Powering a cruising catamaran
It is 9pm Thursday night, Hurricane Matthew is breaking all sorts of records and is starting to pummel Florida with category 4+ fury. But, here in Prickly Bay on the south coast of Grenada, 1700 miles to the south east, we are finally having a nice calm anchorage.
I am lounging on the front deck, sipping a local dark rum on ice and thinking about our generator; reminding myself that the water for the ice maker, and then the ice and the electricity for my Mac were all made on Ad Astra.
The surface of the bay is just ripples, which is a welcome change for after Matthew passed over us a week ago at tropical wave strength. Since last week Matthew has been sending back good sized waves from the rare west. While catamarans normally handle rolly anchorages far better than monohulls, the winds were from the east but Mathew’s waves from the ABCs refracted up into the bay causing us to wobble side to side like a monohull for the last week.
Even with the seas from the west and the winds from the east reducing our options we could have moved into one of the better protected bays on the south coast with barrier reefs. However, Prickly Bay is the center of the cruiser world here with dozens boats with people all over the world riding out the hurricane season. Grenada capitalizes on the storm season with some of the best technical marine services, boat yards and chandeliers in the Caribbean.
“How long are you guys here in Grenada?”, a fellow cruiser asked us yesterday.
With all seriousness and no thought, “Until I clear The Boat List.” I replied.
With a load snort, “Ha! Well then you are never leaving!” and she waved goodbye.
What is The Boat List?
The Boat List is the Things To Do list for your boat. Every time you check off one item of your list you roll 1D4 to determine how many new items get added to The Boat List.
When I said I was going to stay until I cleared the list, I gave away how much of a noob I am to full-time cruising.
You never clear the boat list.
I agree that you should be out cruising, not waiting for the boat to reach a mythical perfect state before weighing anchor. But hey, it *is* hurricane season, and Grenada *is* a free port (duty free) — now is the best time and place to get Ad Astra in better shape for extended offshore cruising.
So what is on Ad Astra’s List?
The center of a boat’s list is how to power all of your systems, I will start there.
You can divide cruisers into two broad classes: the salty types that carry no refrigeration, no water making, no ice making, no air conditioning, no electric winches or windlass vs those with all of those comforts. The salty types are better humans that I am unable to match. Ad Astra definitely falls into the comfortable side of that grouping. All of those luxuries and comforts require [lots of] electrical power.
On Air Conditioning
Air conditioning is such a power hungry system that you must run your generator full-time to power it (or not go anywhere and remaining tied to your dock with shore power). When we ordered Ad Astra, AC was an option but it was about $25–30k for the larger generator and the 5 AC units. Between the cost and the need to run the generator full-time I decided to skip the AC.
After cruising for a bit, it is certainly nice to step inside someone else’s boat with AC, but I still stand by the decision. The only time I regret not having AC is when we are forced to tie-up in a marina for some extra ordinary reason, and I do not see need on the horizon.
Why do marinas suck ? — Rarely are you lucky enough to be pointed to the wind while tied up, so the boat gets no breeze and you just sweat.
We have been anchored out continuously since June, and the boat naturally points to wind with a breeze that strafes to whole of the boat and open hatches with breeze boosters (think small tent-funnels for capturing wind).
In Bequia we added two new canvas awnings: a huge one covering the whole front of the boat and a medium sized one giving shade to the flybridge deck. With all of this shade and breeze the daily high of the upper 80s is perfectly pleasant and no need for AC.
A friend of mine on a fabulous monohull is having a tough time as his boat has far less natural ventilation, and while he does have a generator large enough to the run his AC — it is a ferocious use of diesel. Frustrated further he is paying the high marina fees to be tied up to get some work done, but his boat is a 60 Hz boat and the marina is only able to supply only 50 Hz. Thus, no AC. Vexation as my Bequian friends would say.
Even without air conditioning the generator is still a vital system of a cruising boat. The generator on Ad Astra recharges our 1050 Amp-hours (Ah) house bank, powers our AC electrical appliances (Macs, Ice Maker, Washing Machine) and delivers the high voltage DC our water maker demands.
The first thing Max does every day is check the house mains and start the generator to recover the 150–200 Ah that were consumed since he ran the generator the previous evening.
During the day we have two Kyocera 255 watt solar panels that peak at about 30 Amps in mid-day and just about 6 Amps at the either end of the day which is enough to cover what we consume during the day plus drive the house bank up to 13.3v. At peak sunlight we can even drive the water maker off that solar.
The solar is very nice, but we are still running the generator in both the morning and the afternoon.
And keeping the generator running is not trivial.
