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post #1 of 1 Old 12-07-2001 Thread Starter
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Multiple Sources for Battery Charging

I am setting up a 46-foot Dufour for long-term cruising. I have a generator on board and will be installing a 2500-watt inverter/charger. The main engine has a high-output alternator and I plan to install a couple of solar panels and a wind generator. Is there a product that will accept multiple inputs from four or five sources and manage the battery-charging functions from these sources? If not, how does one manage all these inputs to the batteries?

Tom Wood responds:
It sounds like you’re getting all charged up to do some serious cruising. Let’s start at the beginning.

If you already have a generator, it will put out 120-volt power to feed the inverter/charger. It may, or may not, also have an alternator to charge its own starting battery—if it does, this alternator will have a regulator.

The high-output alternator on the main engine will certainly have a regulator, and most on the market today come with external, adjustable-voltage, three-stage regulators that are very reliable, solid-state affairs.

The inverter/charger will take 120-volt power either from shoreside or the generator and convert it into a 12-volt charging source. Most have fairly sophisticated three-stage charge regulators already built in, and at least Heart Interface makes an optional regulator that will tie in the high-output alternator if you wish.

So far we have three, and possibly four, charging sources and all are equipped with voltage regulation.

Now let’s add the solar panels and wind generator. The old rule of thumb is that if the charging source is capable of generating two percent of the battery capacity in amps, then it needs a regulator to avoid overcharging the battery bank. This means that if you will install a solar panel array with a peak amperage output of five amps, you could get by without any regulation if the battery, or bank of batteries, it will charge is over 250 amp-hours in capacity. These same principles apply to the wind generator and most big systems need regulation. Every quality solar panel and wind generator sales outlet have voltage regulators for their equipment and recommend them to their customers.

So we’ve added solar and wind power and we now have as many as six possible charging sources, all with their own regulators. Should we look for a regulation system that will replace the six individual regulators?

Let me tell you a story. We have some friends that had what looked to us like the ideal boat-entertainment system, and we were considering buying one. It had a TV, a VCR, two cassette players, a CD player, an AM/FM tuner, and the speakers all in one small portable package. And it ran off AC or DC power—fantastic. First the CD player went, and while it was in the shop, they had no TV or radio. Next a cassette deck went—same result.

The point here is this: if you tie all six charging sources into one regulator, assuming it was even possible, and that regulator fails, you will be left without a single charging source. It defeats the purpose of the redundancy. My tendency would be to stay with discrete, dedicated regulation systems, even though it can sometimes be a pain to get all of them adjusted, orchestrated, and working together harmoniously.

What you might consider is a sophisticated monitoring system rather than have individual voltage and amperage gauges for each output. The inverter/charger usually has an optional remote panel with some wimpy LCD blinking lights that don’t tell you much more than whether the thing is on. These need to be bolstered with a minimum of a good digital voltage reading at the batteries. When trying to "aim" solar panels at the sun, it is especially important to have a good ammeter in the output line to use for fine tuning. But all of the input, charge, and outflow information can be gathered in one place with one high-quality 12-volt system monitor to keep you abreast of what’s happening in the system—even with as many charging sources as you have planned. If the monitor fails in some remote corner of the globe, you may not know what’s going on, but you can still charge.

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