Catalina 400 Power Useage
I just came back from a 9 day trip to Catalina Island. I had a wonderful time and the boat performed wonderfully, as usual, but I want to throw out a question to my fellow sailors regarding power useage. My Adler Barbour Refrigeration is a power hog and I know it but besides the refrigeration, I watch about an hour of T.V. a day and about 2 hours of lighting. Given that, I needed to charge my 2 - 4D House Bank twice a day (approx. 1 hour) to bring the system up to charge. Generally, I would wake up in the morning to find my battery voltage at 12.10 having charged them the previous evening. Does this seem right to all of you out there or do I have some problem I can't figure out?
Windfall C-400 #290
Mike... With 2 4D's as a house bank, you have perhaps a 400 Amp Hour capacity. Usable capacity is 1/2 that since you NEVER want to go below 50% discharge. So..you have 200 amps at most to work with and you probably have more like 150 if your batteries have some age to them and have discharged regularly below 50% (12.25V at REST with no load for at least 1/2 hour).
In my experience the Adler Barbours draw about 6amps...so even runing 50% of the time... you should be using maybe 70 amps a day...leaving plenty for your TV and lighting needs which might add up to 25 or 30 amps. So....something is off here and I suspect the root cause is your charging system. With a battery bank of your size you should have an oversized alternator (say 100-120 amps output) backed by a 3 stage smart regulator that can properly top up your batteries. Stock engines usually come with a 40amp range alternator which will continually NOT fully charge your batteries and eventually cause them to lose capacity. I further suspect that your batteries are less than good at this point and may need to be equalized or replaced...but new batteries will fail if your don't get to the root of the problem.
If the batteries are flooded cells...a hydrometer can check the individual cells and you can get one at any auto store cheap. Make sure there is NO load on them for a while before testing.
I would also get yourself a LINK system to monitor what is going on with your house bank in both voltage and amp usage so you can understand your various loads and adjust your charging regimen.
I've made a LOT of assumptions here in an attempt to answer your question...so let me know if any of them are wrong as it might lead to a different conclusion! Good luck...
Please understand that the following comments are a generalization and may vary from one battery manufacturer to another. Your individual battery manufacturer specifications should be followed.
Open circuit voltage of typical lead acid batteries is 2.1volts/cell or 12.6 volts for a 12V battery. End cell voltage for wet cells is 1.75 volts/cell or 10.5V under load. This is the lowest voltage a battery can typically go before damage and usually also represents the 50% discharge point of most batteries. So your level of discharging your batteries may not represent a major removal of total capacity.
However, the battery voltage to capacity discharge curve under load is not linear. One way to know for sure is to monitor the amp/hours in/out of the battery. Charging the batteries to the float voltage level (typically 13.3V or 2.22 volts/cell) will only replace 80% of the charge. The remaining 20% capacity takes time (about 80% of the time) to fully charge the battery. Some chargers boost the charge voltage to try and minimize this charge time (the three stage charger mentioned previously) but this is NOT recommended for sealed batteries. This boost voltage also increases the water loss of a wet cell and increases the chance of particulate precipitate, a killer of batteries. A good battery monitor, not just a voltmeter, would be a worthwhile addition to your powerboard. Insufficient charge time, leaving your batteries not fully charged, will also kill your batteries.
Another way is with a hydrometer check for each cell as suggested by camaraderie. Be aware the reading will vary depending on the temperature of the batteries, so warmer batteries will have a lower specific gravity reading at full charge then colder batteries.
The open circuit cell voltage method for checking batter capacity is linear but requires that the batteries are without any load for an extended time, ½ hour seems correct. The open cell voltage will also be dependent on battery temperature and can vary over 0.1 points of specific gravity from a hot to cold battery (100°F to 15°F). An open circuit 12V battery voltage of 12.65V is typical for a fully charged battery and 12.24V for a 50% discharged battery.
It all depends on how much reserve time you want on you boat before recharging. Do you have enough? Only you can decide. Your first step should be doing a full energy audit on your system so you know how may amp/hours watt/hours you are using so then you can decide how much battery you need.
Dave...with due respect to your battery knowledge, my 3 stage Balmar charger works just fine with my sealed AGM's. 14.2 Volts Bulk charge then stepped down to 13.1volts float. It also has adjustments for different rates for gels which CAN be damaged by the higher voltage wet & AGM's can take.
Also...around 12.25 V at rest is 50% of capacity...I don't think you meant to imply that 10.5 V (flat) was half capacity. No one should discharge their batteries below a RESTING voltage of 12.25V.
Another link Dave which I think you will find fascinating given your expertise & technical orientation is:
I would be interested in hearing about anything you disagree with him about if you get around to looking at it.
Here is more information that may help you...help me. My alternator is an 80 amp model probably putting out about 65 amps @ 1500 RPM. My charger is a Heart Interface/Inverter (2500W) with a Link 2000 monitor.
