Battery won't charge; sometimes not detected

When connecting (known working) magsafe supply, magsafe LED is briefly orange, then turns green. Battery is either "present=no" or "present=yes" but never has any information in system info. I have tried resetting SMC many times. White power LED blinks 5 times when starting after SMC reset.

Runs off wall power ok. Won't ever charge.

Battery level indicator (physical button) never works (no LEDS).

I have tried replacing battery (with OEM) -- same symptoms.

Can anyone tell me if replacing the small DC board is likely to be of any value? If the battery indicator never works, is this because there is an issue with the SMC on the main board? Or could this be caused by a failure of the DC board?