technical services department of a company, who are unanimously convinced that the dropping diodes are not reliable. Hence dropping diodes shall not be used. I was trying to convince them, but in vain.

Any views or experience in using the dropping diodes for DC UPS system?

Thanks in advance

 

[ScottyUK]

Most series diodes for voltage regulation are generously over-sized, so I'm not sure why there would be a perceived reliability problem. The shorting contactors are handling very low voltage so there's little to trouble them either. It's an old and proven technique, even if it is a bit clunky by today's standards.

 

[wbd]

I think there are more failures due to the filtering capacitors getting old and drying out. Those should be replaced every 10yrs as a minimum.

 

[krisys]

Is there any other way to facilitate the boost charging of the battery bank without overstressing (by the excessive voltage rise) the connected loads?

Without the dropping diodes, the voltage regulation becomes very poor, sometimes even exceeding the permissible voltage variation guidelines.