Differences

This shows you the differences between two versions of the page.

--- electrical:12v:battery_capacity [2017/05/26 19:46]
frater_secessus created
+++ electrical:12v:battery_capacity [2021/05/03 10:38]
frater_secessus [other than 20hr rates]
@@ Line 1: / Line 1: @@
 ====== C notation ======
-Battery capacity in Amp-hours is written as **C**.  This notation is most useful when talking about charging/discharging rates.
+**Battery capacity** in Amp-hours is written as **C**.  100Ah, for example.
+C notation can also be used to describe the **relative amount of current** charging/discharging battery bank. For example a 50A load on a 100Ah bank would be C/2 (100/2 == 50).((technically C/20/2, but that form is rarely seen outside formal documents)). It may also be written as 0.5C.((decimal vs. fractional expression, can be used interchangably))
+Note:  most deep cycle manufacturer's rate capacity at C/20, due to Peukert effect on lead chemistries (see below).((Lithium doesn't not have a significant Peukert effect.  Capacity measured by C/20 and by amp-counting will be nearly identical)).  In other words, a 100Ah battery will deliver 100A with a 5A load over 20 hours.
+===== Examples =====
-Examples:
 If you have a 200AH battery bank then C = 200AH.
-If the manufacturer recommends max //chargign// at C/5 the rate should be at or below 40A (200/5). \\
+If the manufacturer recommends max //charging// at C/5 the rate should be at or below 40A (200/5). \\
-If the manufacturer recommends max charging at C the rate should be at or below 200A (200/1). \\
-Note: the **usual charge rate** for deep cycle batteries is C/10.  Sometimes manufacturers express that Absorption stage is complete((and therefore Float should commence)) when the bank is holding Vabs with C/100 or C/200 of current.
+If the manufacturer recommends minimum charging at C/10 the rate should be at or above 20A (200/10). \\
 If the manufacturer recommends max //discharge// (load) be 3C the rate should be at or below 600A (3x200). \\
-Note:  most deep cycle manufacturer's rate capacity at C/20, due to Peukert effect.
+If the manufacturer says that [[electrical:12v:charging|Absorption stage]] is complete when charging current has dropped to C/100 or C/200 then the current to watch for would be 2A (200/100) or 1A (200/200).
+===== other than 20hr rates =====
+Because of the Peukert effect, lead bank //measured// capacities are strongly affected by dicharge rate. Sample data below is for flooded lead acid.  C/20 capacity is multiplied by the factor below to find projected capacity at given discharge rates.
+Example:  our battery is rated at 100Ah when drained at 5A over 20 hours.  If it is drained at 20A in 5 hours it will have an observed capacity of 70Ah (100Ah x .7).((again, Li will deliver rated capacity at all practical discharge rates))
+Hour = .3 \\
+Hour = .5 \\
+hour = .6 \\
+hour = .65 \\
+hour = .7 \\
+hour = .75 \\
+hour = .8 \\
+hour = .85 \\
+hour = .9 \\
+hour = .95 \\
+hour = 1 \\
+hour = 1.05 \\
+hour = 1.1 \\
+hour = 1.25 \\
+hour = 1.30((vhttps://www.solarpaneltalk.com/forum/off-grid-solar/batteries-energy-storage/11731-peukert-law-batteries-and-you#post11731))

RV and vandwellers wiki

User Tools

Site Tools

Differences

Page Tools