Join Date: Aug 2007
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MS's great tutorial notwithstanding, I have a basic question re battery monitors in general, particularly the "state of charge" function, common to all brands I know of.
I understand (I think) that in order to ascertain how much charge is left in a battery bank...starting from a fully charged battery or bank, one must tell the monitor how big the battery was in the first place...similar to the way the gas gauge works in your car...if you didn't know how much gas the tank could hold, how would you determine when it was half full, for instance.
So suppose you had a house bank of 200 AH. That's the capacity of "the tank" you would program into the monitor and, as energy is consumed, SOC would diminish accordingly and all be well. But what if you decide somewhere along the way you wanted to switch another battery into (or out) of your bank via the 1-2-B switch.
I have a client who does just that. He has a two-battery house bank, a start battery, and an "at large" battery which can be dedicated (by switch) to either house or start function. He likes the sense of redundancy he says this configuration gives him. He makes his decision, where to put the orphan battery, based on the SOC he reads from his monitor.
He brought the boat in complaining that his batteries were unreliable...says his system works all the time that way and there's something wrong with his monitor and would I replace it...and his batteries.