Panasonoc Ni-Cd battery condition and charging circuit

[Hasan2017]

Hi There,
I got a part of vacuam cleaner machine driven by DC charger. May be it was manufactured in 2018.
User might through it away because it was troubling.

9 pcs of P-130SCS 1.2V 1300mAh has joined togeter to get 1.2×9 Vdc.
https://www.digikey.in/product-detail/en/panasonic-bsg/P-130SCS-A06/P162-ND/530492

Basically it was using for drive a 9 v DC motor. Manufacturer recommended to plug it with 9V/300mA charger for use it 8 hrs, may be charging time was for 15 mins.

1. Does it risky to use this battery after a long time?
2.It may damaged?
3. How can I charge it with another way?
4. Take a look the charging and discharing circuit and battery bundle.

Recommend me any safe mode charing topology or particular circuit.
Hope you will help

 

[BradtheRad]

Almost certainly one or more cells are weak (typical reason for the owner to throw it out after a few years). It's easy to leave such appliances charging continually, although it's not great for the batteries.

A weak cell can be pushed into reverse polarity by the good cells.

You ought to test each cell voltage individually. Charge the pack overnight. (15 minutes is not enough time.) Since the cells are 1300 mAH, a reasonable charge rate is 130 mA. Check this with your meter because it's possible the charger is at fault.

See if each cell can hold a charge. You don't absolutely have to separate them all to do this. Peel away plastic to get at the terminals.
If any cell has much lower voltage than the others, you should remove it from the pack.

 

[Hasan2017]

Almost certainly one or more cells are weak (typical reason for the owner to throw it out after a few years). It's easy to leave such appliances charging continually, although it's not great for the batteries.

A weak cell can be pushed into reverse polarity by the good cells.

You ought to test each cell voltage individually. Charge the pack overnight. (15 minutes is not enough time.) Since the cells are 1300 mAH, a reasonable charge rate is 130 mA. Check this with your meter because it's possible the charger is at fault.

See if each cell can hold a charge. You don't absolutely have to separate them all to do this. Peel away plastic to get at the terminals.
If any cell has much lower voltage than the others, you should remove it from the pack.

Thank you for such comments l.
Yes, reverse polarity might kill others. Did you see my posted circuit , its not used for peak voltage detector? If I just charge single one then do you have any circuit in your mind using LM358 or LM317?

 

[Hasan2017]

I have 3 chargers , let me know which one is best. Some has lost their stability.

1. 9 v /800mA ( witten as 6v/300mA
2. 10 v/ 880mA( written as 7.5V/300mA)
3. 12 v/900mA.

For whole battery pack those are not suitable you said.

 

[BradtheRad]

When you charge the battery pack your charger ought to reach a voltage of 1.5 V per cell. 12V is insufficient for 9 cells. You can wire two of your power supplies in series to produce sufficient total voltage, but one or both must be transformer-based.

It's important to limit charging current. The simplest way is to install a series resistor inline.

A problem cell can become faulty by developing very high internal resistance, or very low internal resistance.

If merely one cell becomes high impedance then it prevents the pack from carrying sufficient current. In that case you must disconnect the faulty cell.

Or a cell can become very low impedance like a short circuit. You can charge it forever but it never reads more than 0V. This is the reason you must install a safety resistor to limit charging current.

It's likely you'll find you must break up the pack.

 

[Hasan2017]

When you charge the battery pack your charger ought to reach a voltage of 1.5 V per cell. 12V is insufficient for 9 cells. You can wire two of your power supplies in series to produce sufficient total voltage, but one or both must be transformer-based.

It's important to limit charging current. The simplest way is to install a series resistor inline.

A problem cell can become faulty by developing very high internal resistance, or very low internal resistance.

If merely one cell becomes high impedance then it prevents the pack from carrying sufficient current. In that case you must disconnect the faulty cell.

Or a cell can become very low impedance like a short circuit. You can charge it forever but it never reads more than 0V. This is the reason you must install a safety resistor to limit charging current.