Let the discussion begin.
Michael...OK...you have the link monitor and you have a good dockside charger but I assume you are charging from your alternator when at anchor (unless you have a generator you haven't mentioned). We need more questions answered:
1. What charging voltage does your Link report once you've turned on your engine and waited about 2 minutes? It should be showing something over 14V.
2. The alternator...should be ok for charging your bank if just a bit small. Does it have a separate regulator or did it come standard on the engine with built in regulator?
3. How old are your batteries and are they standard wet cells or another type? When you say your batteries are at 12.1 in the AM...do you mean that is the voltage at REST after 1/2 hour of everything else off...or is that just the voltage you read with other things on or just recently turned off? When you get a reading like 12.1 ...if you turn everything off...does the voltage come back up a bit after a while?
You probably don't have the answers to all of the above but you need to find out to fully diagnose the problem.
I bow to your experience with AGM batteries and chargers on a boat. The technology (AGM) in my industry does not have the life expected, even with carefully controlled environmental and charging conditions. (Although, none of the VRLA battery technology today has the life expectancy of good wet cells. I have seen studies that “20 year” batteries give 5 years in a controlled environment if you’re lucky.)
My figure of 1.75V/cell (10.5V on a 12Vstring) is for a battery under constant load, defined typically as a minimum of 1A for 100AH of battery. I use a low voltage disconnect to make sure my batteries do not fall below this level (actually I have the disconnect level set for 1.8V/cell or 10.8V to give me reserve time to crank up the engine to charge the batteries).
If you remove the load at the 10.5V level, batteries in good condition will drift up to 12.24V.
I agree with your advice to Michael, everyone needs to understand the operating conditions of the electrical system in order to diagnose any potential problems. Correct me if I’m wrong, but doesn’t the Link 2000 have all of the information needed to diagnose the system, average current draw, peak current draw, capacity, etc? I’ve not used one and am considering putting the Link 1000 in my present boat.
Michael, more information of this type will be needed in order to give you a meaningful answer. A data dump from your instrumentation will definitely help in addition to the answers of the questions from Camaraderie.
Boy, you guys are good.
Forgive me for not giving all the details from the beginning. I do also use a Honda EU 2000 generator for charging. I typically charge the batteries , in the morning, using the generator (plugged into the A/C in on the back of the boat). This, of coarse, uses the Heart smart charger to do it's business. I would run the generator about 45 min-1 hour until the link 2000 started the float stage of the charge. In the late afternoon or early evening, the batteries would be down around 12.45 and I would charge again. This time with the engine alternator so battery charging and water heating could go on together.
The Engine alternator has a built in regulator and all voltage readings were made by just looking at the readout on the link. It was a good suggestion to turn off all breakers and see if the voltage recovered at all. Who knows, the refrigerator may have been running to cause to voltage to read low.
OK Mike... so you can check out the at rest voltage on your Link and as Dave says, you can even get a much fuller report on your battery charging state and routine use and results by a thorough reading of your Link manual about the menu system. This is definitely something you should do. One thing you said has me thinking that perhaps your batteries are somewhat sulphated and in need of Equalizing (which I think you can do with your Heart)...you said you've been charging up to "float" which means that you are perhaps putting in only an 80% or less charge. You need to see those flashing green lights on your link when you're on a cruise...if not every day...then at least every few days!
I'd also recommend a higher power alternator and separate 3 stage regulator which will both treat your batteries better and mean less engine running time.
Finally...I'm assuming you have wet cell batteries with water caps. You have checked the individual cells AT REST and you do keep them topped up with DISTILLED water right? Dockside charging will boil off the water and leave the plates exposed killing the battery life. If you don't have wet cells...DON'T Equalize the batteries with the "Heart until you've contacted the manufaturer for instructions or things could get rather explosive!
Mike, I agree with camaraderie, I think you are only charging you batteries up to 80%. This will reduce the life of your batteries.
The rule of thumb is that it takes 20% of the charge time to charge to 80% capacity, and 80% of the charge time to charge the remaining 20%. If you run your generator 1 hour to get to the float voltage level, you wound need to run it at least four more hours to fully charge your batteries.
The only way to know for sure is with the specific gravity reading of each cell or the open cell (unloaded) voltage of the batteries. If you use the open cell method you would preferably disconnecting each battery from the others to identify any bad cells/blocks. (The specific gravity reading of each cell will identify if you have any “bad” cells in each block. Unfortunately this option is not available if you have AGM batteries.)
If you identify a bad cell/block, equalizing may bring it back. IF you have AGM batteries you MUST follow the manufactures recommendations. Most of the manufacturers are online so all you have to do is identify the manufacturer and download the specific instructions. NEVER NEVER NEVER equalize a battery, or charge a battery, outside the manufacturers specifications.
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