Q & A of the Day - UPS below 13A (batteries in series)

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19.10.2007

 

Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This one, concerning uninterrptible power supplies (UPS) and their batteries wired in series, is answered by MGE UPS Systems:

UPS - take care of the batteries.

Question: I have a question regarding two batteries in series to make 24V. Take, for example, a fire alarm system. If battery A fails (see attached drawing) and it was left in this condition, and battery B is OK on next inspection, would you replace the two batteries or just the failed battery A?

If you need to replace both, what is the reason? And if you only need to replace battery A, could there be any damage to battery B?

Click on the button below to download the drawing attachment.

Answer: MGE O.P. Systems, in this instance, would recommend swapping both batteries to minimise the risk of further issues.

This is an interesting question, and is more a case of maintaining a chemical equilibrium within the battery system. Depending on the instability, the effect of the loss of battery A caused to battery B is the deciding factor as to whether or not to replace solely the failed cell. However, the question should be considered in terms of risk for not replacing it, and the reward for replacing the failed cell. This is purely down to site-specific situations. In one scenario, it may be worthwhile looking at the cost of replacing battery B on a call out cost basis and the inspection time table, when considering Total Cost of Ownership issues. Mixing battery ages is typically not recommended and needs to be reviewed against engineer time, MTBF, maintenance regime, total cost of ownership (TCO) etc, and the service level agreed with the customer. MGE O.P. Systems, in this instance, would recommend swapping both batteries to minimise the risk of further issues.

To see many more Q & A in Voltimum UK’s Experts Area, please click on the link:

http://www.voltimum.co.uk/consult.php?universe=consult.index.questions

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Downloadable attachment(s)

UPS battery diagram (small .jpg file)

Related contacts

MGE UPS Systems Orion House, 171-177 High Street, Wealdstone, Harrow HA3 5EA Tel: 0845 077 1945 Fax: 0845 077 1946 Email: mgesalesuk@mgeups.com Web: www.mgeups.co.uk

MGE UPS Systems

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Source: MGE UPS Systems - James Hunt