spokewrench
Active Member
- Region
- USA
Fifty years ago I acquired a copy of the BCI manual on maintaining lead acid batteries, with all kinds of stuff about design, specific gravity, state-of-charge voltages, and charge rates. I had a 6-amp and a 1-amp charger. Often, an alternator wouldn't keep a battery charged, especially in winter. Even with the trickle charger, charging could make a battery worse. I figured voltage was the problem, so I bought a 10-amp "automatic" (voltage regulated) charger with a switch for trickle charging. Charging could still make a battery worse.
Twenty-five years ago, a neighbor bought a 2-year battery for his car. It quit in 2002, so he replaced it and for some reason put the defunct battery on his back steps. Two years later, another neighbor was throwing out an antique Sears battery charger. Curious, I asked for it. I didn't want to risk my car battery, so I used the defunct one from my neighbor's steps. I figured that on top of being junked, it had sat sulfating for two years, so it probably wouldn't even accept current. At least I could see if the strange charger would put voltage on the terminals.
It made the junk battery almost like new. It outperformed the one in my car, so I swapped them. With a scope, I found that it charged in pulses, 8ms IIRC. Evidently, the simple circuit sampled voltage between pulses. As that terminal voltage increased, the time between pulses increased.
Every few weeks, I'd put the strange charger on it overnight. For 9 more years, that battery performed faithfully!
I looked up the 1955 patent. The inventor had fork lifts in mind. Like me, he'd discovered that DC charging is detrimental. That's why chargers had timers as well as voltage regulators. His could be left on a battery indefinitely without harm. Lately, researchers have found out why. DC charging causes unwanted chemical reactions. Those unwanted reactions can reverse between pulses. When my battery was junk, the pulses had broken down the lead sulfate without accumulating undesired byproducts.
The antique was labeled 8 amps, and the meter read to 8 amps, but it behaved as a trickle charger; maybe after 50 years a capacitor was bad. I bought a smart charger. A scope showed that the width of the pulses varied, rather than the time between them. It had no gauge, so I monitored it with a wattmeter.
Once I asked a neighbor about a van that had sat in her yard six months. She said her son had run out of gas, poured in more, and run the battery down trying to start it. A car battery that had been run down and left that long sounded unsalvageable, but the pulses from my smart charger brought it back.
Another neighbor had restored a 1955 Pontiac. The battery would run down from sitting or from a bulb drawing current. It would also run down trying to crank the engine with stale gas and an automatic choke that didn’t work. He’d use a regulated analog charger. He’d forget and leave it charging for days at a time. I told him that was bad for the battery. I offered to let him use my smart charger. He wasn’t interested.
One day it was too weak to turn the engine although the voltage showed it was half charged. I figured my smart charger would bring it back. The watt meter indicated the battery was taking 2 amps. After 48 hours, it was still pulling the same wattage. I shut it off and found that the battery wouldn’t do anything.
This was the first time it appeared that my smart charger had made a battery worse. I tried again 4 days later. This time it took a 6 amp charge. Like a new battery, it would maintain over 11 volts while cranking that big engine indefinitely.
IIRC, the grids of so-called maintenance-free batteries have cadmium. DC charging can cause the cadmium to migrate to the surface of the plates, where it interferes with the flow of ions. My theory is that pulse charging had broken up the undesired cadmium compounds, but the battery wouldn’t work until the cadmium had migrated back into the grids.
I have two smart chargers now. Their percent reading is not reliable. Often, my watt meter will show the current slowing way down although I know the battery isn’t fully charged. If I let the battery rest a few minutes or an hour, it will charge normally. My theory is that ions or something can accumulate along plates, and the microprocessor won’t charge normally until I let them dissipate.
Both smart chargers have AGM settings, and both have trouble with my AGM mower battery. My 1955 pulse charger with the analog gage will top it off beautifully. I guess that’s why the battery performs like new after 8 years.
