IEC 60601 Main requirements for Lithium Ion Battery Powered Device

S

Subr_Ree

Dear All,

We have a ECG medical device with embedded Rechargeable Li-ion battery (CE Certified - Non Removable by the user) which is intended to be charged using a USB cable/USB charger/Power Tank or (importantly) a computer for both charging and data transfer.
So the max voltage is (5V).

The body of the device is made from (ABS, Noryl, Nylon & Polycarbonate) plastic enclosures with respect to the European Union’s RoHS Directive 2011-65-EU
.

The devices has two Sockets

  • USB Micro socket for charging and data transfer.
  • Circular LEMO Connector for Patient cable containing the lead wires (All Of the Patients Lead wires are CE certified)
The device can be charged during its connection to patient

I have some questions regarding the standard and i hope someone can answer me:

1) Regarding the charger:

  • can i use any (CE Certified) charger for the charging of the battery (e.g Samsung or Huawei or any cellphone charger) and then write in the User's manual that the operator must use that charger and it will be sell with the product.
  • And also if the charger has the (CE LOGO) on it, does it means it's applicable with our standard, or we should use another charger applicable to other standards.
2) i have read the standard so many times, but i didn't find an specific requirements for our equipment.
and i want to know the following

  • Is the device considered as an INTERNAL ELECTRICAL POWER SOURCE or CLASS II in the two cases on operation (Charging the battery - Operation from the battery)?

  • And I'm asking about all the cases of charging the battery as i mentioned before (From CE Certified Cellphone Charger / CE Certified Power Tank / Computer)

  • What are the SUPPLY MAINS in our case?

  • About sub clauses 8.6 and 8.7, is the Earthing and Everything about the LEAKAGE CURRENT is applicable to us?
Please Help me, I'm so confused.

And If I can provide you with any further details regarding the device please let me know.

Thanks in advanced.
 
Last edited:

Mark Meer

Trusted Information Resource
Hi Subr_Ree, and welcome to the Cove! :bigwave:

I can't give you any authoritative answer, but I can hopefully start a conversation...

My main advice would be: ask an accredited test lab. They will know the standard, and requirements as well as anyone.

If I were to guess, I think the biggest concern for you is the the fact that you can charge WHILE the device is connected to the patient. This means that you must consider that there is a line (albeit indirect) from the supply-mains to the patient.
Hence, I'm pretty sure that all clauses that assume a continuous supply-mains connection will apply.

Risk management will be key, and it will be important to document consideration of the unknown/uncontrolled power-source. The limitations of USB may be a risk mitigating measure, however.

Like I say: ask the test-labs. If they give you an answer please post! ...would also be curious to know!

MM.
 
Last edited:

Mark Meer

Trusted Information Resource
Some more musings, for what it's worth...

[*] can i use any (CE Certified) charger for the charging of the battery (e.g Samsung or Huawei or any cellphone charger) and then write in the User's manual that the operator must use that charger and it will be sell with the product.
[*]And also if the charger has the (CE LOGO) on it, does it means it's applicable with our standard, or we should use another charger applicable to other standards.

Yes. There are definitely such devices on the market that have passed 60601-1 testing.
I don't think the CE logo on the charger you supply is necessary. Ultimately, whatever charger you supply will be tested as a system component.

Is the device considered as an INTERNAL ELECTRICAL POWER SOURCE or CLASS II in the two cases on operation (Charging the battery - Operation from the battery)?

Clause 6.2. Says "INTERNALLY POWERED ME EQUIPMENT having a means of connection to a SUPPLY MAINS shall comply with the requirements for CLASS I ME EQUIPMENT or CLASS II ME EQUIPMENT while so connected, and with the requirements for INTERNALLY POWERED ME EQUIPMENT while not so connected."

So, in other words, both. Your device operates in two "mode" connected/charging, and disconnected/internally-powered. Both modes will have to be tested according to the applicable clauses.
 

Peter Selvey

Leader
Super Moderator
The critical point in this case is the isolation between the USB circuit and the ECG. I assume that the system has at least 4mm/1.5kV isolation as required for Type CF applied parts.

If yes, the standard has a few options for handling the power supply:
- designated 60601-1 certified power supply
- designated 60950-1 certified power supply, tested with the device
- designated 60950-1 certified power supply, tested as an "ME system"
- generic 60950-1 power supply (e.g. USB supply from any PC), tested as an "ME system"
- instructions may also state if the device is allowed to be connected to the patient or not during charging or data transfer, which can influence the assessment

Each one of these has some plus/minus points (costs, risks, practicality) but they are all theoretically possible. For example, in the case of a generic power supply the user may asked to run it through an isolation transformer or add extra grounding and/or measure system leakage currents before connecting to the patient - theoretically possible but practically questionable.

There is also a risk that the user does not follow the instructions, which is a particular concern in this case. The risk management file should identify reasonably foreseeable misuse, such as connection to the PC while the patient is still connected (even if the operation manual says not to), or using a generic PC, or failing to apply the ME system instructions/warnings.

To address these risks, many designers would opt to increase the isolation barrier to 8mm / 4kV as such parts are easily available. That way, even if the user ignores all instructions or connects to a cheap and nasty junk PC there is still a double insulation barrier to the patient/ECG electrodes.

Another (weaker) option can be to automatically disable the monitoring functions whenever the device is connected USB, and/or if the device has a screen to show some warning message to disconnect from the patient.
 
S

Subr_Ree

Many Thanks for all of you for your replies.

Okay, that's good.

But i still have questions regarding the earthing and the productive earth terminals.

Let me first give you a small background about the device.

  • The device contains a PCB with built in power supply which takes its power from internal LI-ion battery (3.7V).
  • There's a USB connector responsible for the charging of the battery and the data transfer for the device.
  • Charging can be done from three sources.
    • Power Tank.
    • CE Certified class II USB Charger. (will be send to the test lap, and will be sold with the product, and will be mentioned in the ACCOMPANYING DOCUMENTS, and using any other charger may cause HAZARDOUS SITUATION)
    • USB From PC.
  • The (5V) from the three previously mentioned power source is isolated inside the PCB using DC/DC isolator IC.
So, Will every state of operation has its own test/RISK/Operations?

For Example if the device is charging using a power tank (which is considered as a DC Small Battery, and i think in this case it will act as part of the ME EQUIPMENT) is the Earthing and LEAKAGE CURRENT tests will be Applicable to me?

I think the case which will be questionable will be during the connection of PCB or USB Charger??

And the Main question here, If i disabled the device working during the charging process, are all of these tests won't be applicable to the device?

If I can provide you with any further details regarding the device please let me know.

Thanks in advanced.
 
Last edited:

Peter Selvey

Leader
Super Moderator
I think you need to consider two broad situations:

(1) using a 601 certified power supply: in this case the touch currents should meet the 601 limits (whether Class I or II) and no further action is needed

(2) using a 950 certified power supply: in this case touch currents often exceed the 601 limits so "additional measures" are required. This can happen for both Class I and Class II supplies. The additional measures can include isolation transformers, internal or external isolation devices, additional protective earthing, or designing your module to have no accessible plastic parts etc etc.

As always with safety it's not the test that matters, the test just confirms good design.

If you start with the assumption that the external power supply is 950 certified, and has leakage that exceeds 601 limits (regardless of Class I or Class II), then you need to decide on a strategy or design to keep the touch currents around your device below the 601 limits.

Once you have the design, then you can test to make sure it works as planned. For example you could find a PC with really high earth leakage (usually a desk top type), break the earth and then measure how much leakage comes out of your device (for patient and operator).
 
Top Bottom