It's likely you'll find you must break up the pack.

Well said.
In previous comment I understand why you want me to apply charging current 130mA because 10% of capacity represents charging current.

Now beside high and low impedance batteries or internal resistance power consumption s I got a idea.

I had another charger for Sayno 1400 twicell which gives 1.2v /550mA and that battery should be 1.2 v , 1100mAh, in this case charging time will be 2 hrs.
If its 1300mAh then charging time will be 2.5 hrs.

Dont you think I could use that charger just for single battery? It wont be a quick charger?

 

[dick_freebird]

If you have time to kill I'd just use a power supply
in current-limited mode at the C/10 charge rate,
charge them one by one looking at cell voltage
and then discharge it hard (like into a 1 ohm
wirewound power resistor) watching the output
voltage again (full charge loaded current, and
how long it takes to drop to an unsuitable level -
like maybe 100mV below initial loaded voltage).

Log each cell and soon it will be evident which
one(s) are strong or weak.

 

[BradtheRad]

another charger for Sayno 1400 twicell which gives 1.2v /550mA and that battery should be 1.2 v , 1100mAh, in this case charging time will be 2 hrs.
If its 1300mAh then charging time will be 2.5 hrs.

Dont you think I could use that charger just for single battery? It wont be a quick charger?

1.2V is not enough voltage to push current into a cell, because it rises to 1.2V after a short time.

You need to apply enough voltage so that the cell goes up a few tenths of a volt higher than that during the charge sessison (say 1.6 to 1.8 V). This requires a power supply of 2 or more volts.

When I take a nicad/NIMH off the charger, its voltage normally reads 1.44V. After a few hours it settles to 1.38 V.

Don't try to quick charge a cell if you're not sure it's healthy. Quick charging heats up a cell which tends to shorten its useful life.
1/2 Ampere heats up a C or sub-C (which looks to be the size of your cells) making it noticeably warm. It's a reason to install a safety resistor.

 

[Hasan2017]

If you have time to kill I'd just use a power supply
in current-limited mode at the C/10 charge rate,
charge them one by one looking at cell voltage
and then discharge it hard (like into a 1 ohm
wirewound power resistor) watching the output
voltage again (full charge loaded current, and
how long it takes to drop to an unsuitable level -
like maybe 100mV below initial loaded voltage).

Log each cell and soon it will be evident which
one(s) are strong or weak.

I got your point but not much clear view on it. You want me to use some current limiting techniques. Take a look this idea

Yes, it is easy to see how fast this battery can discharge. If you add 18 ohm in the emmiter path then the battery will get 100 mA. In put voltage should be 6.5~10 Vdc. I think base current can be calculate for this configuration. Collector current might be goes high so wattage is double than normal one.

Let me know if you think this circuit is useless. Some one said me that 1.2v/550mA charger wont be suitable for Ni-Cd, it is not linear charging rate.

--- Updated Mar 17, 2021 ---

1.2V is not enough voltage to push current into a cell, because it rises to 1.2V after a short time.

You need to apply enough voltage so that the cell goes up a few tenths of a volt higher than that during the charge sessison (say 1.6 to 1.8 V). This requires a power supply of 2 or more volts.

When I take a nicad/NIMH off the charger, its voltage normally reads 1.44V. After a few hours it settles to 1.38 V.

Don't try to quick charge a cell if you're not sure it's healthy. Quick charging heats up a cell which tends to shorten its useful life.
1/2 Ampere heats up a C or sub-C (which looks to be the size of your cells) making it noticeably warm. It's a reason to install a safety resistor.

Nice lesson indeed.
I have not try yet with 1.2v/550mA that was dedicated for 1.2 v sanyo 1400 Twicell batery. Charger company said to use it 2.5 hrs. But somhow sanyo gets charge.

I did see in every charger (not smart phone charger)output can fluctuates more or less 10% its normal. Because system sets stable after few time.

 

[BradtheRad]

dedicated for 1.2 v sanyo 1400 Twicell batery. Charger company said to use it 2.5 hrs. But somhow sanyo gets charge.

