Nasa Clipper BM1 Battery Monitor

Battery management on a narrowboat is one of the most important parts of living aboard – without power, you have no lighting and no running water. And no way to charge up those devices that have become so important to enable us to keep in touch with what’s going on in the world.

In this vlog, I install a Clipper BM1 Battery Monitor, made by Nasa Marine, onto the narrowboat. It was a simple process and the instructions in the booklet were clear. It is worth noting that this device is NOT designed to work with Lithium batteries, only lead acid.

Caution should be taken such are removing jewellery and not using solid metal tools when working in the battery bank. You don’t want to kill the batteries as they are expensive to replace!

What’s in the box?

  1. The battery monitor
  2. 100 Amp Shunt
  3. 5 metre cable
  4. 10 point terminal connection block
  5. Short black cable
  6. Instruction booklet

Getting Started

First up, mark out the section on the wall where the monitor is going to be installed. The dimensions for this are in the book. Make sure there are no obstructions behind the hole and that there is adequate space around for the front of the battery monitor to sit.

Cut the hole. I did this by drilling 4 pilot holes – one in each corner – so that my jigsaw blade could go through. I then made 4 cuts with the jigsaw and removed the block of wood. Finally, I had to make some fine adjustments to get the monitor to fit because my cuts weren’t 100% accurate. For this, a chisel and some sand paper might come in handy.

Next up, I ran the 5 mitre cable from the battery bank in the engine bay to the cupboard with the hole. For me, this was best done from the outside as the end of the cable that will connect to the monitor was blunt whereas the other end had connectors already attached. This took me a while because the hole in the hull is small and there were several cupboards to go through.

At this point, I did attach the shunt to the wall in the battery bank as well but I had to remove it because the connecting wire provided that goes from the shunt to the battery bank was too short. However, it is much easier and safer to work if the shunt is attached to the wall now.

Connecting the battery monitor

When the staging is all done, it is time to connect the wires. The instruction booklet is very clear on this and tells you the order in which to do this work. Everything should be powered off at this point too – no charging to the batteries and no current should be being drawn either.

First, the monitor and the 5 metre cable are connected using the terminal connection box.

Next, the monitor cables and the wire to the instrument panel in the boat are connected to the shunt. And any other wires that are on the negative terminals of the batteries.

Atย this point, there should still be no charging apparatus attached – so no solar or shore line power and the engine / generator should be off too.

Finally connect the shunt to the batteries and the positive wire from the 5 mitre cable to the positive terminal on a battery.

Testing the battery monitor

Follow the instructions in the booklet to set the total capacity of your battery bank. When you are happy everything is connected, power on a few things one at a time to make sure everything is working. Start with a light or two. You should see that the battery status and a small discharge that changes as you power things on and off.

Leave the battery monitor for a few minutes monitoring the discharge before connecting any solar panels or turning on the shore line battery charger. When these are connected, you should see a charge going in and a voltage change.

That’s it! Now you clearly see which items in your narrowboat have the biggest drain on your battery bank.

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