LiFePO4 batteries AFTER Class 2 power supply

[Malini6702]

Hi All,
So we have a device, essentially powered by 4 x LiFePO4 batteries that are unlisted, but meet the requirements for Class 2 batteries (is there such a thing?). The device is always connected to power, but in the event of a power outage it will still function 30 times on battery power alone. ADA requirements.
I'm not an electrician but, is it even possible to install batteries after a power supply/charger, if the batteries exceed the power output of the charger?
Again, arguing with Intertek. I'm convinced they are just looking for more tests to do to meet a potential invoice goal.
Your intelligent thoughts and well-considered advice would be greatly appreciated.
thank you in advance.

 

[ron]

A power supply / charger changes AC to DC, which can be used to charge batteries or power the load (or both). If the load is DC, then you are all set, if the load is AC, then an inverter finishes the deal, like a UPS.

 

[Malini6702]

Thank you Ron. The power supply is also a Class II inverter so we are good there.
Next question... if the batteries are installed after the class 2 power supply, they are considered part of the Class 2 circuit? Even if the device is effectively powered by the batteries?

 

[ron]

If you are asking related to a UL Standard, I don't know. The NEC Section 725.121(A) defines a Class 2 or 3 Power Source which includes a battery source that is listed and identified as Class 2.

There is a lot of energy density in a battery (modern) which typically exceed the limits permitted for Class 2 power supplies, which is why they require it to be listed itself as Class 2.

 

[Malini6702]

Good to know. Thanks so much Ron