What surface resistance should a charger module tote have?

Answer: Between 1×10⁶ and 1×10⁹ Ω, designed around 1×10⁷ to 1×10⁸ Ω: low values concentrate the discharge, high ones fail to bleed it in 30 s.

Is eight modules per tote too few?

Answer: Eight matches 28 kg, the ceiling for a two-person lift. At 12 modules the tote weighs 34 kg, needs a trolley, and the pick cycle goes from 40 s to 90 s.

Can the stack go to six high?

Answer: Only with 24 kg totes. At six high the bottom unit takes 168 kg and the top face sinks 3.6 mm, past the 3 mm line that forces a pallet.

Does folding 1:3 cost stacking strength?

Answer: Some. A 1:4 shell splits its walls into three segments, adds two joints and loses 18% stiffness, capping the stack at 3 high.

Charger Module Tote

Quick answer: A charger module tote holds 8 modules at 28 kg, keeps surface resistance at 1×10⁶ to 1×10⁹ Ω and stacks 5 high, so static and floor space settle together.

Surface Resistance Sets the Static Spec
Eight Modules, Eight Millimetre Dividers
Five High: What the Bottom Tote Carries
Folding 1:3 and the Return Trip
Fork Pockets at 100 mm and a 200-Cycle Life
FAQ

1. Surface Resistance Sets the Static Spec

One tote carries 8 modules 40 m from moulding to burn-in, 12 trips a day. Static is not made on that walk; it builds on every lid lift. The number that decides it is surface resistance, held between 1×10⁶ Ω and 1×10⁹ Ω.

Both ends matter. Below 1×10⁶ Ω the shell acts as a conductor and dumps charge into one contact point, worse than an insulator. Above 1×10⁹ Ω half the charge is still there after 30 s, and a hand on the lid carries a few thousand volts.

The working range sits nearer the middle, at 1×10⁷ to 1×10⁸ Ω. Measure with parallel electrodes at 100 V, read after 60 s, at 23 ℃ and 50% RH. At 30% RH the same tote reads a decade higher, so a unit that passes in the lab can spark in a dry bay.

A coating is not the answer: paint loses 0.2 mm a year while a tote wears 0.5 mm. Compound the body so volume resistivity lands between 10⁴ and 10⁶ Ω·cm, then check the ground path; castors at 1×10¹¹ Ω leave no drain, so clip a 2 m strap to the side-wall insert and hold contact resistance under 10 Ω.

2. Eight Modules, Eight Millimetre Dividers

Eight modules per tote, 2 rows by 4 columns, each pocket 210 mm by 150 mm by 60 mm behind 8 mm PP hollow sheet. Eight is a weight decision: 28 kg leaves 14 kg per person at 1.2 m/s, while anything heavier needs a trolley and stretches the pick cycle from 40 s to 90 s.

Charger module tote mould milled on a four-spindle CNC machine, black bellows guards, orange frame, shallow case outlines cut into the bed

The 8 mm divider is arithmetic. A 4 mm sheet bows under five-high load and 3 mm of bow tilts the module until pins take load sideways; a 12 mm sheet adds 1.8 kg and breaks the 28 kg ceiling. Hollow sheet at 8 mm deflects 1.2 mm under 200 N over the face, and it drains when washed, where solid sheet gains 0.4 kg in 24 h.

Pocket layout	Pocket size	Divider	Modules	Tote weight	Handling
2 × 4	210 × 150 × 60 mm	8 mm	8	28 kg	two-person lift
1 × 6	260 × 150 × 60 mm	8 mm	6	26 kg	two-person lift
2 × 6	210 × 120 × 60 mm	8 mm	12	34 kg	powered trolley
3 × 4	210 × 120 × 60 mm	8 mm	12	33 kg	powered trolley

Leave a 5 mm finger notch at the bottom of each pocket, or picking means tipping the tote 96 times a day. Number the pockets with a 0.1 mm laser mark; a tote is washed 40 times in five years and paper labels lift after three.

3. Five High: What the Bottom Tote Carries

At five high the bottom tote carries four others, 112 kg. The load is not the problem, the path is: a flat lid passes everything into four side walls, and 2 mm of wall lean puts it on two corners with triple the stress.

So the lid gets 3 ribs at 6 mm tall and 90 mm apart, and the base gets matching grooves; rib into groove holds lateral slip inside 5 mm. Over 72 h at five high the top face sinks 2.1 mm and returns to 0.4 mm after unloading.

Stack height	Bottom load	Top sink	Wall bulge	Where it fits
3 high	84 kg	0.9 mm	0.6 mm	line-side buffer
4 high	112 kg	1.5 mm	1.0 mm	stores bay
5 high	140 kg	2.4 mm	1.6 mm	dispatch area
6 high	168 kg	3.6 mm	2.4 mm	pallet required

Six high works only with 24 kg totes, and the extra layer does not pay back two more pick trips. Pallets matter too: 3 mm of surface variation pushes the load aside, and at 15% off-centre the wall bulge climbs from 1.6 mm to 2.3 mm.

4. Folding 1:3 and the Return Trip

Folding 1:3 means three empty totes take the height of one. A tote stands 300 mm tall and folds to 100 mm, so 60 empties fill the floor space of 20 and one return run clears the lot.

Charger module tote store: a worker lifting one sand-coloured box, film-wrapped stacks, yellow-framed five-tier empty rack, palletised black cases

Four hinges and 2 catches do the work: a tote folds in 12 s and the catch runs under 60 N, light enough for a gloved hand. By 200 folds the hinge bush has worn 0.15 mm and the ratio slips to 1:2.6.

Higher is not better: a 1:4 shell needs three wall segments, two more joints and 18% less stiffness, capping the stack at 3 high. Cap the empty stack at 8 too; from the ninth tote the lower catches take shear.

5. Fork Pockets at 100 mm and a 200-Cycle Life

Fork pockets run 100 mm high and 200 mm wide, 400 mm apart centre to centre. A hundred millimetres is 1.6 times the fork thickness of a manual pallet truck, the margin that stops a misaligned entry from splitting the pocket edge. Round that edge at 8 mm; below 5 mm the corner shows a 0.5 mm crack after 200 entries.

Two hundred cycles is a downgrade line, not a warranty. Three readings decide it: divider deflection past 3 mm, hinge bush play past 0.3 mm, base corner wear past 1.5 mm. Hit any one and the tote moves to spare-parts duty.

Checkpoint	Cycles	Reading	Limit	Action
first use	0	surface resistance	1×10⁷ Ω	log and mark
mid-life	100	divider deflection	2 mm	trend it
life limit	200	bush play	0.3 mm	change bush
downgrade	260	corner wear	1.5 mm	spare-parts duty

Mark the base right-hand corner by inkjet at a fixed position, so a scanner reads it in 0.5 s.

Conclusion

Four numbers draw a charger module tote: surface resistance of 1×10⁶ to 1×10⁹ Ω, 8 modules behind 8 mm dividers to hold 28 kg, five high to put 112 kg on the bottom unit, and 1:3 folding to halve the return runs. Fork pockets at 100 mm, an 8 mm edge radius and a 200-cycle rule are the details that get missed.

This article discusses container-side specifications and design implications only, and does not cover any handling, loading or use of the contents.