My plain dumb charger has worked fine since I replaced the full-wave bridge rectifier in the 1970s, Mostly I put it on just long enough to get a battery’s electrolyte stirred up. I wish I could see what my "dumb" 1955 pulse charger could do if it worked like new. They don’t seem to make pulse chargers without microprocessors anymore.
Twenty-five years ago, a neighbor bought a 2-year battery for his car. It quit in 2002, so he replaced it and for some reason put the defunct battery on his back steps. Two years later, another neighbor was throwing out an antique Sears battery charger. Curious, I asked for it. I didn't want to risk my car battery, so I used the defunct one from my neighbor's steps. I figured that on top of being junked, it had sat sulfating for two years, so it probably wouldn't even accept current. At least I could see if the strange charger would put voltage on the terminals.
It made the junk battery almost like new. It outperformed the one in my car, so I swapped them. With a scope, I found that it charged in pulses, 8ms IIRC. Evidently, the simple circuit sampled voltage between pulses. As that terminal voltage increased, the time between pulses increased.
Every few weeks, I'd put the strange charger on it overnight. For 9 more years, that battery performed faithfully!
I looked up the 1955 patent. The inventor had fork lifts in mind. Like me, he'd discovered that DC charging is detrimental. That's why chargers had timers as well as voltage regulators. His could be left on a battery indefinitely without harm. Lately, researchers have found out why. DC charging causes unwanted chemical reactions. Those unwanted reactions can reverse between pulses. When my battery was junk, the pulses had broken down the lead sulfate without accumulating undesired byproducts.
The antique was labeled 8 amps, and the meter read to 8 amps, but it behaved as a trickle charger; maybe after 50 years a capacitor was bad. I bought a smart charger. A scope showed that the width of the pulses varied, rather than the time between them. It had no gauge, so I monitored it with a wattmeter.
Once I asked a neighbor about a van that had sat in her yard six months. She said her son had run out of gas, poured in more, and run the battery down trying to start it. A car battery that had been run down and left that long sounded unsalvageable, but the pulses from my smart charger brought it back.
Another neighbor had restored a 1955 Pontiac. The battery would run down from sitting or from a bulb drawing current. It would also run down trying to crank the engine with stale gas and an automatic choke that didn’t work. He’d use a regulated analog charger. He’d forget and leave it charging for days at a time. I told him that was bad for the battery. I offered to let him use my smart charger. He wasn’t interested.
One day it was too weak to turn the engine although the voltage showed it was half charged. I figured my smart charger would bring it back. The watt meter indicated the battery was taking 2 amps. After 48 hours, it was still pulling the same wattage. I shut it off and found that the battery wouldn’t do anything.
This was the first time it appeared that my smart charger had made a battery worse. I tried again 4 days later. This time it took a 6 amp charge. Like a new battery, it would maintain over 11 volts while cranking that big engine indefinitely.
IIRC, the grids of so-called maintenance-free batteries have cadmium. DC charging can cause the cadmium to migrate to the surface of the plates, where it interferes with the flow of ions. My theory is that pulse charging had broken up the undesired cadmium compounds, but the battery wouldn’t work until the cadmium had migrated back into the grids.
I have two smart chargers now. Their percent reading is not reliable. Often, my watt meter will show the current slowing way down although I know the battery isn’t fully charged. If I let the battery rest a few minutes or an hour, it will charge normally. My theory is that ions or something can accumulate along plates, and the microprocessor won’t charge normally until I let them dissipate.
Both smart chargers have AGM settings, and both have trouble with my AGM mower battery. My 1955 pulse charger with the analog gage will top it off beautifully. I guess that’s why the battery performs like new after 8 years.
My plain dumb charger has worked fine since I replaced the full-wave bridge rectifier in the 1970s, Mostly I put it on just long enough to get a battery’s electrolyte stirred up. I wish I could see what my "dumb" 1955 pulse charger could do if it worked like new. They don’t seem to make pulse chargers without microprocessors anymore.
