Fish Finders, Epoxy and Measuring Battery Charge State

Rye Gewalt (ryeg@vais.net)
Thu, 03 Jun 1999 05:32:01 -0400


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West Wight Potter Website at URL
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Scott:

Glad we have another Humming Bird fish finder running successfully out
there. I put mine in using epoxy at the suggestion of JJ Falkanger and,
as JJ mentioned, it's almost as much fun as TV and most of the time the
programming is better -- those fishies are great actors.

One thought on the Epoxy:
I think that both the cure time (as you mentioned) and the viscosity are
important. Some epoxies come in cans and have the consistency of thick
peanut butter when mixed up -- which would allow air bubbles to be
trapped within the transducer to hull bond. The epoxy that I used had
the consistency of thick honey --- i.e. the air bubbles would slooowly
move to the top, but the stuff would not run out from under the
transducer. I think this is similar to the clear stuff that Radio Shack
and Hardware Stores sell in the double syringes. I also suspect that
the clear epoxy is better than the stuff that is colored since the color
indicates a filler which may not be as conductive to the ultrasonic
energy as the clear 100% epoxy resin.

The built in voltmeter is a real bonus. It allows measurement of the
battery voltage to a tenth of a volt -- which is hard to do with a
regular meter since the needle bounces around so much and the accuracy
of mechanical meters is always questionable at that level. (I collect
antique meters: http://www.vais.net/~ryeg/MeterMuseum.html )

A few tenths of a volt change in battery voltage gives a real indication
of the state of charge in your battery. The great Deep Cycle Battery
FAQ ( http://www.ee.ualberta.ca/~schmaus/dcbat.html ) gives a table of
battery voltage versus charge state as shown below:

Open Circuit Approximate Average Cell
Battery Voltage State-of-charge Specific Gravity
12.65+ 100% 1.265+
12.45 75% 1.225
12.24 50% 1.190
12.06 25% 1.155
11.89 0% 1.120

Leaving a battery sit for a long time with only a partial charge is bad
for the battery, so it's good to check the voltage and recharge when
things look to be getting much below the 75% point (12.4V). In my
experience you can make a battery last longer than the normal 2-3 years
by keeping the state of charge (and water level) up to snuff.

You get a lot of really cool technology in those little boxes for
$89..... aint it amazing!

Regards All

Rye Gewalt
Grace II
'90 HMS18 Short Rig

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Scott:

Glad we have another Humming Bird fish finder running successfully out there. I put mine in using epoxy at the suggestion of JJ Falkanger and, as JJ  mentioned, it's almost as much fun as TV and most of the time the programming is better -- those fishies are great actors.

One thought on the Epoxy:
I think that both the cure time (as you mentioned) and the viscosity are important.  Some epoxies come in cans and have the consistency of thick peanut butter when mixed up -- which would allow air bubbles to be trapped within the transducer to hull bond.  The epoxy that I used had the consistency of thick honey --- i.e. the air bubbles would slooowly move to the top, but the stuff would not run out from under the transducer.  I think this is similar to the clear stuff that Radio Shack and Hardware Stores sell in the double syringes.  I also suspect that the clear epoxy is better than the stuff that is colored since the color indicates a filler which may not be as conductive to the ultrasonic energy as the clear 100% epoxy resin.

The built in voltmeter is a real bonus.  It allows measurement of the battery voltage to a tenth of a volt -- which is hard to do with a regular meter since the needle bounces around so much and the accuracy of mechanical meters is always questionable at that level. (I collect antique meters:  http://www.vais.net/~ryeg/MeterMuseum.html  )

A few tenths of a volt change in battery voltage gives a real indication of the state of charge in your battery.  The great Deep Cycle Battery FAQ ( http://www.ee.ualberta.ca/~schmaus/dcbat.html ) gives a table of  battery voltage versus charge state as shown below:

  Open Circuit          Approximate           Average Cell
 Battery Voltage      State-of-charge       Specific Gravity
      12.65+               100%                  1.265+
      12.45                 75%                  1.225
      12.24                 50%                  1.190
      12.06                 25%                  1.155
      11.89                  0%                  1.120

Leaving a battery sit for a long time with only a partial charge is bad for the battery, so it's good to check the voltage and recharge when things look to be getting much below the 75% point (12.4V).  In my experience you can make a battery last longer than the normal 2-3 years by keeping the state of charge (and water level) up to snuff.

You get a lot of really cool technology in those little boxes for $89..... aint it amazing!

Regards All

Rye Gewalt
Grace II
'90 HMS18 Short Rig
 
 
 
 
 
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