So out of curiosity... what math do these things do to compute amp hours and all the rest? Knowing the overall capacity of the battery bank, could a note card with voltage and their amp hour or % equivelants be listed... do the same job?
Seems like all they can read is voltage in the battery, any long hand that turns that into something meaningful?
Yeah, I was there a few years ago:
I used my analog volt meter to "calculate" how far up or down I was as far as the house bank capacity.
The good book says to not go below 50 % as that would shorten the life of yer battery.
50 % was right around 12.4 volts if memory serves right...?
I used 75 % instead: 12.6 volts, a good and fat safety
margin due to the crude measuring method.
(The above numbers came from Calders book, my bible, as well as the co-bible written by the Dashew's)
Cruised around like that for 6 years on present boat and was fat, dumb and happy.
The numbers worked, no problems noted.
2 years ago a friend donated one of them battery monitor gizzmos to my boat.
I did not think I needed one, but installed it anyway, with the optional temp sensor.
Got a wake up call on how in-accurate the analog voltage system really was. Also woke up to how much power I really consumed in a day.
With solar panels
these electronic gizzmos becomes really useful as you can see exactly how much is going in and how much is going out.
If ya are sitting at the dock
all the time with shore power
plugged in 24/7, no need for a battery monitor.
If not, they are quite useful.