I know this isn't the answer you're looking for, but the Link series was
bought by Xantrex, and they have 4 models of Ah/Wh meters for sale all
over the net (Google searches gave me about 2 pages of valid links) and
many sell the device without the shunts.

If you're truly serious about making an Ah meter, check out the Analog
ADE7756 (www.analog.com), it can be run in a DC mode  like this and is
pretty slick (despite no mention of it in datasheets, it's really no
different, you just need to disable the filtering it uses to clean up AC
noise).

> My sailboat has (or at least had) a battery monitor on it.
> You start with a full battery, and this monitor displayed a
> number which represented how many amp hours had been used.
> (Usually a negative number, but you could overcharge the
> battery and have a positive number).  Alas, my monitor seems
> to have been murdered. :-(
>
> The boat took a lightning hit while in the slip, and
> apparently some of the electronics in the monitor got zapped.
>  Although I could buy another one, a large part of the cost
> is the shunt, which was not harmed.  They won't sell the unit
> without the shunt, so I figure I should be able to use a PIC
> to build another monitor.  The shunt is just a resistor, and
> is described as
> follows:
> "When current flows through the shunt, a small voltage is
> developed across the shunt which is proportional to the
> current flow. The battery monitor accurately measures this
> very low voltage and converts it to the "amps" reading on the
> meter. The resistance, which is the ratio between the voltage
> across the shunt and the current flowing through it, is a
> constant for any particular shunt" So the PIC would measure
> the voltage coming from the shunt and use that to calculate
> the corresponding current, and use a timer to convert to amp
> hours.  The shunt itself is a dual MKB-500/50 (the dead
> monitor was a Link, made by Heart Interface).
>
> NOW, please don't flame me for not having a specific,
> detailed question to ask!!  I merely want to know if someone
> on the Piclist might have done something like this, or have
> information that would be helpful to me in designing and
> building such a critter.  If so, would appreciate such info
> -- offline or online, as you choose. :-)
>
> Thanks,
> John

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