DS2438 with 12V lead acid battery

[monkeytennis]

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

[adrian]

[monkeytennis]

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