Battery Tester with USB-IO-24-Cable [130019-I]

A PWM output controls the logic FET BUK101-50 (or IRLIZ44N). This FET switches the discharge current through 2 resistors. A 0.1 ohms resistor is used for the current measurement.

A PWM output controls the logic FET BUK101-50 (or IRLIZ44N). This FET switches the discharge current through 2 resistors. A 0.1 ohms resistor is used for the current measurement.

Because we are dealing with a PWM signal, the voltage across the resistor is filtered with an RC filter (1k/10uF).

1. Capacity measurement

At first, the desired current and discharge voltage is entered into the software and the discharging is started.

After that the voltage and current are constantly monitored.

The software displays the discharge voltage in a diagram.

Discharging stops when the discharge voltage is reached.

2. Internal resistance measurement

The voltage of the battery is measured before load is applied.

Then the battery is discharged with maximum current (PWM = 1023) for a short time, and the voltage and current are measured again.

After this, the voltage across the the load is measured.

The average voltage before and after, minus the voltage under load, devided by the load current = Ri

Ri = ((Vbefore-Vafter)/2 - V under load) / I under load

3. Battery refresh

Every 10 seconds a current pulse is drawn from the battery to break off the sulfate build up.

The required PWM value can be set in advance.

The refresh ends manually or when the discharge voltage is reached.

/*********************************************\
/**********Original German text***********\
/*********************************************\

Akkukapazitätstester mit USB-IO24 Kabel

Schaltungsbeschreibung:

Mit einem PWM Ausgang wird der Logik FET BUK101-50 (alternativ IRLIZ44N ) angesteuert.

Dieser schaltet den Entladestrom durch die beiden Hochlastwiderstände. Der 0.1 Ohm Widerstand

wird zur Strommessung verwendet. Da es sich um ein PWM Signal handelt, wird die am Widerstand

abfallende Spannung mit dem RC Glied 1k/10μF gepuffert.

Die Software regelt den PWM Ausgang entsprechend des dort eingestellten Stroms automatisch nach.

1. Kapazitätsmessung

Es wird der gewünschte Entladestrom und die Entladeschlußspannung eingegeben und die Entladung

gestartet

Dann wird kontinuierlich Spannung und Strom gemessen und aufaddiert

Die Entladespannung wird als Diagramm dargestellt

Ist die Entladeschlußspannung erreicht, wird die Messung beendet.

2. Innenwiderstandsmessung Ri

Es wird die Spannung vor Belastung gemessen

Dann wird kurzzeitig mit maximalen Strom (PWM=1023= belastet und die Spannung und der Strom

unter Last gemessen

Danach wird die Spannung nach Belastung gemessen

Mittelwert der Spannung vor und Nach minus Spannung unter Last geteilt durch den Strom unter Last

= Ri

3. Akku Refresh

Alle 10 Sekunden wird ein Stromimpuls entnommen um Sulfatablagerunge zu lösen

Der dafür verwendete PWM Wert kann vorher eingegeben werden.

Der Refresh endet amnuell oder spätesten, wenn die Entladeschlußspannung erreicht wird.

Projektelemente

General construction (PCB V2) (JPG, 1.4 MB)

FET mounted underneath (PCB V2) (JPG, 1.22 MB)

Fan connected to header (PCB V2) (JPG, 1.52 MB)

kaptesterschaltplan.jpg (JPG, 113.76 KB)

kaptesterdiagramm.bmp (BMP, 718.63 KB)

kaptesterlayout.bmp (BMP, 499.82 KB)

kaptestermain.bmp (BMP, 403.67 KB)

kaptestermainfertig.bmp (BMP, 403.67 KB)

PCB_Eagle_V3.1.zip (ZIP)

PCB and Gerbers

Material_List.zip (ZIP)

List of materials

BatteryTest_German.zip (ZIP)

Original German version of the software

BatteryTest_English_V1.1.zip (ZIP)

Updated English version

Diskussion (4 Kommentare)

midopple vor 10 Jahren

Hi,

I like the Akkutester, simple and work always :-)

I had a wish for the Software, would it be possible to save the values to a log file, Time, Current, Voltage and C. So i can put the value in a Excel sheet to compare with older Tests.

Thanks

Mike

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patrickwie vor 11 Jahren

http://youtu.be/uXWbZhIMxjs

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TimUiterwijk vor 11 Jahren

An update for the software (English version) has been added.

It is now possible to adjust a correction factor for the current measurement.
This can be done in the KAPTESTER.INI file.

The COM port used for the USB IO cable can (like in the old version) be adjusted in the USB_IO_AD.VAL file.

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TimUiterwijk vor 11 Jahren

Created a new PCB in Eagle.

Keeping in mind an easy construction of the hardware.

Since a lot of power is dissipated in the 0,1 and 0,33 ohms resistors they had to be cooled.

The FET that discharges the battery also needs to be cooled.

Because a large heatsink is not practical, the choice was made to use an actively cooled heatsink, a heatsink with a fan mounted on it, commonly used in computers (for cooling the processer).

The project (both software and hardware) already included control of a fan, so this was very convienent.

Heatsinks with a fan are relatively small but still have low thermal resistance.

With this one sided PCB and an active heatsink, a very compact solution is possible.

The construction is as follows:

The PCB has 4 holes in the corners. An extra hole is placed in the middle of the PCB for the FET.

All components are mounted on top of the PCB except for the FET.

Bending the pins on the FET places the hole in the FET beneath the hole in the PCB. A 5mm spacer can then be placed between the FET and the PCB.

2 5mm or 1 10mm spacer should be placed between the PCB and the heatsink in the 4 corners.

This way, the PCB and FET are firmly mounted to the heatsink.

The 4 holes in the corners are placed so that they fit the profile of the heatsink (less holes to drill).

2 aluminium housed high power resistors are chosen for the 0,1 and 0,33 ohms resistors.

Both have 2 holes for mounting them to a heatsink.

The are mounted on the sides of the heatsink, because the airflow generated by the fan is directed sideways.

Mounting the resistors in the airflow maximizes cooling.

The PCB includes 6 Faston PCB connector pins. 2 for connecting the battery, the other 4 for connecting the resistors.

A 2 pin header is placed for connecting the fan.

There is a 25 pins SUB-D connector on the PCB for connecting with the PC using the USB I/O Cable (project nr.: 120296).

A 6 pins header is also present for connecting your own measurement tool.

The software however is written for the USB I/O cable.

faston-m-5.jpg (4kb)

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Battery Tester with USB-IO-24-Cable [130019-I]

Projektelemente

Diskussion (4 Kommentare)

midopple vor 10 Jahren

patrickwie vor 11 Jahren

TimUiterwijk vor 11 Jahren

TimUiterwijk vor 11 Jahren

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