Odd battery charging voltage

[Cursitor Doom]

Hi all,

I came across a novel situation yesterday. I yanked this
in-need-of-a-charge battery out of a 3 litre diesel BMW to top it up
on my bench charger. It's one of those with the status window:
'replace', 'charge' or 'OK' and that window was black/blank,
indicating a charge was in order. Things seemed to be proceeding
normally according to the charger current meter (started off at ~5A
and gradually came down over a few hours) but when I checked the
terminal voltage (with the charger attached and on) I got 15V which
seems an awful lot for a trickle charge. The status window remained
unchanged. I'm not happy about the 15V bit. It came down to a more
normal 12.4V after being turned off for a while, though.
Does that 15V indicate some issue with the battery?

[Fredxx]

Post by Cursitor Doom
Hi all,
I came across a novel situation yesterday. I yanked this
in-need-of-a-charge battery out of a 3 litre diesel BMW to top it up
'replace', 'charge' or 'OK' and that window was black/blank,
indicating a charge was in order. Things seemed to be proceeding
normally according to the charger current meter (started off at ~5A
and gradually came down over a few hours) but when I checked the
terminal voltage (with the charger attached and on) I got 15V

Once fully charged a lead acid is effectively o/c and terminal voltage
dependent on the charger and the voltage across the plates from
electrolysing the electrolyte. Since you're using electrolyte it's not a
good position to be in.

Most old trickle chargers could easily get to 15V and nothing to really
worry about.

It does indicate a full charge, or as full as it's going to get.

Post by Cursitor Doom
which
seems an awful lot for a trickle charge. The status window remained
unchanged. I'm not happy about the 15V bit. It came down to a more
normal 12.4V after being turned off for a while, though.
Does that 15V indicate some issue with the battery?

Most indicators rely on the electrolyte on a window, and the reflection
dependent on level only.

I guess it might be possible for the reflection be dependent on the
electrolyte refractive index which no doubt will be sensitive to SG.
Perhaps someone will be along to confirm or say is nonsense?

How confident are you the electrolyte is above the plates?

[Cursitor Doom]

Post by Fredxx

Post by Cursitor Doom
Hi all,
I came across a novel situation yesterday. I yanked this
in-need-of-a-charge battery out of a 3 litre diesel BMW to top it up
'replace', 'charge' or 'OK' and that window was black/blank,
indicating a charge was in order. Things seemed to be proceeding
normally according to the charger current meter (started off at ~5A
and gradually came down over a few hours) but when I checked the
terminal voltage (with the charger attached and on) I got 15V

Once fully charged a lead acid is effectively o/c and terminal voltage
dependent on the charger and the voltage across the plates from
electrolysing the electrolyte. Since you're using electrolyte it's not a
good position to be in.
Most old trickle chargers could easily get to 15V and nothing to really
worry about.

I prefer the 'dumb' chargers. In fact I prefer *everything* I own to
be of the 'dumb' variety. I find with the so-called 'smart' products -
whatever they may be - there's far too much going on under the
surface for my liking and one gets to the point where it's like a
battle between me and the device to get it to do what I want. I've
noticed just about everything described as "smart" seldom is from the
PoV of the customer and that applies to electricity meters, those tiny
cars and motorways as well as more mundane things like battery
chargers and mobile phones.

Post by Fredxx
It does indicate a full charge, or as full as it's going to get.

Post by Cursitor Doom
which
seems an awful lot for a trickle charge. The status window remained
unchanged. I'm not happy about the 15V bit. It came down to a more
normal 12.4V after being turned off for a while, though.
Does that 15V indicate some issue with the battery?

Most indicators rely on the electrolyte on a window, and the reflection
dependent on level only.
I guess it might be possible for the reflection be dependent on the
electrolyte refractive index which no doubt will be sensitive to SG.
Perhaps someone will be along to confirm or say is nonsense?

You're probably right. I'd never thought about it too deeply and just
assumed they use some sort of micro-power LED 'traffic light' system
deep in a tube with lenses to make the dim glow more visible on the
exterior.
I'll check out the electrolyte level. It's supposed to be
maintenance-free but...... best check in case....

Post by Fredxx
How confident are you the electrolyte is above the plates?

[Cursitor Doom]

On Sat, 06 Feb 2021 18:47:19 +0000, Cursitor Doom <***@nowhere.com>
wrote:

I think I need to correct myself here. It's not the "smart" device
itself that's the problem, neither the hardware nor the software or
firmware for that matter. The battle is against the mind of whoever
programmed the damn thing and thought he knew better than the end
user. OK, in very many cases, he probably does. But for those of us
who like total, manual control over systems and are prepared to take
the risk of breaking something if we get it wrong, it's a giant PITA
to contend with.

[Peter Hill]

Post by Cursitor Doom

Post by Fredxx
Most indicators rely on the electrolyte on a window, and the reflection
dependent on level only.
I guess it might be possible for the reflection be dependent on the
electrolyte refractive index which no doubt will be sensitive to SG.
Perhaps someone will be along to confirm or say is nonsense?

You're probably right. I'd never thought about it too deeply and just
assumed they use some sort of micro-power LED 'traffic light' system
deep in a tube with lenses to make the dim glow more visible on the
exterior.
I'll check out the electrolyte level. It's supposed to be
maintenance-free but...... best check in case....

