+1 on all of that Steve said. A proper battery monitor with a shunt that senses the actual power usage is the way to go if you need to rely on your electrical system. That's what I had on my 35-footers, and it is the only way to truly keep track of what is going on. That being said, on my CD22, which has a rudimentary electrical system and which is only used for short cruises, I just have the original analog volt meter. Since your CD30 has refrigeration, you are certainly at the level of complexity that a proper battery monitor is worth the investment.Steve Laume wrote:I doubt your batteries were at 13.2 volts when at rest. A fully charged battery, should show about 12.8V when at rest. Voltage tells you very little about amperage use. I run a battery monitor on Raven and it will tell me much more about the state of my batteries. I can scroll through, voltage, percentage of charge in amps, amperage draw or input, and actual number of amps left in battery bank. It is the percentage of charge that I find most useful.
When you are charging your batteries, you will see much higher voltages in the 14V range. After you stop charging, the voltage will slowly drop to give you an at rest voltage, if nothing is drawing on the batteries, this will give you a vague idea of amp hrs in the battery. If you draw current out of the battery at any time, the voltage may drop, below the at rest state, temporarily. This is why a volt meter is not a god way to judge battery state.
With a battery monitor, you can see exactly what your percentage of charge is. I have a pretty good solar array that usually keeps my batteries well charged. If for some reason they do discharge to the point that I feel the need to run the engine, I can see exactly how many amps the batteries are accepting. In the bulk charge phase I might be adding 25 or 30 amps. At some point it will fall off to single digits and it doesn't really pay to keep running the engine. I can also figure out if I should add additional amps to my battery bank to get through the night, when there is no solar energy, input.
Good batteries are not cheap. A battery monitor is a very good investment in keeping them in good condition as well as not finding yourself in a situation where you have run the batteries down to the point that you might not be able to start the engine and recharge your bank.
I still have the original CD panel with a Blue Seas sub panel. The original battery meter was pretty worthless but my battery monitor fit in the original hole. All the readouts are digital, down the tenths, so there is no guessing about any of the numbers.
You can't manage your energy if you don't have any data, Steve.
As a rough data point, eMarine's web site says a marine fridge typically draws about 45 amp hours per day. My assumption was that the fridge shown would be less efficient than a typical water-cooled fridge, but the calculated 44.4 amp hours, while perhaps low for an air-cooled unit, is in the right ballpark. I wonder what the environmental conditions were for John's 20 amp hour figure--perhaps his trip to Michigan, where ambient temps are pretty low?JD-MDR wrote:I see JS says his "Engle" uses less than 20 amp per day So it doesn't look low to me, Or Jim is just saying its seems low for my particular unit. Any way I'm getting some understanding of it.. I will try to figure out how to use a battery monitor and hook up the solar Panel .. A neighbor at La Paz gave me a 50 watt semi flexible panel. I set it up to test with clamps to the battery. It put out 14V. I havent used it yet.wikakaru wrote: it is averaging about 1.9 amps. Over the course of a day that is about 44.4 amp hours. That sounds low to me, but maybe it's right.
Dang, I'm getting too much stuff (one of my worst nightmares)
Thanks for all the help.
Again, +1 on what Steve says. One rule of thumb about charge controllers says that if you have more than 1 watt of solar panel output for every 25 amp hours of battery capacity, you need a regulator. I'm guessing the system you describe exceeds that threshold--you would need to have a 1,250 amp hour battery bank to support an unregulated 50 watt panel and I seriously doubt you have that large a battery bank. MPPT controllers are relatively cheap, especially when compared to how expensive batteries are to replace if damaged by an unregulated charging source.Steve Laume wrote:Be very careful with that solar panel. They typically put out 18 volts and however many amps the size of the panel and the amount of sun will provide. This is way too much for your battery to accept. This is especially true when it nears a full charge. You definitely need a charge controller. This is like a voltage regulator on your alternator. A good MPPT controller will optimize your panel output and is more cost effective than a PWM controller and a larger solar panel. This is especially true, since we only have limited space for panels.
There is a lot to learn in managing batteries and setting up a solar system, Steve.
Smooth sailing,
Jim
