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Old 04-15-2019, 02:55 PM
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Doug Huffman Doug Huffman is offline
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Location: Washington Island, Wisconsin, thru Death's Door
 
Join Date: Apr 2015
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Mein Auto: CPO2012 X5 35d M57(E70)
The car knows more about the condition of the battery than the CTEK does.

The BULK charge phase ends when nominal charge voltage (you selected 14.4 VDC) is reached while charging at 4.3 Amps. Then the charging voltage is held constant while the charging current declines to some unstated value, when 'charging' is ended with the ANALYSE phase.

The car tracks State of Health - SoH - which is available for query by a capable communications program. SoH is a ratio expressed as percent of some unstated actual current battery parameters compared to those parameters at registration. The / a parameter may be minimum voltage during starter operation maximum current.

You can roughly track the declining battery capacity by noting the time required to recover your typical battery use discharge.

Battery capacity primarily diminishes due to loss of electrolyte water. As the water is lost the electrolyte level decreases making a smaller plate area available to the process. That reduces AH capacity. Also as water is lost the acid becomes more concentrated and that raises apparent battery voltage.

As the battery ages the charging will end sooner at lower capacity, which you will see as shorter and shorter completion times.

I usually charge with my CTEK 4.3 MUS weekly, the winter charges are longer, by about twice, than the summer charges. You can estimate the capacity charged as one-half of the hours charged times the maximum charging current 4 Amps. I charge about 10 AH in the winter and 5 AH in the summer. Milady Wife loves the bun warmers and as soon as the engine is running she has the bun warmers on. Also, in Wisconsin, the 1000 Watt 80 Amp PTC electric heater is on more often and longer.

What the ECU knows about the battery comes from the Intelligent Battery Sensor - IBS - which measures and reports Coulombs discharged, Coulombs charged, battery (system connected) voltage, and temperature. A Coulomb of charge per second is an ampere.
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