This story is really a story of what we have had to do since August to keep our 5kW diesel Onan generator happy:
After running every day from June 28th to August 21st, the generator failed to run with the error code — no raw water. After checking the raw water strainers and the lifting pump, we diagnosed that we must have a problem with the impeller inside of the engines’ water pump.
We had a spare impeller, but this would be a new job for us to take apart a good bit of the generator.
While keeping a picture & video record of what we were doing, Max, Kyle and I took apart the water pump on the generator and indeed find that the impeller had imploded into 20 bits of rubber, we put the jigsaw puzzle together of the rubber bits to ensure that we found them all, installed the new impeller and the generator was running like a kitten.
But the oil was quite dirty, and I knew the generator was overdue for an oil change. After putting off the task for a few days, I finally decided that This Morning was going to be the morning to Change The Oil — No Matter What. The boys got the tools together, and removed all the sheet metal covers off the generator. We pumped out the oil by hand and replaced the dirty filter. And just we were about to finish up when it started to rain. Sometimes it is a little sprinkle, sometimes it is a downpour and sometimes it is difficult to tell the difference.
What I should have done is simply stop and close the cover and finish up later. But I had Plans for the Day. Stuff To Do. So I rushed it, I ended up not firmly enough screwing on the oil filter. (I had been warned by many people to not *over* tighten the oil filter…) The generator started up just fine, but about 10 minutes later the low oil pressure sensor went off and it shut itself down. We opened the generator housing to find oil splattered everywhere.
Damn — I killed my generator.
Rain coming down.
Oil discharging into the ocean.
Quick! Get more of the oil absorbent pads!!!
Stuffed the compartment with $50 of pads and closed the hatch to stop more rain from coming — and stepped away.
After the rain passed and calming down, I screwed on the oil filter properly, and added some more oil. Ran the generator and it failed again from low oil. Added some more oil. Checking the dipstick each time a couple of times. Snap! The freaking dipstick *breaks off* the last 4 inches.
Generator still complaining of low oil. But now I do not know how much oil is in the engine. After discussing with my South African cruising friend JK, he rationally directed that I re-drain ALL of the oil out of the system and simply re-fill it again with 2.2 liters of new oil.
Did that. Generator ran like a kitten again!
Happy dance! I Did not kill the generator! Happy Dance!
The good mood lasted for 24 hours. Then we smelt something weird burning and the Onan shut itself down with an error code complaining of a loss of AC voltage sense.
After exhausting the collective wisdom of the United Nations anchored in Bequia, I went on a fantasy quest chain the ended with me meeting Kerry Ollivierre the Scottish wizard breathing life back into any engine and master of all marine systems.
Kerry figured out that we melted the plastic housing that holds two magnets on springs that are the brushes in the actual AC generating system. With a dull box cutter he cut away and re-shaped the plastic housing and popped it back into the generator and it was running again!
We went ahead and changed the fuel filters while we were there and ordered a few new proper plastic housings for those magnets. We also ordered a new oil dipstick, although to install that we need to lift the entire generator up and get access to the oil pan on the bottom. Later.
Now the generator was running again, but we were running the generator 2–3 hours each morning and every evening to keep the house bank above 12.2v (50% charge on a deep cycle battery). What’s wrong? Are the batteries nearing end of lifecycle? Is the battery charger too small? Should we get more solar? After discussing with my fellow cruisers and online research it was clear that the *tiny* 25 Amp battery charger that Ad Astra was supplied with from the factory was woefully undersized against the 1050 Ah house bank.
The rule of thumb is that the battery charger should be about 20–25% the size of your house bank. That means that Ad Astra ideally should have 250 Ah of battery charging. Ad Astra was off by an order of magnitude.
Time to buy a big charger, after doing some online research and discussing with other cruisers I chose the Xantrex Freedom 3000 — a huge $2500, 150 Amp, 3 kWatt battery charger / inverter. While not 250 Amps, at 150 Amps at least we are inside a factor of 2. We were in Bequia at the time, so it made best sense to have it shipped to Grenada where there is a duty-free Budget Marine.
Hurricane Matthew pushed us to sail down to Grenada, and an amazing happy coincidence Kerry the Marine Wizard happened to be down here in Grenada this week working on a superyacht. Together we installed the new Xantrex in 4 hours. I found a great place to mount it in the aft starboard cabin next to the solar MPPT controller, and it was a snap to use the existing mousing lines to run the cables.
