Most BatteryInfoView fields describe stored energy. The Charge/Discharge Rate field is different: it describes energy on the move — how fast your battery is gaining or losing charge at this moment. It is the field that answers questions the capacity figures cannot, such as why the battery fell so fast in the last hour, whether the charger is keeping up with your workload, or what a particular program costs you in runtime. This page explains what the field shows, how to read its sign and size, and how to use the F8 log to turn a flickering instantaneous number into evidence. If you have not tried the tool yet, get it from our download page — the main button there uses the official NirSoft file — and then work through the checks below. For the wider topic, see the Battery Health hub.
What the field is
Charge/Discharge Rate is field 12 in NirSoft’s official field list, described as usually in milliwatts (mW). A milliwatt is a unit of power — the rate at which energy is transferred — as opposed to the milliwatt-hour (mWh), the unit of stored energy used by the capacity fields (see Designed Capacity vs Full Charged Capacity). The relationship is the familiar one: energy divided by time is power, so a sustained discharge rate of 10,000 mW — 10 watts — consumes 10,000 mWh of stored energy per hour.
The display has been refined over the program’s life: in version 1.13, a thousands separator was added to the Charge/Discharge Rate value, which is why a modern build shows a figure like 12,500 rather than 12500 — a small change that makes five-digit rates considerably easier to read at a glance.
Reading the sign: charging versus discharging
One field covers both directions of flow, and the sign is how you tell them apart: the rate is shown as a positive or negative value depending on whether the battery is charging or discharging at that moment — check the sign on your own machine alongside the Power State field (field 5, which reads Charging, Discharging, AC Power or Critical), and the two will agree. Power State tells you the situation in words; the rate tells you how fast it is happening. A laptop can be in Charging state with a small positive rate — the charger is connected but the workload is consuming almost everything it supplies — and that combination is far more informative than either field alone.
Expect the instantaneous value to move. It is a live reading in the Battery Information view (F7), which refreshes every 10 seconds by default, and real workloads are bursty: opening programs, compiling, video calls and background updates all spike demand and then release it. A single glance therefore tells you little. The patterns to look for are sustained levels — a rate that stays high during work you consider light, or stays near zero while plugged in and supposedly charging.
Why the rate connects to the 30-second estimates
The rate field is also the key to understanding BatteryInfoView’s four estimated time fields (fields 16 to 19). Those estimates are calculated from the change in Current Capacity Value over the last 30 seconds — effectively, from how fast the battery’s stored energy has just been moving. When the recent rate has been high, the remaining-time estimate shrinks; when the machine idles, it stretches. This is why estimates swing when your workload changes, a behaviour explored in full in BatteryInfoView’s Estimated Time Fields. Reading the rate directly shows you the cause; the estimates only show you the effect.
Using the F8 log to spot abnormal drain
For anything beyond a glance, switch to the Battery Log (F8). The log adds a line with battery status every 30 seconds by default — the interval is changeable in Advanced Options (F9) — and each line captures the state at that moment, so a working session becomes a series you can review rather than a number you had to catch live. A line is also added on suspend and on resume, which makes standby drain visible: compare the capacity and the elapsed wall-clock time across a sleep period and the overnight or in-bag loss stops being a guess.
- Establish your baseline: log a period of genuinely light work — reading, writing, a few tabs — and note the typical discharge rate range.
- Compare like with like: a sustained rate far above your baseline during the same kind of work is the definition of abnormal drain worth investigating.
- Change one thing at a time: close or pause a suspect program, keep logging, and see whether the rate settles. The log turns suspicion into a before-and-after comparison.
- Watch the charging direction too: on AC power, a persistently tiny positive rate at a low percentage, or a rate that cannot keep the battery level during heavy work, is charging evidence you can quote when seeking help.
Mechanics for saving and exporting the log are in the Battery Log guide and How to Export a Battery Report; a saved csv of a bad afternoon is worth more in a support conversation than any recollection of percentages.
What the rate cannot tell you
The rate is a whole-battery figure. BatteryInfoView offers no per-process power breakdown, no per-cell voltage and no temperature field, so the rate can tell you that drain is abnormal, and when it started, but not which component or sensor is responsible — narrowing that down is the change-one-thing-at-a-time work above. The rate also says nothing about capacity or wear by itself: a battery can discharge at a perfectly normal rate and simply have less to give, which is the territory of Battery Health % and When Should You Replace a Laptop Battery?
Used together — capacities for how much, rate for how fast, log for how it behaved over time — the three views cover most battery questions a user can ask. The rest of the topic map is in the Battery Health hub, and the tool itself, as the official NirSoft file, is linked from the download page.
Frequently asked questions
My rate jumps around constantly. Is something wrong?
Movement is normal for an instantaneous reading refreshed every 10 seconds against a bursty workload. Judge the sustained level in the log, not individual spikes.
The rate is near zero on AC power. Is the battery charging?
Read it with Power State and the % Capacity trend over several log lines. Near the top of a charge, or when the workload consumes what the charger supplies, a small rate is expected behaviour rather than a fault on its own.
Can I see the rate for each program?
No. BatteryInfoView reports the battery-level rate only. Identifying a culprit is done by observation — logging while you change one thing at a time, as described above.