Saturday, May 17, 2008 at 11:37
Hi Sandman
You need to view things a little more dynamically rather a simple literal message.
Remember these points
The loss of capacity is the combined effects of temp and time and charging voltage.
The longer and higher the temps with-out a reduction in charging voltage the worse the problem.
This is determined by each individual case and takes into consideration the following parameters.
Veh charging voltage
Climatic conditions, both latitude and Seasonal (
Darwin 33oc year round, Vs Tassie 12oC winter to 22oC summer Ave)
Batery location in engine compartment and under bonet temps
Vehicle usage patterns (Long haul truck Vs
Grey Army migration)
In a later post you make the very interesting comment, which strikes to the heart of the problem with AGM's, their low internal resistance, and Therefore reaching full charge quicker, where the charge voltage should be reduced to float and temperature compensated (Somthing that dosnt happen in a veh charging system)
Quote "This is not specific to AGM batteries. In fact an AGM battery charges quicker and more fully than an equivalent sized standard wet cell deep cycle battery"
As to your comments re the external use of AGM's yes temps can get high in external positions but this is climate dependant and time of day dependant.
And the Average conditions needs to be considered
This has an impact on the length of the batterys exposure to high temps while under charge (Remember the conditions while under charge comment as it is important later point)
i.e.
Darwin 33oC day, 24oC night year round
Tassie Summer 12oC night to 24oC day
Winter 4oC night to 12oC day
In tassie your battery would love the external enviroment as it is optimal operating temperatures, but jam the same battery under the bonnet and its temp will go to >50oc within the hour.
Re the cooling comment, I tried oh how I tried Insulated and ducted air, but that battery 56oC charge cutout, just kept kicking in.
Now here's the kicker, when a battery is under the bonnet, the only time it will charge is interestingly enough, is when the motor is running, which generates heat >50oC bat temp after 1 hour, when the charge volt needs to be reduced as
1) Due to AGM's quick charge aceptance is charged and should be now in float mode (DOD depandant)
2) As its temp is now high, requires a reduced float voltage
Keep driving for annother 2l, 4, 8 hours (depending on your driving habbits), you reduce its life "Proportional" to the duration of these conditions.
Now if the battery was outside Hmm
Specifics gentlemen Specifics not dogma.
Harrow
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