Battery Status At A Glance
If you have a boat or RV and like to spend time away from the dock or out in the woods without a A/C grid power hookup, you may already know how important it is to have accurate knowledge of the condition of your batteries - particularly if you have an inverter and/or "all the comforts of home" on board! Unfortunately many people just "fly blind" and hope for the best - but they quickly find out this is not so great an approach when they can't start their engine or generator after an extended day on the water or at the campground because someone forgot to turn off the toaster oven!
You have a gas gauge for your car - why not for your batteries?
Would you feel comfortable driving a vehicle without a gas gauge? Of course not! That would be very stressful, not to mention inconvenient and possibly dangerous. Well when you are away from a reliable power source, isn't it just as foolish if you don't know the status of your stored power source - your batteries?
Boats and RV's have complex systems these days with all manner of electrical equipment drawing power. Do you REALLY know what is going on? Do you know with certainty how much power is being discharged (or charged) over long periods of time? I can tell you from personal experience how eye opening it is when you finally DO know what is going on - you become empowered with the ability to not only know details about something you could only guess about before, but you gain the feedback needed to more effectively manage and maximize the power you have available to you - the net result is your DC power system becomes more efficient and reliable.
I'll give you an example - did you know a typical 2000 watt inverter uses about 50 watts just idling? Without even doing anything, just powered on! Even with a huge battery bank that is a significant amount of power drain - in fact on my boat that's more power than the fridge uses! Once my battery monitor showed me what a power hog this thing was, I immediately adopted a policy to only enable it when it was needed. In another case, I found I had a "mystery" discharge of about two amps all the time, even with all the breakers off - I eventually traced it to a "hidden" audio amplifier that some previous owner had wired directly to the battery bank.
The "Gas Gauge" analogy explained - this is way more than just an ammeter folks!
You may be thinking "well I have an ammeter so I can already see the current drain, what more do I need"? Well that's a good thing and you are to be commended - you're on the right track. An ammeter will let you know how much power you are drawing from (or providing to) the batteries at any given instant in time. A battery monitor will of course tell you this tidbit of info too and yes it is an important piece of knowledge to have. BUT, power loads will vary widely over time, particularly if you have appliances like refrigeration, so unless you sit in front of your ammeter and write down the loads you see every few seconds, all day long, how are you going to know the TOTAL power consumed from your battery bank over minutes, hours and days?
That's where a battery monitor really shines - it actually continuousy tracks the power moving in and out of the batteries and will give you an accurate indication of how "full" (or "empty") it is at all times, hence the "gas gauge" analogy. PLUS, it will predict how much more running time you have, based on the current loading, which really is a step beyond a gas guage - more like a trip compter! Can your ammeter do that? You just tell the LinkPro your battery capacity (in Amp Hours) and chemistry type (Flooded/ATM/Gel) and it does all this for you.
Let's say you're boat has been at the dock all week and your batteries have been charging, the Link Pro recognizes this and sets itself to a "full" indication. On the weekend when you unplug and head out to your favorite swimming spot and shut the engines down, you immediately begin discharging the batteries - the LinkPro constantly monitors this discharge and tracks the energy used.
It will tell you in "percent" how full your batteries are at any point in time (and/or how many amp hours have been used), and it can even trip an alarm or automatically start your genset if the state of charge drops below a pre-determined value. This is very important because as you should know, good battery health depends on them not being fully discharged - yes, even with deep cycle batteries you should avoid frequent deep discharges to extend their life. A good rule of thumb is to avoid discharging your batteries below the 50% threshold, your batteries could last for many, many, many years if you practice this good hygiene principal.
So, it's been a sunny day out on the water and besides you, your clean, silent & efficient solar panel has been soaking up the rays. Meanwhile, while you've been enjoying yourself, the LinkPro is duitifully tracking the load from the icebox compressor, stereo, TV and other appliances as well as the current input provided by the solar panel to give you an accurate indication of yor battery state - looks like you won't need to fire up the genset just yet!
So without abattery monitor is there a way to know when you've reached the 50% discharge threshold?
Maybe, but in my opinion not very accurately. Theoretically when your batteries reach a specific voltage level they could be considered a certain percent discharged. But folks, we are talking about tenths or even hundredths of a volt here, and yes a good digital voltmenter will tell you precisely what the voltage is (oh, and just forget trying this from those analog guages on the dash!), but there are other factors that influence a battery state of charge, such as battery type (flooded, AGM, Gel), temperature and a few other factors, so there's a wide margin for error here.
So yes, you could maybe get in the general vicinity of the ballpark to knowing the charge state, if you had a good grasp for battery chemistry and were able to apply the proper temperature compensation (of the battery) to your voltmeter readings. Sounds like, um '"fun" - I suppose if you enjoy that sort of thing you probably don't get out much anyway!
Oh, and by the way besides telling you the percent of charge, the LinkPro will ALSO give you those precise battery voltage readings too - even temperature compensated (with the optional temperature sensor).
OK, but how difficult is a battery monitor to install?
Not too difficult if you're reasonably handy, the hardest part is installing the shunt. The shunt looks like a large heavy duty fuse block with batttery terminal sized lugs and has a very small and precise resistance which generates a tiny voltage drop - this miniscule voltage is then used by the LinkPro to calculate the current flowing to/from your battery bank(s). The standard shunt can handle up to +/-600 Amps so is plenty big for most applicaitons, others are available for even heavier loads up to 10,000 Amps.
The shunt goes between the negative battery terminal and the DC ground in your vessel or RV. So, normally you will take the cable off your battery negative terminal and connect it to one side of the shunt, then you will need another length of heavy cable (not included) to go from the other side of the shunt to your battery negative terminal.
Now you run a 6 conductor light gauge (AWG 20) multiconductor cable (not inlcuded) from the battery and shunt to the area where you will be mounting the battery monitor. Drill a 2-1/8" diameter hole for the LinkPro, hook up the wires and you're done.
Defining the amount of energy available in a battery is a complex task since battery age, discharge current and temperature all influence the actual battery capacity. High performance measuring circuits, along with complex software algorithms, are used to exactly determine the remaining battery capacity. A new shunt selection feature enables the LinkPRO to measure currents up to 10,000 Amps.
The battery monitor selectively displays voltage, charge and discharge current, consumed amphours, remaining battery capacity and the time remaining of your battery bank. Using a clear backlit LCD Display and an intuitive user interface, all parameters can be recalled with just a button press. A second battery input is also provided to monitor voltage on a second battery.
It is equipped with an internal programmable alarm relay, to run a generator when needed or to turn off devices when the battery voltage exceeds programmable boundaries.