An amp hour counter like the trimetric is a wonderful, enlightening tool. But do not think they are 100% accurate, and the percentage remaining does not take into account the reduction in battery capacity as the battery ages, nor could it do so accurately if it were designed to do so. It claims to take peukert into effect too. Each battery will behave differently to the larger loads where peukert says you have less capacity, so if you are running a microwave (100+ amps) for 10 minutes, don;t assume the trimetric saying you only used 15% of your battery bank to be accurate. Those kinds of loads are extremely tough on batteries and they get all punch drunk after such a demand.<br><br>The 'Amp hour from Full' screen is the most useful, but I know some people need to see a percentage. I just ignore that screen personally<br><br>I have the BlueSky IPN pro remote which works in tandem with my Bluesky 2512i solar controller.<br><br>I have it wired so it can read Alternator current. Do do this all vehicle grounds must run through a 500 amp shunt. Sounds more complicated than it is. Don't let it put you off if you are considering such a device. Basically nothing can go to the battery (-) terminals directly, but the cable from one side of the shunt, all other ground wires which would usually tie directly to negative battery post must go to the other side of the shunt.<br><br>There are some voltage under load percentage charts on the net, but they also do not account for differences in batteries, or their health, and would not be accurate on an older battery of different capacity and make and age and temperature and load State of Charge and ..... you get the point<br><br>To determine State of charge by voltage alone is difficult unless the battery is rested, no loads or charging sources applied for a good amount of time. Even taking temperature compensated specific gravity readings is not reliable unless you know what the maximum SG is on your batteries when they were new and fully charged. My cells ranged from 1.285 to 1.305 when new and fully charged on some Crown true deep cycles, not the all too popular dual purpose wally world "deep cycles" which excel neither at engine starting or recovery from deep discharges but fall somewhere in between, and closer to the starting battery than the Deep cycle.<br><br>But if one wants to do some math, after watching the clock and taking many voltage readings AND knowing the exact load of the appliance draining the battery, then one could make a fairly accurate guess, and then later on make estimations after noticing trends and tendencies of battery voltage after a certain amount of time and load.<br><br>But much easier to press a button and see 12.5v, 19 amp hours from full under a 1.3 amp load.<br><br>My particular battery monitor allows me to see how much AH the solar has returned to the battery, how much the solar itself is making at any given time in daylight, and adjust solar charging voltages and durations of acceptance and float, among some other features.<br><br><br>As I said, a great enlightening tool to have, but also ignorance was bliss, at least until yet another battery failed prematurely. I, like so so many, assumed the alternator was quickly and fully recharging the battery in relatively short drives. My battery monitor showed me how incredibly untrue this assumption is/was/will always be, despite how badly the masses choose to believe otherwise.<br><br>Other products exist that are much cheaper which can count amp hours.<br>The following product can only count amp hours either into or out from a battery bank. Two meters would be needed to count both in an out, and some basic arithmetic applied. One should not use this to count alternator current as to do so it must be wired into the vehicle grounds, where the starter current also flows, and starter current can easily exceed this meters ability.<br><a href="
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=10080" target="_blank" rel="nofollow">
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=10080<br><br>S</a>uch a product would be great to put onto an auxiliary battery ground Buss bar/Stud/termial and see how much one uses night to night, but not knowing the starting point will make estimations of SOC (State of Charge) more difficult.<br><br>As always, Surface charge, fools everybody without a battery monitor, into thinking their batteries are at a higher SOC after driving than they actually are.<br><br>Another great tool to have is a DC clamp on Ammeter.<br><br>One can just isolate one wire of a circuit, and clamp this meter over one wire, and it will show you how much current is passing through the wire without having to open up the circuit.<br><br><a href="
http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P" target="_blank" rel="nofollow">
http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P<br><br>t</a>his is the model I have. Seems pretty accurate when compared to my Shunted battery monitor, and goes to 2 decimal places.<br><br>It is also a full function digital multimeter, but not in the same class as a Fluke.<br><br>All digital multimeters can measure current, BUT, most are limited to no more than 10 amps or the magic blue smoke emerges. Also, one must open the circuit and run the current through the test leads. One must also move a test lead to another port on the multimeter for current testing, and then after testing, if one goes to take a voltage reading without moving the lead back to the other port, magic blue smoke is possibly released, but hopefully just a fuse blown in the meter, but good luck finding another fuse as they are usually an odd size and amperage. I have a few 3$ HF Cen-tech DMM's with the blown fuse wrapped in Aluminum foil and re inserted.(not recommended)<br><br>Do note that when Items that list their wattage or amperage on the back, that is the maximum that appliance can draw. It might just be the start up current, or it could be the actual running current.<br><br>Both battery charging and monitoring can be taken to extremes. One can either get the pricey tools and trust them to a certain degree, or just get some dull tools and spend some time and effort, do some math and get a general idea, or get the good tools and the lab coat and chart and go all big bang theory on it.<br><br>The trimetric is a good product, but don;t think it is 100% accurate, perhaps 90%, and the little fuel gauge , battery capacity remaining gauge is kind of a joke when it is set to 230 amp hours of batteries, and the batteries have already lost half their capacity. I estimate my batteries have 40% of their original capacity and have adjusted my amp hour capacity down, but I still mostly ignore the % percentage remaining and look at the AMP HOURS FROM FULL screen.<br><br>I do reset it after a while so that it re zero's itself on the next charge, Usually after I plug into the grid and use the schumacher to bring them near full, so that the solar has no issues holding my acceptance voltage(14.5) for the 90 minutes I have it programmed for. Sometimes my fridge or passing clouds will have the voltage 'yoyo' ing when trying to hold acceptance voltage.
