I have a customer with battery problems. The boat is a Niad 44, maybe 7 yrs old. There are 6 Lifeline Group 31 batteries in 3 banks of 24v. The 3 battery banks are each wired to a common bus bar of pos and neg. The pos, thru an on-off battery switch. 12 v needs are taken off a 24-12 convertor. There are no power drains off any battery. In each battery bank of 2 batteries, 1 battery is failing. Testing was done with a Midtronics tester, 250cca on a 600cca battery. Lifeline refused to accept the results (they say the tester is junk) so I confirmed the results with a full charge and resting voltage test. Charging is directly to the pos buss, with a Balmar 24v alt or Mastervolt charger. The batteries are only 1 year old. These are the 4th set of batteries. Like everyone, they probably don't get a regular full charge. Voltage drop is minimal. My question is would it be better to wire the 3 banks in parallel to make 1 large bank, with 1 single pos and neg to the bus bars. Would it promote more even charging? I don't want to replace the batteries without making some change to a system that's not working. What would you recommend, and why? Thanks for your help.