Battery charger voltage

[fxman]

motco said:

I'm afraid it will have an impact. As someone previously said, if the combined internal resistance of your batteries is such that the current drawn exceeds the charger's capacity, only two avenues lie ahead: shut down by overload protection, or voltage depression until the terminal voltage of the load rises. For the output to remain at >=14Vdc regardless of load you'd need a voltage source with unlimited current delivery.

Fair point. Let me modify the rule then:

Voltage measurement across the battery posts when not connected to charger must be lower than after connecting the live charger for the charging to be effective.

Examples:

Battery voltage 12.0v. After connecting charger: 12.2v. Charging is effective.
Battery voltage 12.0v. After connecting charger: 14.7v. Charging is effective.
Battery voltage 12.0v. After connecting charger: 10.0v. Charging is ineffective.
Battery voltage 12.0v. After connecting charger: 12.0v. Charging is ineffective.

[motco]

fxman said:

motco said:

I'm afraid it will have an impact. As someone previously said, if the combined internal resistance of your batteries is such that the current drawn exceeds the charger's capacity, only two avenues lie ahead: shut down by overload protection, or voltage depression until the terminal voltage of the load rises. For the output to remain at >=14Vdc regardless of load you'd need a voltage source with unlimited current delivery.

Fair point. Let me modify the rule then:

Voltage measurement across the battery posts when not connected to charger must be lower than after connecting the live charger for the charging to be effective.

Examples:

Battery voltage 12.0v. After connecting charger: 12.2v. Charging is effective.
Battery voltage 12.0v. After connecting charger: 14.7v. Charging is effective.
Battery voltage 12.0v. After connecting charger: 10.0v. Charging is ineffective.
Battery voltage 12.0v. After connecting charger: 12.0v. Charging is ineffective.

Quite so. But do you know: a) open circuit charger voltage, b)open circuit battery voltage, c)terminal voltage on charge - one battery only. Once connected the charger and battery will show the same voltage, obviously, and that will rise over time providing current is flowing into the battery and the battery is healthy but low on charge.

[fxman]

motco said:

Quite so. But do you know: a) open circuit charger voltage, b)open circuit battery voltage, c)terminal voltage on charge - one battery only. Once connected the charger and battery will show the same voltage, obviously, and that will rise over time providing current is flowing into the battery and the battery is healthy but low on charge.

Well, I am shallow and content with the bare minimum I need to know.

I do know now with 100% certainty that after charging all night a 10v battery and attaining a final voltage of 8v indicates a knackered charger.

[richard sails]

What are the voltages of the batteries BEFORE you connect the charger, if much less than 11V you will probably find it difficult to charge using your intelligent charger. In that case use a dumb charger to get them up to a reasonable state of charge first.

[Dogwatch]

richard sails said:

What are the voltages of the batteries BEFORE you connect the charger, if much less than 11V you will probably find it difficult to charge using your intelligent charger. In that case use a dumb charger to get them up to a reasonable state of charge first.

I've dug out the manual for my Lidle charger (T4X). Says if the detected voltage is below 7.5v, open circuit or reverse polarity it disengaged and goes back to standby to protect itself. So won't deal with completely flat batteries.
Usual output is 14.4 to 14.7v

Apologies for autocorrect

[fxman]

richard sails said:

What are the voltages of the batteries BEFORE you connect the charger, if much less than 11V you will probably find it difficult to charge using your intelligent charger. In that case use a dumb charger to get them up to a reasonable state of charge first.

The technique to trick the rather dumb intelligent chargers is to connect a good battery to the bad. Once the charging starts, or some time after, the good battery can be taken off.

The batteries were 4v. Since the charger sometimes worked, the batteries were taken beyond 10v. Now the charger can reliable charge at 8v, and that's where the batteries ended up.

[AW10]

Before you condemn the charger to an early grave what happens if you connect it to a known good battery?

[fxman]

AW10 said:

Before you condemn the charger to an early grave what happens if you connect it to a known good battery?

Donno. But I can't afford to have my working battery to be at 8v. So I won't even try.

The germans over-engineer their stuff. Hopefully, the cheap chinese made replacement will work better. I should have it in the next couple of days.

Don't worry, you will hear the end of the story. Should be a happy ending unless my luck gets me a DOA charger.

[E-bmw]

TBH it is a case of horses for courses.

If you understand how batteries & chargers work a "dumb" charger is fine & I heave done with them for years & will do for many more.

Having said that, not everyone does as per the whole conversation above.

A "smart" charger will only charge what it thinks will take a charge based on certain logical criteria & so for many they are also fine.

[fxman]

E-bmw said:

TBH it is a case of horses for courses.

If you understand how batteries & chargers work a "dumb" charger is fine & I heave done with them for years & will do for many more.

Having said that, not everyone does as per the whole conversation above.

A "smart" charger will only charge what it thinks will take a charge based on certain logical criteria & so for many they are also fine.

