My measurement devices


5. Accu loading and measuring

click on picture to enlarge it.

ELV has produced ALM devices for testing and loading accumulators with unique design and similar wiring.

The predecessors of all the devices below were ALM7000 and ALM7001 with identical front panels.



   device       max U       max I       digits       outputs       accu types       serial conn.       +feature   
ALM 700230 V3.5 A42NiCd, NiMH, Pb, Li-ionno ext.temp.sensor
ALM 700318 V1 A31NiCd, NiMHno.
ALM 700418 V1 A41NiCd, NiMHY.
ALM 700518 V2 A31NiCd, NiMHnofan
ALM 700618 V2 A41NiCd, NiMHYfan
ALM 701030 V3.5 A42 NiCd, NiMH, Pb, Li-ionYext.temp.sensor

ELV ALM 7006 - NiCd and NiMH loading (charging) and measuring device.
PC control and data logging software for controlling, drawing, and storing graphical values using RS232 connectivity. Working with 80C32 processor and 14 bit analog to digital dual slope converter. Maximal charging voltage 18V (12 elements), loading current 10 mA - 2A settable, automatically finishing of charge and discharge phase.
Unload power transistor: BD249 NPN max.125W and 25A. Load power transistor BD244 PNP max 65W and 6A.

ELV ALM 7006 - fan and temperature control.
After replacement of the power transistor BD249, which was destroyed together with his emitor resistance 0.18Ω after reversed connecting the poles of an accumulator I have also put a new white paste to both temperature sensors SAA965. The first sensor on the trafo is only pressed to the trafo plates, the second one on the cooler is better adjusted.

After these changes during loading of an accumulator after approx. one hour the fan started to run.
At this moment the temperature of the trafo plates was 50°C, the temperature of the cooler was only 35°C.
Measured values: The voltage at the sensor: 1.58 V, at begin: 1.4 V.

From datasheet:
0°C20°C25°C40°C50°C 60°C80°C100°C
810Ω960 Ω1000Ω1120Ω1210Ω 1300Ω1500Ω1700Ω

The resistance-temperature characteristic of the sensor SAA965 (working as PTC resistor) is nearly linear.
There is a potential divider between 5 V, a 2.55kΩ resistor, SAA965 value and 0 V (see diagram).
Calculated values:
At the start the sensor temperature was 25°C ==> 1000Ω. Calculated divider voltage: 5V * 1000 / 3550 = 1.4 V is the same as value measured.
At the end the sensor temperature was 50°C,==> 1210Ω. Calculated divider voltage: 5V * 1210 / 3760 = 1.6 V, what is nearly the same as measured.

The potential is multiplexed to the processor and he gives the command to run or stop the fan.
The fan is noisy, therefore I have released a bit the contact of the sensor with the trafo plates.
But my suspicion is, that there went something wrong with the trafo and therefore it produces more heat as before the destruction of BD249.

The comparative measurements below show, that even if the trafo in ALM 7006 has the highest power consumption and heating, it is still acceptable.

ALM 7004, ALM 7006, ALM 7010 transformer measurements of active power(W), apparent power(VA), power factor(cosΦ) and temperature.
There are 3 different dimensioned transformers used in these 3 ALMxxx devices. It was interesting for me to compare them.
The measurements were executed at 238 V on the primary winding.
Not loading - only the indicator and number LEDs are powered with current from secondary winding.
Loading was done with 3.6 V NiMH battery and the loading current was 160 mA.
Temperature was measured at the end of loading.

Used for measurement: Voltcraft Energy logger 4000.
ELV ALMtrafo
load max.
(V / A)
not loading
(W / VA /cosΦ)
(W / VA /cosΦ)
ALM7004?7218 / 16.0 / 13.3 / 0.4510.0 / 16.0 / 0.6040
ALM70062*8V / 300mA + 9.7V / 7A3218 / 28.6 / 16.6 / 0.5011.4 / 19.0 / 0.5950
ALM70102*8V / 500mA + 27V / 3.5A1830 / 3.58.4 / 28.0 / 0.30 8.9 / 27.0 / 0.3235

ELV ALM 7004 - same as ALM 7006 with maximal charging current only 1A.
Bought from second hand, discharging was not working. The reason was a defective operating amplifier IC10D from quadruple OA TLC274. I disconected the output and replaced it with one half of double OA LF412, which was disposable and soldered it directly on the input pins of TLC274, as seen on the picture.

ELV ALM 7010 - NiCd, NiMH, Pb, Li-ion loading (charging) and measuring device with 2 outputs. Socket for external temperature sensor, RS232 connectivity for PC controlling and data logging software. Maximal charging voltage 28V, loading current maximal 3.5A settable. These 2 outputs work one after other, not simultaneously.
inside - trafo,    inside - detail,   inside - PCB.

