From Newsgroup: uk.d-i-y

I'm having trouble with the Eneloop/Panasonic and Fujitsu cells that I use
in the electric toothbrushes.
For a while I was charging them on 150mA but it takes a long time for 12 + other cells (done in batches), so started using the default of 350mA.
Now they'll run the brush but slowly and little torque.

The two brushes are alternated so that they can be lubed a bit and they've
been running well. Tried two ordinary Eneloops and ran OK.

Managed, over several days, to get two cells down to about 1.15V, slow
charge, lot better but not quite there. Both bushes are the sam.

I need some way of getting the cells down to about 1.1V that's simple and
not too fast.
--
Peter.
The gods will stay away
whilst religions hold sway
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From Newsgroup: uk.d-i-y

On 10/10/2025 22:15, PeterC wrote:

I need some way of getting the cells down to about 1.1V that's simple and
not too fast.

Why?
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From Newsgroup: uk.d-i-y

PeterC <giraffenos.pam@homecall.co.uk> wrote:

I'm having trouble with the Eneloop/Panasonic and Fujitsu cells that I use
in the electric toothbrushes.
For a while I was charging them on 150mA but it takes a long time for 12 + other cells (done in batches), so started using the default of 350mA.
Now they'll run the brush but slowly and little torque.

The two brushes are alternated so that they can be lubed a bit and they've been running well. Tried two ordinary Eneloops and ran OK.

Managed, over several days, to get two cells down to about 1.15V, slow charge, lot better but not quite there. Both bushes are the sam.

I need some way of getting the cells down to about 1.1V that's simple and
not too fast.

Stack up Schottky diodes until their combined forward voltages are about
1.1V. Then put in a series resistor to limit the current to some maximum
based on the starting voltage of the cell (and the power dissipation rating
of the diodes).

Although it might be worth investing in a smart charger that can charge and discharge cells at different currents while measuring their capacity.

Theo
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From Newsgroup: uk.d-i-y

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time for 12 + other cells (done in batches), so started using the default of 350mA.

Are you saying that you're charging these in parallel?

I can only recommend getting a half decent charger that detects the end
point, not just a timer variety of charger.
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From Newsgroup: uk.d-i-y

On Fri, 10/10/2025 5:15 PM, PeterC wrote:

I'm having trouble with the Eneloop/Panasonic and Fujitsu cells that I use
in the electric toothbrushes.
For a while I was charging them on 150mA but it takes a long time for 12 + other cells (done in batches), so started using the default of 350mA.
Now they'll run the brush but slowly and little torque.

The two brushes are alternated so that they can be lubed a bit and they've been running well. Tried two ordinary Eneloops and ran OK.

Managed, over several days, to get two cells down to about 1.15V, slow charge, lot better but not quite there. Both bushes are the sam.

I need some way of getting the cells down to about 1.1V that's simple and
not too fast.

Build yourself a push-pull regulator. The linear regulator ADR510, could discharge at 10mA on its own. Amplified with a ua741, that raises
the drive level to 25mA or so. This OpAmp (DIP package, 8 legs),
can sink or source 80mA. The OpAmp is a "rail-to-rail" design,
well not really, but close enough to that property, for this
project to work. There are a few OpAmps that swing right down to
zero volts (using a negative bias generator internally).

https://www.st.com/resource/en/datasheet/ts921.pdf 80ma

VCC=3V VOH=2.63V VOL=0.18V # Rail to Rail swing, 1V output possible VCC=5V VOH=4.4V VOL=0.30V

Eneloop 1.45V off the charger 4.7 ohms or 5.6 ohms to a 1V discharge terminal
1.27V rough median while discharging (57mA)

This is a 1.000V reference. ADR510ARTZ. SOT23 (eye sight test!)

https://www.analog.com/en/products/adr510.html

Amplify the voltage reference with a voltage follower OpAmp (8 pin dip) amplifier config.

+-----------------+ Output resistor to avoid
| | more than 80mA, assumes battery
| VCC | didn't come off charger, seconds ago :-)
| | |
| 7 | |
VCC | +--------+ |
| +---- | 4.7 ohms
R1 33K 2 6 |
| ---+----- R2 -------- Eneloop
+--------------- TS921 |
1 | 3 Voltage |
ADR510 +--------+ Follower GND
2 | 4 | OpAmp
| | Configuration
GND GND

If you want less than 80mA, make R2 have a higher resistance value.
R1 isn't too critical, and you could use 10K there if you wanted.

Vdiff^2
----- = Pdiss of Resistor R2, 1/4 watt resistor is fine for the 4.7 ohm resistor
R2

The purpose of this circuit, is not just discharge. You can leave
this on the battery all day long if you like, as the discharger
will not allow the battery to go below 1.0V . Regular discharge
circuits (that resistor that was burning your hand), they could
drag the battery below the knee you were trying to hit. With a
push pull regulator, that can't happen.

