Issue link: http://read.uberflip.com/i/2107
bow to stern 18 Houseboatmagazine.com Without electricity, your houseboat is going nowhere fast. Recently, Houseboat forum member dcrainmin discovered that his boat was missing a three-bank battery charger and came to his fellow forumers for advice on how to replace it. Luckily, Houseboat readers are a knowledgeable bunch, so he got the help he needed quickly, with some ad- ditional information, to boot. [dcrainmin] told the story: We are re- modeling an 86-inch, 62-foot Stardust cruiser at Lake Ouachita in Arkansas. It originally had a three-bank battery charger in the engine compartment. It is no longer there. It charged a bat- tery for the engine, plus one for the generator and one for the accessories. Can anyone tell me what amp charger I should replace it with? There are so many on the market, and some are just for the recharging of trolling motors. I need one to permanently mount in the basement of the boat. Thanks for any help. [abdiver] answered: It isn't an easy answer without knowing the configura- tion of your batteries, their size, and how you will use them. If you anchor out a lot and would prefer to keep the generator use to a mini- mum, then you might want a very high capacity charger that will bring the batteries up to 80 percent in an hour or less, which might require a charger capable of 100 amps or more. This will be hard on the batteries, however, so you may prefer to run the generator longer and treat the batteries a little more gently so they will give more years of service. A good rule of thumb is to limit the charge rate to no more than 20 percent of the amp-hour capacity, so if your battery bank is 200 amp-hours then you wouldn't want to charge more than 40 amps. On the other hand, if you stay at the dock most of the time and run the generator whenever you are away from the dock, you can get by with a much smaller battery charger. To handle multiple battery banks (house, engine, generator) you can either get a charger with separate outputs or you can use a single output battery charger and "battery combin- ers." A combiner is an electronically- controlled relay that will connect two banks of batteries together whenever either battery is getting charged. For a three-battery system you would want to connect the battery charger to the house battery, then use one combiner between the house and generator bat- tery and another combiner between the house and engine battery. This does require that all the batteries be the same type, either all flooded lead acid or all AGM. The size of the batteries can be different as long as they are the same type. The advantage of the battery combiner is that it is bi-directional. When you are plugged into shore power, the battery charger will be charging the house battery. When the voltage on the house batteries has come up to about 13.2 volts, the combiner closes the relay and connects in the engine battery so it will also be charged. When you disconnect from shore power and start the engines the engine alternator will provide charging, first to its own bat- tery, and then when the voltage reaches 13.2 volts it will connect in the house battery so it gets charged while you are cruising. Once the house battery has been charged enough it will even add in the generator battery! [Jeepster04] thought about the ques- tion: If we ever need to replace the charger on our boat, I'm not sure what I would go with. It currently charges two starting batteries for the engines and one D-8 battery for the heads (two nice-sized motors), all the DC light- ing, Jet-Ski winch, etc. It often has big loads placed on it, and I'm not sure how those new charges would handle that. Right now the charger will just give whatever needs charging the charge it needs. I would say the best, but not cheapest, route would be to get a 20-amp charger for the D-8 battery and a dual-bank (10amp and 10amp) charger for the starting batteries. It would be nice to find a three-bank 20-10-10 charger. [Sideways] made a recommendation: Another way to do it is to use Blue Sea Systems ACR, instead of a combiner. They list for around $95 and are virtu- ally trouble-free, plus you can use any style battery you want. We install about 40 or more a year and no longer have warranty issues like we did with combiners. I believe the Blue Sea part number is 7600. [stmbtwle] asked Sideways a question: Sideways, what's the difference between a "combiner" and an "ACR"? It was my impression they were different names for the same critter. [Sideways] answered: Interestingly, one of the major differences with their 7600 ACR is that it restricts incoming amperage to 60. That is the feature that extends the life of the AGM's that we use. If we used standard batteries it would not be so important. There are a couple more items that separate their ACR from other "combin- ers." The bottom line is you are correct, but Blue Sea has made the product choices and adjustments that make their product work trouble-free for us. [stmbtwle] followed up: I can see how the current limiting feature of the 7600 model would work to your advantage, as it would protect the secondary battery when combined. It seems to me your primary battery would still be subject to the full charging amperage, though, unless you actually used TWO ACR's with the charger output between them. It would end up sort of like a battery isolator but without the voltage drop. Most ACR's I've looked at (even Blue Sea), don't have the current-limiting feature of their 7600. This brings up a question: When you use a battery combiner between a starting battery and a large house bank, which battery do you connect the charger or alternator to? The house bank can handle a lot more current, but usually the starting battery is the one you want charged "first." This dilemma has always puzzled me. How do you guys do it? [Sideways] answered: My primary re- sponsibility is thruster installations, so I concentrate on performance and reli- ability at the most reasonable cost. The Forums From the Excerpts from recent Houseboat Forum exchanges at www.houseboatmagazine.com