Technical Assistance Requested — ADI EVAL-AD5941BATZ / CN0510 Battery Voltage Limits

Embedded Development Boards, Kits, Programmers
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1

Hello DigiKey Technical Support Team,

I purchased the following Analog Devices evaluation hardware through DigiKey:

I am using this hardware to develop a battery impedance monitoring system for four series-connected Exide PowerSafe 12 V, 18 Ah VRLA batteries, forming a 48–55 V battery bank.

The evaluation setup is operational, and I have successfully tested impedance measurements using AAA and AA cells.

Before connecting a 12 V VRLA battery, I need to confirm the maximum permissible battery voltage for the unmodified EVAL-AD5941BATZ hardware. I also need to establish whether an external interface is necessary for measuring individual batteries in the series-connected bank.

I have consulted the AD5941 datasheet and CN0510 reference-design documentation and have attempted to obtain clarification through Analog Devices technical support.

Could DigiKey please assist by:

  1. Confirming whether the relevant board documentation specifies the maximum supported battery voltage.

  2. Helping route this question to the appropriate Analog Devices applications engineer or technical support contact.

  3. Identifying any official reference design or documentation covering 12 V VRLA battery impedance measurement with this hardware.

I am not requesting a complete custom circuit design at this stage. I primarily need the verified operating limits of the evaluation hardware so that I can proceed safely.

I can provide the DigiKey order details, board revision, photographs, and my existing Analog Devices support-case reference if required.

Thank you for your assistance.

Best regards

Ved

2

Hello @vedpsahu,

Welcome to the DigiKey TechForum.

Fundamentally, you are asking a question regarding the front end of this circuit.

In this case, a load is applied to the battery when the control line CE0 turns on the Darlington load pair. This CE0 control can be a “full power” pulse or a “Potentiostat” low power signal.

I have two things to share:

  1. The design max voltage was not readily apparent. In fairness, this may simply be me looking in the wrong place. Hopefully another engineer with better eyes can find the data.

  2. If CE0 is a pulse, there will be a point where the TIP31 transistor and the resulting AIN1 to the AD5941 will be stressed.

Unfortunately, without that design maximum, I’m unable to offer a reliable (non-circuit damaging) answer to your question.

It looks like you have already posted the request to ADI EngineerZone. We shall wait for ADI’s authoritative answer.

Cordially,

Aaron

P.S. As a side note, be careful if you walk this test instrument across a series string. The circuit may or may not be fully isolated. I’ve been bit by the USB to PC connection being part of the circuit.

Front end schematic of the development board.
Front end schematic of the development board.714×850 52.5 KB

3

Hello Aaron,

Thank you for reviewing the CN0510 design and sharing your observations regarding the CE0 control signal, TIP31 transistor pair, and AD5941 AIN1 input.

I understand your concern that, without a confirmed maximum operating voltage, recommending a higher-voltage battery connection could risk damaging the evaluation hardware. I will not connect the 12 V VRLA battery or the 48–55 V battery bank until the applicable limits have been established.

I have already posted my technical query on ADI EngineerZone and submitted support requests through ADI’s support channels. Unfortunately, I have not received a response or a clear escalation path to an AD5941/CN0510 applications engineer.

Since the EVAL-AD5941BATZ and EVAL-ADICUP3029 were purchased through DigiKey, could you please help escalate this question through your Analog Devices supplier/distributor channel or connect me with the appropriate ADI Field Applications Engineer (FAE)?

The clarification I need is limited to the following:

  1. The maximum permissible battery voltage for the unmodified CN0510 / EVAL-AD5941BATZ hardware.

  2. The voltage limits of the TIP31 load stage, AIN1 input path, isolation capacitors, and other relevant components.

  3. Whether the existing hardware can support impedance measurements on a single 12 V VRLA battery, or whether an external interface is required.

My objective is to establish the safe operating limits of the existing evaluation hardware before proceeding with my battery-monitoring prototype. I am not asking DigiKey to take responsibility for a custom circuit design; I am requesting assistance in obtaining an authoritative technical clarification from the manufacturer.

If direct escalation is not possible, could you please advise the appropriate DigiKey technical contact, ADI account representative, or supplier-support route through which this request can be raised?

Thank you for your time and assistance.

Best regards,Ved

4

Hello @vedpsahu,

Looking closer at:

I concur with the ADI engineer Akila that the demo board was not designed for higher voltages.

Note that the S+ and S- are connected across the test cell. A low pass filter is inserted between the sense terminals and the AD8694ARZ buffer amp.

  • According to the BOM, the LPF associated circuity has 10 VDC capacitors for C5, C6, C36, C37, C38, C39
  • The surrounding circuitry including the op amp rails are 3.3 VDC

Recommendations:

  • Consider changing the scope of the project. For example, characterize a single lead acid cell or explore alternative technologies such as flooded nickel.

  • Consider adapting the demo board for high voltages or reconstructing instrumentation of your own design to perform the same function.

Best wishes,

APDahlen

5

Hello Aaron,

Thank you for reviewing the CN0510 documentation and highlighting the voltage limitations of the sensing path, filter capacitors, and surrounding 3.3 V circuitry.

I understand that the unmodified evaluation board should not be assumed suitable for 12 V VRLA batteries or for measurements within my 48–55 V series-connected battery bank. I will not connect it to either until the applicable limits and required interface have been established.

For the next step, could you please advise whether Analog Devices can provide either:

  1. A manufacturer-reviewed modification approach for measuring a single 12 V VRLA battery using the existing AD5941 evaluation platform; or

  2. An alternative ADI evaluation platform or reference design suitable for battery impedance measurement at this voltage.

My longer-term objective is to measure each of four series-connected 12 V, 18 Ah VRLA batteries independently. I understand that this may require a separate protected and appropriately isolated measurement interface, particularly for batteries at elevated common-mode voltages.

If DigiKey cannot assess these design modifications directly, I would appreciate any assistance in routing the question to an appropriate ADI applications engineer or FAE.

I am happy to provide the board revision, schematic, and other relevant details if needed.

Thank you for your guidance.

Best regards
Ved

6

Hi @vedpsahu,

Let’s back up and take a closer look at the AD5941.

  • We can describe this as a highly specialized device that integrates the precision instrumentation required to characterize cell impedance. This includes precision voltage references, ADC, DAC, and a control mechanism to coordinate the measurements.

  • The AD5941BATZ is a demonstration board to showcase the AD5941. It is a highly specialized evaluation platform, not finished test equipment like an oscilloscope. We can safely assume that the demo board was built alongside the application note. Together they provide engineers an easy runway to test the product.

We have reached a point where the demo board is insufficient to measure at the desired voltage. Stated another way, we are now fully in the realm of the design engineer. This is also where I must depart the conversation.

  1. Can the AD5941BATZ be modified. Perhaps, but I have yet to see a documented approach. If I were to investigate this product, I would reproduce the transistor clamp and voltage amplifier off board. This will allow us to test the circuitry in isolation to better understand the dynamic characteristics including the spike that occurs when the battery is connected.

  2. Back to the AD5941, its strength is the deep integration and coordination of cell measurement instrumentation. There are alternative data collection systems. For example, a tool like Labview could be used to control traditional test equipment like an oscilloscope and power supply. Likewise, a microcontroller or even a PC with a python script could control the analog circuitry. I suspect you will still need to produce some of the specialized hardware such as the precision excitation circuitry.

I wish you the best in your studies.

Sincerely,

Aaron