It still approaches the desired voltage asymptotically. If the
amp had a good quality current limit behavior, you could remove R2
entirely, safe in the knowledge more than 80mA would not flow.
The reason I put R2 in there, is to "avoid surprises". With R2
gone, it gets to 1.0V a lot faster. As the Vdiff gets smaller
and smaller, the discharger becomes less and less effective due
to R2 being there. The discharger could "slap the battery silly"
... if it was allowed to run using its internal current limit to
fix the behavior.

Paul
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From Newsgroup: uk.d-i-y

On Fri, 10 Oct 2025 22:30:53 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

I need some way of getting the cells down to about 1.1V that's simple and
not too fast.

Why?

So that I can recharge them slowly.
--
Peter.
The gods will stay away
whilst religions hold sway
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time for 12 + >> other cells (done in batches), so started using the default of 350mA.

Are you saying that you're charging these in parallel?

I can only recommend getting a half decent charger that detects the end point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4
separate channels that can be adjusted individually.
--
Peter.
The gods will stay away
whilst religions hold sway
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 11/10/2025 17:54, PeterC wrote:

On Fri, 10 Oct 2025 22:30:53 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

I need some way of getting the cells down to about 1.1V that's simple and >>> not too fast.

Why?

So that I can recharge them slowly.

How will that help to "recharge them slowly"?
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From Newsgroup: uk.d-i-y

On 11/10/2025 17:56, PeterC wrote:

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time for 12 + >>> other cells (done in batches), so started using the default of 350mA.

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

I can only recommend getting a half decent charger that detects the end
point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4 separate channels that can be adjusted individually.

Or provide details of the charger?
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Fredxx wrote:

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

Didn't he say the charger had 4 individual bays?

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From Newsgroup: uk.d-i-y

On 12/10/2025 07:55, Andy Burns wrote:

Fredxx wrote:

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

Didn't he say the charger had 4 individual bays?

A re-read does say that and I now understand what he's trying to say.

It does seems that at 350mA the end point is being detected early.
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From Newsgroup: uk.d-i-y

On 17:56 11 Oct 2025, PeterC said:

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time
for 12 + other cells (done in batches), so started using the
default of 350mA.

Are you saying that you're charging these in parallel?

I can only recommend getting a half decent charger that detects the
end point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4 separate channels that can be adjusted individually.

Presumably the conditioning the charger is doing is to run the cell down
(to a voltage like the 1.1V you mentioned) and then charging up.

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From Newsgroup: uk.d-i-y

On 12:19 12 Oct 2025, Fredxx said:

On 12/10/2025 07:55, Andy Burns wrote:

Fredxx wrote:

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

Didn't he say the charger had 4 individual bays?

A re-read does say that and I now understand what he's trying to say.

It does seems that at 350mA the end point is being detected early.

AA Eneloops hold 2000 mAh and he's charging at a slow rate (350mA is
approx 0.2C). Maybe the charger is detecting some trivial voltage
fluctuation long before the full charge point. For this reason I prefer
0.5C (even C) for AA cells.

However he's been charging his cells for some time before this problem.
So perhaps the cells are exhausted, as Eneloops tend not to have a
memory effect.
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From Newsgroup: uk.d-i-y

On Sat, 11 Oct 2025 20:24:58 +0100, in uk.d-i-y you wrote:

On 11/10/2025 17:56, PeterC wrote:

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time for 12 + >>>> other cells (done in batches), so started using the default of 350mA.

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

4 separate channels. It'll take, e.g., Eneloop at 150mA, Fujitsu at 375mA
and a lithium in another.

I can only recommend getting a half decent charger that detects the end
point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4
separate channels that can be adjusted individually.

Or provide details of the charger?

Nitecore Digicharger, as recommended in this group when I asked.
--
Peter.
The gods will stay away
whilst religions hold sway

--
Peter.
The gods will stay away
whilst religions hold sway
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sun, 12 Oct 2025 14:51:09 +0100, Pamela wrote:

On 12:19 12 Oct 2025, Fredxx said:

On 12/10/2025 07:55, Andy Burns wrote:

Fredxx wrote:

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

Didn't he say the charger had 4 individual bays?

A re-read does say that and I now understand what he's trying to say.

It does seems that at 350mA the end point is being detected early.

AA Eneloops hold 2000 mAh and he's charging at a slow rate (350mA is
approx 0.2C). Maybe the charger is detecting some trivial voltage
fluctuation long before the full charge point. For this reason I prefer
0.5C (even C) for AA cells.

However he's been charging his cells for some time before this problem.
So perhaps the cells are exhausted, as Eneloops tend not to have a
memory effect.

They are Pros - 2.4Ah - good for 'up to' 500 charges. Mine, allthough
several years old, get recharged every 18 weeks, so haven' been charged many times (<3x/year.

