A single battery reading tells you where you are. A log tells you how you got there — and how fast you are still draining when you think the laptop is asleep. BatteryInfoView’s Battery Log, opened with F8, records a new status line at a regular interval and at the moments that matter most for standby drain: suspend and resume. This guide covers turning the log on, changing its interval, saving it automatically to a file, and reading it to find overnight drain.
Get the tool from the download page (official file via /go/batteryinfoview) and see the Tutorials hub for the companion guides, starting with the basic health check.
What the Battery Log is (F8)
Press F8 to switch to Battery Log view. In this mode BatteryInfoView keeps a running table where a new log line, containing battery status such as Power State and % Capacity, is added every 30 seconds by default. Leave the program running and the table grows into a timeline of your battery: charge level over time, whether the machine was charging, discharging, or on AC power, and the other status values captured at each interval.
Contrast this with Battery Information view (F7), which shows the current values in a single table refreshed every 10 seconds by default. F7 answers ‘what is true now?’; F8 answers ‘what has been happening?’. For drain investigations you want F8 — and you want to leave BatteryInfoView running for the whole period you are investigating, including overnight if standby drain is the question.
The two extra log lines that reveal standby drain
The interval lines alone would miss the most interesting moments, so the log adds a line at two extra events: a log line is also added when the computer suspends (standby/hibernate) and when it resumes. That design is deliberate — NirSoft notes it means the standby drain rate can be seen.
To use it: note the % Capacity on the suspend line when you close the lid or put the laptop to sleep, then compare it with the % Capacity on the resume line when you next open it, and note how much time passed between the two timestamps. A small drop over a long sleep is unremarkable; a large drop over a short sleep means something kept drawing power while the machine was supposed to be suspended. Repeat over two or three nights before drawing conclusions — a single night can be distorted by an update, a wake event, or a peripheral. If the readings themselves look implausible, sanity-check them with Capacity Readings Look Wrong? and the Troubleshooting hub.
Changing the logging interval in Advanced Options (F9)
Thirty seconds is a sensible default: frequent enough to show a drain curve, sparse enough to keep a day’s log readable. You can change it in Advanced Options (F9), which controls the log interval as well as the Battery Information refresh interval. Shorter intervals give finer detail for a short test — for example watching drain during a video call — while longer intervals keep multi-day logs compact. Advanced Options also gained more controls over which event types are added to the battery log (v1.12), and two log-related options worth knowing:
- ‘Automatically Scroll Down On New Log Item’ (added in v1.20) — keeps the newest line visible as the log grows.
- ‘Sort Log On Every Update’ (added in v1.26) — keeps the log sorted as new lines arrive.
There is no documented command-line switch for logging — do not go looking for a /log flag; the complete official switch list is in Command-Line Options: The Full List, and logging setup lives in the GUI’s Advanced Options.
Auto-saving every log line to a file (v1.20+)
A log you have to remember to save is a log you will lose when you reboot. Since v1.20, BatteryInfoView can automatically save every new log line to a comma-delimited or tab-delimited file, configured in Advanced Options (F9). Turn this on before a long investigation and each new line is written out as it appears, building a CSV-style record you can later open in Excel or another spreadsheet to chart capacity against time.
Separately, at any moment you can select log lines (or all of them) and press Ctrl+S (Save Selected Items) to export the selection to text, CSV, tab-delimited, HTML, or XML, or copy the selection to the clipboard and paste it into a spreadsheet. The export formats and use cases are covered in full in How to Export a Battery Report. For a drain investigation, the auto-save file is the raw timeline and a Ctrl+S export is the tidy snapshot you share or archive.
How to run a simple standby-drain check
- Charge the laptop to a comfortable level and unplug it (standby drain is a battery-only question).
- Open BatteryInfoView, press F8, and confirm new lines are appearing. Enable auto-save in F9 if you want the file record.
- Put the laptop to sleep the way you normally do — lid close or Start menu — and leave it for a known period, ideally overnight.
- Wake it, find the suspend and resume lines in the log, and compare % Capacity and the elapsed time between them.
- Repeat on another night. Consistent large drops point to a real standby-drain issue to investigate in Windows’ own sleep settings and connected devices; BatteryInfoView’s role is to give you the trustworthy before-and-after numbers.
The same log answers daytime questions too: how fast the battery falls during your normal work, whether the Charge/Discharge Rate (usually in milliwatts) spikes with a particular app, and how the estimated time fields behave. Those estimates are calculated from the change in Current Capacity Value over the last 30 seconds, so the log is literally watching the data they are derived from. See Charge/Discharge Rate Explained for reading the rate column.
What the log cannot do
BatteryInfoView displays and logs information — it does not fix drain, block wake events, switch power plans, or limit charging. If the log proves your laptop drains in standby, the remedy lives in Windows settings, drivers, and attached devices, not in this program. The log also only exists while BatteryInfoView is running: it is the program’s own timeline, distinct from the history Windows itself records, which NirSoft’s sister tool BatteryHistoryView can surface — see BatteryHistoryView: See the Battery History Windows Already Records.
Frequently asked questions
How long should I log for?
Long enough to include the behaviour you are investigating: an hour for a workload test, a full sleep period (ideally repeated) for standby drain, a full discharge for a runtime picture. With auto-save on, longer is safe — the file simply grows line by line.
Does logging itself drain the battery?
BatteryInfoView is a tiny portable utility adding one line at your chosen interval. Any tool running uses some power, but at a 30-second interval the logging overhead is negligible compared with the drain rates you are measuring — and lengthening the interval in F9 reduces it further.
I closed BatteryInfoView — is my log gone?
If you enabled auto-save, the file on disk keeps every line that was written. Without auto-save, use Ctrl+S to export before closing. Make auto-save part of your setup for any investigation longer than a few minutes.
Next steps: take a dated snapshot with Export a Battery Report, re-check overall health with Check Battery Health, or return to the Tutorials hub.