I am sure of 2 things: both the 'smart' charger and the maintenance-free batteries are designed to sell more batteries. The smart charger will tell people their batteries are gone when in fact a non-smart charger could bring them back. The battery sellers couldn't ask for a better profit making tool. For the more aware, even the completely dead batteries could be bought back if there is access to the individual cells. So now they glue the battery shut and tell you they are doing it for your good. But, not really. They'd rather you didn't bring them back.

[AW10]

fxman said:

Donno. But I can't afford to have my working battery to be at 8v. So I won't even try.

Ah, give it a go for 5 minutes with your voltmeter attached.

[GreenV8S]

fxman said:

even the completely dead batteries could be bought back if there is access to the individual cells.

I'm not at all convinced about that. Deep discharging these wet car batteries is very bad for them and will distort the plates, sometimes even to the extent that they form ain internal short. Even if you manage to get all cells to take a charge afterwards, in my experience the battery is never as good afterwards. Being able to put current through an individual cell doesn't address the fact that the cell is stuffed.

[fxman]

AW10 said:

Ah, give it a go for 5 minutes with your voltmeter attached.

I suspect you are trying to do my battery an injury! I am sitting quite comfortably at my computer. You wouldn't want me to move now would you? trust me, or rather trust my gut, it's right.

[fxman]

GreenV8S said:

I'm not at all convinced about that. Deep discharging these wet car batteries is very bad for them and will distort the plates, sometimes even to the extent that they form ain internal short. Even if you manage to get all cells to take a charge afterwards, in my experience the battery is never as good afterwards. Being able to put current through an individual cell doesn't address the fact that the cell is stuffed.

May be true in some cases. Mostly it's not. The prime killer is sulfation. It's is not reversible electrically, but possible chemically. This is why they glue the batteries shut now, to block off the route of salvation..

[AW10]

fxman said:

I suspect you are trying to do my battery an injury! I am sitting quite comfortably at my computer. You wouldn't want me to move now would you? trust me, or rather trust my gut, it's right.

No, my guess is that your charger is fine and that your batteries are https://imgur.com/gallery/ghCzIyf

[fxman]

AW10 said:

No, my guess is that your charger is fine and that your batteries are https://imgur.com/gallery/ghCzIyf

Ok, we'll see in a couple of days with the new charger.

The game plan: revive 2x 063 batteries. One is 2-3 months old that's gone through a single cycle of complete discharge owing to a parasitic draw. The other is 8+ years old with maintainable cells. It sat for 6+ month and completely discharged with one cell completely dead (0v) but revived chemically. Both batteries were 4.x volts.

[fxman]

The chinese charger is in. The difference is immediately apparent. While connected and charging, the measurement across the posts is 12.5v. With the charger not connected, the measurement is 5.5v. These measurements are for the batteries connected in parallel.

People betting on the original charger being good have lost their money. As for whether the batteries are bad or not, I am fairly certain of being able to revive the maintainable old battery back to full health. I am not so sure of the non-maintainable new battery. But, because it is new, there is a reasonable chance of it coming back alive. If not, I'll try destructive disassembly of the cover to see if I can gain access to the cells. If I have cell access, I am back in business.

I am now right off the cheap german crap. I bought various other lidl car gadgets in the past and they have all failed with very little use. I am suspicious of their stuff being "designed" to fail rather than bad manufacturing. From now on, the chinese get my money.

[GreenV8S]

fxman said:

I am now right off the cheap german crap. ... From now on, the chinese get my money.

I expect you'll find the 'cheap German crap' was made in China. And I think you'll find the problems you have are the result of it being cheap, not the country that made it.

[fxman]

GreenV8S said:

I expect you'll find the 'cheap German crap' was made in China. And I think you'll find the problems you have are the result of it being cheap, not the country that made it.

The lidl charger definitely says german at the back. The chinese charger doesn't say anything at all. But one can just tell it's made cheaply and where it came from. I wouldn't hesitate to say the german one is pro-class in terms of quality of impression. But it's crap-class in terms of effectiveness.

Anyway, the non-maintainable new battery appeared to have been revived. Since I don't have a load-tester, I have no way to know for sure. But my gut says it's servicible if I were to put it back in a car.

The 8 year old battery, appears to have 2 weak cells. I'll continue to work on that. I can hear that battery bubbling when connected to the chinese charger.

[fxman]

Ok, here's the end of the story.

The non-maintainable battery was completely revived. Full marks to the dumb chinese charger. It can reach places where "smart" chargers can't go. My friends, it's not cheap that's the deciding factor, but to know.

All the cells in the maintainable battery have been revived to perfection. But, it was a complete failure. Polarity in 2 cells were completely reversed. These cells may have been like that since the beginning. But the idea they could be like that was so alien to me that I was blind to them even if I did see them. The battery now has 4v = 2v + 2v + 2v + 2v - 2v - 2v. Based on my searches, this may be fixable by completely discharging the battery and then recharge.

I am working at my limit now. So I may well dispose of the battery should I become tired of the play. Neither battery is needed for anything. I am doing them purely for fun and to re-validate my battery cell revival method. The re-validation was a success, and I am very confident of keeping the unrelated 14 year old battery in my car going indefinitely until I run out of chemical supplies.

Edited by fxman on Sunday 22 April 12:59