Ammeter

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John McGrath

Has anyone installed an ammeter to monitor their power consumption? I've installed a voltmeter to tell me the condition of the batteries, but I'd like to install something (not costing several hundred dollars) that would allow me to keep a closer eye on consumption. It seems to me I need something that will allow me to read from 1A or less up to maybe 70-80A. Most of the off the shelf type I've found find can't read beyond 10A. I gather they can be made to work using a shunt, but don't have a clue on how to set one up. Any one know of a source for information on this? Thanks, John
 
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Ron Doescher

The main circuit you are measuring must be broken & the shunt inserted in series with that circuit. The wires to the meter are then run to the shunt. A shunt is always wired in parallel across the ammeter terminals. The shunt MUST be designed specifically for the meter to be used; each meter has its own internal resistance & the shunt's resistance (very low, much lower than the meter -- will look like zero on most ohmmeters) has to be sized to the right proportion with the meter's internal resistance in order for the meter scale calibration to be correct. Try to keep the wiring between the shunt and meter as short as possible, with the smallest guage (smaller guage = thicker) wire as practical as it (wire & connectors)can have resistance approaching that of the meter, which can upset that resistance proportionality. Some are tempted to add a series fuse in one of the wires to the meter. Don't, as the fuse also has resistance & will upset that proportionality again.
 
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Justin - O'day Owner's Web

Link 10

I _know_ you don't want to spend the bucks, but the Link 10 is really worth the price of admission. Wired correctly, it will let you know how much power is going in, out, is in the battery, and how long at any given rate of consumption you have before you need to charge. I have used one on a charter boat, and a friend's boat and will add one to my own boat this winter. Justin - O'day Owner's Web
 
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John McGrath

Thanks!

I think I'll settle for the Blue Sea, 100A version. Thanks, John
 
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