You just said it was "an open or high resistance cell." I thought by
"high resistance" you meant a slow internal drain.
It's easy if you read the numbers on the meter. If you have one shorted
cell, you'll see about 10.5V.
You've introduced the concept of partial shorting. They're all like
that. I believe a new conventional lead-acid battery on the shelf will
drain in a month or so at room temperature. (Maintenance-free batteries
drain more slowly.) New batteries have "partial shorts" and most work fine.
If you nhave a totally dead battery you will too, or if you have
several partly shorted cells. But you are right, GENERALLY a battery
that is down roughly 2 volts AND STILL CRANKS AN ENGINE has a shorted
No, new batteries do not have "partial shorts" they have self
discharge, which is "normal" but it won't drain in a month. A GOOD
lead acid battery will hold about 80% charge for 6 months.
A "pure lead" battery = no calcium or antimony, will hold a LOT longer
than that. A Hawker Genesis EP has a "shelf life" of almost 3 years.
A totally dead battery won't show 10.5V with the lights on.
What would be the point of trying to crank the engine? If five good
cells cranked it one day, they might not do it the next. Under a big
load, they could produce less than 8V.
All batteries have electrical leakage within the cells.
which is "normal" but it won't drain in a month. A GOOD
On the shelf, a typical car battery will be down to 80% in 12 days at
100F, 30 days at 80F, and 100 days at 50F. A particular model may
discharge faster or slower.
That's lead-tin stored at a cool temperature. Are they practical?
Car manufacturers use batteries intended to start the vehicle after two
weeks parked. If you disconnect the battery, the time you can park and
still get started varies from 1 to 6 months, depending on the
temperature and the model of battery.
Charging voltage and fully charged voltage are NOT the same.
Charging voltage can be as high as 14.6 volts, which can leave a
surface charge of 12.9, +/- for a short time after charging, but a
FULLY CHARGED Lead Acid battery is 2.1 volts per cell ( so 12.6
volts). It takes 2.15 volts per cell to START to charge the average
lead acid battery, so anything less than 12.9 volts is not charging
13.8 volts is the "recommended" maximum charging voltage according to
Best way to check BATTERY voltage is to turn on the headlights for 2
or 3 minutes, then turn of the lights and check the voltage.
Checking with the headlights on and comparing the voltage will give an
indication of the batterie's internal resistance.
The battery behaves pretty well. I haven't bothered to check cranking
voltage because it sounds good. It's in a van belonging to a couple who
are away most of the time. I've been charging it occasionally because
extended sitting without charging harms batteries. A few weeks ago they
were about to replace the battery because the van wouldn't start, but I
found resistance at the positive terminal connection.
I checked the meter on a battery that I'd charged two days before. 12.6.
In that connection, I had switched to 10A to check the charging current.
Then I checked voltage across the terminals. Zero... uh-oh, the plugs
were in the 10A jacks. I've damaged meters that way before, and I never
learn. This time there was no arc. At home, I checked it on a 5A
source and got a good reading. Could my cheap DMM have circuit
protection on the 10A inputs? I need to take it apart and see!
The water level is good. As I don't know where the battery came from, I
don't know what it was filled with.
Decades ago, I got a manual a major manufacturer had published for
dealers. It said that a battery sold in Toronto may have a stronger
electrolyte than one sold in Miami. Higher acid concentrations help in
cold weather but shorten battery life in hot weather.
I think some batteries are shipped dry, and the dealer adds a mixture of
distilled water and acid drawn from a bulk container. Suppose the
dealer used a mixture 30% too weak, perhaps for longer hot-weather life
or because he didn't have enough acid or because he wasn't good at
measuring. I wonder if that could cause the effect I see.
If the battery has sulfation too hard for the charger to break down, I
guess that, too, could keep the battery from charging fully.
all batteries today are wet charge, time in transit before sales are
short and warranties long
there are definetely differences, batterys for hot place like phoenix
and cold places like canada,
final test is capacity checked by load test.,
Then I wouldn't worry too much. Especially if they are not there
much, now is no time to buy a new battery. It depends on their
personalities and how much money they have. I at least would rather
have a crummy battery and buy a new one only when i was home, using it
every day or two, and actually having trouble starting.
Between the battery cable and the positive post? Certainly possible.
Clean it off with baking soda and water. Once I was in a hurry,
taking a friend to catch his train back to NYC. The car stalled at a
red light something was so bad. I touched the battery posts and one
was burning hot. That's not the powerful post, it's the bad
connection. Put on a glove and I just twisted the cable back and
forth until I got a better connection. After I dropped my friend at
the train station, I took the cable off and cleaned it and the post
with a two-endded battery brush. The connection was so bad, I
couldn't even chargethe battery from the car. (I had been having a bit
of trouble but didn't identify it until on the way to the train
OK. Well 12.3 is's low.
