Information on lead acid batteries
Accelerated testing procedures
The most relevant characteristic for selecting the most suitable battery in a
renewable energy application is its lifetime. In general, testing procedures do
not give very reliable information on the lifetime expectancy for the tested
batteries. This is caused by the complexity of the (combination of) stress
factors and ageing mechanisms. In theory the only reliable way of lifetime
testing of the battery in a certain application is to subject the battery to
the very same conditions as in the intended application.
As a consequence of this the testing period would last as long as the battery's
lifetime in the real application. Of course this is not very practical. For
this reason various accelerated lifetime testing procedures were developed,
each reflecting a certain way of application of the battery or focusing on a
certain stress factor or ageing mechanism. An overview of existing lifetime
testing procedures and how strong they provoke four ageing mechanisms, from "no
degradation" to "high level", are given below (reference [7]).
Short description of the test procedures (the numbers refer to the figure):
| 1. |
IEC 61427
-
Reproduces seasonal cycles; low & high SoC
-
Accelerates the corrosion mechanism
|
| 2. |
NF C 58-510
-
Reproduces daily and seasonal cycles
-
Cycling conditions of temperate countries
|
| 3. |
PPER
-
Representative of Solar Home System conditions
-
Short test duration
|
| 4. |
QUALIBAT
|
| 5. |
Test around 10% SoC
-
Strongly emphasises stratification and sulphation
-
Reproduces situations of prolonged bad weather
|
| 6. |
Test around 40% SoC
-
Emphasises stratification and sulphation
-
Representative of Solar Home System conditions
|
| 7. |
DRE
-
Short test duration
-
Accelerates stratification and sulphation in very few cycles
-
Shows the ability of the battery to recover from stratification
|
The designer and user of the renewable energy system must decide which testing
procedure or procedures are the most appropriate for the intended application,
so that the most suitable battery can be selected by comparing the results of
the various candidate batteries from those particular tests.
For each particular category of similar battery use a recommended test
procedure was defined to produce comparative test results for the candidate
batteries. This assists the designer and user of renewable energy systems with
the selection of a suitable battery type and manufacturer.
Some of these "category-specific" test procedures are composed of 2 of the 7
above-mentioned procedures (combinations). The ratios for combinations of test
procedures were determined on the basis of the normalised ageing effects
resulting from use of the individual procedures. These ratios have to be
adapted to give the time ratio for combining test procedures, by taking the
duration of lifetime tests into account. The duration of test procedures can be
found in reference [7] and the ratios of time
durations are shown in the following table.
Ratios of time durations of the combined test procedures.
| Combination of test procedures |
ratio of normalised
ageing effects |
ratio of time duration
of test sequences |
| IEC61427 plus Qualibat (1 :1.5) |
1 : 1.5 |
1 : 0.57 |
| IEC61427 plus Qualibat (1 : 0.3) |
1 : 0.3 |
1 : 0.11 |
| NFC58-510 plus PPER (1 :1) |
1 : 1.0 |
1 : 0.41 |
More information on the "category-specific" test procedures is given in
reference [3].