That is possible if there is no smoothing capacitor at the output. Evidently the raw waveform peaks higher than 1.2 V. In that case you can use it to charge one nicad/nimh.

A 1.2VAC sine wave has peaks of 1.7 V. (Assuming the unit contains a transformer.) When rectified it becomes pulsing DC with peaks around 1.6 V. A meter reads its average voltage which is 1.1 or 1.2.

To take a correct measurement requires an oscilloscope. (Although there are some meters with an Output jack which extracts just the AC component giving an idea of the shape of the waveform.)

If your unit were an everyday power supply then it would contain a smoothing capacitor so that the output is smooth DC with an average level at 1.2V. As a result we're not always certain whether we're talking about a battery charger specifically, or an everyday power supply.

 

[Hasan2017]

That is possible if there is no smoothing capacitor at the output. Evidently the raw waveform peaks higher than 1.2 V. In that case you can use it to charge one nicad/nimh.

A 1.2VAC sine wave has peaks of 1.7 V. (Assuming the unit contains a transformer.) When rectified it becomes pulsing DC with peaks around 1.6 V. A meter reads its average voltage which is 1.1 or 1.2.

To take a correct measurement requires an oscilloscope. (Although there are some meters with an Output jack which extracts just the AC component giving an idea of the shape of the waveform.)

If your unit were an everyday power supply then it would contain a smoothing capacitor so that the output is smooth DC with an average level at 1.2V. As a result we're not always certain whether we're talking about a battery charger specifically, or an everyday power supply.

One of the promissing and knowledged based reply for sure.

You started from PS design, at the beginning all rectifier section contains ripple or pulsating DC might appear, depending on charger/PS design. Since I have a complete product then transformer or AC components should not get priority now.

But, I checked with multimiter charging voltage is not stable it is moving from 1.2 v.

We can consider that charing is going by a cycle Some one said.

Ni-Cads have 'memory' (crystalisation)that reduces its power delivery over time, even though they're fully charged - just replace the pack.

Some people say they've managed to recharge them by burning the crystalisation away with shorting the battery, then recharging.
But be carefull with this as shorting a battery is not a recommended practise.
/QUOTE]

 

[Audioguru]

Years ago when I still had some Ni-Cad cells, I tried charging a Ni-Cad AA cell and a Ni-MH AA cell in the same charger.
I can't remember which but one got warmer and the other got cooler while charging.

I found two old AA Ni-Cad cells (one says 2006 and the other says 2019). I will try charging them in series with some new AA Ni-MH cells later.

 

[Hasan2017]

Years ago when I still had some Ni-Cad cells, I tried charging a Ni-Cad AA cell and a Ni-MH AA cell in the same charger.
I can't remember which but one got warmer and the other got cooler while charging.

I found two old AA Ni-Cad cells (one says 2006 and the other says 2019). I will try charging them in series with some new AA Ni-MH cells later.

Dear Sir Audioguru,
Well come back!
Hope in this pandemic you were safe and healthy.

I think It should work.
Calculation says charging time will be less compared to predicted one.

"State of charge " and how quickly it will discharge is a fact.

I got a good result with 4.7 volt Lithium rechargeable battery.
LM358 plays well.

 

[Audioguru]

My made in 2019 Chinese 600mAh AA Ni-Cad cell in series with a made in 2019 American 2300mAh Ni-MH cell charged in only a few minutes instead of a couple of hours maybe because the "600mAh" one is actually only 60mAh. Both had 0V when the test began.

The charger is a Duracell one made in China. It shows a full charge and both cells show a fully charged voltage but can produce very little current for a short amount of time. The made in 2006 Ni-Cad AA cell did not charge.

 

[BradtheRad]

Since I have a complete product then transformer or AC components should not get priority now.

But, I checked with multimiter charging voltage is not stable it is moving from 1.2 v.

I guess it moves upward? Then Yes the cell really is charging and you can use this charger on individual cells in the pack.