Originally Posted by OldFrog75
1. Assuming a boat has an inverter but not a dedicated starter battery, when the inverter is "on" does it draw power uniformly from all the batteries in the bank simultaneously regardless of how the battery selector (1, 2, both, off) is set or can one choose which battery to power the inverter?
2. Is the battery test gauge on the DC panel a reliable indicator for how many amp hours a battery has left before it needs to be charged?
1) An inverter can be thought of as a LOAD. Anything that draws power and uses it can be considered a LOAD. It really doesn't matter if it is an inverter, a radio
, some lights, etc, they all do the same thing. They draw power from the batteries. So in the interest of simplifying your question, I suggest you think in these more general terms. You also bring the battery selector into your question. Why? The selector is "usually" there to select which bank of batteries will be used to feed the loads. If it is selecting a certain bank, you can usually assume that the bank it targets will be feeding the loads. So why bring it into the question? Are you confused about the wiring
of it? You need to separate these things out and understand the building blocks instead of conflating things into a single
unanswerable question. Lets look at a simple and more approachable questions that might get some meaningful and easy to understand answers:
Do the loads on my battery bank draw uniformly from all batteries in that bank?
This depends on how the batteries are wired. There is much information on this in several other threads that explain the optimal ways to wire batteries so that they will have a uniform state of charge. I suggest you make up a diagram which shows how your wiring
is setup and include what type of batteries are in use and where the switches are. You may also want to see this:
Does my battery selector switch work as intended, isolating or combining the battery banks I select?
Please see above. Show us what is in YOUR boat so we can help answer.
How much power will my inverter draw?
What model inverter? What will it be powering?
Does my DC panel gauge (voltage gauge) give me an accurate picture of the number of amps left in my battery bank? Does it give me an accurate picture of the state of charge?
It can be used as a very very rough guess. There are more accurate ways to determine the state of charge (SOC). The most accurate way is probably to measure specific gravity of the batteries which involves opening each battery and using a gauge to determine its SOC, but this is a big pain. Use of a smart battery meter can help to give you a better educated guess than just a voltage alone. You might want to check out these this article:
Installing A Battery Monitor Photo Gallery by Compass Marine at pbase.com