LEAD ACID BATTERY
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From: john on 31 Mar 2006 11:10 Hi thanks for ur reply. But I am using BP13-6V. and it does not have high capacity as GC6V200. Its rated as 13AH battery over 20AH. First I do not understand this 20AH thing? plus would you think that this battery will last that long like 12 hours, if I draw 700 mA from it? Thanks John > Lessee...700mA times 12 hours equals 8.4 Amp-Hours. Multiply that by > 20 (assuming C/20) for a battery rating of 168 AH. > That rate will allow approximately the voltage you specified near the > end time period of 12-15 hours. > The Interstate GC6V200 (6V) is rated at 170AH, their SG-8D (12V) is > rated at 190AH, their SG-4 (12V) is rated at 164AH, and their SG-4D > (12V) is rated at 154AH. They have a UPS rated battery, the UPS6-600 > (6V) rated at 180AH. > Other manufacturers have equivalents; these are heavy duty batteries. > Be advised that right after charging,the battery will be much higher > than 18V for the first ten seconds. > All of this assumes constant current discharge at 25C / 77F. > Be advised that temperature will be a significant factor in terminal > voltage and life.
From: John Fields on 31 Mar 2006 11:42 On 31 Mar 2006 08:10:00 -0800, "john" <conphiloso(a)hotmail.com> wrote: >Hi >thanks for ur reply. But I am using BP13-6V. and it does not have high >capacity as GC6V200. Its rated as 13AH battery over 20AH. First I do >not understand this 20AH thing? plus would you think that this battery >will last that long like 12 hours, if I draw 700 mA from it? --- Learn to post properly. 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." -- John Fields Professional Circuit Designer > >Thanks >John >> Lessee...700mA times 12 hours equals 8.4 Amp-Hours. Multiply that by >> 20 (assuming C/20) for a battery rating of 168 AH. >> That rate will allow approximately the voltage you specified near the >> end time period of 12-15 hours. >> The Interstate GC6V200 (6V) is rated at 170AH, their SG-8D (12V) is >> rated at 190AH, their SG-4 (12V) is rated at 164AH, and their SG-4D >> (12V) is rated at 154AH. They have a UPS rated battery, the UPS6-600 >> (6V) rated at 180AH. >> Other manufacturers have equivalents; these are heavy duty batteries. >> Be advised that right after charging,the battery will be much higher >> than 18V for the first ten seconds. >> All of this assumes constant current discharge at 25C / 77F. >> Be advised that temperature will be a significant factor in terminal >> voltage and life.
From: john on 31 Mar 2006 15:22 Hi thanks for ur reply. But I am using BP13-6V. and it does not have high capacity as GC6V200. Its rated as 13AH battery over 20AH. First I do not understand this 20AH thing? plus would you think that this battery will last that long like 12 hours, if I draw 700 mA from it? Thanks John > Lessee...700mA times 12 hours equals 8.4 Amp-Hours. Multiply that by > 20 (assuming C/20) for a battery rating of 168 AH. > That rate will allow approximately the voltage you specified near the > end time period of 12-15 hours. > The Interstate GC6V200 (6V) is rated at 170AH, their SG-8D (12V) is > rated at 190AH, their SG-4 (12V) is rated at 164AH, and their SG-4D > (12V) is rated at 154AH. They have a UPS rated battery, the UPS6-600 > (6V) rated at 180AH. > Other manufacturers have equivalents; these are heavy duty batteries. > Be advised that right after charging,the battery will be much higher > than 18V for the first ten seconds. > All of this assumes constant current discharge at 25C / 77F. > Be advised that temperature will be a significant factor in terminal > voltage and life.
From: RHRRC on 31 Mar 2006 16:26 john wrote: > Hi > thanks for ur reply. But I am using BP13-6V. and it does not have high > capacity as GC6V200. Its rated as 13AH battery over 20AH. First I do > not understand this 20AH thing? plus would you think that this battery > will last that long like 12 hours, if I draw 700 mA from it? > The amp-hour capacity you can get from a battery, in practice, depends to an extent on how fast it is discharged. A high discharge rate (i.e. high current) will give a lower capacity than a low discharge rate (i.e. low current). To give some standardisation to the amp-hour rating of batteries they are rated to the capacity (amp hours) obtained when they are discharged to flat in a given time. For lead acid batteries of the type you are considering this time is 20 hours (for NiCads it is 5 hrs for example). Your 13Ah battery will give 13Ah if it is discharged at (13/20=) 650mA. At a discharge current of 2amps your fully charged 13Ah battery will *not* last (13/2=) 6.5hrs - it will be a shorter time than this. You will have to look at the manufacturers data for how long it will last. 'C' is merely a short-hand way to refer to the capacity of a battery at its declared (20hr) discharge rate.
From: Robert Baer on 31 Mar 2006 17:35
john wrote: > Hi > thanks for ur reply. But I am using BP13-6V. and it does not have high > capacity as GC6V200. Its rated as 13AH battery over 20AH. First I do > not understand this 20AH thing? plus would you think that this battery > will last that long like 12 hours, if I draw 700 mA from it? > > Thanks > John > >> Lessee...700mA times 12 hours equals 8.4 Amp-Hours. Multiply that by >>20 (assuming C/20) for a battery rating of 168 AH. >> That rate will allow approximately the voltage you specified near the >>end time period of 12-15 hours. >> The Interstate GC6V200 (6V) is rated at 170AH, their SG-8D (12V) is >>rated at 190AH, their SG-4 (12V) is rated at 164AH, and their SG-4D >>(12V) is rated at 154AH. They have a UPS rated battery, the UPS6-600 >>(6V) rated at 180AH. >> Other manufacturers have equivalents; these are heavy duty batteries. >> Be advised that right after charging,the battery will be much higher >>than 18V for the first ten seconds. >> All of this assumes constant current discharge at 25C / 77F. >> Be advised that temperature will be a significant factor in terminal >>voltage and life. > > There aer published discharge curves that one can look at to see how long a battery terminal voltage will stay within a given voltage range. The greater the discharge rate, C/n, the sooner that the voltage will start dropping "rapidly" below the previous long-term voltage. So i looked at the curves to see what discharge rate would give the desired "tight" specs mentioned, and C/20 was the highest rate possible. Next, i took the 700mA times the 12 hours to get the discharge rate of 8.4 amp hours. Then multiply by 20 to get the needed rating of the battery. It is clear that the battery you chose grossly lacks the capability you mentioned, if used directly as a power source. BUT. You *can* use a switching supply, which would allow the battery to be used over a larger terminal voltage range, thereby making more efficent use of the total storage capabilities. And many others have suggested that approach, which was obvious to me. But it seemed that you were somehow tied to using only batteries. |