Implications of Mixing Flooded and AGM Batteries?

Question:

Hi Jeff, you upgraded my electronics on board my Hunter 50 cc. Now three years later I am in Asia, along the Thailand Malay border. My question is I have all AGM batteries on board with smart battery management on board. My starter battery is not holding charge and I need to replace it. They have no AGM batteries here in Langkawi. How serious is it if I get a non-AGM starter battery and what can go wrong? There is an ACR between house and start.

Answer:

Hi George, it is nice to hear from you. Not great to mix battery types. But it’s a manageable situation; worst case will be the starter battery will slowly overcharge. If possible, get a flooded starter lead acid battery that has vent caps so that you can top-off the electrolyte as it boils quicker than usual.