Re: [Repeater-Builder] Battery Back-up Question

[Doug Zastrow]

Kevin,   Thank you for the dimensions...  That helps a lot.   I took a look at several different lead-acid batteries at work today and calculated an AMPERE-HOURS per cubic inch factor.  Applying that to the dimensions of your cells I am almost certain the battery specification you are seeing is 460 AMPERE-HOURS at a 10 hour discharge rate.  So the manufacturer has rated them to deliver 46 amps continuously for ten hours before dropping to the rated discharge voltage.  (AMPERE-HOURS = AMPS multiplied times HOURS)   Based on a 10 amp *continuous* current draw you should get at *least* 46 hours of operation if the cells are in good shape.  From my experience in the telecom world I wouldn't be surprised to see 60-70 hours.  Again, assuming the cells are in good shape.   As you've concluded, the real test will be to place the batteries into service and see what you actually get out of them.   Now would be a great time to label the cells 1 through 6 and start a log book for them.  Initially you'd record the voltage of each individual cell and it's specific gravity.  Measure them from time-to-time and record what you find.  That will give you a good history to watch for any cell degradation.   Sounds like a nice battery string to have for backup.  Good luck.     Regards,   Doug ----- Original Message ----- From: Kevin & Natalia To: Repeater-Builder@yahoogroups.com Sent: Monday, February 13, 2006 3:19 PM Subject: Re: [Repeater-Builder] Battery Back-up Question Hi Doug,   The battery is made up of 6x 2 volt cells. Each cell is large, can be lifted by one person, but not easy or light. (Talking from lifting them myself) Each cell is about 400mm high, 200mm wide, and 130mm deep. They have 2 positive and 2 negative terminals. The casing is heavy clear plastic, so one can see through into the cell for the level. On top are 2 venting caps.   When all the cells are put together, they make a fairly large(long) battery.   What I was working on, if it can run for 460amps for 10hrs, then 460a * 10hrs = 4600/10a = 460hrs. Calculation was way out.   Thanks to everyone who provided help. The real test will be a real test, but if I can even get 80-100 hrs, I would be happy.   Regards   Kevin.   ----- Original Message ----- From: Doug Zastrow To: Repeater-Builder@yahoogroups.com Sent: Tuesday, February 14, 2006 1:40 AM Subject: Re: [Repeater-Builder] Battery Back-up Question Kevin,   Before I take a stab at this could you give me a rough estimate of the physical size of the battery?  Where I'm headed with this is I'm trying to ascertain if your cells are truly rated at 460 amperes for a 10 hour duration or whether it's actually 460 ampere-hours (amps multiplied by the number of discharge hours) which is common for industrial cells in the US.   If truly *460 amperes for 10 hours* then your cells are capable of 4600 ampere-hours or 460 amps continuously for 10 hours.   If *460 ampere-hours at a ten hour rate* then you're looking at 46 amps over 10 hours.  A considerable difference.   (The physical size of the cell will hint as to which is correct.)   The other caveat is that the longer the discharge time (generally) the more effective ampere-hours that a cell will deliver before it is discharged.   If the cell is truly rated at *460 amperes for 10 hours* then you're looking at well over 460 hours at a ten amp continuous load.   If rated as *460 ampere-hours at a ten hour rate* then 46 hours at a ten amp continuous load.   As mentioned in an earlier post, the true load will play a factor.     Doug     ----- Original Message ----- From: Kevin & Natalia To: Repeater-Builder@yahoogroups.com Sent: Monday, February 13, 2006 12:07 AM Subject: [Repeater-Builder] Battery Back-up Question G'Day All, I am about to install a set of back-up batteries for our repeater. Designed for back-up use. These are 2volt cells, 460amp/hr over 10hrs. What is written on them So we have 6 cells connected together to give 12volts. We are pulling , when everything is running, no more then 10amps. As a rough caculation, I am guessing the batteries should last for around 400+ hours. Anyone got a full caculation to find out how long they will last? Regards Kevin.   Yahoo! Groups Links <*> To visit your group on the web, go to:     http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to:     [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to:     http://docs.yahoo.com/info/terms/   YAHOO! GROUPS LINKS  Visit your group "Repeater-Builder" on the web.    To unsubscribe from this group, send an email to:  [EMAIL PROTECTED]    Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.