Originally Posted by capecodphyllis
I'm looking at a DC-wired boat that has a two bank system - four AGM batteries on the house bank, and one AGM crank on the starter bank. The electrical panel features a volt meter and an amp meter. The battery charger consists of a single 110 volt automatic, 40 amp with temperature sensor. Not sure of the brand.
Does the charger have two outputs, or just one? My guess would be that it already has two outputs, as most chargers above 30Amps generally do.
1. Wouldn't it be much better to have dedicated amp and volt meters for EACH of the four batteries, for a total of eight meters? Or can one have too many wires connected to each battery? (I would prefer to see the condition of each battery at a glance.)
Doing that is both overkill and gives you a lot more points of failure. A single monitor will tell you how each bank is doing... if the monitor indicates that you may have a problem, then you can always pull out the handheld volt-ohm-meter, and check each individually...
Wouldn't it be better to have 1 dedicated smart charger for each battery? Or is there a smart charger available that can deliver the right flow to 4 batteries that are not identical?
Again way overkill, and introduces multiple points of failure as well as serious problems in isolating the batteries, so that the multiple chargers don't interfere with each other. Also, this is a very expensive proposition.
Generally, a smart battery charger will sense voltage levels and taper off the charge rate based on the voltage level sensed. If you have multiple chargers, they would sense the voltage of each other, since they're all hooked in parallel on the house bank, and the bank wouldn't charge properly...as each charger came on—it'd sense the voltage of the other chargers and promptly drop the charging output it would give. You can't really isolate the batteries from one another and still have the act as a single battery bank realistically.
This is also one reason it is recommended that the batteries in a single bank be of all the same brand and age if at all possible. As batteries age, their charging characteristics change slightly, as does their ability to hold a charge and maximum voltage.
If I introduce a wind generator, would I have to buy a seperate smart charger just for that? Then another if I add solar? In other words, what about inputs to the charger/chargers? Is there a charger available that can accept simultaneous connections from all my preferred DC charging options - diesel alternator, Honda generator, wind, and solar?
This gets a bit more complicated. Solar panels have some specific issues, as do wind generators. Wind generators generally require the charge controller to have a line that will trigger the braking feature of the generator when the output rises too high. Solar panels don't shut off, and some of the solar panel chargers essentially short the inputs to stop the incoming charge. Two generators is kind of overkill... and why do you need so much electrical generation capacity on your boat??? You really should size your generation capability to your usage plus some percentage for future expansion...
What about AC shore power? Would I require anything other than a combination inverter/charger? How do I monitor that? Would I need to install an AC electrical panel? (I run my power tools and other AC appliances off a portable generator.)
Most inverter/chargers have battery monitoring capabilities, either built-in or as an accessory. If you're going to have shore power, you really do need to have an AC-dedicated panel. BTW, if you're putting in such a system, you could run your power tools off the AC-side of the boat fairly easily, especially given the size of the battery bank. It really wouldn't be an issue if you had a diesel genset... and I don't really see a point in having the portable generator.
5. Does it make any sense to purchase a single 200pd AGM battery? Do the benefits of fewer wires/less complexity outweigh the difficulty of getting the damn thing on and off the boat? (Apparently not, since I've never seen this on a 42 ft boat. Isn't it true that every AGM battery consists of smaller batteries, or 'cells' anyway?)
The advantages of smaller batteries, hooked in parallel to present as a single larger bank are: 1) The individual batteries are lighter and easier to handle; 2) if any one battery fails, you lose a smaller percentage of your actual battery capacity; 3) you can often use the same batteries for the house and start side, and if the start batttery fails, you can swap one out temporarily to keep the redundancy in the system; 4) battery placement is a bit more flexible with the smaller batteries.
Perhaps someone can direct me to a URL offering boat electrical schematics so that I may better understand the options. I haven't been able to find much doing keyword searches. (Calder's book is on its way.)
If you call up any of the big marine electrical panel suppliers or charger suppliers and ask for their catalog, most catalogs have some pretty decent basic battery/charger diagrams in them. They will be company part specific, but it is relatively easy to generalize them.