Is this thing even worth having? It was on my boat when I bought it. It displays only volts, which tells me very little unless the battery is badly depleted ... right?
Battery meter?
- Thread starter Gene Neill
- Start date
Battery voltage changes depending on the state of charge of the battery and whether or not it is under load. It can indicate the effectiveness of your charging system and whether you have a bad cell. The value lies in knowing the voltage should be under certain conditions, because if it's not, then there's a good chance you have an electrical problem somewhere. There is a wealth of information about this subject on line. Good luck.
I use a volt meter to monitor my batteries. As a liveaboard, with a volt meter at the chart table (my like office/computer space) and I always know the state of charge, from the read out. There are all kinds of fancy battery condition monitors out there, but if you are always around, I think a volt meter will tell you nearly as much.
it can tell you if your battery is charging.... it can tell you the current state of charge left in the battery.... it can tell you if you are approaching the 50% limit of depletion for maintaining battery longevity.. if you care.
and although I dont know how sensitive it actually is, the digital readout goes to hundreths of a volt, which with a bit of knowledge of your battery, over time you would be able to get a fair idea of how many amps your using over a short period of time....
but all these things will become boldly apparent to you sooner or later anyway, so maybe the gauge is only taking up precious cabin space.... I can help you free up that space if you would only send the intruding item to me, and I will safely dispose of it for you....
Most good electrical books about boats will explain what it can do. Centerline described it quite well. Nice to have. I have an analog one and have learned how to read it. Having digital is very good. A true battery monitor is even better. Depends on what you want to learn and how you use your boat. You might want to noodle around the Ample Power website and download their primer about batteries. The Ample Power Primer http://www.amplepower.com/primer/primer.pdf I've always figured that the more you know about your electrical system the safer you'll be.
I just scored a Victron BMV-600 battery monitor for a little over 100 bucks. They are being clearanced right now to make way for the updated 700 series. At that price it was too good to pass up.
It is worth having as it tells you more about your battery's condition than you would know without it. And, the price was right.
Ah, yes indeed, that is exactly what I needed! Now that I google the phrase "battery state of charge", I see that that chart is common. But I was unaware of it's existence until this very moment.
Thanks, Jackdaw!!
Thanks, Jackdaw!!
Dixie,
You might want to take a look at our short video on our energery monitor. It's at; http://www.youtube.com/watch?v=JUJ0o3SO1y0&list=UUyGH1-xOhCotpV_zhSzQq7g&feature=share&index=3
MUCH better than just a volt meter. Keeps my wife very happy! ;-)
Greg
You might want to take a look at our short video on our energery monitor. It's at; http://www.youtube.com/watch?v=JUJ0o3SO1y0&list=UUyGH1-xOhCotpV_zhSzQq7g&feature=share&index=3
MUCH better than just a volt meter. Keeps my wife very happy! ;-)
Greg
Excellent video, Greg, very informative! I will definitely want a meter like that in the future.
So, don't keep me in suspense: what's the OTHER thing you and your better half couldn't live without?? You never did say!
So, don't keep me in suspense: what's the OTHER thing you and your better half couldn't live without?? You never did say!
only good when your battery is in a resting state which could be quite a while after all loads are removed.
...and after all charging sources are removed.
A sophisticated battery monitor, capable of tracking Amp-hour load, Amp-hours used, and voltage is well worth the cost.
We haven't posted the video yet on the other item yet. Jill's worried about being called a "potty mouth" on it. It's our Lavac head......
We are cruising just now, so will post the video when we get some extra time.
Greg
We are cruising just now, so will post the video when we get some extra time.
Greg
Both totally correct.
But guys, it's a 22 foot boat! A simple analog DC voltmeter was standard equipment on all of our 35+ foot boats. Surely the same (in digital no less!) will suffice for the time being on his Catalina 22.
It has nothing to do with boat size. A voltmeter simply is not an accurate way to measure battery capacity on any boat. You apply a load the meter will go down. A charging source will make it go up. Remove any load and charging source, wait overnight and it may be close. Maybe if you keep your boat at a mooring and you check it when you first arrive assuming you have no charging source and something like an automatic bilge pump had not be running recently.
Btw, just because it was standard equipment on a boat does not make it a good tool.
But wait a second, not as easy as reading a chart. The same battery with the same estate of chart can give you different voltage readings. The closest voltage reading to reality can be obtained when the battery is at rest for at least 2+ hours. If you take a voltage reading from a battery that has been recently charging it will show higher than actual but if on the other hand the reading is taken from a battery recently subjected to a load the reading will be lower than actual. Back to square one? Not really. Here is where your brain turns as simple volt meter into a battery monitor. You can estimate estate of charge if you know the battery's recent activity. The high end is easy, anything over 12.6V equals 100% charge. I know more or less the number of amp/hours I subject the battery bank to so use mental calculations to roughly approximate the amount of capacity discharge and use the voltmeter to confirm the possibility of my calculations being correct. It is highly impractical when sailing to rest the battery to take a reading but approximations can be good enough for our purpose. More important than approximating is comparing readings. Allow your brain to build a comparison data base of readings based on sets of circumstances and the day you see a different reading the alarms bells will go off before you realize what's happening. For example a boat that spends all night hooked up to a powered inboard charger should show similar readings (whatever they are) day after day when first opened up in the morning. The day you get a different reading is cause to check the charger, shorepower supply and separately confirm the estate of health of the batteries. When on the hook I might take an hour to let the batteries rest some and then take a quick reading; all I want to know is some ranges in the state of charge 100% to 75%, 75% to 50% or less than 50%. That is useful information for me not necessarily any less useful if I had had a true reading of 12.42V. As my estimates approach 50% of capacity I start to exert my recharge options. The volt meter also indicates the state of health of the alternator. Once I crank the engine I expect to see 13+V. When they say learn to read your voltmeter they are really saying use your intuition and powers of observation to make sound deductions.
This is all very temperature dependent. At 80F the rest is normally 12-24 hours for an accurate reading. At 30F I have had batteries sit at well beyond full for many WEEKS before the surface charge burns off.
Full charge for this battery is 12.72V...
Dec 11, 2012 10 minutes off charge = 13.77V:
Dec 14, 2012 3 days off charge = 12.90V
February 26, 2013 nearly three months off charge = 12.72V
With just 0.1V representing 10% of capacity it can be tough to track SOC via voltage while simultaneously using the boat.
That said the volt meter shown is invaluable and can tell you "trends"... If for example you always woke up and the batteries were at 12.4V, and now they are at 12.0V, then you have something going on. Volt meters are good trend/change predictors. So long as you are not trying to narrow down the SOC to 10% or less then a volt meter is something every boat should have.
Do be aware that the point in the system to which the volt meter is connected can give you "false" readings. I see this so often it is not even laughable any more.
Any volt meter should be direct connected to the battery bank to avoid system wiring voltage drops and erronious readings.
I had one customer who was running his engine multiple times per day in a panic his banks were getting killed. His volt meter was connected to the DC panel which was fed by 10GA wires (a whole other can of works on that boat) and had about a 6% voltage drop at his "standard" loads.
This 6% voltage drop meant roughly a 0.75V differnce between the actual battery voltage and the volt meter readings. If his bank was really at 12.5V he was panicking because he saw 11.75V at the volt meter.... I simply ran new wires direct to the battery bank with a fuse and he was all fixed...
The volt meters that plug into a cigarette lighter are even more of a joke. Cut the end off, run the volt meter wires to the battery bank, with a fuse, and they work 10X better.