Site Survey Checklist

Goal: capture everything on-site that can't be researched from home, so off-season planning never stalls on “if only I knew X.”

Convention: mark items done by changing [ ] to [X]. Photograph liberally — storage is cheap, return trips are not. When in doubt, take the photo.

The battery bank is the most dangerous thing on the property. It is more dangerous than the generators and more dangerous than the AC side, for reasons that are easy to underestimate:

• The bank can never be turned off. Opening every disconnect on the property isolates the wiring, not the batteries. The terminals are always live, always capable of full fault current. Treat them as energized 100% of the time.
• The hazard at 24V is not shock — it's current. 24VDC generally won't push lethal current through dry skin. But a large lead-acid bank can deliver thousands of amps into a short circuit. A dropped wrench across terminals doesn't spark — it arc-flashes, welds itself in place, sprays molten metal, and can rupture the battery case and throw acid. A wedding ring bridging a terminal to ground can heat white-hot in under a second and take the finger with it.
• Hydrogen gas. Charging (and especially the “gurgling” already noted on this wiki) produces hydrogen, which is explosive at concentrations as low as 4% in air. It pools at the ceiling. One spark — a disconnected cable under load, a brushed power tool, a lighter — can ignite it.
• Sulfuric acid electrolyte. Causes chemical burns to skin and permanent eye damage. It also wicks up onto terminals as conductive, corrosive film.

• [ ] Remove ALL metal from your body: rings, watch, bracelets, necklaces, belt buckle if you'll be leaning over the bank. No exceptions. This is the single most important rule.
• [ ] Eye protection: safety glasses at minimum; a face shield over glasses for hydrometer work and any terminal wrenching.
• [ ] Gloves: nitrile or rubber (acid-resistant), not leather work gloves (leather soaks acid).
• [ ] Old clothes / apron: electrolyte eats cotton holes you won't see until the next wash.
• [ ] Neutralizer on hand: a box of baking soda and a jug of clean water within arm's reach. Mix ~100 g baking soda per litre of water for washing surfaces. For skin/eyes: flush with plain water immediately and generously (15 minutes for eyes), then worry about everything else.
• [ ] Insulated tools: proper insulated wrenches if available; otherwise wrap all but the working face of each wrench in several layers of electrical tape. Never carry loose tools over the bank; never set a tool down on top of a battery.
• [ ] Ventilate first: open the battery compartment/room and let it air out 15–30 minutes before working, especially if the bank has been charging. No smoking, no open flame, no brushed power tools (drills, angle grinders) in the space.
• [ ] Work with dry hands, dry floor, good light, and ideally tell someone what you're doing and when you expect to be done.

• One wrench, one terminal, one hand. Never have tools on two terminals at once.
• Cover what you're not working on. Lay a rubber mat, plywood scrap, or heavy cardboard over adjacent terminals so a slip has somewhere harmless to land.
• Never connect or disconnect a cable under load. The break spark is a hydrogen ignition source and will pit the terminal. Kill loads and charge sources first (sequence below).
• Never put a multimeter in current (A) mode across a battery. This is a direct short through the meter — it will blow the meter fuse at best. Voltage measurements only, meter set to DC Volts, and sanity-check the meter on a known source (e.g., a AA battery ≈ 1.5 V) before trusting readings.
• Lift smart. Individual stationary cells can weigh 30–60+ kg. Plan the move before touching them; don't rock them by the terminal posts.

1. Turn off all AC loads, then turn the inverter OFF at its own switch.
2. Open the PV DC disconnect (Trace disconnect module) so the MidNite controllers stop feeding the bank. Confirm on the controller displays that output current has dropped to zero.
3. Confirm both generators are off and cannot start (keys out / start batteries disconnected if they have auto-start).
4. Open the main battery disconnect/fuse if one exists between bank and inverter.
5. Verify with the meter that the downstream side of each opened disconnect reads 0 V.
6. Remember: the battery terminals themselves are still fully live. Isolation protects the wiring runs, nothing more.

Context: 12 × NCT-13 lead-calcium cells in series (nominal 24 V bank, ~2 V per cell). Because it's a pure series string, one weak cell limits and eventually poisons the whole bank — which is exactly why per-cell data matters and whole-bank voltage alone tells you almost nothing.

Do the steps in this order. Steps 2.1–2.5 are measurement-only and can be done with the system live. Step 2.6 (cleaning/torquing) requires the isolation sequence above.

