Battery charge tests - running a battery to 0 frequently - checking re-charge times

No.

This is charging the battery, not starting the car. When the battery is sufficiently charged, the battery is connected back to the car, and you try to start it.

Second.

To increase the amps going to the battery, you have to increase the voltage given by the charger. There is no other way. Of course, the transformer and rectifier must be able to maintain the voltage at the current that results.

Stop going round what I said. It is exactly what I said, a lead-acid charger that provides a *brutal voltage* to the battery to charge it very fast.

Maybe you don't use this method over in your country. Maybe they decided it is not worth it, because it destroys batteries and cars if misused. Even if not.

That is untrue. If anything increasing the voltage decreases the current. But the reality is that the voltage on battery chargers is regulated so it does not exceed the maximum safe voltage. For charging lead-acid batteries you'd be hard-pressed to find any high-current charger that goes over 15 volts for a 12 volt battery. The "boost" setting increases the current so the car can be started from the charger, which isn't possible from a charger that is supplying only 2 amps or 10 amps (the two common settings on small chargers).

Sorry, but what you have stated makes no sense, including your belief that the only way to increase the current to the battery can only be achieved by increasing the voltage. Constant voltage/constant current (CVCC) is the best way to charge lead-acid batteries, CV is the second-best way.

It is not used in any country.

yes.

the above description is correct.

some people do disconnect the battery, usually because it's easier to charge it indoors where there are mains outlets, however, that's optional and has nothing to do with what you describe.

there is no first, let alone second. stop digging.

nope. that is completely wrong.

so fast that the battery is destroyed in the process, possibly more if it explodes.

lead acid batteries do not care what country they're in.

charging is based on electrical theory, not geography.

yep, it's completely wrong.

that is not the reality.

lead acid battery chargers regulate the *current*, at least for the initial bulk charge phase.

actually, it's very common to go above 15v as part of a restoration cycle (see link below).

small chargers are generally 1-4 amps. the smallest ones are 1/2a for trickle/maintenance charging.

the best way is multistage, initially constant current (bulk), followed by constant voltage (absorption), and finally with a trickle charge to keep it topped off (float).

one example:

correct.

Most of those old-school big honking garage chargers are not regulated at all. Just a big honking multi-tap transformer and a big honking rectifier on a big honking heat sink.

Small consumer chargers and float chargers can be regulated.

Nope. Applying momentary high voltage to a lead-acid battery is one way to break up the layer of lead sulfide that has coated the plates because the battery sat around too long in a discharged state. Momentarily "zapping" the battery does a tolerable job of breaking off the lead sulfide. However, if donw too much or too often, such as trying to charge the battery at excessive voltages and currents, the lead sulfide will fall to the bottom of the plate frame and eventually produce a short between plates.

High voltage or current charging can also cause problems is the 6 cells of the typical lead acid battery are not equalized. Presumably, if such a "brutal" overcharge is necessary, it's a fair assumption that at least one of the cells is at a very low voltage point and possibly shorted. I've managed to boil off the electrolyte and produce hydrogen gas doing that when I was young and stupid.

On Wed, 11 May 2022 17:38:16 -0700, Jeff Liebermann snipped-for-privacy@cruzio.com wrote: (...)

A bit more.

Most of todays "lead acid" batteries are really lead calcium batteries. They're mostly the same but with some subtle differences: "Difference Between Lead Acid and Calcium Batteries"

There are also differences between "gel cells" and AGM batteries. Most of today VRLA batteries are AGM batteries: "What is the Difference Between AGM and GEL Batteries"

When following advice on charging and discharging a battery, make sure that the advice applies to the specific type of battery, and not something else.

That's the theory anyway.

There are a bunch of chargers out there that will zap the battery with high-voltage/low-current pulses in an effort remove some sulfation. There's little evidence that this does much of anything.

I experimented with this with an AGM battery out of my vehicle that was not holding a charge. I repeatedly measured the capacity using a 25A load to discharge the battery, then charged it using the "reconditioning feature." The RC (Reserve Capacity) went from 30 minutes to 54 minutes (after many cycles), but that’s still less than half of the 118 minutes or so RC for a new D23 battery. Also, it’s possible that just the repeated deep-discharge/recharge cycles would have achieved the same increase in reserve capacity without the pulse mode being activated. See

for the setup.