That's strange. You probably blew a fuse. Even some cheap ones have a
You can also replace the resistor if you burned out one of those. If
you can't determine what the resistance shoucl be, often there is
apattern, 2 ohms 20, 200, 2k, 20K, 200k, 2Meg. Or maybe 5.1 etc.
Plus maybe you can find the schematic.
Maybe. It might even have what's it called, that lets the current go
ahrough when the voltage is high enough.
Absolutely Delco advertised for decades that its batteries were
dry-charged, shipped without acid. I think that means they don't
discharge or age in any way when they sit on the shelf in the
warehouse or the store. Maybe they don't do that anymore, but the
motorcycle I bought 2 years ago was like that. It came with a plastic
bag/box of acid for me to add.
Could that actually happen? I always thought the acid was pre-mixed.
It certainly was with the motorcycle battery I bought. I am opposed
to shipping water around (like the pre-mixed windshield washer fluid)
but no6 in this case.
Slow charging, with a 1-amp charger, works best, but takes over 24
hours to charge a fully discharged battery. Now that I have a job,
I'm happy to use my 10 amp max charger, which puts enough in to start
the car after 10 minutes. After the car started, I used to then keep
the heater fan on high (which uses a lot more current than headlights
do, and is actually sufficient to lower the charging rate) while I
drove, so that the battery would charge more slowly. Now that the
stupid new cars don't even have ammeters, and the thrill of installing
one only lasted me through one car, I don't even bother. It doesn't
really seem to have shortened my battery life. I still get 5 years,
and I had never been able to get more than that anyhow.
I opened the meter. It's about 40mm of wire, about 12 gage, between the
10A and Common terminals. No sign that it has been hot. On meters I've
damaged, the only visible sign was discoloration of the wire, but they
would no longer give consistent amp readings.
It's a cheap meter. I've often had to use contact cleaner to get
continuity at the input jacks. My theory is that due to invisible
corrosion, the contact patch between the test-lead plug and the jack was
so small that when the battery surge hit, it immediately overheated,
breaking contact and protecting the meter. What luck! Cheap stuff
I have another theory now. Whenever you start an engine with a battery
that's not fully charged, you may pop sulfate off the plates. Batteries
have room at the bottom where it can settle without causing electrical
leakage between plates. The sulfate that pops off is lead and acid that
can't be recovered by charging.
I'll bet that battery has been used countless times to start when not
well charged. I'll bet sulfate at the bottom of the battery accounts
for my inability to charge it above 12.3V. (About 60%?)
That is what is known as a "shorted" cell. And it is not sulphate,
necessarily. It is "active material" which is spongy lead and lead
oxide.. When a battery is dead, both plates are basically lead
sulphate (pbS04) and the electrolyte is basically water. Fully charged
the electrolyte absorbs the sulphate, becoming H2S04 leaving one plate
pb and the other pb02.
Poly-fuses are getting pretty cheap these days and are used for a lot
of those applications. It's like a conductive wax thet melts when it
gets hot - and doesn't conduct when melted, but when it cools it
reforms and conducts again.
That is NOT the exact explanation of how it works. Note I said it is
LIKE - so don't bother flamong me if you happen to be an electronics
If you are looking for the smoking gun, you have found it. The battery
has not been getting a good charge for who knows how long. The
battery, left in a partially discharged state for even a few weeks
would have sulfated. That battery may still take a charge, and appear
okay, but it has lost CAPACITY. The somewhat low voltage measurements
after charging indicate exactly that.
Thanks, it looks like a gold mine.
I see you can expect 1000 starts if your battery is typically at 60%
charge and 13,000 starts if it stays at 100%. That's why I made a panel
meter to alert me when my battery needs topping off.
I'll see if the site leads me to a chemical explanation of why voltage
works as an indicator of the state of charge.
That's simple - the electrical potential difference between dislike
materials. Lead to lead oxide is 2.15 volts, more or less. Between
lead sulphate and lead sulphate is 0 volts. The percentage
concentration of lead sulphate difference between the plates indicates
the level of charge and the potential difference between the plates.
Not normally. Normally the water evaporates, especially if there is
over charging, and the remedy is to add distilled water until you see
the miniscus, the place where the water level rises above the
rectangular area and reaches the 1" round tube that extends down from
the battery cap.
"Maintenance Free" batteries are supposed to be even less likely to
lose water, but I'm sure they still can.
Do you have reason to think electrolyte has been spilled out, then
replaced with only water?
How old is the battery and how long the guarantee (which is their best
prediction of product-life.)
Maintenance Free batteries still gas, but at a much lower rate. Most of them
will benefit from an electrolyte level check once a year, as most
"maintenence free" batteries still have cell covers that you can take off.
The manufacturer considers them maintenance free because they usually
outlast most of the warranty without needing water added to them. I check
mine once a year, and they are usually just a little low and only need a
small amount of water.
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