• [ ] Photograph the whole bank from several angles, then each cell individually, close enough to read any label, date code, or stamped marking (check tops of terminal posts — date codes are often stamped there).
• [ ] Note and photograph: case bulging or cracking, electrolyte weeping/wet spots, white/green terminal corrosion, discoloured or sagging plates visible through translucent cases, sediment (mud) at the bottom of cases — sediment touching the plates means that cell is at end of life.
• [ ] Sniff test from the doorway: a rotten-egg smell means a cell has been overcharging/cooking — note which end of the bank it's strongest at.
• [ ] Record battery room ambient temperature (matters for interpreting every reading below, and for future lithium eligibility — most LiFePO4 can't charge below 0 °C).
• [ ] Measure and record the battery compartment: interior dimensions, door/hatch opening size, and how the cells got in there (this constrains every future replacement option).
• [ ] Photograph the interconnect cables and record their gauge (printed on jacket) and lug size.

Take three sets if time allows: under charge (midday, sun on panels), resting (ideally after 4+ hours with charge sources disconnected and loads off — overnight before dawn is perfect: solar is off and loads are minimal), and under a known load (e.g., run the well pump, note what's on).

For each set:

1. Meter to DC Volts. Verify meter on a known source first.
2. [ ] Whole bank: red probe on the bank's most-positive terminal, black on most-negative. Record to two decimal places, with time and conditions.
3. [ ] Each cell: probe the two posts of one cell at a time, working down the string in order. Keep probe tips firmly on lead, not on corrosion. Record every cell in the table below. This takes 10 minutes and is the second-most valuable dataset you'll leave with.
4. Watch for: any cell more than ~0.05 V below its siblings at rest, or any cell that sags dramatically more than the others under load, or reads higher than the others while charging (a weak cell hits gassing voltage first). Flag it in Notes.

Reference points for lead-calcium (verify against an NCT-13 datasheet when home): resting full charge ≈ 2.05–2.10 V/cell; float ≈ 2.17–2.25 V/cell. Absolute numbers matter less than the spread between cells — a healthy string is tightly matched.

This is the single most valuable measurement of the whole trip. You need a battery hydrometer (glass float type preferred over the cheap ball type) — if there isn't one on site, this alone justifies a trip to a parts store.

Timing rules (they change the answer):

• Best case: bank has been fully charged, then rested 2+ hours with no charging and no significant load. Readings taken mid-charge or right after equalization read artificially high and stratified.
• Do NOT take readings right after adding water — fresh water floats on top and reads falsely low. If cells need water (see 2.4), take SG readings first, unless plates are exposed.

Procedure, per cell:

1. Face shield on, gloves on, baking soda and water within reach.
2. Unscrew/pop the vent cap. Set it upside-down on top of its own cell so caps never get mixed between cells.
3. Insert the hydrometer tip into the electrolyte. Squeeze and release the bulb 2–3 times to draw and return electrolyte — this rinses the instrument to that cell's acid and dislodges bubbles.
4. Draw enough electrolyte that the float rides freely — not touching the top, bottom, or sides of the barrel. Hold the hydrometer vertical at eye level.
5. Read the scale at the bottom of the meniscus (the flat surface, not where liquid climbs the float stem). Record the raw reading.
6. Note the electrolyte temperature. Better hydrometers have a built-in thermometer; otherwise use the room temperature and accept the small error.
7. Return every drop to the same cell it came from. Never move electrolyte between cells.
8. Replace the cap snugly, wipe any drips with a baking-soda-dampened rag (caps ON, so soda can't enter the cell — soda in a cell neutralizes the acid and kills it).
9. Rinse the hydrometer in clean water when finished with all 12 cells, before storing.

Temperature correction (hydrometers are calibrated at 27 °C / 80 °F):

• Add 0.004 to the reading for every 5.5 °C (10 °F) above 27 °C; subtract 0.004 for every 5.5 °C below. A cool Ontario battery room means you'll usually be subtracting. Record both raw and corrected values.

Interpretation (rough, for typical flooded cells — confirm against the NCT-13 spec, as some stationary lead-calcium designs use lower-gravity acid on purpose):

• ~1.265 corrected ≈ full charge; ~1.225 ≈ 75%; ~1.190 ≈ 50%; ~1.155 ≈ 25%.
• The killer diagnostic is spread: after a full charge and rest, a difference of more than 0.025–0.030 between the highest and lowest cell means weak/failing cells, and equalization is unlikely to rescue lead-calcium cells with sediment or chronic low gravity. This number, more than any other, tells you whether you're planning a battery replacement or not.

• [ ] With caps off (one cell at a time), record each cell's level: plates fully covered? Level relative to the fill ring/split ring in the fill well?
• If plates are exposed: add just enough distilled water only to cover them, note it, and know that SG readings from that cell are now suspect.
• If plates are covered but low: the correct practice is to water after a full charge (electrolyte expands when charging; filling a discharged cell causes overflow later). Fill to the ring, never higher, distilled water only — never tap/lake water, never acid.
• [ ] Record how much water the bank took overall — heavy water consumption corroborates the overcharging/“gurgling” story and is itself a data point about controller setpoints.