On first try the inverter was up and running and bam! 13.8v delivered to the main house bank. It was midday and we didn’t actually need to charge the house battery, so we shut it down. The next morning we fired up the generator to see how the Xantrex would handle a hungry house bank at 12.1v. Flip! After just under 10 minutes the circuit breakers both on the panel and next to the Xantrex flipped. Checked the 3-wire AC wire we installed to the Xantrex and it was *warm*, not yet hot. But warm. This is actually great for it meant that Ad Astra’s safety systems were working well. Back to budget marine, and I bought 21 feet of over-sized 8-gauge 3-wire for $100. We installed that wire in just about 30 minutes, and the system fired up and ran again right away. But again, it was midday and so it was not yet a true test of the system. The next morning, with the new huge 3-wire we gave it another test. Ran for about 5 minutes and then Flip! The 100 Amp circuit breaker we installed next to the Xantrex flipped. Tried again, 3 minutes — Flip! Sigh. Giving it a little thought, I realized that the Xantrex really *is* a 150 Amp battery charger and the house bank is actually big and hungry. Back to budget marine, searching harder I found a 150 Amp circuit breaker.
Installed it yesterday, and then tried the real test — this morning — Saturday October 8th — and Boom! Charged up the mains in just one hour! No circuit breaker flips.
I skipped over something subtle; how did we charge the main house bank over these days when the circuit breaker kept flipping? We had no generator right? Yes, we have solar during the day, but that is not enough to get us through the evening or to recover in the morning before the sun gets high enough in the sky to deliver real amps. No generator and no solar, but we still need electrical power… behold the magic of a catamaran!
So much redundancy: one each hull we have a 55 horsepower Yanmar diesel engine, that engine comes with an 80 Amp alternator — woot! That is over 3x as large as the puny 25 Amp battery charger the factory installed.
Ad Astra’s Electrical Power sources:
- 5kW Onan Generator driven through a Xantrex 150 amp battery charger
- 510 watts of solar driven through an Outback Flex 60 MMPT
- Port 55HP Yanmar driving an 80 amp alternator
- Starboard 55HP Yanmar driving an 80 amp alternator
- 110v shore power routing through a 40 amp battery charger
- 220v shore power routing through a 60 amp battery charger
(Note: we are keeping the older 25 Amp battery charge as a backup until we finish shaking down the Xantrex.)
When the house is so low that the massive Xantrex wants to shove in 150 Amps and that overwhelms our circuit breakers, we simply turn on one engine (choosing port to offset the diesel consumption from the generator on starboard) for about 10 minutes. That first 10 minutes is that rocket taking off part of the curve on the bulk phase in the diagram below:
That brings up the charge on the house battery rapidly, and soon enough the house bank has enough charge that it begins to resist taking on more charge, and we can shut-off the port engine and the Xantrex takes it from there with a bit less amps flowing through the circuit breakers.
Why? Lead batteries have an asymptotic charging curve (AGM and Gel have better, but similar curves). Where they charge up pretty darn fast initially, but as they fill up they have more and more resistance to further charging.
Wait! I am not done.
During these test runs with the battery charger, the generator simply stopped running and gave an unknown error code. Kerry and I were planning on getting together to get some craft beers later that evening, so I called him up and he came over early. He knew right away it was not a problem with the electrical side, he said unknown error is always lack of fuel. STBD fuel tank was reading at 50%, but Kerry admonished me to not trust the modern digital fuel gauges. While I was pouring in some diesel from jerry jugs I keep on board, Kerry did some more investigation — 3 minutes later he called me over to show me that the primary fuel pump had stopped running and the reason was not a *blown* fuse, but instead the fuse’s legs had disintegrated from saltwater corrosion. With a quick twist he shorted out the fuse connection and the generator was happily running again.
Still not done.
The generator also stopped running this week with a low oil pressure warning. Remember I still do not have a dipstick. So I poured in 0.75 liters of oil in 3 increments of 0.25 liters each step. Each time the generator would fail from low oil pressure. I searched online and gave it some thought and decided that the oil sensor must be bad. Looking at the isometric diagram from the parts manual I figured out where this oil sensor should be. Back into the generator compartment, remove the sheet metal again and dug around until I found this really ugly rusted sensor. Looked like a total piece of garbage, knowing it was another part to order and have shipped in I was feeling defeated.
Max asked me, “Well how do you get rid of the corrosion.”
“Let’s try some WD-40.”, I replied with some hope in my voice.
Spraying a rag and massaging the ugly sensor for a couple of minutes I was able to make it look less ugly.
Fired up the generator. It was happy and was running again!
So as a re-cap many repairs were made on the generator, and the new battery charger is a monster. But we still have to install the new dip stick (as I probably have a little too much oil in there now) and need to order and install a new oil pressure sensor.
This is a lot of progress, but I still do not like running the generator for an hour in the morning and again in the afternoon. We do get our laundry, water & ice making and laptops charged up in these windows. But still, feels ugly to burn 0.5 gallons of diesel an hour.
