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Thursday, May 10, 2012

Updating & Installing a Fancy New Energy Monitor

We can all agree that it is vitally important to monitor how much power you are using when not connected to shore power or running the generator. It's never fun to run out!  Since RV's have limited space, there is a maximum amount of battery storage that can be carried. Sometimes due to weight, but mostly physical size issues. When I added Solar Power to the mix I wanted to know how much I was using AND putting back each day.

When I bought my RV had an existing Energy Storage Monitoring system, it was a decent working system, but had some problems. Mainly the display was the size of a pocket calculator and the backlighting was so dim you couldn't tell whether it was on or off. It would either tell you what the volts of your battery bank were OR the amount of amps going in or out. You could also toggle a switch to let you know what it believed you had used from the bank (or put back in) But only one at a time. I wanted to be able to read the status of the battery bank at a glance. All the info on one screen AND one I could read from a distance, in the dark.

Most battery monitoring systems sense how much power you are using by running all your loads through a device called a SHUNT These take the large amperages you draw for running your lights, inverters, water pumps, etc. and turn it into a tiny amount of current called a millivolt. This can then be read and displayed by a gauge or computerized battery monitoring system. It sees millivolts, you see amps on the screen. if you didn't use a shunt and hooked the monitor up would be bad. Melting stuff bad. A long time ago, a friend told me all electronics contain "magic smoke" if it gets released the component will not work anymore.

A Variety Of Battery Monitors
I started looking at all the commonly available battery and energy monitoring systems. First off, if you wanted a lot of features and a nifty display, it looked like the costs was VERY high. Around $800.00 plus the cost of the SHUNT which would be around $80. I was becoming afraid that I would have to "bite the bullet" and cough up around $1,000.00 to accomplish my goal. I could have gone the other way and used a much less expensive system, but it really would not have solved the problems I had.

Oh well, back to the internet!

After much exploration I found a product built in the U.K. (and sold here under a different name) that sure looked like it was the right tool for the job. Big backlit display, all the info on one screen....looked to good to be true. I sent some email to the company in England and waited. And waited some more. Then sent another e-mail and waited. And waited. No reply. I managed to track down the U.S. distributor of the product and left a few messages. No reply. Why does it seem that manufacturers and vendors seem to NOT want to sell any merchandise? We are willing customers.....shouldn't they WANT to sell to us?  I gave the distributor one final call...behold, someone answered. We chatted about the product. They had a new version that would read 200+amps, which was exactly what I needed for my RV. The biggest possible power draw for me is my 1,800 watt inverter which could draw 150+ amps. That left me a bit of safety overhead. The entire kit for this monitoring system came in around $200 including the shunt! Needless to say, I bought one right then and there. There were some problems with delivery to the distributor from the manufacturer in England, but it arrived in a few weeks.

New 200 Amp Included Shunt

The install wasn't terrible. I removed the older, much larger shunt. (a 400 amp one) and managed to put the newer one in its place. There was some fiddling with heavy gauge wires and the inevitable dropping of screws in impossible to reach places. (Thanks to Passenger Pete for the retrieval!) All in all, it wasn't bad. If you don't have a shunt already in place, it may be a bit tougher since ALL negative load cables to the battery must feed through the shunt to get accurate totals for the monitor.

Next was the installation of the display unit. I thought I had measured it perfectly. Nope. One day, I will get through an entire project without so much as a single "gotcha!" Wasn't going to be today. Seems that the old flush mount panel was an 1/8" larger than the new surface mount display. Bleh. I'm good, but not good enough to UNCUT an original hole in my dash. Ultimately, I used some leftover self sticking, closed cell foam to fill the gap until I can find a nicer trim solution. I am also not crazy about the fact it sticks out from the dash about 1 1/2". I'll learn to live with it!

Finally, we were ready to wire it all together. I re-used the 4 conductor wire that was part of the original energy monitor system. Due to thick headed-ness I wired a couple of the conductors backward and wasn't getting a reading and blew the 5 amp fuse. Once I figured out why the display wasn't displaying (no power, duh.) I swapped the wires and had an operational system.

New Battery Monitor Display (Backlight On)
Looks nice in the dark. AND I can read it from my bed. That was a bonus! Now I have to figure out how to turn on the backlight remotely....ah well, I'll put that on my list.

After figuring out how to calibrate the new system, it seems to be giving precise readings. I'll be testing it in the real world in the coming weeks to see if it's as accurate as advertised.

Be Seeing You.... Down the Road,

Rich "The Wanderman"


  1. What is the name of the unit?

    1. Anon,
      If you look closely at the pictures, you'll see it's a BM-2 from NASA Marine (ClipperUSA) The BM-1 is identical EXCEPT it will only handle a 100AMP load. Make sure you get the BM-2 which will do 200AMPS (plus a tiny bit more)

      Rich "The Wanderman"


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