The Fleet That Discharges While Docked
A regional parcel carrier operates 60 rugged Android tablets mounted in delivery vans. Drivers scan 400-600 parcels per 10-hour shift, and the tablets run GPS, a cellular data connection, and the scanning app continuously. The devices are 28 months old on a 36-month warranty. Since a firmware update six weeks ago, 25 drivers report batteries falling from 100% to below 20% within six hours, and one van's tablet has a screen lifting away from the chassis. The in-dash cradles supply 5 V at 1.5 A. The fleet is managed by an MDM that reports battery health, installed apps, and last sync time. Replacement batteries cost $95, a refurbished unit $310, and a new unit $520.
1. The operations manager wants to push a battery-optimization MDM profile and defer all hardware action until the next refresh in eight months. What is your triage plan, and what do you tell them?
Read the worked answer
Separate safety from performance first. A screen lifting away from the chassis is a swollen cell, which is a fire risk. Pull that unit today, stop charging it, tag it, and isolate it away from combustible material. That item is not deferrable, and it reframes the conversation from "wait" to "triage."
Then quantify before acting. Pull design capacity versus current capacity for all 60 units from the MDM. Anything below 80% of design capacity at 28 months is out of spec and explains most of the 25 complaints; units near 100% capacity that still drain fast point at the firmware or the charging path. Split the fleet into "degraded battery" and "healthy but draining" - they get different fixes.
Then check the power budget, not just the battery. A 5 V / 1.5 A cradle delivers 7.5 W. A tablet running GPS, cellular, and a scanner radio under load can exceed that, so the device discharges while docked and goes through a deep cycle every shift. That accelerates wear and is a fleet-design fault, not a driver fault.
Recommendation: quarantine the swollen unit, replace batteries on units below 80% under warranty (about 25 x $95), upgrade cradles to at least 15 W USB-PD, then re-measure over five shifts. Replacing whole units at $520 apiece is not justified while warranty remains.
2. Design a test that proves whether the drain is caused by firmware/app behavior or by the charging hardware. State which result would change your recommendation.
Read the worked answer
Run a matched-pair crossover, not a spot check.
- Select 6 complaining and 6 non-complaining units with the same app version and similar shift routes.
- Baseline both groups on the existing 1.5 A cradles for one shift, logging mAh consumed per hour, screen-on time, GPS active time, and cellular signal strength from the MDM, plus a USB power meter inline to record actual delivered watts.
- Cross over: run the complaining units from a bench supply at 15 W and the non-complaining units from the 1.5 A cradles.
- Roll back firmware on 3 complaining units under change control as the decisive single-variable test.
Interpretation: if the complainers still drain on the bench supply, the cause is the firmware or app (wake locks, aggressive GPS polling) or a weak cellular signal forcing the modem to transmit at high power - check the coverage map for the affected routes before blaming code. If they stop draining on the bench supply but the non-complainers begin draining on the cradles, the cradles are the bottleneck for the entire fleet.
What changes my answer: a cradle-driven result means battery replacement alone buys a few months and the problem returns. In that case the cradles get fixed first and the battery spend is re-evaluated rather than assumed.
3. Six months later, 18 of the 60 lines exceed a 22 GB throttle threshold and two lines are above 90 GB. The carrier's unlimited tier costs $8 more per line per month. What do you investigate, and what do you recommend?
Read the worked answer
90 GB on a barcode scanner is anomalous, not a plan problem. A device that scans parcels and syncs text-sized records should be in the low single-digit gigabytes. Two lines at 90 GB point at tethering/hotspot use, a runaway app sync, or full-resolution photo/video upload - none of which an unlimited plan fixes.
Investigate before buying: pull per-app data consumption and hotspot usage from the MDM per line. Look for a device configured as a Wi-Fi hotspot for the driver's personal phone, a scan app uploading uncompressed images over cellular instead of batching on the depot Wi-Fi, or a sync loop that retries against a failing endpoint.
Do the arithmetic: 18 lines x $8 x 12 months = $1,728 per year for the upgrade. That is cheap compared to engineering time - which is exactly why it is tempting and exactly why it is the wrong first move. Upgrading hides a misbehaving app, and the data volume keeps climbing.
Recommendation: fix the two outliers first (restrict hotspot via MDM profile, configure the scan app to compress and defer uploads to Wi-Fi), re-baseline for one billing cycle, then choose the tier from the post-fix numbers. If 18 lines still exceed 22 GB after remediation, the upgrade is justified - but justify it with data, not with the invoice.