On Mon, 20 Jun 2005 14:26:33 +0000, mg wrote:
> Hello All,
>
> I posted a few months ago about building a discharger for a DeWalt 18v
> battery. Thanks to everyone who contributed suggestions and ideas. We
> have our first one built and working.
>
> A bit of background - We have a DeWalt 18v recip saw on our rescue
> van. We have used it during extrications where we have a great deal of
> water (i.e. a stream). We use our corded recip saw in less hazardous
> environments. We have three DeWalt batteries. Each battery rotates
> from 1) charger to 2) saw to 3) spare every week. It's not unusual for
> this recip saw to go unused for almost a year at a time. We needed
> some way to check the batteries. So, we decided to build a discharge
> unit to determine the condition of the batteries.
>
> We would like to add one additional feature to our discharger. Some
> sort of voltmeter that we could hold the last reading. This would
> allow us to double check that we stop the discharge process at 15v.
>
> We have a DPDT relay that we use to control a timer. This allows us to
> monitor how much time it takes for each battery to drop to 15v. We
> hope that this will allow to determine when we need to replace a
> battery.
>
> Does anyone know of a voltmeter that would allow us to hold a reading
> via some sort of external relay or contact?
Wouldn't it make more sense to, rather than just try to see what the
volts were when the timer timed out, monitor the volts to see when
the discharger's done, and see how long it takes? You could use an
ordinary (analog) electric clock - when your controller says, "15v!" you
shut down and the clock stops. You don't even have to set it to "real"
time - set it for noon, or something, start your discharger, and read
the hours right off the clock face at your leisure.
Good Luck!
Rich
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