Since it was an AGM battery, and sealed, I could not open it up to do this procedure

which, as the text states: "With the plates "de-sulfated" to some degree, they will re-acquire some percentage of their lost storage capacity. It's not a total cure-all, but it can indeed give some life extension to old lead acid batteries." If you recall "VX-6" sold by places like JC Whitney, it was just magnesium sulfate, but the procedure described in the link would have better success than just adding magnesium sulfate. It's a lot of work, and you also need to buy some battery electrolyte to do the procedure properly.

I didn't mention anything about whether "zapping" worked. I was just trying to distinguish between *MOMENTARY* zapping and applying a

*brutal voltage* to the battery. Momentary might work, but continuous overcharging is guaranteed to do something disgusting. In my case, I have two white formica covered lab benches, both of which have tan colored acid burns from where the blew the side out of the battery and hot acid leaked out.

Here's a guaranteed to work method of raising a battery from the dead: "Brilliant technique of lead acid battery restoration"

(11:22) "Amazing Restoration Technique of an Old Lead Acid Battery" (10:49) "Dead Old Battery Restoration - How To Repair Battery" (19:15) "Amazing Technique of Making Lead Acid Battery Plates & Restoring a Dead Battery" (14:34) The last URL has some contact info:

Those vids are great. Proves the old adage that where there's a will there's a way.

Thanks. I listed only a small number of those claiming to repair, restore, rejuvenate or resurrect batteries. Seems to be a popular occupation in 3rd world countries. Most of the videos seems to be from Pakistan, India, Sri Lanka and the USA. More:

What most videos don't show are any clues as to:

1. How to dispose of the old sulfuric acid.
2. How do deal with the lead sulfide residue, old separators, lead oxide slag, etc.
3. Testing the seals. Hot melt glue isn't very strong and will eventually leak.
4. Shock mounting the internal cells so that the vehicle vibration doesn't shake the cells excessively.
5. Safety equipment and procedures.

When I was young and stupid, I rebuilt a few batteries in a similar manner. Some worked for a few months. One exploded from a hydrogen explosion. Most of them leaked electrolyte because I was using tar as a sealant. I recommend that everyone interested try rebuilding one battery. That's one and no more. I suspect that the effort necessary to do it correctly, and the generally mediocre results, will discourage any further attempts.

I have zero experience with hot melt glue on batteries, and my comment isn't about using hot glue in this way, but my experience with hot glue is that most of the time, hot glue failure is due to improper heating. What I do is to preheat the surface to which the glue is to be applied with a heat gun (assuming the material can handle the heat). It takes much longer for the glue to set, but I've found the glue is *much* stronger and its adhesion far better when it it's allowed to get to a much thinner liquid than the thicker goop which is what generally comes out of a cheap or hobby type hot glue gun. Even if the glue gun does a good job getting the glue hot enough, too often the surface to be bonded acts like a heatsink and cools the glue before the pieces can be assembled. Preheating the surface really helps to get the glue thin.

Well, it was not "momentary", the thing was connected for something like a quarter an hour.

I'm sure that the charger had a rate limiter, though.

The problem was that the "mechanic" was not sufficiently familiar with the thing. She should have called one of the proper mechanics instead of trying to do it herself, but being close to closing hour they were probably leaving the premises at that time. I was there to pay and collect the car after routine servicing at the end of their day.

They would have known that to use the fast charging mode the battery has to be removed from the car, or the high voltage applied destroys the electronics - which did happen, but months later. An slow fault. And long after that I chanced to read documentation for a similar charger, and indeed they said this.

If that were the case, they would have noticed the situation earlier and installed a new battery on the spot. I was having the car serviced for "everything" that the book said had to be done periodically. Apparently they "tested" the battery, and they discharged it too much. Bad on them, too.

The idea of this quick charge was so that I could leave and get a new battery promptly - which I did. Just not from them.

Well, you know the approximate voltage. Instead of about 14V, the charger was delivering about 20V. You also know the current that was being drawn, which should appear on the ammeter on the charger. My guess would be 10 to 30 amps. Total power would be in the range of

200 to 600 watts. Now, where did this power go? It wasn't dissipated inside the charger in some kind of rate limiter (also known as a regulator) because it was measured outside the charger with the battery attached. Therefore, the battery had to deal with 200 to 600 watts, which is could only convert to heat. I'll call it 400 watt hours to make the arithmetic easier. The battery was charged for 1/4 of an hour, so that's 100 watt-hours or 0.36MJ (Mega-Joules). That's about what it takes to boil a liter of water.

If she used an automotive battery charger that was similar to the monster charger I used when working at an auto dealer, it has two general settings. The lowest charge rates are properly regulated and the charger will do its best not to blow anything up. The other is the "start" position, where the regulator is bypassed, and the full DC power available is applied to the battery. This is used to start a car when there is no spare starter battery available. The switch is spring loaded to underscore that it should be used momentarily, not continuously.

