I have two 25 plus year old trucks and after full charge and the charger automatically turns off. The BDI read 2 to 3 bars on the display. If I unplug it for a minute and plug it back in. The charger starts up for a couple of minutes I turn the charger off manually the BDI will read full charge on the display and the truck will run all day. If I don't do this the truck will run about an hour and the red dead battery light flashes and no lift.
They are both GE sx controllers.

Is this a programming issue or a part issue? I think I can get access to a laptop and software but what do I do with it, if it is a programming issue.

Thanks for any help.