The histrory of V-228 or T-228 9V Ni-MH / NI-CD Charger 120V 60Hz

[Kiriakos GR]

One decade back, I got from the USA four of 9V Ni-MH batteries these branded as Tenergy.
The batteries were offered with one Plug-In Type Ni-MH/Ni-Cd Battery Charger, two ports 9V Block Model T-228.

Due the fact that this charger is not supporting 240V, I did test it once with step-down transformer, and I just keep it as a spare one.
The charger came with out datasheet, and or carton packaging.

This week I did discover a photograph of retail packaging, and the information's over it this was a blast to me.
Charger technology this is ancient, as it was primarily designed to charge 9V NI-CD 
I never owned any 9V NI-CD, so I was totally unaware that these batteries they are supporting 120 mAh as Max regarding capacity.

Long story in sort, all 9V Ni-MH they support much higher capacity.
But this specific charger, USA import, this only supporting slowest charging rate because it was designed to retain compatibility with NI-CD 120 mAh as Max

If you own such a charger, just be aware that its simply slow by design.
Below are photographs giving you a hint of charging times when using higher capacity Ni-MH.   

[Kiriakos GR]

Today I decided to run few tests on this charger.

There is a back plate, this informing of maximum charging current this be 12mA.

Inside there is a copper transformer  120V to 12V AC.
The charging circuit per port,  this has two transistors, few resistors , few diodes, and not a single capacitor. 
This is 100% analog technology.

I am currently testing an aged 9V NIMH, the charger does not look able to output more that 9.5 mA and voltage output this is 9.600 V
I do plan to leave the charger active overnight, my PC this logging voltage and current simultaneously due my FLUKE 8846A and it special measuring function.

Personally I do own two modern ANSMANN chargers, the Energy 8 along of the  Energy 16 model.
Both able to deliver 70mA per 9V port.
This is named as fast charge mode .

But I am now very puzzled, at 2018 I got four 9V NIMH with the specification of 42mA as charging current.
And today they are not at the best shape, while one of them stopped working.

The new question is,  did I got poor quality cells?
Or ..
Did the high performance ANSMANN chargers, was too much for these average quality cells?

Either way, I am now researching  this sector of 9V NIMH and chargers.
In a few days I will have enough clues.   
   

[Kiriakos GR]

Regarding charger model, I found another rebrand of it in the USA ( This available at the Year 2015)

Lenmar PRO 9V2 battery charger

Key Features and Benefits:
Charges in 10-16 hours
Plugs directly into AC outlet
LED as charge activity indicator / LED goes off when battery this is removed.

----------------------------------
Either way, due these analog chargers, I came closer to older NIMH charging knowledge. 
This Low-Current charging at 10mA, this is also named as constant charge, this be absolutely harmless for the 9V cell.
Permanent charge 10~12mA this is the grandfather of modern Trickle charge = 7mA.

Current flow of 10~12mA this is very dependent to battery internal resistance.
Therefore an old battery with high internal resistance this will not aloud us to measure a high current flow from the charger.