Reply to thread

Message

<blockquote data-quote="Thnking" data-source="post: 2406033" data-attributes="member: 571105">A couple of corrections:[quote name=SyKo13;2492000However&#039; date=&#039; this effect is non-linear. The available capacity at the C/100 rate (100 hours to discharge) is typically only 10% more than at the C/20 rate. Conversely, a 10% reduction in available capacity is achieved just by going to a C/8 rate (on average). Thus, you are most likely to notice this effect with engine starts and other high-current applications like inverters, windlasses, desalination, or air conditioning systems.For example, the starter in an engine will typically quickly outstrip the capacity of the battery to keep cranking it for any length of time. Hence the tip from mechanics to wait some time between engine start attempts. Not only does it allow the engine starter to cool down, it also allows the chemistry in the battery to &quot;catch up&quot;. As the battery comes to a new equilibrium, its available capacity increases. A very elegant equation developed in 1897 by a scientist called Peukert describes the charging and discharging behavior of batteries. 10% isn’t a very realistic typical percentage when comparing discharge rates C/100 and C/20 or C/8.&nbsp; That number can vary from a small percentage to over 50%.Peukerts formula can’t be used in that form, because it wasn’t devised to find relationships between varying discharge rates using a specific battery capacity.&nbsp; It’s a pretty common mistake with textbooks.How it’s written for specific battery capacity is:[T/(R*C)]*[i/(C/R)]^n=CWhere R equals the battery amp hour rating ( ie, 20 or 8 or etc)</blockquote>

[QUOTE="Thnking, post: 2406033, member: 571105"] A couple of corrections: [quote name=SyKo13;2492000 However' date=' this effect is non-linear. The available capacity at the C/100 rate (100 hours to discharge) is typically only 10% more than at the C/20 rate. Conversely, a 10% reduction in available capacity is achieved just by going to a C/8 rate (on average). [I]Thus, you are most likely to notice this effect with engine starts and other high-current applications like inverters, windlasses, desalination, or air conditioning systems.[/I] For example, the starter in an engine will typically quickly outstrip the capacity of the battery to keep cranking it for any length of time. Hence the tip from mechanics to wait some time between engine start attempts. Not only does it allow the engine starter to cool down, it also allows the chemistry in the battery to "catch up". As the battery comes to a new equilibrium, its available capacity increases.[I] A very elegant equation developed in 1897 by a scientist called Peukert describes the charging and discharging behavior of batteries. [/I] 10% isn’t a very realistic typical percentage when comparing discharge rates C/100 and C/20 or C/8. That number can vary from a small percentage to over 50%. Peukerts formula can’t be used in that form, because it wasn’t devised to find relationships between varying discharge rates using a specific battery capacity. It’s a pretty common mistake with textbooks. How it’s written for specific battery capacity is: [T/(R*C)]*[i/(C/R)]^n=C Where R equals the battery amp hour rating ( ie, 20 or 8 or etc) [/QUOTE]

Verification