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Old Aug 11, 2011, 04:47 PM
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United States, MA, Walpole
Joined Dec 2003
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Originally Posted by utx View Post
Well, I am starting to suspect that there is only one V2 camera, but two versions of car charger:
- 5V (?): Fully charges the battery while driving but probably overcharges.
- powering one - 4.20V: Starts to power the camera when the battery is nearly depleted.

I have the second version of the car "charger".

I measured behavior of pin 4 powering and tested the protection circuit with my new equipment.

The protection breaker activates when the voltage on battery terminals reaches 4.76V-4.88V and charging current 0.25A-0.33A. In that moment charging current drops abruptly to 0A. I am not sure whether it is current activated or voltage activated, but both values are unsafe for terminals of a fully charged battery. And yes, the breaker resets somewhere above 3V.

Pin 4 voltage reaches in that time 4.88V-5.00V. To be sure that the protection activated, I had to use at least 5.01V.

Powering pin 4 with 4.54V, the battery terminal reached 4.20V/0.03A. It means that everything above that voltage on pin 4 is unsafe.

If somebody built a special pin 4 cable to power the camera from USB:
- If USB provides 4.88V or less, your battery is overcharged forever and quickly dies.
- If your USB provides 5.01 or more, your battery is overcharged only for a limited time and dies less quickly.
- Using a standard silicon diode in the power line may improve things a bit. Two diodes in series should be safe even if USB provides 5.5V.

Here is new corrected list of pin 4 power voltage safety:

- 4.32V and less: safe, but battery partially depletes while recording
- 4.38V-4.52V: unsafe: Charging voltage is correct, but charging never finishes.
- 4.56V-4.88V: quick battery damage: Battery is overcharged potentially forever.
- 5.01V and more: less quick battery damage: Battery is strongly overcharged, but then charging stops.

The emergency charger provides 5.624V without any load => it overcharges the battery. I stopped my experiment at 4.22V at battery terminals and 4.54V on the charger. Current was 19mA and slowly raised.
I think what we have is one camera V2, two versions of car charger, and MANY different voltages from the different battery protection circuit boards! Quality control and/or voltage control accuracy on these boards may not be very good. I have one from a battery that came on my first #11 camera, and lost half its capacity in less than a month. I may see if I can test it for functioning (if it's still good).
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