Good day.
Last week I came across one of those emergency light power supplies, the type with a 6 volt lead battery inside that are constantly hooked to a charger.
I took it home and plugged it in after attaching the battery (6v 7Ah). The yellow charge light came on. I left it for several days. Today I took the battery out. I measured the voltage. It read -3.x volts (lets say -4 volts). I had the common lead on the meter connected to the black post (clearly marked negative) and I had the other lead connected to the red post on the battery (also clearly labeled positive). I tried again.
-3.x volts. As if I had the meter connected backwards. "This isn't right" I thought. Impossible. Something is backwards here"
I took my meter and tested the voltage across a battery I knew was good, a
12v 7Ah I had been using for years. Red to red, black to black I read +12 volts or so. No problem with polarity.
BAck to the 6v battery and I see -3.x volts. I place a 6v lightbulb across the battery leads. It lights up. Not bright, but there is current flowing.
I check the charger. The dark wire (blue) connects to the circuit board at a spot clearly marked - bat. The red wire connects to the board at a spot marked +bat. I connect the red wire to the red post of the battery. The blue wire to the black post. Just like I did when I got the thing home last week.
Turned on the charger. I read -1.85 volts across the battery terminals. When the battery charger is removed the voltage reads -3.3 volts but slowly climbs to -3.7 volts (within 2 minutes).
What the hey is going on??? Is this battery shot? If so, can someone explain the chemistry going on? It is like I have not only drained the battery, but actually drained it past the 0.0 volt level and taken it into a state where a reverse reaction is going on.
Anyone?