Some examples. Sorry about the focus problem:

If you look at the labels, these will show 10/2/55 maps. The 55 is the "start" position. Incidentally, all these died when left to charge batteries at a radio site. The regulator failed by shorting, causing the battery to boil off the electrolyte. I took the photo just before hauling all of them to the dump for recycling as eWaste.

Well. Haste usually creates waste. So, what are you going to do to prevent something similar from happening again? I suggest beginning with understanding how batteries and chargers operate.

Good point. 20V on the electrical system of a car is not a good idea. I think 15.5V is the official maximum, but I suspect they're designed to handle momentary overloads.

Older automobile electrical system testers used a carbon pile load. Basically, a big resistor. Modern testers use an active load. Both get rather hot when testing a battery. They usually include a spring loaded "test" switch to prevent leaving it on and setting fire to the tester. A good battery will usually survive, while the shop burns to the ground. Notice the spring return toggle switch:

Sigh. Notice that the name of my domain is, LearnByDestroying.com. One doesn't really understand how things work until after they've destroyed and fixed it.

they did, except that those are now obsolete.

nope. modern testers do not get warm, let alone hot.

they perform an instantaneous check which measures cold cranking amps (cca), internal resistance, health (soh), state of charge (soc) and more.

there's no need to destroy things to learn, although it's easy to destroy stuff without learning anything.

then it wasn't 'brutal voltage'. if it was, the battery would have been destroyed long before that.

as you've been told by numerous people, a fast charger is high

*current*, not high voltage, and stops when the voltage reaches a threshold, about 14.4v, depending on which type of battery it is (flooded, agm, gel, etc.).

it did, to limit the *current*.

that describes negligence, which means you have/had the makings of a lawsuit.

the battery does not need to be removed for fast charging, although it can be if its more convenient to do so, such as a lack of mains outlets near the vehicle (e.g., street parking).

if the failure occurred months later, then it wasn't anything they did.

damage due to high voltage would have been immediate, certainly not 'months later'.

it sounds like there were other electrical issues in the vehicle, which would have happened anyway.

if it's the charger you previously linked, that was high *current*.

we're still waiting for *any* link to a 12v car battery charger that supplies 20-30 volts or documentation of why that would be beneficial and not destroy anything.

unless you saw what tests they did and what the results were, there's no way to be sure whether the battery was weak (likely), electrical issues in the vehicle (also likely, given your description of a delayed failure) or if they were lying (possible, but nowhere near as common as people think).

quick charge is high *current*.

it is *not* high voltage.

The mechanic who works on my 2001 Subaru has one with a carbon pile load. I know because I've repaired it a few times. Several of the auto shops that I frequent also have ancient chargers. Sorry to report, but the old stuff doesn't just disappear.

Yep. I totally forgot about ESR battery testers. I use an ESR meter to testing batteries. However, it was made for testing capacitors, not batteries. Thanks for the correction.

I also have a battery discharge tester:

The graphs it produces are far better than anything produced on a typical ESR tester. For example: I don't have the optional large heat sink and load necessary to test automobile batteries. However, it does well for testing and matching LiIon cells:

Guilty as charged. I'm 74 years old and officially retired. I borrow one of these when I need one.

Incidentally, someone possibly in this newsgroup, mentioned that none of my test equipment was newer than about 1985. That's really old school:

I wouldn't mind having the latest and greatest, but if the old stuff works, it's good enough.

True. However, the cost of destroying something tends to reinforce the learning experience. Incidentally, the slogan came from my college days, where the school motto was "Learn by Doing".

they might not disappear, but it does mean that those mechanics do not have modern tools. there's also old-school think that's resistant (no pun intended) to change.

In the olden days they used a high-wattage/low-ohm resistor, like 0.5 ohms at 300 watts to cause the battery to put out about 25 amps (though as the voltage fell the current fell slightly). You time how long the battery takes to fall to 10.5 volts and then you have the reserve capacity. The resistor gets very hot of course.

A more accurate way to measure RC is to keep the load at 25 amps. You can design an active load using multiple MOSFETs. Of course those get hot as well, and you need to heat sink them well and distribute the load between multiple devices.

For all intents and purposes, a high-wattage resistor is sufficient for testing the reserve capacity of a lead-acid battery. DC load and AC conductance tests only take a few seconds but they don't give any indication of reserve capacity. There is little, if any, correlation between the internal resistance of a battery and reserve capacity.