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Please take care with large batteries !

 
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adam2
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PostPosted: Thu Feb 25, 2010 3:39 pm    Post subject: Please take care with large batteries ! Reply with quote

This link illustrates the dangers of mistakes when working with large banks of batteries.
Two electricians were required to reconfigure a large battery bank from 240 volts nominal to 120 volts nominal.
Lacking suitable experience, they made a mistake that could well have proved fatal.http://www.hss.energy.gov/csa/analysis/oesummary/oesummary2010/OES_2010-01.pdf

The above link contains reports of two accidents, the second one is about the battery.

The first story, though not about batteries is also interesting and shows that hydroelectric power can suffer from large scale blow-ups with substantial loss of life.

Any work on large battery banks should be very carefully planned indeed.
A mistake even at 12 or 24 volts can easily kill, not by electric shock but by burns or explosion.
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Last edited by adam2 on Thu Feb 25, 2010 10:13 pm; edited 1 time in total
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emordnilap



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PostPosted: Thu Feb 25, 2010 3:49 pm    Post subject: Reply with quote

Quote:
At 29 years and 10 months, Turbine 2 was at the end of its
expected 30-year life.


Pretty good 'use by' date, I'd say!

The battery incident is a salutary lesson for us.
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hardworkinghippy



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PostPosted: Thu Feb 25, 2010 7:15 pm    Post subject: Reply with quote

Shocked
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Kentucky Fried Panda



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PostPosted: Thu Feb 25, 2010 7:32 pm    Post subject: Reply with quote

The so-called electricians need some training, they didn't check the polarity or output voltages, or interpret the drawing correctly. Any 1st year apprentice could have done that job.
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adam2
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PostPosted: Fri Feb 26, 2010 11:55 am    Post subject: Reply with quote

Haggis wrote:
The so-called electricians need some training, they didn't check the polarity or output voltages, or interpret the drawing correctly. Any 1st year apprentice could have done that job.


Agree entirely, many electricians have a good knowledge of rules and regulations, but lack a fundamental understanding of basic electrical theory.
In my own work I have been suprised at the number of electricians who state that something cant be repaired "because the parts are no longer available", they lack the knowledge to choose an appropiate replacement, and not for hi-tech complex parts, but for generic relays, contactors, transformers, lighting ballasts, batteries, and so on.
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mobbsey



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PostPosted: Tue Mar 02, 2010 11:39 am    Post subject: Reply with quote

I once welded a spanner across a 24 volt busbar before the cables had chance to melt. Damn spectacular thing to be stood next to! (provided you don't get spattered with molten metal).

If you individually fuse each battery (30A auto fuses, or something similar -- something I learnt AFTER the spanner incident) before you connect to the busbar you're unlikely to get a major surge. The problem, like the example in the PDF, is when you have long strings to create a high voltage. You can fuse the jumper cables, but if you're using the bank for providing very large currents this is difficult to do on a single string.
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adam2
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PostPosted: Wed Mar 03, 2010 11:20 am    Post subject: Reply with quote

If connecting a number of batteries in paralel, there is a lot to be said for fusing each battery.
At home I have 20 batteries each 12 volt 90 a/h all connected in paralell, via 13 amp fuses. That gives a total load capacity of about 2.5 KW at 240 volts, after allowing for inverter loses.

If connecting batteries in series, there is a lot to be said for a fuse in the middle of the series string, since this will protect against any fault, failure or mistake that may occur at the ends of the series string.

In the case of battery strings of more than 120 volts, then several fuses spaced along the series string would be desireable in order to gaurd against mistakes or faults in several places.
Also remember that a battery string of say 240 volts or more is a definatly lethal voltage, and allways live.
The fitting of 3 fuses at the 60 volt, 120 volt, and 180 volt points in such a battery would facilitate safe maintenance since the removal of the fuses would reduce the potential shock voltage from 240 volts to 60.

For 12 volt or small 24 volt systems, vehicle fuses can often be used.
For higher voltages, or for large 24 volt systems, more sophisticated fuses are required, in insulated holders that can be safely handled whilst live.
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adam2
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PostPosted: Mon Oct 03, 2011 2:09 pm    Post subject: Reply with quote

I thought it worth reviving this old thread in view of a recent accident at my workplace (not involving myself)

Two "electricians" were called upon to replace the batteries in a UPS system.

