 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeDiscussion GroupsElectronicsBasicsRepairDesignCADComponentsEquipmentElectrical Engineering ElectronicsKB.com Contact UsLink To UsSearch & Site Map |
Electronics Forum / Basics / March 2006LEAD ACID BATTERY
Hi, I have to design a voltage source ( +/- 18volts, 13A ) using lead acid batteries. My circuit draw is 700mA and requires plus minus 18 volts to operate efficiently. I need batteries that can atleast run for 10 to 12 hours before the voltage drops to +/- 17 volts. I am thinking of adding three 6 volts, 13AH ( rated for 20AH ) batteries in series to produce +18 volts and adding three 6 volts to generate -18 volts. I choose the battery ( BP13-6V ), http://www.zbattery.com/zbattery/ub13-6.html. Can anybody advice me that am I doing the right thing that will these six batteries last for 10 to 12 hours maintaining +/- 18 volts @ 600mA. Thanks Regards John > Hi, > [quoted text clipped - 9 lines] > six batteries last for 10 to 12 hours maintaining +/- 18 volts @ > 600mA. It looks as though these batteries are good for at least 12 AH in the current range you're looking at: http://www.powerstream.com/bb/bp13-6S.pdf The discharge rate curves show them staying above 6.0V for over 12 hours at a discharge rate of 650mA. So you should be okay. >Hi, > [quoted text clipped - 9 lines] >six batteries last for 10 to 12 hours maintaining +/- 18 volts @ >600mA. --- The capacity of most lead acid batteries is defined by how long they can deliver current into a load, at a particular rate, until the voltage across the battery terminals falls to a particular value, usually about 5.25V for a 6V battery. the battery you've chosen has a capacity of 13 ampere hours at a 20 hour rate, which means that if you start off with a freshly charged battery, the voltage across the battery's terminals will fall to about 5.25V in 20 hours if you discharge the battery at 13 AH/20H = 0.65A. Since you have six batteries in series, that corresponds to 31.5V, and since you're using the center tap of the string as common, you can expect that the voltages on the ends will decay to 15.75V after 20 hours. Since I don't have the discharge curves for the batteries in front of me, I can't say what the battery voltage will be after 12 hours of discharge, but I'd guess that you're cutting it kind of thin.  SignatureJohn Fields Professional Circuit Designer Hi, The charts for the battery is available at the following website http://www.powerstream.com/bb/bp13-6S.pdf Please advice! John >Hi, > [quoted text clipped - 4 lines] > >John --- From: http://groups.google.com/support/bin/answer.py?answer=12348&topic=250 "Summarize what you're following up. When you click "Reply" under "show options" to follow up an existing article, Google Groups includes the full article in quotes, with the cursor at the top of the article. Tempting though it is to just start typing your message, please STOP and do two things first. Look at the quoted text and remove parts that are irrelevant. Then, go to the BOTTOM of the article and start typing there. Doing this makes it much easier for your readers to get through your post. They'll have a reminder of the relevant text before your comment, but won't have to re-read the entire article. And if your reply appears on a site before the original article does, they'll get the gist of what you're talking about." SignatureJohn Fields Professional Circuit Designer > I have to design a voltage source ( +/- 18volts, 13A ) using lead acid > batteries. My circuit draw is 700mA and requires plus minus 18 volts to [quoted text clipped - 11 lines] > Regards > John Why dont you use 2 12 volt batteries, or rather 4 12 instead of 6 6volt. Then use regulators to set your output to 18 + & -. If then your batt volts drop a little, you still have some to spare. Would be cheaper that way also. Use the ldo still regulator or low power switching regulators to improve efficiancy. Jim.. > Hi, > [quoted text clipped - 8 lines] > Can anybody advice me that am I doing the right thing that will these six > batteries last for 10 to 12 hours maintaining +/- 18 volts @ 600mA. You'd have to either ask the battery manufacturer for their discharge curves, or get one and try it with a 700 mA load - about 8.5V ohms, at least 10 watts, a meter, and a clock. :-) Good Luck! Rich > Hi, > [quoted text clipped - 14 lines] > Regards > John You won't have much fun with lead batteries, if you repeatedly discharge them all the way down. Even if you choose deep cycle or gel cells. If you have to depend on this kind of cheap technology, choose them to have at least double the capacity needed, so you discharge never more than 50%. Then you also don't need to worry about the voltage drop. Well maintained they will then last for 10yrs instead of 10 months. The charger will be another challenge for you, I doubt you will find one for 36V. So you have to take them apart each time and charge them in parallel or better one at a time, because otherwise you won't get them full. If you have 50% left, this will take 7h each, so you can set your alarm clock every night. :-( Ian suggested the right thing, take a single 12V battery with sufficient capacity(60-70Ah) and operate a switching dual supply from that. Signatureciao Ban Apricale, Italy |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.