3 documentsElectrical & Power
Boat Electrical & Power Systems
Everything between the charge source and the load: what stores the energy, what generates it, and what spends it. A DC bank is the one system aboard that is expensive to get wrong and impossible to judge by eye.
- pages in all
- 118
- live fields
- 2,268
- models
- 18
- each
- $97
Each record works the same way. You transcribe the figures for your own installation once, onto a reference page: your cell manufacturer's charge voltages and cutoffs, your BMS thresholds, your panel's temperature coefficient. From then on, every reading you log is measured against your own equipment rather than against a number written for somebody else's boat.
None of these documents publishes a voltage, a current or a limit of its own, and none instructs you to fit a fuse, size a cable or program a battery management system. Those decisions belong to a qualified marine electrician. These records capture what was fitted, what it was set to, what it measured on day one, and how far it has drifted since.
Guides
Guides for this system
Electrical and power
Almost every autonomy problem aboard is an accounting problem wearing an electrical costume. What goes in, what comes out, and what is actually left. Three documents, one per question.
The number your battery monitor does not show you
A monitor reports a pack voltage and a state of charge. A lithium bank does not fail as a pack. It fails at one cell, quietly, while the pack figure still looks correct. The useful early signal is the spread between the highest and the lowest cell, and it is precisely the figure no dashboard puts in front of you. Your BMS knows it. Almost nobody writes it down.
Read once, a cell spread means nothing: you have no idea whether it is normal for that bank. Read at commissioning, then again at the same state of charge each season, it becomes a trend, and a trend is what lets you and your electrician see that something changed, while there is still time to ask why.
The register that keeps that recordInstantaneous watts, and the figure that decides your day
A panel rating is a laboratory figure, measured under laboratory light at a laboratory temperature. Your array is on a boat. On a sailboat the boom, the mast and the rigging walk a shadow across it from morning to evening, and a partly shaded panel does not lose a proportional share of its output. It collapses. Peak watts, read off the controller at noon, describe a moment you cannot bank.
What you can bank is accumulated amp-hours from sunup to sundown. No manufacturer publishes a daily yield for your array, at your latitude, under your rig, on your mooring, and none ever will, because it depends on your boat. So it gets measured, logged against a shading survey done once, and compared season to season.
The record that turns an array into a measured yieldThe plate figure and the shunt figure are not the same number
Every load aboard carries a rated draw on its data plate. What each one actually draws aboard is a different number, and only that one belongs in your budget. A fridge compressor does not run continuously. It cycles, and how often it cycles depends on the water temperature, the insulation and how many times the lid was opened. The plate cannot know any of that.
An energy budget built from plate figures and estimated hours produces a number that feels rigorous and is not. One built from a measured draw and an observed duty cycle, regime by regime, at anchor, on passage, alongside, produces a figure you can size a bank against.
The worksheet that does that arithmeticWhere to start, by your situation
Commissioning a new bank, or inheriting one with no history. The DC System Record. A baseline can only be taken once.
Living aboard, and the bank does not last the night. The Load and Energy Budget Worksheet. Start with the loads nobody measured, before anybody resizes the bank.
Cruising and about to spend on solar. The Solar and Hydro Yield Record, with the shading survey done before anything is bought. It is the cheapest part of the job and it decides the rest of it.
What you will not find in any of them
No cell voltage limit. No absorption duration. No recommended days of autonomy. No safety margin, no efficiency factor, no rule of thumb.
Not one published threshold, tolerance, rate or service life, here or anywhere else in this catalogue. Those figures exist, and they belong to your manufacturer's documentation in the revision matching your serial number, to the professional who worked on your boat, and to your own installation. A document that prints them has copied somebody else's equipment and handed you the risk.
Every register here opens the same way. A reference page where you transcribe your own figures, with the source document and its revision beside each line. A commissioning baseline. Then a deviation log measured against both. The models do the arithmetic from there.
That is not a limitation we apologise for. It is the product.