The number that decides where an EnerSys NexSys+ charger goes is 28 inches, and it is not measured from the wall. The manual recommends mounting the charger at least 28 inches radial distance away from the closest top edge of the battery. Read that as a planner and the reference point is the battery, the dimension runs in whatever direction the two objects happen to be offset, and the wall is only where the hardware hangs.
That changes the first question in a charging area. Instead of hunting for free wall, you ask where the path above the battery stays clear and where the charger's vent openings stay open to air. Everything below follows the NexSys+ manual and applies to that model, because one charger's 28 inches is not a category standard; a different unit has to be read against its own document.
Clearance Starts From the Battery, Not the Wall
Radial distance is the straight-line gap between the battery's top edge and the charger, taken in any direction: vertical when the unit hangs above the truck bay, horizontal when it sits on a stand beside the bay, diagonal when both are true at once. A tape held along the wall tells you none of that.
Why the battery top rather than a wall corner or an aisle stripe comes down to what leaves a battery during charge. A vented lead-acid battery gives off gas from its cells while it charges, and that gas leaves through the top of the case, so the shortest unobstructed path between the rising plume and the charger's air intake is the quantity worth controlling. That means the measurement starts where the gas starts.
The practical consequence catches people who plan in plan view. A charger bolted flat to a wall directly above a battery bay can be a long way from the far corner of the room and still come up short on the radial measure, because the battery is not in the far corner but directly underneath. The reverse holds too: a unit on a stand across the aisle can look distant on a floor plan and land inside 28 inches once the tape runs diagonally up to that edge.
What Charger Ventilation Openings Are Actually Doing
The vent openings are the intake and exhaust paths formed into the enclosure, and the manual's requirement is one line: do not obstruct the openings in the charger for air ventilation. Obstructed does not mean sealed. A carton of stretch wrap leaned against the face, a charging hose coiled on a hook in front of the louvers, a shelf pushed tight to the side panel, and the path is closed.
The mechanism behind the rule is heat balance. A charger converts AC to DC, that conversion is not lossless, and the losses become heat inside the cabinet. Heat leaves by air moving through the openings, cooler air in low and warmed air out high, so airflow is the only heat-rejection mechanism the unit owns. Because of that, the deciding question is not whether the room is air conditioned or whether the dock stays cool in January. It is whether there is an unblocked low-to-high path through this particular enclosure with whatever the crew has stacked beside it.
The manual passage stops at the openings themselves. It does not prescribe ducting, supplemental fans or a cubic-feet-per-minute figure, so airflow rates, if a site wants them designed, are engineering work for that facility rather than numbers this document supplies. What the passage does do is make ventilation a housekeeping and layout question as much as a building question: the vents are only compliant if nothing in the charging area grows into them after commissioning.
Screening the Location Before You Drill
The second screen is environmental, and the manual states it as a list of exclusions: choose a location free of excess moisture, dust, combustible material and corrosive fumes, and avoid high temperature above 113°F (45°C) or potential liquid spill on the charger.
Three of those exclusions concern what the air carries into the unit. Moisture, dust and corrosive fumes all enter with the cooling air and stay inside, settling on terminals and boards. The reason the manual groups them is that the same airflow the charger needs for heat removal is the path that delivers contaminants, so a location that fixes one of the three usually fixes the others. Combustible material is the odd item: it is about what accumulates around the cabinet rather than what enters it.
The temperature figure stands apart. 113°F (45°C) is the ceiling this manual states for this model, applied to the air at the charger, not a general warehouse threshold. The distinction matters because the number people quote for a charging area is usually the shaded aisle reading off a clipboard round at seven in the morning. A wall facing a south or west roll-up door, or a spot under a low roof deck with no air movement, can read comfortable at dawn and run past the limit on an August afternoon. That is a pattern worth checking on site rather than assuming from a single reading.
Spill exposure disqualifies more spots than crews expect. A charger under a battery watering station, on a wash-down wall, or below a roof seam that drips in heavy rain sits on the wrong side of that clause even after the anchors are in the block.
The Install Order That Keeps You Out of Trouble
Screen the location first, against the exclusions and the temperature limit the manual names, and do it before a single hole exists. A rejected spot at that stage costs nothing but a walk; a rejected spot after mounting costs a patch, a re-hang and a conversation with whoever owns the wall.
Then measure the radial distance from the top edge of the battery to the proposed charger position, with the tape running to the battery rather than to the wall behind it. Confirm the mounting surface and orientation next, since the charger must be mounted on a wall, stand, shelf or floor in a vertical position, upright rather than laid flat on a shelf or tipped back on a stand to fit under a mezzanine. Where more than one unit shares the wall, the minimum distance between two chargers must be 12 inches, measured between the units themselves and not from either one to a post or column.
The radial check and the charger-to-charger gap get reworked most often. Both are measured from objects that move.
Electrical scope closes the sequence but should be settled early with the electrician, because the user must provide suitable branch circuit protection and a disconnect method from the AC power supply to the charger to allow for safe servicing. That is a facility responsibility stated in the manual, not hardware the charger arrives with, and servicing is the reason it exists, which is why the people who will work on the unit should know where it is. Sequencing it last on paper is fine; sequencing it last in the calendar is how a hung charger sits dead for a month.
How to Confirm the Layout Before Power-Up
A confirmation pass is cheap right after mounting and expensive after the conduit is landed, because once the unit is on the wall its own body is what blocks the tape. Walk the finished layout and re-run every dimension: radial distance from the nearest battery top edge to the installed unit against the 28-inch recommendation, gap between adjacent chargers against the 12-inch minimum, and orientation against the requirement that the unit stand vertical on a wall, stand, shelf or floor.
Then walk the enclosure itself, face, both sides, top and bottom, clear of cartons, wraps, hoses and shelving so the ventilation openings keep an unblocked low-to-high path. Re-check the surroundings against that same exclusion list, because a spot that screened clean in planning can acquire a new neighbor between the walk-through and the install, whether that is a wash station, a scrap bin or a relocated pallet position.
Finish on the electrical side by confirming that branch circuit protection and a disconnect method exist and that the people who will service the charger know where they are. Who signs off on the finished layout is a facility decision; no manual passage names that role, and this one does not either.
When the Only Free Wall Fails the Clearance Test
Suppose the charging area has exactly one open wall, and it sits beside the battery bay. Run the tape and the radial distance to the closest battery edge comes up short of 28 inches, while the same wall crowds the vent face behind a bay guardrail. That outcome is normal in a tight charging area, and it is worth planning for before the electrician gets booked.
Three options, none of them free. Move the unit to a stand or shelf position that restores the radial distance while keeping it vertical as required, and pay for it in aisle floor space the trucks want back. Re-sequence the area so the battery is not parked under or beside the charger position, which changes traffic flow and driver habit more than it changes hardware. Or accept a longer DC run to a spot that passes, adding cable, voltage-drop questions for the electrical designer and more conductor lying in the traffic path.
State the tradeoff plainly: the 28-inch recommendation and the 12-inch charger-to-charger minimum describe this model in this manual. Another charger's document sets its own figures, and nothing here transfers to it. When the only free wall fails, the call belongs to the facility and its electrician working from this model's manual plus the real layout, not from a general notion about how much room chargers like.
Today, before any electrical work is scheduled, walk the charging area with a tape and a marker. Measure each candidate position against the battery and against its neighbors, and mark every spot that misses the 28-inch recommendation or that gives a carton, a hose or a shelf somewhere to lean against the vents. Moving a spot on a drawing costs an eraser; moving it after the anchors are in costs a week.