The battery bank consisted of two battery strings, each of 108 volts at 24 A/H, intended to be parraleled, to give twice the capacity, but still at 108 volts nominal.

It is not clear exactly what was done, but I suspect that they made a mistake and connected the two battery strings together with oposite polarity, thereby creating a 216 volt short circuit.
There was certainly a substantial blow-up with considerable damage, and some injuries.

This again shows the need for great care with large battery banks.
For batteries strings of more than about 50 volts I believe that fuses should be inserted in the middle of the string, not at the ends.
Had each 108 volt battery had a fuse in one of the series connections, then missconection would simply have blown these fuses.

Please be careful.
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JavaScriptDonkey



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PostPosted: Wed Oct 12, 2011 9:37 pm    Post subject: Reply with quote

Why were electricians called to do that job? Any work on a UPS should only be carried out by an engineer trained to work on that brand of UPS. That may or may not be an electrician but he probably will be an electrical engineer.

Electricians are certified to correctly maintain and install electrical supply circuits, not random electrical devices.

I'd have a word with whoever carried out the the risk assessment and point out the damage that their incompetence caused.
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adam2
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PostPosted: Sat Oct 15, 2011 1:48 pm    Post subject: Reply with quote

JavaScriptDonkey wrote:
Why were electricians called to do that job? Any work on a UPS should only be carried out by an engineer trained to work on that brand of UPS. That may or may not be an electrician but he probably will be an electrical engineer.

Electricians are certified to correctly maintain and install electrical supply circuits, not random electrical devices.

I'd have a word with whoever carried out the the risk assessment and point out the damage that their incompetence caused.


You may well be right.
Whilst I consider myself competant to work on large battery banks, whether attached to a UPS or otherwise, this may not be true of all electricians.

Last time that a similar job had to be done, I did it, as I have many times in the past.
My employers may have concluded, that becuase I had done similar work, that anyone in their employ could do it.
Obviously not !

It is however a cautionery tale regarding large battery banks as might be used for an off grid home or for standby purposes.

Large batteries make me nearly as cautios as large volumes of petrol.

The risks are far less with a single 12 volt battery, but care should still be taken, and advice sought if in doubt.
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JavaScriptDonkey



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PostPosted: Sun Oct 16, 2011 10:23 pm    Post subject: Reply with quote

Ah well, you can keep us informed as the legal case progresses. No doubt getting sued by the injured will educate your employers about their obligations to employee safety.
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adam2
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PostPosted: Thu Jan 19, 2012 11:41 am    Post subject: Reply with quote

JavaScriptDonkey wrote:
Ah well, you can keep us informed as the legal case progresses. No doubt getting sued by the injured will educate your employers about their obligations to employee safety.


Update time.
The two engineers involved recovered from their injuries without any permanent harm being done.
One has been dissmised for not following the correct procedure for battery replacement as detailed in the method statement with which they were supplied. The man in question expressed every confidence in his capabilities.
The other engineer has resigned.

The incident was reported to the HSE who concluded that the engineers did not have sufficient experience and should have sought advice before proceeding.

I now have plenty of nearly new batteries Smile
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SleeperService



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PostPosted: Thu Jan 19, 2012 12:03 pm    Post subject: Reply with quote

The girlie is working in the local A & E department at the moment.

They had a guy in a couple of weeks ago who died after being hit with 240v mains. Apparently he was putting a new face plate on a power socket in his house.

Your two guys could easily have been in the next chiller cabinet Shocked
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PostPosted: Thu Jan 19, 2012 5:51 pm    Post subject: Reply with quote

There are two "consumer units" in our house, the larger of which has a big f-off red switch right in the middle. I assumed it shut off the entire house, but found out by chance one day that it didnae. Luckily for me, I wasn't doing anything critical at the time. It didn't half give me a lurch in the guts, though. I could have joined all the aforementioned guys in the chiller.
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PostPosted: Fri Jan 20, 2012 1:16 am    Post subject: Reply with quote

Yep things aren't always as they seem. She had to go to the coroner's inquest today and took me along for moral support. Not sure what I was expecting but the coroner looked like a well fed salesman in a good suit and was very good with people.

Turned out the deceased had taken a jolt up one arm and down the other, an unknown (to the family) underlying heart condition did the rest. Accidental death natch. All for a fancy socket faceplate Crying or Very sad
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