At each scheduled stock review, order a battery model up to a target level: your expected use across the supplier’s lead time and the review interval, plus a small safety stock you have chosen on purpose. Subtract your stock position from that target, round up to the supplier’s pack size, and check that confirmed deliveries arrive before usable stock runs out. Work this out per model number from your own repair tickets. The result gives a small shop a regular order decision and an order size, and it makes rare models easier to leave off the shelf.
The worksheet does not forecast market demand, and it cannot tell you how much your shop will sell next quarter. It tidies the numbers you already have so that each reorder rests on real use and confirmed supply terms.
The numbers you need for each model
- Weekly use. Count batteries installed per model over a recent period, such as the last 8 to 12 weeks, then divide by the number of weeks. Leave out one-off bulk jobs and note them separately.
- Supplier lead time. Measure from placing the order to having units checked in and ready for the bench. Use your own past deliveries where you have them, and confirm the current figure with the supplier for each order.
- Review interval. Use the actual number of weeks between your scheduled stock reviews.
- Usable on hand. Count units you could install today, including any set aside for a booked job. Exclude held, suspect and returned units.
- Timely confirmed incoming. Count units confirmed by the supplier, with an expected arrival date inside the period the target covers: lead time plus review interval, starting today. A verbal “should ship soon” stays out of this number, and so does an undated delivery or one due after that period.
- Committed units. Count usable units already promised to booked work that weekly use leaves out, such as a one-off bulk job filled from stock. Routine repairs are already in weekly use, so do not count them twice.
The arithmetic
This is a periodic review policy. You check stock on a fixed schedule, and each order brings stock position back up to the target. There is no separate trigger level, so do not wait between reviews for stock to fall to a threshold.
Safety stock is an extra buffer above expected demand during the replenishment period. Here, that period is the supplier lead time plus the review interval, because an order placed today has to carry you until the order from your next review arrives. For a small shop, choose safety stock by judgment and adjust it from experience. Part or all of a week’s use is a simple place to start for a model you repair often, and a late shipment history may justify more.
- Target level = average weekly use × (supplier lead time in weeks + review interval in weeks) + safety stock
- Stock position = usable on hand + timely confirmed incoming − committed units
- Order quantity = max(0, target level − stock position), rounded up to the supplier’s pack size. The max(0, …) step means you order nothing when stock position already meets or exceeds the target.
Fictional example
Every figure in this article’s examples is invented for an imaginary shop. None is an MRG Platform lead time, pack size, stock level or policy. A model uses 6 batteries a week, supplier lead time is 3 weeks, the shop reviews stock every 2 weeks and the owner keeps a safety stock of 4. The target level is 6 × (3 + 2) + 4 = 34.
The shop has 14 usable units, 10 units confirmed to arrive within the five-week period and no committed units. Stock position is 14 + 10 − 0 = 24. The order before pack rounding is 34 − 24 = 10.
Pack size then sets the final quantity. With a fictional pack of 10, the shop orders 1 pack, or 10 units. With a fictional pack of 8, 10 ÷ 8 = 1.25, which rounds up to 2 packs, or 16 units. That lifts stock position to 40, which is 6 above the target, and the extra units reduce the order at the next review.
Changing one input changes the result. If 4 of the 14 usable units were committed to a one-off job, stock position would be 14 + 10 − 4 = 20 and the order before pack rounding would be 14. If the 10 incoming units were dated six weeks out, they would fall outside the five-week period. Stock position would be 14 and the order before pack rounding would be 20, so ask the supplier whether that date can move before you place the larger order.
Reorder worksheet
Complete one row per model number in each table. The first row repeats the fictional example, using the fictional pack of 10.
Step 1: set the target level
| Model number | Average weekly use | Supplier lead time (weeks) | Review interval (weeks) | Safety stock | Target level |
|---|---|---|---|---|---|
| A0000 (fictional) | 6 | 3 | 2 | 4 | 34 |
| Your model | |||||
| Your model | |||||
| Your model |
Step 2: work out the order
| Model number | Usable on hand | Timely confirmed incoming | Committed units | Stock position | Target level | Order before pack rounding | Pack size | Order after pack rounding |
|---|---|---|---|---|---|---|---|---|
| A0000 (fictional) | 14 | 10 | 0 | 24 | 34 | 10 | 10 | 10 |
| Your model | ||||||||
| Your model | ||||||||
| Your model |
Step 3: check arrival dates for gaps
Confirmed quantity alone does not establish timely coverage, so list the expected arrival date of each delivery and project usable stock week by week. This fictional projection assumes even use, no committed units, and arrivals at the end of the week. The 10 confirmed units arrive at the end of week 2, the 10 units ordered today arrive at the end of week 3, and the order from the week 2 review arrives at the end of week 5.
