How to Fix A Lithium Battery
by John Beale 4/11/01
You can attempt to fix an InfoLithium battery which has developed passivation by a process of charging and discharging several times. The TRV900 has a built-in battery charger. When the camera is off, but plugged into the AC adaptor, and the battery is on it, the battery will be charging (unless it is already fully charged). When the camera is on and not connected to the AC adaptor, it will run off the battery, eventually discharging it to the point where the low-voltage cutout threshold is reached, where it shuts off.
To charge-cycle the battery you:
A) With battery attached to the camera, unplug the AC adaptor from the camera, turn the camera on, and leave it on until it shuts off due to low battery. Note: don’t leave it in “camera” mode with a tape in, as it will auto-shutoff after 5 minutes in standby. Instead select “memory” mode, or “VTR” mode, where it will not auto-shutoff until the battery voltage drops. Do not put the camera in a padded case when on, as it will get rather warm.
B) Having discharged the battery, turn the camera off (leaving the battery attached) and connect AC adaptor. The battery will now charge until it is full.
C) Repeat steps (A) and (B) several times.
The above method worked for me with two NP-F330 batteries that had develped passivation due to several months of non-use. If after several tries the battery still dies prematurely, then you have to adopt another method, see below.
Secondary charge-cycle method: resistor load
The TRV900 uses a 7.2 V battery and consumes between 3.9 to 5.2 watts of power depending on operating mode. That implies between 540 mA and 720 mA of current, which would be drawn by a resistor ranging from 13.3 ohms to 10.0 ohms. So, you can simulate this load with a 10 ohm resistor rated to handle at least 5 watts (If possible, I’d suggest 10 W or more). Unless you use a physically large resistor, after a short time under load the resistor will get very hot and can burn you so be careful. The tricky part is how long to drain the battery with the resistor, as running the battery “flat” may well do more harm than good.
If the battery is really fully charged, then you should leave the resistor on as long as the “continuous recording time” for the camera drawing that current. A 10-ohm resistor corresponds to using the LCD screen, and a 13 ohm resistor to using the viewfinder. For example, a charged NP-F330 battery with a 10 ohm resistor load should take 50 minutes to discharge, while the NP-F750 should take 220 minutes. Runtime is listed for all operating modes and battery types in your owner’s manual. That page is also online here.