FS7: Charged Battery plays dead

[LennyLevy]

I have Switronix Series 7 EX-L96 batts that I use in my Ex-1 and FS7 . I charge them with those traditional Sony AC power / charger units BC-U1 and BC-U2. Generally they have been workhorses for a long time and show no signs of weakening - However:

Tonight I put a battery that shows its fully charged on the camera and nothing happens . I'm startled to see that none of the LED lights in the back of the battery show any charge at all. It looks dead,.
I go home , put the batt on the charger for a second and press the test button and all 4 lights come on . i put the battery in the camera and it works fine. I've seen this phenomena before. For some reason the battery itself plays dead until it gets the shock of a charge in it .

What the heck is going on here?

Lenny

 

[Wes.]

I've seen a battery need to be put on the charger to "reset" before it worked again. That was something like a power overload or reverse polarity accessory plugged in and broken or something along those lines though. Some sort of power anomaly and then needed to put battery on charger for it to work at all again. I've since retired those batteries from active duty though.

 

[LennyLevy]

Alex Dolgin helped me understand what was going on with this battery and I remember that i had read something about this before. Alex's comments might be instructive to others if you have the same experience:

"Lenny, every Li-Ion battery has a safety chip inside, to make sure the battery does not get stressed out, overheated, etc. What might be happening is the cells (they are many in the large EX-L96) age, and start to misbehave, causing the circuit to disable the pack to keep it safe. Connecting a pack to a charger reboots/resets the circuit. It might be a good idea to start looking for a replacement battery...
This could be also happening if the initial current surge into the camera spooks the chip into thinking “It is a short circuit, shut off fast”. If the protection circuit is not designed well, these random problems could happen.
The thing is the battery designers do not design all these circuits from scratch, but use off the shelf designs. If they do not test the prototypes thoroughly, these things come and go…"

Me:
"This battery always seems to work fine and hold a solid charge if it doesn't do the initial turn off. Is it possible that some ways of starting the surge might be worse than others.
For example
- putting the battery in a camera that is already switched to on?
- In my FS7 if the viewfinder is not plugged in would that be a safer way to start - less surge?"

Alex:
"Exactly, it will be trial and error until you know how to negotiate the startup.
I would say they do not like sudden changes like turn on/off – so once you are rolling it should be safe. "

So I'm going to be extra careful about how I start the camera with a fresh battery. So far I can't get the battery to die again even under the high stress though. I hate intermittent problems.