Before sunrise
I’d gotten some strange leg cramps during the night; that hasn’t happened to me before. I felt the cramp coming on and had to get up to stretch the calf muscles before they tightened up too much and that kept me awake more than it should have. I got going early in the morning and attempted to close off some open tasks in the remote office but didn’t have much success.
Afternoon
Once the office work had completed, I installed my new battery monitor, a BMV 712 Smart battery monitor from Victron. This would integrate with the rest of the charging system and give me a clear picture of the state of the batteries. I got out my tools and switched off the power and then disconnected the battery bank while working on the system. The old shunt was a big one, but I got it removed and installed the new smart shunt that comes as part of the battery monitor. This is basically two massive blocks of copper for the terminals connected by a very slightly resistive metal strip. The difference in voltage between the two terminals is in the millivolt range and that is measured by the monitor to see how much energy is flowing in either direction, without losing energy to heat. I was very careful to tape off the positive and negative terminals to avoid electrocuting myself (the battery bank has 700Ah@24V so about 17KwH which is a third of the power of a Tesla). That went relatively quickly, at least compared to the next step.
I needed to run a cable from the control panel to the battery bank, I tried dropping the cable down the back of the panel and seeing if I could retrieve it below. No luck. I tried taping a 17mm wrench to the wire to see if it would penetrate but had no luck. Even worse, the wrench dropped into the area, and I cannot get it back out, so I’ll need to replace it from a hardware store ASAP. I disassembled even more of the panelling but still had no luck in getting the cable run or retrieving the wrench. After many attempts I finally got the cable pulled through the 3 feet behind the panel and hooked it up. But the monitor remained dark and unresponsive.
High side and Low side
I looked at the schematics and it dawned on me. My old Xantrex system is a low-side measuring one; that means the shunt is on the “-” negative line leaving the battery. But the Victron measures the “+” high side and that is why it didn’t work. I then removed the new shunt and replaced it with the old one and attached the new shunt to the high side of the battery and powered up the boat again. Success!
It was 18:00 by now, and the sun was approaching the horizon. I got in the shower and had just lathered up when the water stopped flowing. Dripping water and soap, I went back to the main panel and saw that I’d been running the boat off the solar panels and once they no longer produced enough power the systems shut down. I turn the main breaker on a that produced immediate results.
Ashore
Freshly showered I dinghied ashore to the SMYC and then walked up the street and tried to decide where to eat. I saw that the Captain’s Rib Shack was empty and tried my luck there again. This time my luck held, and I was served promptly, and the food was good, although gone are the halcyon days of LoLo prices. And the bill was a creative masterpiece of misdirection. Hidden in there was a 15% service charge. And then, printed below the sum was a table of recommended tips from 15-30%; meaning that the unsuspecting customers that think they are tipping 15% are actually tipping a bit over 30%! This type of underhanded charging is quite irksome.