Summarising NET current on a house bank.

[GILow]

Hi all,

I am studying at the moment, so, of course, my mind is wandering. And today's wander has pretty well stopped my studies in their tracks.

Here's a summary of the house 12v power system, starting with power inputs:

760 watts of solar, coming in through two separate controllers. (reasonably likely to reach this peak output from time to time as the panels can be all free from shade at times and all point upwards.)

360 watts (or, more accurately, 30 amps) of wind generation. (Only likely to hit that kind of power in 30+ knot winds)

100 amp, engine driven alternator, manually switched, so it does not have to run if the engine is running. (Hitachi, so unlikely to reach 100 amps for more than a minute or two, and likely to be fitted with a smart external regulator to slow it down if I find I need to do any significant charging with it.)

So, at any time it would not be unreasonable to expect battery bank charging currents of 100 amps or more, if I were to run the alternator during a sunny time of day.

Battery bank will be 600AH (or maybe 800AH) of pretty conventional lead acid batteries.(Currently a temporary 200AH bank)

On the output side I have no significant loads, other than a 1500 watt inverter that is only used to run the vacuum cleaner from time to time and the coffee machine for a few minutes plus the anchor winch, which I guess draws 50 amps. Fridge is very efficient and draws 4.5 amps, lighting is all LED, laptop draws 12 watts, etc etc. You get the picture, really not much power used on the boat and no big items like aircon or microwaves.

I have an older, but perfectly serviceable battery monitor system that keeps track of battery capacity and net use etc.

So, the brain freezing dilemma is:

I REALLY like analogue displays, and I have drawn up my dream electrical panel which groups all the input ammeters in one area, the outputs in another, and has a "summary" section for system voltage and NET current. But I realise, as I have drawn it, I'd need a NET current meter that had a range of maybe 150 amps either way to handle the charging range, which would make it USELESS for the normal state of affairs, when the net current is usually +/- 5 to 10 amps. It's this normal state where you want to spot electrical problems early enough so that they do not become a major problem. (FWIW I would plan to bypass the net current meter with the inverter and the anchor winch as they are so infrequently used and both are separately switched and wired to the battery bank for minimal voltage loss.)

Has anyone seen a clever solution to this display range challenge? I know I could go digital, and I am tempted to program up a LCD panel that displays an analogue style meter, but there's something wonderfully simple and reliable about moving coil meters that makes me really want to solve this without resorting to digital processors.

I wonder if there is a way of having two separate meters, that automatically select themselves based on the current, or perhaps a log scale meter?

Matt

[Jd1]

How about a full range shunt and two meter ranges either manually or electronically switched. Accuracy will likely suffer a bit on the low range.
Have a standard full range display and a momentary pushbutton switches it to the low range.

[GILow]

Originally Posted by Jd1

How about a full range shunt and two meter ranges either manually or electronically switched. Accuracy will likely suffer a bit on the low range.
Have a standard full range display and a momentary pushbutton switches it to the low range.

Yes, a push button switch to low range would work when I think about it. This feels consistent with pausing by the electrical board to check that "all's well". Not quite as satisfying as a casual glance, but still good, thank you. Had not considered push-button.

I am reluctant to go electronic auto-range switching as it feels like the slippery slope towards a fully electronic option, but I suppose I could put BOTH in then have the peace of mind that comes from a not-too-technical backup.

[smac999]

Grow up and go digital.

I would never use an analog current or volt gauge in a boat again

[GILow]

Originally Posted by smac999

Grow up and go digital.

I would never use an analog current or volt gauge in a boat again

Grow up and learn some manners.

I don't CARE what you would or would not use. After 25 years of IT systems building and electronics fabrication I am smart enough to know what I do and don't want to use in my boat.

If you don't like my preference, please keep a civil tongue and find some other thread where you can make a worthwhile contribution.

Matt

[Jim Cate]

Originally Posted by GILow

Grow up and learn some manners.

I don't CARE what you would or would not use. After 25 years of IT systems building and electronics fabrication I am smart enough to know what I do and don't want to use in my boat.

If you don't like my preference, please keep a civil tongue and find some other thread where you can make a worthwhile contribution.

Matt

Well said, Matt. A deserved rebuke IMO.

Jim

[GILow]

Originally Posted by Jim Cate

Well said, Matt. A deserved rebuke IMO.

Jim

Oh crap, you've sprung me "not studying"!

I promise I have done lots and lots and LOTS of study today, but this one was niggling at me so I figured I'd call on CF to free up my brain cells.

It worked, and JD1 has given me a good option.

[john61ct]

Originally Posted by Jim Cate

Well said, Matt. A deserved rebuke IMO.

+1

The idea, that digital vs analog implies anything about "maturity" ??!

Your boat your call