Guess type of battery

Thread Starter

xblitz

Joined May 2, 2021
6
Hi! I hope someone help me!
In these days I try to restore a old AEG battery screwdriver. The screwdriver should be build in 1985. It works very well but, of course, the problem are the batteries: they are KO after many years of unuse. So I don't know if they are Ni-MH or Ni-Cd batteries. The battery pack is encapsulated in the screwdriver's handle and it's a set of two C-type batteries in series. The battery pack have 3 terminals: anode cathode and "sense" terminal which is the same cathode. The voltage of battery pack is 2.4V. The next step was open the crewdriver battery charger in order to find some clues about the type of batteries. Unfortunately I found only BA6105 IC and I don't found any datasheet but I found this thread: https://forum.allaboutcircuits.com/threads/finding-datasheets-for-hard-to-find-parts.113347/

Now, screwdrivers are energy eaters items and in 80's the Ni-MH tecnology was early born so the battery charger should be designef for Ni-Cd batteries but I'm not sure... so, someone know how to determine the type of my batteries?

Thanks!
 

KeithWalker

Joined Jul 10, 2017
1,919
The batteries will be Ni-Cad for sure from that era. I have one of similar vintage. I replaced the two Ni-Cads with a single 18650 Li-Ion cell. It Has more voltage and twice the capacity of the original batteries and it left enough space to build in a 5V charger circuit. It works far better now than it ever did.
 

Thread Starter

xblitz

Joined May 2, 2021
6
@BobaMosfet
According to the thread wich I linked the BA6XX series by ROHM is a custom IC's without any criteria over the nomenclature (it seems reasonable: the 6109 is a driver motor, the 6104 UVmeter....), so no datasheet no party ;-)

yes, I can try to ask AEG the type of batteries but: the screwdriver don't have any kind of marker (model, serial, date of production....) and I suppose that the helpdesk guys are younger the screwdriver!

Anyway the charger is a set of transformer and a little PCB, on the PCB there are a SCR, 2 power diodes and other stuffs like 2 BJTs, some resistors and diodes and in the middle of all the BA 6105. Curiously the sense therminal go straight in a pin of IC and I suppose that the function of this battery pack terminal is to say to the charger "wake up a battery is plugged in".
 

Thread Starter

xblitz

Joined May 2, 2021
6
Ok, even if I'm not sure to the year of production of the screwdriver I agree with you to the type of batteries.... but I have another question. All the stuffs born because I wish to use the original charger but I don't forecast to use this screwdriver heavily, so a Ni-MH battery pack could be more suitable of a Ni-Cd? (lazy battery effect)

what could be happen if I use the charger (suppose it's a charger for NiCd) with Ni-MH battery pack? I read somewhere that Ni-MH battery pack should be equipped with a little IC wich protect the sigle cells in the charge process (it's related to a reverse of polarity that a cell could be subject during the charge process, but for 2 cells it seems unlikely.

My goal is keep alone the charger without something go wrong and burn my home :)

PS: I don't clarify before, but the charger stop the process when the battery pack is charged and because there aren't some sensor it must use a voltage measurement.
 

KeithWalker

Joined Jul 10, 2017
1,919
The charger you have will over-charge and damage Ni-MH batteries. Ni-Mh batteries Do not self-discharge as quickly as Ni-Cads but are still not a good choice for intermittent use. A single Li-Ion battery would be a much better choice.
 

BobaMosfet

Joined Jul 1, 2009
1,850
Battery charging is a bit more complex than most people think, depending on battery chemistry. Good battery chargers not only sense voltage and/or current, but can also sense thermal/temp changes in the batteries (some get colder when fully charged, others get hotter), and in some cases, even dimensional sensing, because batteries can swell or shrink at proper charge. Then there is a trickle aspect for some and so forth.
 

BobaMosfet

Joined Jul 1, 2009
1,850
@BobaMosfet
According to the thread wich I linked the BA6XX series by ROHM is a custom IC's without any criteria over the nomenclature (it seems reasonable: the 6109 is a driver motor, the 6104 UVmeter....), so no datasheet no party ;-)

yes, I can try to ask AEG the type of batteries but: the screwdriver don't have any kind of marker (model, serial, date of production....) and I suppose that the helpdesk guys are younger the screwdriver!

Anyway the charger is a set of transformer and a little PCB, on the PCB there are a SCR, 2 power diodes and other stuffs like 2 BJTs, some resistors and diodes and in the middle of all the BA 6105. Curiously the sense therminal go straight in a pin of IC and I suppose that the function of this battery pack terminal is to say to the charger "wake up a battery is plugged in".
One of the things I noticed in my digging yesterday was that the BA61XX was not always used for it's stated purpose- I saw some as LED Dot/Bar display drivers etc. The main thing I was getting at, is that the information I provided *might* give you the ability to determine the pin-out for the BA6105, which could go a long way towards creating your own datasheet. I also reached out to Rohm, and a few other places and am waiting for a response.
 

Thread Starter

xblitz

Joined May 2, 2021
6
A single Li-Ion battery would be a much better choice.
I agree with you: a complete retrofitting should be better but Li-Ion battery voltage is 3.7V but the voltage of my batteri pack is 2.4V. I open the screwdriver: nothing in it, only the motor (it looks like a brush motor) and two switches (on-off and rotation). So what happen when the motor will be receive a 3.7V? It don't sounds good... 3.7V means about 50% of nominal voltage :-/
 

KeithWalker

Joined Jul 10, 2017
1,919
I agree with you: a complete retrofitting should be better but Li-Ion battery voltage is 3.7V but the voltage of my batteri pack is 2.4V. I open the screwdriver: nothing in it, only the motor (it looks like a brush motor) and two switches (on-off and rotation). So what happen when the motor will be receive a 3.7V? It don't sounds good... 3.7V means about 50% of nominal voltage :-/
Mine has been working great ever since I converted from two Ni-Cads to one 18650 five years ago. It gets a little warm if I use it a lot over a short period of time but it just keeps on going. The motor is fairly rugged and works much better with the higher voltage.
 

Thread Starter

xblitz

Joined May 2, 2021
6
Hi guys, finally I cut the Gordian knot: open the charger was useless, open the battery is the answer: in my digging I found that the Cd(OH)2 in the NiCd batteries dissolves in NH3 so I take some material from one cell and I notice this fact.

In these days I found another screwdriver to restore - of course with the same problem. So I decided to repeat the test and I found a NiMH cell - nothing dissolved in NH3.

Of course I used glowes and doing my experiments outdoor. Finally I give all materials to a recycling center.
 

Tonyr1084

Joined Sep 24, 2015
6,269
Ni-Cad battery voltage per cell is 1.2V. In the 80's - yeah, NiCad's for sure.

NiCad's - I've observed a peculiar thing: I accidentally charged one in reverse polarity. And it worked (in reverse polarity). But this was a large 50 amp cell. I wouldn't' recommend trying it - but if you're out of options - - - . But you should be able to find NiCad batteries on Amazon or Ebay or likely many other sources. If you opt to change to Li-Po or Li-Ion - you need to get the proper charger. Mishandling Lion batteries can be dangerous. Same of Lipo's.
 
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