Ok, you guys that have the fancy battery status panel with amps in, amps out, charge level, etc... don't laugh... :))
In our older coach (1991) the battery and alternator status going down the road is pretty limited. Here is a cheap ($5) tester that works amazingly well Amazon: Easy Instant Car Battery & Alternator Tester - Test Battery Condition & (http://www.amazon.com/Easy-Instant-Battery-Alternator-Tester/dp/B005ZT5UEC/ref=sr_1_4?ie=UTF8&qid=1362325607&sr=8-4&keywords=alternator+tester) . It will tell you battery charge level when the engine is off, and the alternator output when the engine is running. I plan to wire 2 of these to both sides of the boost relay, and then double-stick tape them up in the cockpit somewhere. A word of caution, any time you connect directly to the batteries, put an inline fuse in the circuit, the one I will use is in the photo (5 amps).
Could connect to the engine solenoid just under the dash top. One of the cigar lighter plugs is house, the other engine so this would also be an option.
I bought a couple of these for the cars: 12V 24V Cigarette Lighter Socket Port Battery Monitor Voltmeter Voltage Meter | (http://www.ebay.com/itm/12V-24V-Cigarette-Lighter-Socket-Port-Battery-Monitor-Voltmeter-Voltage-Meter-/121074382425?pt=Motors_Car_Truck_Parts_Accessories&hash=item1c30987659&vxp=mtr)
Less than $3 delivered and they work great.
The colored lights on yours will get your attention even out of the corner of your eyes.
Pierce