I was using 150mA then got impatient and went to 375mA; that's when the
trouble started.
--
Peter.
The gods will stay away
whilst religions hold sway
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 12/10/2025 17:50, PeterC wrote:

On Sat, 11 Oct 2025 20:24:58 +0100, in uk.d-i-y you wrote:

On 11/10/2025 17:56, PeterC wrote:

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time for 12 +
other cells (done in batches), so started using the default of 350mA. >>>>

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

4 separate channels. It'll take, e.g., Eneloop at 150mA, Fujitsu at 375mA
and a lithium in another.

I can only recommend getting a half decent charger that detects the end >>>> point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4
separate channels that can be adjusted individually.

Or provide details of the charger?

Nitecore Digicharger, as recommended in this group when I asked.

There are 6 models that take 4 batteries. I've looked at a couple and
they charge at much higher currents than 150mA.
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 17:56 11 Oct 2025, PeterC said:

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time
for 12 + other cells (done in batches), so started using the
default of 350mA.

Are you saying that you're charging these in parallel?

I can only recommend getting a half decent charger that detects the
end point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4 separate channels that can be adjusted individually.

I believe the Nitecore Digicharger (which you mentioned elsewhere in this thread) doesn't condition batteries first.

As an test, I wonder how complete cells get charged if you charged at 750
mA. (Use only 2 cells in slots 1 and 3.)

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From Newsgroup: uk.d-i-y

On Mon, 13 Oct 2025 16:23:37 +0100, Pamela wrote:

On 17:56 11 Oct 2025, PeterC said:

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time
for 12 + other cells (done in batches), so started using the
default of 350mA.

Are you saying that you're charging these in parallel?

I can only recommend getting a half decent charger that detects the
end point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4
separate channels that can be adjusted individually.

I believe the Nitecore Digicharger (which you mentioned elsewhere in this thread) doesn't condition batteries first.

As an test, I wonder how complete cells get charged if you charged at 750 mA. (Use only 2 cells in slots 1 and 3.)

that is correct. It will go to 750mA for a start then drop back to 350mA. It will do that on all 4 slots - as I have said several time the slots are completely separate.
--
Peter.
The gods will stay away
whilst religions hold sway
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sun, 12 Oct 2025 19:02:11 +0100, Fredxx wrote:

On 12/10/2025 17:50, PeterC wrote:

On Sat, 11 Oct 2025 20:24:58 +0100, in uk.d-i-y you wrote:

On 11/10/2025 17:56, PeterC wrote:

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time for 12 +
other cells (done in batches), so started using the default of 350mA. >>>>>

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

4 separate channels. It'll take, e.g., Eneloop at 150mA, Fujitsu at 375mA
and a lithium in another.

I can only recommend getting a half decent charger that detects the end >>>>> point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4
separate channels that can be adjusted individually.

Or provide details of the charger?

Nitecore Digicharger, as recommended in this group when I asked.

There are 6 models that take 4 batteries. I've looked at a couple and
they charge at much higher currents than 150mA.

When it's 350mA, pressing and holding the lower button for about 1S will
change it to 150mA. (Holding in the top button for a couple of seconds turns off the backlight).
--
Peter.
The gods will stay away
whilst religions hold sway
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On Sun, 12 Oct 2025 19:02:11 +0100, Fredxx wrote:

On 12/10/2025 17:50, PeterC wrote:

On Sat, 11 Oct 2025 20:24:58 +0100, in uk.d-i-y you wrote:

On 11/10/2025 17:56, PeterC wrote:

On Fri, 10 Oct 2025 22:54:52 +0100, Fredxx wrote:

On 10/10/2025 22:15, PeterC wrote:

<snip>

For a while I was charging them on 150mA but it takes a long time for 12 +
other cells (done in batches), so started using the default of 350mA. >>>>>

Are you saying that you're charging these in parallel?

It might be helpful to answer this question.

4 separate channels. It'll take, e.g., Eneloop at 150mA, Fujitsu at 375mA
and a lithium in another.

I can only recommend getting a half decent charger that detects the end >>>>> point, not just a timer variety of charger.

It does that. If necessary it conditions the cells first. There are 4
separate channels that can be adjusted individually.

Or provide details of the charger?

Nitecore Digicharger, as recommended in this group when I asked.

There are 6 models that take 4 batteries. I've looked at a couple and
they charge at much higher currents than 150mA.

OK, sort of solved the discharching.
I've a couple of puck lights that take 3 AA cells. One is at the side of the ped and the other in the bathroom. They save using clacky pull-switches
during the night. Eneloops in, leave bathroom one on all night, bedroom on
all day. Couple of days or so they go to around 1V. Into charger, let them
run at 350 mA for a couple of minutes then down to 150mA. 17 hours they're charged (no trickle current) and are at 1.48V.
Next is to try them in a brush.
--
Peter.
The gods will stay away
whilst religions hold sway
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