LEAD ACID BATTERY
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From: john on 29 Mar 2006 13:49 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
From: Tim Wescott on 29 Mar 2006 14:07 john wrote: > 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. > When you say 18V 13A, do you mean 13AH? Or do you mean that your circuit usually pulls 700mA but sometimes pulls 13A? Everyone rounds cell voltages shamelessly. A '2V' lead-acid battery can be expected to have a cell voltage around 1.8V at the end of its useful charge -- this would translate to around 16V in your application. The only definitive way is to find the discharge curve for the battery and check it against your application -- if you can't find a discharge curve then you should either distrust that battery, or you should find another battery manufacturer that does support their product. Switching regulators are so easy to design these days, and 12V deep-discharge batteries so easy to obtain, why don't you use a +/- 18V switching regulator powered off of 12V? Design (or buy) the regulator to work from 11V to 15V to accommodate the full charge to discharge characteristic, and just go to town. You'll have to do some calculation to get the actual current draw as a function of battery voltage, but you may find that your total package is smaller and possibly even less expensive. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/
From: john on 29 Mar 2006 14:12 hi, Its 13AH. Regards jonn Tim Wescott wrote: > john wrote: > > > 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. > > > When you say 18V 13A, do you mean 13AH? Or do you mean that your > circuit usually pulls 700mA but sometimes pulls 13A? > > Everyone rounds cell voltages shamelessly. A '2V' lead-acid battery can > be expected to have a cell voltage around 1.8V at the end of its useful > charge -- this would translate to around 16V in your application. The > only definitive way is to find the discharge curve for the battery and > check it against your application -- if you can't find a discharge curve > then you should either distrust that battery, or you should find another > battery manufacturer that does support their product. > > Switching regulators are so easy to design these days, and 12V > deep-discharge batteries so easy to obtain, why don't you use a +/- 18V > switching regulator powered off of 12V? Design (or buy) the regulator > to work from 11V to 15V to accommodate the full charge to discharge > characteristic, and just go to town. You'll have to do some calculation > to get the actual current draw as a function of battery voltage, but you > may find that your total package is smaller and possibly even less > expensive. > > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com > > Posting from Google? See http://cfaj.freeshell.org/google/
From: Ian Stirling on 29 Mar 2006 14:32 john <conphiloso(a)hotmail.com> wrote: > 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. > Possibly not. Have you considered one 12V battery, and a DC-DC converter to generate +-18? Are you making one or many? Is volume/weight/cost most important? How many cycles do you want the abtteries to last (cycles).
From: john on 29 Mar 2006 16:07
Hi, No, I did not think about DC-DC converter. Would u advice me that how will it work. What DC to DC converter I need? Thanks John Ian Stirling wrote: > john <conphiloso(a)hotmail.com> wrote: > > 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. > > > > Possibly not. > Have you considered one 12V battery, and a DC-DC converter to generate > +-18? > > Are you making one or many? > Is volume/weight/cost most important? > How many cycles do you want the abtteries to last (cycles). |