Solar Upgrade V2
So we are going to do a large solar upgrade. Going to take Ad Astra from 500 watts to 2000 watts of solar power — combined with the 3kW inverter we should be able to do most of our power hungry chores midday under solar alone. Tomorrow, I will get a quote from a reputable English stainless steel guy to create an arch that will span the back of Ad Astra above the dinghy davits to hold six more panels. Back in Bequia, Kerry has a line on high quality German manufactured solar panels that are super cheap and coming in on private containers for the foreign mansions on the windward side of Bequia, so he will do the solar install back there.
In the back of my mind though, I am still wondering about the health of the main batteries. With 1050 Ah banks, and 12 hours of darkness, running ~<15 Amps of stuff we should only be using at most 200 Amp hours each night. That should only be ~20% to 25% of the house bank’s charge and we should not be at 12.2v in the morning. So I think new batteries are on the list for Ad Astra. Lithium is on the wish list:
Lithium as marine deep cycle batteries are just entering consumer-level production. Lithium batteries have so many advantages:
With traditional deep cycle batteries you can only go down to 50% charge without damaging your batteries. Combined with the non-linear charge curve where you are very rarely at 100% changed and instead most likely peak at 80% charged you have a practical house bank at 30% of your nominal Ah. In the case of Ad Astra we have 1050 Ah x 30% = 315 Ah. In practice we are really seeing about 180–200 Ah from our house bank, or about 50–60% of even that 30% we should be getting. Lithium on the other hand is quite happy to be discharged down to 20%, and to be fair Lithium also resists charging that last 5–10%, but even so call it 90% down to 20% and you have a practical bank that is 70% of the nominal Ah vs 30%.
Linear charge curve means that you can get your batteries charges so much faster, and they will happily take all the amps you have to charge them right up to at least 90%. This means less time running a generator, the faster the solar gets the bank up to full charge, and then later more surplus energy for running other appliances via the inverter under sun power.
Another advantage is the weight savings — Lithium batteries are more than 5x lighter than the weight of traditional deep cycle batteries. Now with a big boat would you really care? In our case our we have 5 Lifeline 255 Ah Sealed AGM batteries that weigh 156 pounds each for a total of nearly 800 pounds of lead on our starboard side of the boat. The Lithium equivalent would be 30%/70% * 255 Ah = 110 Ah Lithium battery needed for the equivalent practical house Ah and weighs just 28 pounds! Across the whole bank that is a savings of 640 pounds. That means we could carry 16 more cases of beer on Ad Astra without affecting the waterline!
The specific Lithium battery I have my eye on is the Smart Battery 260 Ah in the same 4D form factor as I have now.
With a single 260 Ah Lithium at 70% discharge duty we would have 180 Ah of practical house bank matching what we currently have with the tired Lifelines.
But if I had 5 of these Lithium beats, I would have a ridiculous 1300 Ah of nominal house and 900 Ah of actual practical house bank, which would be the equivalent of being able to run 90 Amps an hour over night! Or 6x what we currently consume.
Obviously, we do not need 5 of these Lithium giants. I am trying to decide between 2 and 3 of them to start with.
What’s the catch? Cost. Each of these Lithium 260 Ah monsters is $3,000. Compare that to the Lifelines at $540 each. The whole bank of Lifelines is the same cost as one Lithium battery.
But here is the final advantage — Lithiums are expected to have between 3000 and 5000 life cycles, where sealed AGM batteries life cycles are between 300 and 1000 (varying wildly on how carefully one keeps the batteries above 50% charge).
As Ad Astra was in charter, her batteries were routinely discharged below 50% as the charter guests must pay for the diesel they consume at the end of the charter; but there is no practical way to detect if they failed to keep the house banks above 50%.
Let me assume that my current bank is dead and it is time to buy a new bank, if I buy 5 replacement lifelines for ~$3500 (shipping down to the islands will be expen$ive), and then I take over careful charging. Say I get the maximum 1000 lifecycles — how does that compare to Lithium?
I would need at least two big Lithium monsters for ~ $6500 (including shipping); assume the low end of Lithium at 3000 cycles, or 3x more lifetime.
1000 life cycles @ $3500 vs 3000 life cycles @ $6500
Doing the math, Lithium actually comes up 60% cheaper! And I would have a practical Ah of 364 Ah vs 300 Ah giving me a 20% boost in capacity. Spend another $3k and get almost 2x our previous capacity.
If I start with just 2 of these Lithium 4D form factor beasts, I would still have open space for 3 more if we start running some sort of power hungry chemistry lab on Ad Astra.
So, I think Ad Astra will be getting two new Lithium batteries.
Next time I will discuss the dinghy portion of Ad Astra’s Boat List…