Saturday, February 16, 2013


I guess I should explain why I am doing this instrumentation project. When I first converted to electric propulsion I had a Xantrex XBM battery monitor. I ordered it with with the Asmo Marine Thoosa 9000 electric propulsion system. It worked well except for the fact that even though the specifications claimed it was "splash proof" it did not say anything about it being sun proof. So I had to move it to a location in the cockpit where I could still see it but, was not view able without opening one of the cockpit hatches.
In addition it could only read the battery pack voltage and current. It did not read the individual battery voltages.
In my researching for an electric propulsion system I came across postings for another battery monitor called a Paktrakr.  It had been used by a number of electric vehicle enthusiasts. Unlike the XBM it could read the individual voltages of the four batteries in BIANKA's 48 volt propulsion bank. Here it is showing the voltage of battery number one in the 48 volt string:

It  could also show the entire pack voltage in a digital display and as a fuel guage:

It would also even tell you the temperature of the battery compartment:

It provided a lot of information in a small package.  It could with an additional sensor also read current and also had the ability to download battery data (with an optional cable) into a computer for analysis. I thought it would be a good backup the XBM since monitoring your battery bank in a boat with electric propulsion is like having a fuel gauge on a boat with a diesel engine. So a year after I converted to electric propulsion I bought a Patrakr and installed it in the main cabin so I could keep an eye on the battery bank without having to go out into the cockpit to look at the XBM monitor. It had a nice small display and it fit very nicely on the door to BIANKA's  wind, depth and speed instraments:

It worked well for several years. At first I just used it for voltage measurements of the battery bank. But, soon I ordered the current sensor so I could see how the battery bank was charging too. A few years later I ordered the data cable. So I could see how the battery bank was charging over the winter layup with the solar panels.
Then early last spring I went on board and found out one of the 8A4D AGM batteries in my 48 volt string was not completing it's charge cycle. I could not see a reason why this battery would suddenly time out when charging. The only thing different between this battery and the other three is the Paktrakr takes it's power from this battery. Even though it's only drawing 25 milli amps of current for the basic unit I had recently added the data recorder and so it might have been drawing more. How much I don't know but, I decided to disconnect from the battery bank full time. I was able to eventually get the troublesome battery to accept a full charge. But, I decided that I needed an alternative battery voltage and current monitoring system to the Paktrakr. One that does not take power from one individual battery like the Patrakkr did. That's the reason I embarked on this instrumentation project.

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