Charge indicator built into battery is just a battery hydrometer. A
float that when the battery is charged will float higher and becomes
visible in the window.

Some have 2 concentric floats. A ball that shows charge and 2nd one that
shows level of electrolyte.

[Dave Plowman (News)]

Post by Peter Hill
Charge indicator built into battery is just a battery hydrometer. A
float that when the battery is charged will float higher and becomes
visible in the window.

Had one in a Delco battery ages ago. Stopped working correctly long before
the battery needed replacing. Seemed to me an excellent way of selling
more batteries.

[Cursitor Doom]

Post by Peter Hill

Post by Cursitor Doom

Post by Fredxx
Most indicators rely on the electrolyte on a window, and the reflection
dependent on level only.
I guess it might be possible for the reflection be dependent on the
electrolyte refractive index which no doubt will be sensitive to SG.
Perhaps someone will be along to confirm or say is nonsense?

You're probably right. I'd never thought about it too deeply and just
assumed they use some sort of micro-power LED 'traffic light' system
deep in a tube with lenses to make the dim glow more visible on the
exterior.
I'll check out the electrolyte level. It's supposed to be
maintenance-free but...... best check in case....

Charge indicator built into battery is just a battery hydrometer. A
float that when the battery is charged will float higher and becomes
visible in the window.
Some have 2 concentric floats. A ball that shows charge and 2nd one that
shows level of electrolyte.

Thanks. It's now become visible once more. Must have got stuck for
some reason deep down in its tube.

[Peter Hill]

Post by Cursitor Doom

Post by Peter Hill

Post by Cursitor Doom

Post by Fredxx
Most indicators rely on the electrolyte on a window, and the reflection
dependent on level only.
I guess it might be possible for the reflection be dependent on the
electrolyte refractive index which no doubt will be sensitive to SG.
Perhaps someone will be along to confirm or say is nonsense?

You're probably right. I'd never thought about it too deeply and just
assumed they use some sort of micro-power LED 'traffic light' system
deep in a tube with lenses to make the dim glow more visible on the
exterior.
I'll check out the electrolyte level. It's supposed to be
maintenance-free but...... best check in case....

Charge indicator built into battery is just a battery hydrometer. A
float that when the battery is charged will float higher and becomes
visible in the window.
Some have 2 concentric floats. A ball that shows charge and 2nd one that
shows level of electrolyte.

Thanks. It's now become visible once more. Must have got stuck for
some reason deep down in its tube.

Yes sometimes it needs vibration of a "go drive" cycle.

[steve robinson]

Post by Cursitor Doom
Hi all,
I came across a novel situation yesterday. I yanked this
in-need-of-a-charge battery out of a 3 litre diesel BMW to top it up
'replace', 'charge' or 'OK' and that window was black/blank,
indicating a charge was in order. Things seemed to be proceeding
normally according to the charger current meter (started off at ~5A
and gradually came down over a few hours) but when I checked the
terminal voltage (with the charger attached and on) I got 15V which
seems an awful lot for a trickle charge. The status window remained
unchanged. I'm not happy about the 15V bit. It came down to a more
normal 12.4V after being turned off for a while, though.
Does that 15V indicate some issue with the battery?

With some of the trickle charger / maintenance chargers its not
unusual for them to output 15 or 16 volts part way through their
cycle, its part of the conditioning cycle it applies to the flat
battery

[Cursitor Doom]

On Sat, 06 Feb 2021 20:54:14 +0000, steve robinson

Post by steve robinson
With some of the trickle charger / maintenance chargers its not
unusual for them to output 15 or 16 volts part way through their
cycle, its part of the conditioning cycle it applies to the flat
battery

I should perhaps have mentioned this is one of the old-style car
battery chargers with no 'brain' at all. Manual selection of 12 or 24V
and high and low charge rates. That's all there is to it.

[newshound]

Post by Cursitor Doom
On Sat, 06 Feb 2021 20:54:14 +0000, steve robinson

Post by steve robinson
With some of the trickle charger / maintenance chargers its not
unusual for them to output 15 or 16 volts part way through their
cycle, its part of the conditioning cycle it applies to the flat
battery

I should perhaps have mentioned this is one of the old-style car
battery chargers with no 'brain' at all. Manual selection of 12 or 24V
and high and low charge rates. That's all there is to it.

Still got a DVM though by the sound of it. My default machine has a
proper moving iron ammeter and no voltage display at all.

[Cursitor Doom]

On Sat, 6 Feb 2021 22:55:35 +0000, newshound

Post by newshound

Post by Cursitor Doom
On Sat, 06 Feb 2021 20:54:14 +0000, steve robinson

Post by steve robinson
With some of the trickle charger / maintenance chargers its not
unusual for them to output 15 or 16 volts part way through their
cycle, its part of the conditioning cycle it applies to the flat
battery

I should perhaps have mentioned this is one of the old-style car
battery chargers with no 'brain' at all. Manual selection of 12 or 24V
and high and low charge rates. That's all there is to it.

Still got a DVM though by the sound of it. My default machine has a
proper moving iron ammeter and no voltage display at all.

No DVM, Newsy. Just the same sort of analogue ammeter as yours. And I
wouldn't have it any other way.