Can POWCO tell if you are using batteries in a grid-tied system?

[Davis White]

I am having fits with the state's energy commission not recognizing my battery technology for my small grid tied system. Can they tell if I have batteries connected to a string inverter?

 

[rickst29]

This should really be an issue with the Power Company, and not the "State Energy Commission". If the batteries will be used to supply 120/240V into the house system (120/240v), then they will be fully inter-connected with the grid-tie - and the battery-associagted "Inverter" must be approved for operating according to power company requirements (low distortion, correct phase, and possibly activating only via an automated disconnect).

All Grid-tied Inverters MUST disconnect the A/C supply when they detect power loss, but your battery bank may have a "separated" Inverter function for running an automatically disconnected household. The equipment is expensive, and it may be more simple to simply move key appliances from household wiring over to extension cords (tied into the battery-powered Inverter, moving them back to household wiring after power recovers.

You are NOT allowed to run a battery bank inverter into the Grid without such an automated device. This is because, in the absence of grid power, your battery bank Inverter becomes "out of phase' with the grid - and when the grid recovers, if your household is still connected to the "dead" grid - horrible out-of-phase Voltage interactions feed back to the grid upon it recovery, blowing up equipment (and maybe appliances within your house as well). They don't trust you to disconnect and reconnect by hand - the disconnect process, and reconnect with AUTOMATIC suppression of the battery-based Inverter happening FIRST - must be completely automatic.

 

[Davis White]

Thank you!!

My inverter is certified as CA Rule 21 and UL 1741 Compliant. Would that not take care of the important concerns you raise?

In my state, the Powco has two permit streams for home PV with battery backup.

1. For inverter, modules, controller, etc.
2. A separate one for batteries ("Energy Storage Systems")

Powco says I am fine with 1, but as for 2, they say that they defer to an "Approved Equipment List" put out by the state Energy Commission. That list contains ONLY lithium iron phosphate batteries (potentially dangerous), and nothing more. Mine are AGM valved batteries: vastly safer. But no AGM batteries are on the List.

The state EC refers to UL Standard 1973, which was written principally for railroad batteries, then lithium, and oh-by-the-way anything else, but has no specific standards for anything else. My battery mfr. says it's not worth it to apply for UL approval.

Trying to figure out what to do. Would you know what harm, if any, could come from batteries behind a 21- and 1741- compliant system?

* By the way, the local fire department exempts AGM batteries from inspection and permitting requirements. They are considered safe. Not so for lithium.