Battery Gassing with MPPT Charge Controller

[Mike Two Moons]

Hello:
I am seeking input as to why I am experiencing problems with my new battery charging arrangement, which I installed last fall. I have not been able to get clarification from either the vendor or manufacturer of my new MPPT250 charge controller by BZ Products (25 amp), which I installed with hope of getting an increase in current and better charge control of the solar panels to the batteries.

Problem:
Over winter I boiled two batteries dry, which I attribute to the MPPT charge controller. After taking the two “cooked” batteries out of service and connecting to the two remaining batteries, I find the battery now connected to the MPPT input is also overcharging/gassing.

Original set-up: (worked OK for 8 years)
- Four 6 volt deep cycle batteries connected in series and parallel to equate to 2 twelve volt units 480 AH capacity
- Two 80 watt solar panels (in parallel – I haven’t been able to get them to work in series) leading through a Flexcharge NC25A Charge controller 25 amp
- KISS wind generator also feeding through the charge controller

Revised set-up:
- - Four 6 volt deep cycle batteries connected in series and parallel to equate to 2 twelve volt units 480 AH capacity
- Two 80 watt solar panels (in parallel) leading through the MPPT charge controller
- KISS wind generator wired directly to the batteries (no charge controller)

Before leaving the boat for the winter (six months) the KISS was decommissioned, so is not part of the problem. The batteries were equalized, fully charged and fully watered. The MPPT is rated for twelve volt, so why is the battery, which is connected to the MPPT so active, yet its’ partner shows little visible activity?

Do you think I have misunderstood the capability of this charge controller completely and it isn’t compatible with 6 volt batteries? The manufacturer’s comments were – wire the solar panels in series and “possibly a PWM controller (pulse width modulation controller???) may be better suited for your purposes”.

It is said that having the solar panels in series is better for the output, but the fact I haven’t achieved that, shouldn’t be a factor……should it?

What am I missing? Before I put things back to how they were I’d appreciate anyone’s input.

I am on the hard in Alanya, Turkey for the summer, so can rely on shore power to keep the beverages cool, but would like to know if I can utilize this MPPT unit, if at all.

Thanks…………..Mike