• [ ] With the bank rested, switch on a known large load (well pump is ideal) and watch bank voltage: record voltage immediately before, the lowest value during motor start, and the settled value while running. Severe sag (e.g., a rested 25+ V bank crashing below ~23 V under a modest load) indicates high internal resistance — aging cells — even if resting voltage looked fine.

• Only after completing the full isolation sequence. Terminals remain live — insulated tools, one wrench at a time, adjacent terminals covered.
• [ ] Scrub corroded terminals with baking soda solution and a brass brush (caps tight first), rinse sparingly, dry.
• [ ] Check every interconnect nut for snugness. If a torque spec is on the battery label, record it and use it; overtightening lead posts cracks them.
• [ ] A thin coat of terminal protectant/petroleum jelly on cleaned connections.
• [ ] Photograph the finished terminals — the “known good” reference for next visit.

Whole bank: charging V @ time / rest V @ time / load V (load = ). Room temp °C. Date coded on cells: .

• [ ] Inverter — make, model, serial, firmware if it has a display. Also photograph every settings/config screen it will show you. (Currently completely undocumented; this is the top nameplate priority.)
• [ ] Power Conversion Center — model, and photos of the interior: every breaker with its amp rating, every fuse with type and rating.
• [ ] MidNite controllers — the label that settles Classic 250 vs 250SL, serial numbers, firmware version, and every settings screen (absorb V, float V, equalize V, temp comp, aux). These photos let you reprogram a warranty replacement from home.
• [ ] Trace DC disconnect — model and interior photo.
• [ ] Solar panels — the sticker on the back of one panel per array (confirms 260P; records Voc/Isc/Vmp/Imp for string math).
• [ ] Onan generator — model/spec/serial plate, hour meter reading + today's date, oil/filter part numbers.
• [ ] Lister generator — same list.
• [ ] Junction box / transfer switch — make, model, interior photo.
• [ ] AC load center — make, model, main breaker rating.
• [ ] Every fuse anywhere in the system — type, physical size, rating (this becomes the spares shopping list).

• [ ] Wire gauge (printed on jacket) and paced-off run length for: each array → controllers; controllers → DC disconnect; battery → inverter; inverter → load center; load center → Ken's; → Jack's; → electrical shed; generators → junction box; junction box → inverter. Note buried / conduit / overhead for each.
• [ ] Array wiring config: how are the 6 panels per array strung (series/parallel)? Trace and sketch it.
• [ ] Panel tilt angle and azimuth (compass app), rack construction photos, condition of mounts.
• [ ] Shading survey: from panel level, photograph the southern horizon at morning, midday, and late afternoon. Note any trees threatening to grow into the picture.
• [ ] Grounding: locate ground rods, photograph bonds, note any surge/lightning protection (or its absence).

• [ ] Map every breaker: flip one at a time, note what dies, write it on the panel directory. Photograph the finished directory.
• [ ] Nameplate watts/amps of major appliances — well pump especially (its start surge sizes any future inverter), fridge, freezer, any heaters or shop tools.
• [ ] What actually exists at Ken's, Jack's, and the electrical shed — sub-panels? Model/photos.
• [ ] Inverter idle draw if measurable: all loads off, read battery current on the controller/inverter display.

• [ ] Diesel tank capacity, current level, approximate fuel age, condition of tank and lines; photograph the valve arrangement.
• [ ] How does generator power charge the batteries? Does AC from the junction box feed a charger in the inverter? Trace it and document — this defines bad-weather resilience.
• [ ] Starting procedure for each generator, written down step by step while someone who knows does it.
• [ ] Last-known service dates; oil type on the shelf; filter part numbers.

• [ ] Each evening at dusk and each morning at dawn: bank voltage + kWh totals from both MidNite displays. A few days of this quantifies overnight consumption — the number every sizing calculation starts from.
• [ ] Daily kWh harvested per controller (they display it) with a note about the weather that day.

• [ ] Cell signal check on every carrier available in the group, at the electrical shed specifically. The MidNite Classics have Ethernet and support remote monitoring — any viable internet path (Starlink, booster) would let the system report home year-round and permanently shrink this checklist.
• [ ] Inventory tools and spares already on site (so home shopping lists don't duplicate).
• [ ] Contact info for anyone local who could physically check something in the off-season.
• [ ] Anything with a manual on site: photograph the cover and any pages with settings/specs.

Imagine posting from home: “My inverter died / my batteries are toast / I want to add panels — what should I buy?” The forum's first questions will be: what inverter model, what daily kWh, what wire gauge and run lengths, what were the specific gravities, what are the controller setpoints. If every answer is on this wiki, the trip did its job.