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monkeytennis
Joined: 18 Feb 2004 Posts: 16 Location: UK
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DS2438 with 12V lead acid battery |
Posted: Wed Aug 25, 2004 5:22 am |
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Hello.
I was just wondering whether anyone had tried using a DS2438 1-Wire Smart Battery Monitor chip with a 12V lead acid battery. The chip includes an 8 bit internal current accumulator, a 16-bit charging current accumulator and a 16-bit discharing current accumulator which can be used to calculate the remaining capacity inside a battery in Ampere-Hours. This current accumulator, however, is designed for batteries which have only a maximum of 2.5Ah capacity so I was wondering whether it was possible to maybe cheat the system into thinking it was a smaller capacitance battery. I already know how to convert the voltage to a measurable range (as the DS2438 requires 1.5-10v input) but am not sure about the current.
One idea I was toying with was to perhaps have a long variable for charge inside the master (in this case a PIC18F252 microcontroller) and every, say, 10 minutes read the values of the charging currents/discharging currents and add/subtract from the internal variable accordingly, thus hopefully enabling me to establish the remaining capacity.
The system I have uses a PIC18F252 microcontroller hosting a Dallas 1-Wire bus to which a DS2438 battery monitor chip is connected. This chip is monitoring the status of a 12V, 84Ah Lead Acid battery from which the system (amongst other things) is powered.
Any thoughts/ideas would be appreciated.
Cheers,
Simon |
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adrian
Joined: 08 Sep 2003 Posts: 92 Location: Glasgow, UK
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Re: DS2438 with 12V lead acid battery |
Posted: Wed Aug 25, 2004 6:36 am |
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monkeytennis wrote: | Hello.
I was just wondering whether anyone had tried using a DS2438 1-Wire Smart Battery Monitor chip with a 12V lead acid battery. Simon |
I have not used this device - but have look at Maxim's APP note 125. |
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monkeytennis
Joined: 18 Feb 2004 Posts: 16 Location: UK
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Posted: Wed Aug 25, 2004 6:49 am |
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Thanks for the reply.
Yes I have already read this appnote but unfortunately it only details the hardware adjustments necessary for using a higher voltage battery pack and not how to use a battery with a greater capacity.
Simon |
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