Lithium & DC System Record PDFConfiguration, Commissioning & Cell Balance Log

The cell spread is the most useful number in a lithium bank, and no dashboard shows it to you.

Your monitor shows a state of charge and a pack voltage. Both look healthy right up to the day one cell drifts away from the others and the BMS starts disconnecting under load. The gap between your highest and lowest cell, read at the top of a charge where imbalance is widest, is the number this record keeps, so a change is on paper long before anyone has to explain a disconnect.

This record holds that number over time, alongside the configuration it belongs to: what cells, what BMS, what fuse, what each charge source is actually set to, and who signed the installation off.

Part I is what your documentation says. Part II is what is actually fitted: the fuse body you read with a torch, the cable marking, the charger set point measured at the terminals rather than assumed from the menu. The gap between those two pages is the first thing a marine electrician will ask about, which is why both are written down here.

Model E2 sets the pack voltage beside the sum of the cells, read with the same meter at the same moment, with the current flowing at that time written down. A difference that grows from one entry to the next, at a similar current, is recorded and taken to your electrician as a question about the links between the cells.

In the Fillable edition every line has a field, sized for a thumb rather than a stylus. Type each cell voltage on day one; in Adobe Acrobat Reader, free on computer, iPhone and Android, the sum of the cells, the spread and the pack difference work themselves out, and every later balance entry shows how far the spread has moved since commissioning. The Pencil & Print edition is ruled for handwriting in GoodNotes or Notability, or on a clipboard in the locker. Both come in A4 and US Letter and work offline.

No page here tells you to fit a fuse, torque a busbar, program a BMS, size a cable or wire a charge source. High-current DC work on a boat is governed by standards, it belongs to a qualified marine electrician, and a lithium bank is the one system aboard that can take the whole boat with it.

Part VI is sixteen lines recording that a competent person verified the installation, and who that person was, with their qualification and the date. Those are questions to put to your electrician, not a checklist for a Saturday afternoon.

The owner who has just had the bank fitted. Commissioning readings, this month, while the cells are new and matched. A spread measured on a new bank is the reference every later reading is judged against, and it cannot be recovered afterwards. Get Part VI signed at the same time, while the electrician is still on the boat.

The liveaboard. The bank decides whether the boat is habitable in February, so the balance entries are your working page. Read at the top of a charge, always at the same point, and the spread is recorded the same way every time, so any change is written down before anyone has to explain a BMS disconnect.

The owner who inherited the installation. Part II before anything else, with a torch. What is actually fitted rarely matches what the previous owner described, and the charge source settings measured at the terminals are where the surprises live.

The coastal owner on shore power most of the year. Few cycles, so wear is slow, but a bank that sits at a high state of charge all winter is not resting. Equivalent cycles and the event register matter more for you than the trend, and they are quick to keep.

The owner facing a surveyor or an insurer. The verification page is the document they want, and it is the one almost nobody has. A qualification, a name and a date turn an installation from an assertion into a record.

This document records, structures and compares figures that you supply. It publishes no voltage, no current limit, no temperature cutoff, no fuse rating and no torque figure, and it reaches no conclusion about any installation. It is not a wiring guide, not an integration manual and not engineering advice.

Those decisions belong to a qualified marine electrician working to the standards that apply where your vessel is flagged and used, and to the documentation supplied with your own cells. A lithium installation that is wrong does not fail gracefully.

Instant download. Your links appear on screen the moment payment clears, and a copy arrives by email, usually within a few minutes. They do not expire.

2026 Edition, Revision 2.1, AML-ELEC-2026-01. Apex Marine Labs designs the organisational process behind good seamanship. Our documents record and organise; they do not replace a certified marine survey, an installation standard, or a qualified marine electrician.