ELV ALM 7002 - NiCd, NiMH, Pb, Li-ion loading (charging) and measuring device with 2 outputs as DIY kit. Socket for external temperature sensor. Maximal charging voltage 28V, loading current maximal 3.5A settable,
bottom side of the main PCB, documentation.

Trafo brum in ALM7010
I bought the ALM 7002 kit, because the ALM 7010 was giving a brumming (growling ?) sound of the net frequency. As I know, that the trafos are same in ALM 7010 and ALM 7002 and an ALM 7002 kit was offered on ebay, I bought it. After exchanging the trafo in ALM 7010 with trafo from the ALM7002 kit the situation was the same. I have then tried to damp somehow the main PCB from the bottom box-part with success, but after mounting the upper box-part the brumming sound came again.

I remembered, that in the valve radios the bigger trafos where tightened to the chassis with rubber washers placed between the trafo and the chassis. I din't use rubber, because I hadn't any, but my next step was to take away the distance tubes (see picture) and the tightening screws and to retract only the trafo plates with 4 shorter screws. This brought success.
The distance of the trafo bottom part from PCB is now 1-2mm and the vibrations of the trafo body are not taken over by the medium of the distance tubes to the PCB and from the PCB to the resonating box.

Accu load device IPC-1

Voltcraft? IPC-1
AA, AAA NiCd, NiMH loader. 4 fully independent boxes, automatic-processor driven delta peak detection. Modes(programs): charge, discharge, test, refresh.
Current (selection): 200, 500, 700, 1000, 1500 or 1800 mA. Unload current = load current / 2.
Display: Voltage, current, time, capacity.

Accu load device Profiline Gamma Accu load device Profiline Gamma Accu load device Profiline Gamma

U.I. Modelltechnik Profiline Gamma
NiCd, NiMH, Pb loader. 4 independent boxes, processor SAB 80535-N driven. Modes(programs): NiCd,NiMH: 1-12 cells charge, discharge, d-ch, ch-d-ch, refresh. Pb: 2V, 6V, 12V charge.
Current charge / discharge settable max. 1.7A all boxes together or max. 1A for one box.
Display: Voltage, current, by pushing CLEAR also time and capacity.

Charging with 10s current and 2s pause, voltage is measured continuously.
The difference between pause and load voltage depends on internal resistance Ri of the accumulator.
Discharging works without pause, voltage is measured under load.
The front panel is connected to the board by a connector. RS232 connector behind enables graphing on PC.
Current and charge voltage on the display is OK. But the discharge voltage is 0.2 V less as measured by a voltmeter.
For such case calibration of charge and discharge current and voltage is possible pushing both CLEAR and ENTER.
Here is the description of this device in german.

Accu load Accu load Accu load Accu load Accu load

Accu loader Graupner for loading NiCd accus 0-12V with constant current.


(2x)Accu loader Titan 333 for loading NiCd accus 0-12V with constant current 22-50-100-500 mA.


Accu loader Titan 603 for loading NiCd accus 0-12V with constant current 22-50-70-140-500 mA

Measuring of voltage-current sources.

icon icon

ELV RIM1000 Internal resistance - Ri measurement device for accumulators, also for non rechargeables.
It was sold also as a kit, therefore a very good documentation exists in the web. Works with short (5μs impuls) load 0.5A - 10A settable. I have replaced the SMD npn T2 transistor with a conventional one, because the T2 couldn't close even if its EB junction was short-connected. But it wasn't the T2, it was a short connection in the plastic foil connector between the keys and the board. Some chemical process has built a bridge between two silver lines of the plastic foil connector. Here some measurements:

voltage & current sourceusageopen volt.[V]load curr.[A]under load [V]Ri [mΩ]
a c c u m u l a t o r s :
AA Sanyo Eneloop 2400 mAhnew1.34111.31130
AA 2000 mAh noname8 years1.3201400
AAA Sanyo Eneloop 800 mAh after charging2 years1.460180
sub-C 3000 mAh accupack (12 elements)1 year heavy duty15.56115.43130
the same accuppack15.56514.91130
for 1 sub-C element11
accupack NiCd 1300 mAh (6 elements)9 years7.621130
b a t t e r i e s ( n o n   r e c h a r g e a b l e s ) :
AA lithium Energizer3 months1.75611.631125
AA alkaline noname3 months1.53311.353180
9V alkaline battery Maxell (6 elements)new9.617.81800

Ansmann Ansmann Ansmann

Ansmann Energy Check LCD
It is usable for battery and also for AA, AAA, C, D NiCd/NiMH accumulator.
The result is rest capacity in tenths of % and voltage under battery type specific load in duration of ca 2s.
I have measured the current drawing from the specific batteries / accumulators.

typeapprox. unload current
AAA/AA/C/D accumulator300mA.
AAA/AA/C/D battery150 mA.
9V battery40 mA
12V A23 battery10 mA
3V CR 2025, 2032, 2320, 2430, 245010 mA
1.5V LR43, 44, 45, 48, 543 mA