So if those are primary cells, then would you expect a diode or switch, that uses them as backup only? Where would I look to find that effective switch?
No. Primary cell means that it is a cell (battery) that is not rechargeable. Rechargeable cells are called secondary cells. With many things primary implies that it is the main and secondary implies that it is a backup. That’s not what primary and secondary mean with batteries though.
2 Likes
So in this case do you think it was just batteries that powered the phone/doorbell.
Or that when utility power was on, it came from utility power. I ask, because they appear to have been connected to the 12V transformer at some point. THAT is what’s confusing me.
1 Like
Yes. It appears that the batteries were the sole source of energy for the doorbell. I can’t explain the connection to the AC source. It would have been useless as a means to recharge the batteries because they are not rechargeable. As Bob pointed out early in this conversation, they are primary cells, so an AC connection could do more harm than good. There may be other pieces to the puzzle that we are not seeing, but short of actually being on the scene, we can only speculate. I doubt it, but the person who installed the system may have believed that the batteries were rechargeable.
1 Like
Tell me as a kid, you didn’t put non-rechargeable batteries in the charger and you’d get some extra life out of them. I know they aren’t rechargeable, I’m not saying that. I’m also not saying it’s safe or recommended, but every kid in the 70s tried it and it works, sorta, once.
I was a little older in the 70s and had a little more sense. Your statement makes absolutely no sense. If the battery was not entirely depleted there is no way you would know whether or not you got “more life” out of them. The same is true for making the same claim about putting them in the freezer. The chemical process in carbon / zinc batteries is irreversible. The chemical reactions inside the battery destroy the active ingredients no matter what you “think” is happening.
2 Likes
We didn’t have small battery chargers when I was a kid in the 60s, but I did a lot of experimenting with electronics. A crystal radio only had about four parts, but I had a pocket transistor radio that had probably a hundred parts. I wanted to know what they all did, so I started cutting parts out one at a time to see if I could figure out what they did. I cut out a lot of parts before the radio eventually stopped working.
2 Likes
Battery dead. Put in charger, get life out of it, not much but something. I’m not a chemical engineer so I looked it up. Apparently putting it in a charger can release some small amount.
The 1970s “Battery Revival” Trick (How It “Worked”)
What Kids Did:
-
Took a dead alkaline battery (usually AA or 9V).
-
Connected it to a power source — often:
-
A 9V battery charger (meant for NiCd rechargeables), or
-
A wall adapter (like from a radio or toy) with exposed wires.
-
-
Applied reverse current briefly — sometimes just a few seconds, sometimes minutes.
-
Tapped or shook the battery during or after.
Why It Seemed to Work Sometimes:
-
Alkaline batteries die when zinc is fully oxidized and manganese dioxide is reduced.
-
But the reaction isn’t perfectly uniform — some unreacted material gets trapped or insulated by reaction byproducts.
-
Charging pushes current backward, which can:
-
Redissolve zinc oxide back into usable form.
-
Redistribute electrolyte and break up blockages.
-
Generate gas (H₂ and O₂) that stirs the internals (hence the tapping).
-
→ Result: Brief voltage recovery — enough to dimly light a bulb or run a weak toy for a few more minutes.
My dad use to fix CB radios and other electronics. First use of an oscilloscope, I was probably 5. I just liked the wavy lines, had no clue what it meant.
I had one of the those 150 in 1 electronics kit at some point. I tore everything apart. heh. Funny thing was in the 70s, dad would modify the CBs for people to have more channels by replacing the crystals. Negative channels, above 40, sideband, you name it. Then we got an amplifier and really juiced out some wattage. It’s how I learned soldering at a young age.
At one point, rumor was the FCC was trying to find the source of all these CBs and who was doing it. We had an old house(1865) and were able to hide all the equipment in the space behind the chimney, accessed through a false panel in the closet. We got a visit one day and I don’t really remember what came of it, other than we didn’t key up the big 400 watt amplifier again for a long long time.
1 Like