Originally Posted by acadianbob
Can you please expand on your comments and talk about why this is the case? I think many, including me, would be interested.
First let's dispense with the voltmeter. It CAN show you that your battery is dead. It can show you what stage your charger is in when you are plugged in (i.e 14V+ = bulk mode, 13.5+= absorbtion, and 13.2+= float. If you have a 4 stage charger you will occasionlly see 14.8+ for equalization cycle.)
It CANNOT show you when your battery is full. It cannot show you the true state of charge of your batteries. i.e. 50% full 75% full etc. because voltmeters cannot account for the surface charge put on a battery during charging AND because the batteries are IN USE in the coach.
Voltmeters are used to check the state of charge of a static and disconnected battery...you must wait 24 hours after charging a battery on a TEST BENCH to get an accurate voltage reading. You can't get one under active use. I see comments here all the time that say "I charged up my batteries to full"....then say it took an hour or two. Impossible...they are relying on an idiot light or a voltmeter that is reading the surface charge of the battery after they shut off the charger. It takes at least 6 hours of charging to fully charge a battery that is less than half full.
Now what a battery monitor does is to monitor the amps in and out of the battery which is really the basis for a whole host of functions. For example...lets say you have a Group 27 battery with 100 amp hours capacity. If you hook up a battery monitor (more on that later) and you are charging it at 10 amps and listening to the radio at 2 amps and lights & computer and propane montitor are using another 10...then after one hour of use...you will be down 2 amp hours. Your monitor will show you with 98% of capacity remaining.
Lets say a day goes by and you've turned off your charger and you check your monitor and see that you're down to 60%capacity having used 40 amp hours. Your charger is capable of providing (for example) 20 amps of charging current in bulk mode so you crank it up...but you KNOW it is gonna take more than two hours to get 40 amphours back into your battery...because battery charge acceptance goes WAY down as the battery gets closer to 100% charged...and you don't have the full 20 amps available since other stuff in the coach is using some current. The battery MONITOR will let you monitor the whole charging process and you can see exactly when the battery is 90% full or 100% full and you can turn off the genny and charger.
Other neat things...you can turn any single item on and instantly know how many amps it draws so you know how watching four hours of TV affects your battery. You can see how many hours at the present rate of use it will be till your battery will need to be recharged.
NOW...Installation...is quite simple and does not require a pro. First lets review the parts. First you have the monitor itself which is simply a round hole mount. Plugged into the back of it is one end of a telephone wire. 2 seconds! The other end of the telephone wire is run to the battery compartment. The next item is the SHUNT...the thing with the two big screws on it. One end of the shunt gets ALL of the negative wires on you battery attached to it. The other end gets a single negative wire (buy the length you need based on where you're gonna mount the shunt. And that negative wire gets attached to the negative battery terminal. Then there's the little red wire that goes on to any positive battery terminal from the screw on the shunt. Finally you plug the other end of the telephone wire into the hole in the shunt and you are up and running. You'll do some setup at the monitor like telling it what size and type of batteries you have...but that is about it.
Hope that is a helpful overview. Monitors pay for themselves by avoiding premature murder of batteries AND extending the life cycle. They also save money so you don't waste gas and generator time charging prematurely or too long.