[Dennis4809]

Can you see evidence that the batteries are boiling over? If you can smell the acid, most likely you’d see wetness around the battery caps. If you have a voltmeter, you could check the voltage at the batteries when plugged in but either way, I’d suspect that your inverter/charger is overcharging the batteries and will need replaced. Newer versions have much closer control over the charging voltage so as not to overcharge.

Good luck,