Inverter Power for a 43 DC

[Bill Root]

Again, thanks to all for the very helpful information. I'll let you know what we deicide and how it works out.

Bill

 

[spartonboat1]

I've been following this thread with great interest, since we are in the process of preparing our 1973 43 DCMY to begin the great loop in April. One of the items we are installing is an inverter.

Our plan is to cruise 8 - 10 hours and hang on the hook at night five days a week. The remaining two days will be spent in marinas using shore power. The boat has new CAT 3126's with 51 Amp alternators and a new Westerbeke 8.0KW generator. The marine electrician I hired to help with the inverter project (since I am an electrical dunce) has recommended a 2000 watt Xantrax Freedom 20 inverter/charger with isolator/combiners, four 8-d batteries for the house, two 4D's as engine starting batteries only, plus a separate battery for the generator. The batteries would fit along the outboard sides of the engines.

The electrician's feeling is that the alternators should be more than adequate to handle the house load and keep the batteries fully charged while underway. The 2000 watt inverter and four 8-D's should provide enough storage to power a few lights, refrigerator/freezer, TV/radio, heads and essential safety equipment through the night while on the hook. I keep pushing for 3000 watts but he keeps telling me I don't need it.

Of course there are probably many ways to get to the same result, but there appears to be no question that an inverter is a pretty essential item if one plans to do any kind of extensive cruising. The cost isn't cheap, particularly if having to pay a professional . I estimate approximately $4,000 all in, but we should be able to reduce generator usage to only those times when we want to be on the hook for an extended period or need to run the AC. Based on a total trip of about a year and 6,000 miles, I figure I should recoup that investment in about a month.

By the way, last week Sam's Club had Champion deep cycle 8D's for $148 each.

I hope this helps.

Bill Root
MV Tucandu
43' 1973 DCMY

I have a 1972 43' DCMY w/6-71N's, and have been running a Heart Freedom 2000 with their special/upgrade control panel with equalizer cycle. I have had this setup for at least 5 years, over the 4 largest 8D's avail, in dual mode as house batts and starting, plus original 7.5Kw Onan genset. Xantrax bought out Heart so my inverter may be a very similar design to that you are considering.

I agree with the configuration your tech is recommending for the most part, esp. the separate battery for the genset. I would recommend an Optimus Gel type battery for the genny, as you want this to be your most dependable battery. They have a 7-10 year life, will discharge to 0 volts, yet come back without damage, charge quickly and hold a charge for a very long time.

Please research the 8D deep cycle vs. golf cart or similar batteries. For some reason, my largest CCA 8D's discharge fairly quickly when running a couple loads at the peak for the inverter, i.e. 2000 watts- say a microwave and coffee maker, or one burner on the Princess stove. Even while underway running the engines and offsetting the inverter discharge with the alternators (55amp each), the 8D's still drop down near 12 volts. So check out golf cart batts.

Regarding the desire for 3000 watt unit, there is a factor to consider on the charging side. A 3k watt inverter also charges harder than a 2k watt unit. The issue occurs when a 3k watt charging cycle, is running at peak into discharged batts, and being fed from your genset. The 3k watt charge load will exceed the 8k output of your genset. I know, I know, the 8k is much higher that the 3k watts. However, talk to a Xantrax tech and they will explain that the inductive load at 3k watts is much harder on the 8k genset. They talked me down from 3k to the 2k unit, so stay with the 2k unit.

Finally, you have not mentioned an A/B transfer switch, which switches the 110v shore or genset source A) directly to the ships panel or B) to the inverter and then back to the panel. Your 110v source should not run directly to the inverter at all times. This is because your ship's panel is rated at 5.0 to 5.5K watts, while your inverter will have a 3KW rated bypass relay, which cannot support the full 5.5K watts of the panel.

The transfer switch installed must easily handle/specified for or exceed the full 5-5.5K input watts, so that when switched directly to the panel, you can run the entire ship at the full rated 5.5K watts. The inverter itself has a bypass relay rated at 50% higher than the 2KW inverter, i.e. 3KW. When 110v is present from either the shorepower or genset and you switch the transfer switch to the inverter, the inverter senses that 110v is present and the bypass relay sends the 110v back to the panel.

However, when the 110v source drops out because a) you remove the shorepower, or b) shut off the genset, then the inverter senses the loss of 110v source and almost instantly begins inverting. Your TV and electronics should not hiccup. The bypass relay drops out and the inverted 110v is sent to the panel. When 110v source comes back on-line, the bypass relay engages sending source 110v back to the panel and the inverting stops.

Some people dedicate certain circuits to the inverter, so that those circuits do not exceed the capacity of the inverter. I myself prefer full flexibility of the ships panel so I can direct inverter power anywhere on the boat. I just have to be smart enough to not run the hot water heater or too many total loads.

Last point. Double check all connections and the installation configuration for dreaded 110v feedback, plus install a transfer switch. My inverter was incorrectly installed on two points. A main feed wire was loose for two years...no holddown nut...yikes, could've burned the boat...found by luckily touching the lead and "noticing"- quickly fixed. Secondly, the tech ran the shore power directly to the inverter, so my poor 3K watts bypass relay was running the entire boat. The inverter went along with this, until the relay burned out. I soon installed a transfer switch.

You can install a totally manual transfer switch or a 110v powered switch...your call.

Share this with your tech, if you are really the dunce you claim you are. Let him vet my remarks.

It will be a great investment and upgrade. We have never regretted it. P.s., while underway and we want to run lots of electrical, we kick on the genset.

 

[Bill Root]

Spartonboat:

Thanks very much for the detailed information. I will share it with my tech when he returns from vacation. And yes, I am the electrical dunce I said I was, but I did buy the book.

Bill

 

[sgharford]

Spartonboat, I 2nd that Thank You. Would not have figured on a transfer switch based on bypass relay, but then again I bought a 24v 4000W inverter for my 12v 43DC so no surprise (did return it). Will definitely print this thread out, along with Calder's book, and a pencil a paper before breaking out any more boat dollars on this project.