thechadmiller":gr0jejpt said:Ok, looking at options from my dealer, I'm seeing "single engine battery distribution closer w/VSR".... Huh? Can somebody explain what this is pretty please?
The VSR (Voltage sensitive relay) is a combining relay, and it costs about $80--easily added later if you wish. What it means, is that the house battery is isolated from the engine start battery at rest and when the engine starts. This protects the electronics from both low voltage and spikes when the engine starts. As the start battery begins to charge, from the alternator, the voltage comes up--when it reaches 13.7 volts, the VSR combines the batteries, so they both charge. When you shut down the engine, and the resting battery voltage drops below 12.7 volts, the relay opens, and there is no risk of depleting the engine start battery during the time the engine is not running. I have had it on all of my C Dorys (in one form or another).
Batteries: The boats come with group 24 batteries, which are on the small side. They are adequate for starting the engine/engines, but a single battery is asking for problems down the line. I change my batteries to a group 31 battery. The "group" number is just a case size, but it also gives some indication of the capacity of the battery. At rest, lights, stereo, refrigeration, etc can drain a battery fairly fast.
Group 24 battery generally is 65 to 85 amp hours,
Group 27 battery generally is 85 to 105 amp hours
Group 31 battery generally is 95 to 125 amp hours.
A fully charged battery should be 12.6 to 12.7 volts at rest, depending on type of battery.
A 50% discharged battery will be approximately 12.2 volts. If the battery drops below 11.8 volts, it is for all purposes dead.
Many of us like to know batter voltage. The small analogue gauge which comes with some engines is not of much value. A good digital gauge is not expensive, and easy to install. Better is a digital gauge which shows the volts of both the house and engine start, and the current current draw, plus total current draw, or state of charge of the house battery. Some of us who run a refrigerator and freezer (yes in a 22), will have 3 AGM group 31 batteries, with a capacity of 125 amp hours per battery. We don't need that much for the engine start battery, but balanced battery banks is important (that the batteries be the same type, capacity and age) for longevity. Thus I have available in my house bank about 125 amp hours before I need to recharge them. When cruising this can be done from the engine, from solar panels, or from a generator and battery charger.