Days 276-277, Sailing Kemah,tx to Galveston,Tx and bach, Real weekend sailing. Installed my design Power supply to Battery automated switch aka UPS
Sailing
Just picture for title |
Early morning in the marina |
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| Getting out of Kemah about 10:20AM |
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Captain VicVic
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| Hiding in the shade of Genoa |
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| Found some motor -sailor in the Galveston canal |
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| Beating hard |
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Wind is getting stronger |
Coming closer to Galveston i clearly understood why i installed AIS transducer and how useful it in tight traffic.
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| We are on the Marine Traffic map when we approached Galveston |
First time to be in such active traffic including cargo ships, barges, fairies, tens of smaller boats was pretty intense. Not near by, not watching traffic, be in it! It was ADULT feeling.
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| Galveston, Coast guard docks |
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| We officially anchored at Galveston on Tea Cup anchorage. |
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| Nice dinner after long day |
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Sunset on the hook |
When I asked on a forum where I could drop anchor in Galveston, I was recommended the TeaCup anchorage. But... people also warned me that there was a lot of traffic nearby and that it wasn't exactly a calm place.
Okay. I'm not looking for an easy life, and it was only for one night.
But after dinner, we realized just how much traffic there really was. The wind kept us positioned almost perfectly sideways to the wake waves, so every 5–10 minutes the boat would roll 15–20 degrees from side to side.
It became pretty obvious that this was not going to be a sweet-dream kind of night.
When I originally asked where to stay, one guy who mentioned the anchorage—though he didn't exactly recommend it—also suggested that I could use a vacant courtesy slip for free at the marina where he lives aboard, only about five minutes by motor from TeaCup.
So I sent him a message.
He answered almost immediately:
"I am on the docks in a yellow shirt. I'll point you to a slip where you can stay overnight."
It was a very heart warming moment!
We pulled the anchor and motored toward the marina in the last rays of sunlight.
D Yami met us at the docks and helped us tie up. Vic thanked him, and then he just quietly walked away.
I sent him another message inviting him aboard for tea, rum, gin, or cider, but he apparently decided that helping two strangers find a peaceful place for the night was enough socializing and left the invitation unanswered.
He had also told us that we could connect to shore power.
That meant we could run the air conditioner overnight.
So instead of spending the night rolling 15–20 degrees every few minutes at anchor, we had a quiet dock, electricity, AC, and a good night's sleep.
Sometimes the best piece of cruising equipment is simply a helpful person on the dock wearing a yellow shirt.
We didn't want to overuse the hospitality—or get "caught trespassing"—so we decided to get away from the dock as early as we could.
Originally, the plan was to get up at 6 a.m., but after a good night of sleep with the AC running, I barely managed to scrape myself out of bed at 7 a.m.
I quickly made a cup of coffee, prepared some breakfast, and then we got everything ready and left the dock ASAP.
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| Symphony of the Seas was docked in 1000ft from us that night! I took picture when we passed her. |
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| Good buy Galveston, city of big ships |
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| On the way back. Followeng East side of the ship canal |
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| Met boat from our marina on the way back. |
These bastards found us on the middle of the galveston bay, hundreds of them!!! They do not bite, donot sting, but annoying too much!
Electrical.
Story first.
I have a NOCO GEN5X3 three-bank charger on board for my Start, House, and Windlass batteries.
It worked quite well for about five years, keeping my lead-acid batteries topped up. Then I switched the House battery to LiFePO₄ and changed that charger bank to Lithium mode.
At first, everything looked good.
I also have a 40A, 14.2V power supply that runs the boat's 12V system from shore power while I'm connected at the marina. The battery and power supply were combined through a 100A ideal-diode module. It works similarly to ordinary diodes, but with a very small voltage drop.
One night while I was sleeping on the boat, I noticed the lights periodically blinking and my main navigation computer restarting every 10–15 seconds.
At first, it was a mystery.
I checked for a heavy load, loose connections, bad wiring, or anything else that might cause the voltage to collapse. Eventually, I noticed that the NOCO charger was showing an "Overvoltage" error on the LiFePO₄ battery.
That was surprising.
I checked the battery BMS, and it showed nothing suspicious—the battery was simply at 100% state of charge.
Then I discovered that the battery BMS was a little too smart. When the battery reaches 100% SOC, the BMS simply disconnects the charging path. It doesn't report a fault; it just puts the battery into a discharge-only state.
This created an interesting problem.
The battery was fully charged, but after resting its terminal voltage dropped back to approximately 13.9–14.0V. The charger saw this voltage and eventually decided that it should charge the battery again.
But the battery was already full, and the BMS had disabled charging.
So when the charger attempted to start charging, the current had nowhere useful to go and produced a short voltage spike of approximately 16.5V.
The battery could not absorb the spike, so it propagated toward the ideal-diode module.
The module detected that the battery-side voltage had suddenly become higher and quickly switched the source selection. Because the pulse was very short, this confused the ideal-diode power-sharing arrangement and produced both a voltage spike and a following voltage dip on the 12V house bus.
My computer's protection socket detected the abnormal voltage and shut the computer down to protect it.
A few seconds later everything recovered—and then the entire sequence happened again.
That experience pushed me to design my own smart power switch like UPS.
Design Requirements
The new system has several important features:
- Shore power has priority.
If the power-supply output is above approximately 12V, the 12V house bus is powered from the PSU regardless of battery voltage. - Complete source isolation.
Each source uses a dual-MOSFET switch arranged so that, when OFF, current cannot flow through the switch in either direction. This completely isolates the battery and power supply from each other. - Minimum battery run time.
If the system switches to the battery because the PSU voltage falls too low, it remains on battery power for at least 10 seconds. This prevents rapid back-and-forth switching if shore-power voltage is unstable. - Break-before-make switching.
There is approximately a 100 µs dead time between disconnecting one source and connecting the other, ensuring that the battery and PSU are never directly connected together during a transition.
From Idea to Installation
What started as a strange blinking-light problem turned into a complete engineering project:
Idea → Solution Research → Schematic Design → PCB Design → Component Sourcing → Assembly → Programming → Functional Testing → Stress Testing → 3D Enclosure Design → Installation → On-Board Testing
After about four weeks of work, everything is installed and working properly.
And now, instead of trusting two power sources and an ideal-diode module to negotiate with each other, I have a power-management system whose behavior I actually understand and keep things under control.
Module installed in the engine compartment.
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