central battery unit

[novernmunkee]

hi guys can anyone help with this one
i have being given the task of maintaining emergency lighting to a large office complex.
the emergency lighting is fed of a ac/ac 230v central battery unit.
under normal conditions 230v flows through the cbu and out to the lighting, under fault condition i.e loss of 230v a bank of dc 110v batteries kick in which is then inverted 110v dc to 230v ac for a specified time
the problem i have is that how do i safely isolate the 110v dc batteries as i need to change them as they are on there way out
any suggestions greatly received and appreciated thanks neil

 

[Engineer54]

Before i will answer in any detail, What type of batteries are they, sealed maintenance free plastic, or the glass lead acid type that needs topping up from time to time?? How many batteries are we talking about here?? And what is the over all rating of the battery system??

By the way, this can be a very dangerous exercise, both disconnecting/removing the batteries and
installing/connecting them!!

 

[Guest112]

agreed im more affraid of batteries than i am of ac , a mate of mine dropped a spanner onto a bank of batteries and the spanner basically exploded

 

[Engineer54]

agreed im more affraid of batteries than i am of ac , a mate of mine dropped a spanner onto a bank of batteries and the spanner basically exploded

This is one area of work, where i would insist that all tools, including spanners and ratchet socket sets are 1000v insulated, ...Very little chance of that happening, dropping one of those spanners!! lol!!!

 

[KINKY]

I would just allow the emergency lights to drain the batteries.

The inverter will have a low battery voltage cut-off device, this will need disabling.

TBH it may be easier to just connect a load straight to the batteries and drain them completely.

 

[Engineer54]

I would just allow the emergency lights to drain the batteries.

The inverter will have a low battery voltage cut-off device, this will need disabling.

TBH it may be easier to just connect a load straight to the batteries and drain them completely.

That's Bad advise!! This could cause a potential explosive build-up of gases/fumes within each battery cell, God forbid if you then accidentally short any +/- connections!!!

It could also damage the internals of the connected inverter trying to compensate for the lower incoming voltage..

 

[Specialist]

agreed im more affraid of batteries than i am of ac , a mate of mine dropped a spanner onto a bank of batteries and the spanner basically exploded

Really not a pretty sight, is it. Was your mate ok or Badly injured ?

 

[Specialist]

That's Bad advise!! This could cause a potential explosive build-up of gases/fumes within each battery cell, God forbid if you then accidentally short any +/- connections!!!

It could also damage the internals of the connected inverter trying to compensate for the lower incoming voltage..

Totally agree with E54 not good advice at all.

 

[Guest112]

Really not a pretty sight, is it. Was your mate ok or Badly injured ?

he was alright just a bit shaken up, he said when he dropped the spanner his reactions made him look away thank god

 

[Specialist]

he was alright just a bit shaken up, he said when he dropped the spanner his reactions made him look away thank god

I'm glad to hear he was ok. A good many years ago now I was installing Sub metering at a Milk Depot & was unfortunate to be present when an Engineer dropped a spanner across the Battery Terminals on an Electric Float. It's a sight & smell i'll never forget, the Guy lost 1 eye & part of his face. Possibly fortunately for him he died in Hospital a few days later.

 

[wildgoose]

1, Ensure batteries are totally isolated from their load. If they are passing current when you disconnect them, you will get arching. Depending on the battery type, this may cause explosions - especially if hydrogen involved.
2, Make sure area has been well ventilated to disperse any gases before battery disconnection.
3, Wear gloves, overalls and full face mask - electrolyte is very corrosive.
4, When disconnected, make sure you can easily lift batteries out for replacement.
5, Observe polarity for reconnection in same way. If batteries are connected in series banks, then be aware of potentially high DC voltages -nasty!!
6, With all new batteries in place and terminals tightly connected, you can then re-energise isolator.

Take care - banks of batteries can be very dangerous

 

[Marvo]

I have to be honest and say if you've got no experience of working on large battery banks maybe get some assistance from a pro. Battery systems are very unforgiving and even a minor error can have spectacular results you really don't want to see. I've heard of several deaths of people from these systems.

 

[Engineer54]

I have to be honest and say if you've got no experience of working on large battery banks maybe get some assistance from a pro. Battery systems are very unforgiving and even a minor error can have spectacular results you really don't want to see. I've heard of several deaths of people from these systems.

Also, depending on the type and amount of batteries, the room they will be housed in, could well come under Ex rules. The ventilation and air exchanges requirements could also come under other explosion-proof room regulations, along with sophisticated gas detection fire alarm system. Battery storage bank rooms can be a very dangerous environment when things start going wrong!!

Almost all of the major project's i've been involved with, have all had such installations for the uninterruptible DC supply related to the main MV/LV switchboards control circuitry generally 110 V/DC...

 

[Specialist]

Well remembered E54 i'd forgotten about EX requirements for Battery rooms, shows how long ago I last did 1. Beginning to feel old now:lol::wheelchair:

 

[novernmunkee]

thanks for all the advice guys much appreciated i'll get as much information as i possably can from the batteries cbu before i proceed any further