After having sailed with Stella Polaris for 8 months we now have a fairly good idea of how she works. We’ve discovered elements that are great and other that are not. We’ve also settled on particularities we need to change. There are a few things you need to have operational on a boat in order to cast off in the first place: the obvious are a non-leaking hull, a motor that works and sails and rigging that will allow you to take advantage of the wind. We had several clear challenges when we bought her (read more about it here): both diesel tanks were filled with contaminated diesel and a foul crust had to be completely cleaned out (a Hell of a job), the battery bank was dead and had to be replaced (not cheap), and the windless was found to be heavily corroded, so she needed to be revitalized.
Now that we have a fairly good idea of both how we sail and how Stella Polaris works, we’ve found that one of the most important issues we needed to fix was charging the batteries, because the system we had, was as far as I’m concerned not working, unless you ran the main engine. We had two 200 watt solar panels and a D400 wind generator on our aft arch. The D400, while I’m sure it’s a great piece of kit, wasn’t doing anything for us, because 95% of the time there wasn’t not enough wind for it to generate anything meaningful. What the wind gen was doing very well was putting a big shadow across our two solar panels, ensuring that they performed sub-par most of the time, unless you were very lucky with the position of the sun. On top of that, one of the two radars (yes, we have had two radars) were placed above and between the solar panels further ensuring that they got as little sun as possible. This is after we removed the sat phone antenna, which also created a huge shadow on the panels … On top of that we had a non-functional wi-fi booster antenna and the Iridium phone antenna that also created shadows, so as you can probably understand, the panels weren’t producing anything remotely close to what we needed.
We wanted to get away from always having to run the engine to charge the batteries, so we had to do something drastic. We decided that the D400 would go into the bilge, to await our return to higher latitudes where there’s more wind (and hopefully more amps to squeeze out of it). It turned out to be a good call, because the two power cables inside the mounting pole was twisted around itself an incredible amounts of times, so it looked like an old fashioned telephone handle chord. It had worn through the cable in many places and was a short circuit just waiting to happen, so we were happy that it can now be fixed and revamped, before we use it again. I also pulled down the aft radar antenna and stashed it in the technical compartment, while the broken wi-fi booster antenna ended in the garbage.
Removing everything that were casting shadows on the panels ensured optimal conditions for the solar panels, because even a small shadow means that you see a huge drop in the power they produce. It became clear that 200 watts of panels weren’t enough, so we pulled them down as well (and stashed them in, the now overfilled, technical compartment). So what started as an optimisation of what we had, ended up being a solar panel install.
We replaced them with 2 x 270 watt Suniva solar panels and an Outback Multiflex 60 MPPT solar charger. I figured installing them would take a couple of days … it took a week … plus a day or two … Making the frame for them, pulling new power cables, installing the Outback … it all took its time, but the result was exactly what we were hoping for: Our house battery bank of 675 Ah (6 x Trojan T105’s) are replenished and in float mode before lunch. The solar panels even allow us to run our EchoTec watermaker, without starting the engine and it has a draw of 38 Ah when it’s cranking out 60 liters of water per hour. In short it’s a great setup.
We have the two panels connected in series, which allows us to use thinner cables than if we had run them in parallel and we only need to run one set of cables. It also means that if one of them is partially shaded then we lose a lot of input from both … I need to investigate a diode that will, supposedly, avoid that from happening.
Of course the charging challenge wasn’t quite over even with the new solar array. I noticed that the battery voltage was a bit low in the morning. Somewhere around 12.3V sometimes as low as 12.2V … This after only the fridge being on at night and it only draws 2-3Ah, plus a fan or two. The fridge needed a defrosting, so it was probably drawing a bit more, but the total draw in a night was never more than 50Ah. And with 675Ah of batteries, we shouldn’t see that much of a voltage drop in 12 hours. I was worried, because on passage, when we were fully charged before sunset and used maybe 100Ah in the course of a night, we were down to 12,0-12,1V. This also felt wrong. I tried equalizing the batteries. The great thing about having 540 Watts of solar panels running at over 60 volts is that you can equalize using them. Trojan recommends that their batteries should be equalized at 16,2V … so I set the Outback charger to Equalize at 16,2V for 4 hours. I did it twice and both times the equalizing never got higher than 15,85 in 4 hours (believe me when I say that I paid close attention). I started getting worried that my batteries were shot, but after testing the specific gravity on all of the battery cells, I found that they were all sound. I did a test where I fully charged them, then disconnected them from all louds and measured the specific gravity every hour for 4 hours. The batteries were in good shape and when I emailed Trojan with a detailed summary and a couple of questions, they responded promptly and after some digging, concluded that my batteries were good … and “don’t worry”! … So while I’m not 100% satisfied, because I think running them down to 12,0-12,1 in the course of a night seems like much, but I’ve heard from others that Trojans tend to show a lower voltage, without anything being wrong.
I think the next time I get new batteries, I’ll aim for a slightly larger battery bank … Maybe 900Ah would be more appropriate … I’m now contemplating a second battery bank, but we’ll see … For now, this set-up should serve us well going through the South Pacific.