Lead Acid Battery Capacity, Peukert’s Law formula in Microsoft Excel
Article here: http://www.batterystuff.com/kb/tools/peukert-s-law-a-nerds-attempt-to-explain-battery-capacity.html
When a battery is given an AH (Amp Hour) rating, it is always accompanied by the number of hours that rate is taken at. The most often listed rate is 20 hours. So, if you were to see a battery rated at 100AH, it would have been tested at a 20 hour rate, unless otherwise noted. This means that the manufacturer slapped the 100AH rating on the battery after testing that battery for 20 hours with an actual amperage drain of 5 amps. What this also means is that your load of 15 amps will not actually last 6.6 hours, as one may think, but a much smaller number. Luckily for us, there is a very handy-dandy formula to figure out exactly how long a lead acid battery will last, under any load. It is called Peukert’s Law. Peukert’s law expresses mathematically that as the rate of discharge increases, the available capacity of that battery decreases.
The formula that states the Law in a usable format is as follows:
H is the rated discharge time, in (hours).
C is the rated capacity at that discharge rate, in (Ampere-hours).
I is the actual discharge current, in (Amps).
k is the Peukert constant, (dimensionless).
t is the actual time to discharge the battery, in (hours).
... nosebleed ka ba sa "formula"?... do not worry, meron formula in Microsoft Excel format... just download the file na nasa dulo ng explanation.
Peukert calculator in Microsoft Excel format
This calculator will allow you to enter the battery capacity, the capacity rating (i.e. 20 hour rating, 100 hour rating etc) and Peukert's exponent for the battery type. It will then calculate a range of discharge currents from very low up to a discharge equivalent to the battery capacity. It then displays what is termed the "peukert corrected amps" (which is the equivalent discharge rate such a load will remove from that particular battery) for each discharge current and the available run time, again for each discharge current (note that the time is shown in hours as a decimal not in hours and minutes). Finally it shows the total amp hours available from the battery at each discharge rate.
There is also a window to allow the user to enter any discharge current and it will calculate all the same values for that particular current.
Finally, there is a graph on the page which shows the discharge current along the bottom, and the total available amp hours up the left hand side.
Typical Peukert exponents vary widely between different manufacturers but an average figure for a true deep cycle battery is about 1.3. For AGMs about 1.10 and for hybrids about 1.15. Have a play. You will be surprised at just how much difference a heavy discharge rate makes to the available run time. And perhaps also surprised at just how many amp hours are available from a battery when the discharge rate is very low.
Download file here: http://www.smartgauge.co.uk/calcs/peukert.xls
Source: http://www.smartgauge.co.uk/peukert2.html
Article here: http://www.batterystuff.com/kb/tools/peukert-s-law-a-nerds-attempt-to-explain-battery-capacity.html
When a battery is given an AH (Amp Hour) rating, it is always accompanied by the number of hours that rate is taken at. The most often listed rate is 20 hours. So, if you were to see a battery rated at 100AH, it would have been tested at a 20 hour rate, unless otherwise noted. This means that the manufacturer slapped the 100AH rating on the battery after testing that battery for 20 hours with an actual amperage drain of 5 amps. What this also means is that your load of 15 amps will not actually last 6.6 hours, as one may think, but a much smaller number. Luckily for us, there is a very handy-dandy formula to figure out exactly how long a lead acid battery will last, under any load. It is called Peukert’s Law. Peukert’s law expresses mathematically that as the rate of discharge increases, the available capacity of that battery decreases.
The formula that states the Law in a usable format is as follows:
H is the rated discharge time, in (hours).
C is the rated capacity at that discharge rate, in (Ampere-hours).
I is the actual discharge current, in (Amps).
k is the Peukert constant, (dimensionless).
t is the actual time to discharge the battery, in (hours).
... nosebleed ka ba sa "formula"?... do not worry, meron formula in Microsoft Excel format... just download the file na nasa dulo ng explanation.
Peukert calculator in Microsoft Excel format
This calculator will allow you to enter the battery capacity, the capacity rating (i.e. 20 hour rating, 100 hour rating etc) and Peukert's exponent for the battery type. It will then calculate a range of discharge currents from very low up to a discharge equivalent to the battery capacity. It then displays what is termed the "peukert corrected amps" (which is the equivalent discharge rate such a load will remove from that particular battery) for each discharge current and the available run time, again for each discharge current (note that the time is shown in hours as a decimal not in hours and minutes). Finally it shows the total amp hours available from the battery at each discharge rate.
There is also a window to allow the user to enter any discharge current and it will calculate all the same values for that particular current.
Finally, there is a graph on the page which shows the discharge current along the bottom, and the total available amp hours up the left hand side.
Typical Peukert exponents vary widely between different manufacturers but an average figure for a true deep cycle battery is about 1.3. For AGMs about 1.10 and for hybrids about 1.15. Have a play. You will be surprised at just how much difference a heavy discharge rate makes to the available run time. And perhaps also surprised at just how many amp hours are available from a battery when the discharge rate is very low.
Download file here: http://www.smartgauge.co.uk/calcs/peukert.xls
Source: http://www.smartgauge.co.uk/peukert2.html
hope it will stay alive and kicking for many years pa!
Now, with Musk, the game changed, so they need to find something to avoid a leakage of consumers who will certainly quit them for solar or wind if they have these batteries!
if you have 24 volt panel, battery and inverter should be also in 24 volts...
