Maretron DCM100 battery monitor

[sailingharry]

The boat I race on just had a DCM100 installed. What a disaster!
* It's a $400 battery monitor, arguably no better than a $150 Victron BMV-702 (but it does have N2K integration, which is very nice and very rare).
* It doesn't have any ability to configure it without an additional $200 computer interface or an additional $400 display
* The Garmin GMI20 at the Nav Station will display battery data -- except for % or Ah, arguably the most important "one glance" data.
* The only way to get Ah is to fire up the chart plotter and either read it on the plotter or use the plotters BlueTooth to read it on the phone.


So, not sure if this should be here, or the Electronics forum, or even the OpenCPN forum (where all the nerds congregate with Pi's and soldering irons).


The skipper really wants to have the ability to easily see his battery % at the nav station. But since he can't spell "Ah," the task falls to me! Any thoughts?
* A new battery monitor. A nice BVM or something, for a fraction of what he already paid. The cheapest answer, but a real kick in the butt.
* Replace the GMI20 with a Maretron DSM410, a functioanlly similar device, that might fit the hole, and will display Ah and/or % (shame on Garmin for leaving that out).
* I don't think that any bluetooth solution will work, because I think the only data path is through the chart plotter -- which defeats the purpose (the chartplotter on my boat consumes 10 times the power of all the other instruments combined).
* A small, cheap(??), one number N2K display would be awesome. I'm sure no one makes it, but is there a DIY solution? Maybe even something from the automotive world (isn't the car network very closely related to N2K?).
* A DIY project would perhaps be fun. Ultra small computer (low end Pi, or even lower than that) with an ultra small program, feeding an ultra small display. We do NOT want a robust ships computer system with bigger displays and buttons and Wall Street ticker tape and all that.


And as an additional irritant, the only way to modify the battery monitor configuration is to buy a $200 USB interface. Skipper got sold a bill of goods on this piece of crap! I'm sure the device itself (the DCM100) is a decent piece of hardware. But the total cost, and the functionality, sucks.