| Week from today | Opening usable stock | Expected use | Stock before arrivals | Expected arrival | Closing usable stock |
|---|---|---|---|---|---|
| 1 (fictional) | 14 | 6 | 8 | None | 8 |
| 2 (fictional) | 8 | 6 | 2 | 10 confirmed units | 12 |
| 3 (fictional) | 12 | 6 | 6 | 10 units ordered today | 16 |
| 4 (fictional) | 16 | 6 | 10 | None | 10 |
| 5 (fictional) | 10 | 6 | 4 | Order from week 2 review | 4 plus that order |
| Your week | |||||
| Your week |
Flag any delivery due after usable stock would run out. In this projection, stock before arrivals never reaches zero, and the 4 left in week 5 equals the safety stock, as the target intends. Now suppose the first delivery slips to the end of week 3. The 2 units left after week 2 cover about a third of week 3’s expected use, leaving 4 repairs short. Stock position stays at 24 and the order stays at 10, because the delivery is still inside the five-week period, so only this check shows the gap.
A larger order placed today would not close that gap, because it also takes 3 weeks. Ask the supplier about an earlier or split shipment, and tell customers with affected jobs about any wait.
Decide what deserves shelf space
Not every model belongs on the worksheet. A simple split can stop slow stock from building up.
| Use pattern | Approach | What to check |
|---|---|---|
| Regular, week after week | Use the periodic review target | Lead time, batch consistency |
| Occasional, a few a month | Keep a very small quantity, or order to a booked job | Whether a customer will wait for delivery |
| Rare or declining | Order per job | Availability when needed, age of any remaining units |
| Single large job | Treat as a separate purchase | Deposit, delivery date, return terms for extras |
Set your own cut-offs, and write them down so the same logic applies at each review.
Supply conditions to confirm before you trust the number
A target level is only as reliable as its lead time and pack details. Fill in the table for each supplier and SKU, and date it, since these answers can change.
| Condition | Supplier’s current answer | Date confirmed |
|---|---|---|
| Lead time to your location | ||
| Expected arrival date for each open order | ||
| Pack size and minimum order | ||
| Shipping method | ||
| Batch or manufacture date supplied | ||
| Storage instructions for loose batteries | ||
| Return terms for unused stock |
Shipping method can move lead time more than a shop might expect. USPS treats individual lithium-ion batteries without equipment as prohibited by air and mailable by surface, with limits, in originally sealed packaging (USPS Publication 52, section 349). Lithium-ion batteries moving by aircraft under the applicable provision must also be offered at no more than 30 percent state of charge unless approved otherwise (49 CFR 172.102, provision A100). Carrier rules vary, so ask how your batteries will actually travel.
Why more stock is not always safer
Older batteries can tie up cash and shelf space, and storage conditions affect them. Apple’s advice for long-term storage of its devices is about 50 percent charge, a cool, moisture-free place below 90°F (32°C), and, for storage beyond six months, recharging to 50 percent every six months, because a fully discharged battery may enter deep discharge and a fully charged one may lose capacity (Apple: Maximizing battery performance). That guidance covers batteries in devices, so ask the supplier or manufacturer for instructions on loose replacement batteries, including any recommended stock rotation.
Issue the oldest usable batch first, and record batch codes on your bin labels. Check your landlord, insurer and local fire rules for any limits on stored batteries at your premises. Batteries that become unsellable have a disposal route to plan for: EPA says most discarded lithium-ion batteries would likely be hazardous waste, and it recommends that businesses consider the universal waste rules and consult their state agency (EPA: Used Lithium-Ion Batteries).
Keep two review schedules separate
Stock and order review. This follows the review interval in your formula. At each review, the fictional shop counts usable stock, updates every expected arrival date, works out the order, runs the arrival check and places any order. Use the interval you really follow. If the fictional shop reviewed stock every 4 weeks, its target would be 6 × (3 + 4) + 4 = 46.
Demand-parameter review. This runs less often, perhaps every 8 to 12 weeks, or sooner if a supplier changes its terms. Recalculate weekly use from recent tickets, compare each promised lead time with the actual one, and reconsider safety stock and pack size. Hold these inputs steady between parameter reviews so that one busy week does not swing the target. If a model hits zero while orders were on time, consider raising safety stock. If stock position stays far above target, lower safety stock or move the model to order-per-job. Keep the sheet alongside your procurement records, and see Warehousing for storage planning questions.
Next step
Run the worksheet for your five highest-use models using the last 8 to 12 weeks of tickets. Then request current lead times, arrival dates for open orders and pack sizes for those lines. MRG Platform confirms availability, price and timing per request, so include your model numbers and quantities on the sample and pricing inquiry page, or review the Batteries section.