A blog about SCAMP (Small Craft Advisor Magazine Project) boats. Covering the build, sailing the boat and the scamp community that has formed around this little portly boat.

Friday, May 5, 2017

Battery meter installation

I always worried about my battery failing if I depleted it fully. I know it is a 79Ah battery, but I never was able to figure out the amperage load when running the motor. I did install a voltage meter in the cigarette lighter/auxiliary port, but a voltage meter is a poor battery gauge.

I know about battery state of charge meters from some of the investigation I had done into building an electric car. A state of charge meter monitors all power coming out and going into the battery. Since it knows the capacity of the battery, it can monitor and alarm when the battery is at 50%, the rough safe zone for battery usage.
After some investigation, I decided on Victron BMV-700.

Since I had designed the circuit and done all the electrical work, I knew how to wire in the SoC meter. It's a simple shunt that goes inline on the ground side of the battery and a long cable with RJ12 telephone jacks that goes to the meter which should be mounted someplace visible.

I've now over drilled all the mounting holes and drilled the through holes for the RJ12 control cable.

After the epoxy cures, I'll mount all the equipment and test everything.

The meter will be on starboard side of B3. The hole is above the hatch.

The shunt (black lead) and the meter just outside the battery well. You can also see the grey control cable in the back.

I'd like to cut that control cable but I don't have an RJ12 crimper. Anyone have one I can borrow?

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