# Parallel connection of old and new gel batteries

I have a battery system shown in the picture, 6 parallel branches of 4 batteries connected in series. The first 3 consist of old batteries which are 2 years old, the fourth branch consists of 1.5 year batteries, and the last two branches are made up of new batteries. Each branch contains battery balancers.

Can someone explain how batteries will work in this system if the charge / discharge cycle is 1 day? How batteries are charging (do they get full capacity)? What should I expect? Please give your recommendations. Thank you in advance for your answers.

PS I hope each answer will contain facts, because I already browsed the Internet, and got very confused. Everyone says opposite things.

UPD1:

At diagram above you can see battery voltage and current.

This diagram shows bus state.

Equipment that I use is Victron quattro 10KVA, Victron smart MPPT 100A, Fronius symo 5 kW, diesel generator 7,5 kW. 24 PV panels 270W connected to Victron smart MPPT and 24 PV panels 265 W connected to Fronius symo.

UPD2:

This is fully autonomous system not connected to the grid.

• Your diagram doesn't show how the batteries are charged, or what is discharging them, so most of the questions can't be answered. – Simon B Oct 31 '18 at 11:18
• @SimonB, Batteries with solar panels and a diesel generator are used in the system of fully autonomous power supply at home. – Jack Vildh Nov 1 '18 at 1:12
• This isn't really a complete answer, but... Your charge/discharge cycle isn't always one day - look at the start of the graph. The batteries aren't lasting that long. Notice that the battery voltage drops rapidly just before the generator starts up. You are running the batteries totally flat. They aren't going to last long treated like that. – Simon B Nov 1 '18 at 10:21
• To elaborate on Simon's comment, you can see a knee point in the voltage graph. After about 47.5V, the voltage drops off very rapidly, indicating the system has little charge left. Increasing your cutoff voltage to this point should greatly increase battery longevity while not perceptibly decreasing system performance. If you discharge them too deeply, in a year, their maximum capacity would be less than the capacity they currently have without deep discharge, except at that point, that decreased amount will be a deep discharge, and the capacity will continue to deteriorate rapidly. – K H Dec 31 '18 at 23:21
• The charge/discharge current will go mostly to the new batteries. The battery bank voltage will be determined mostly by the new batteries. The charge/discharge cycle will be mostly determined by the new batteries. The effective size of your battery bank will be mostly the new batteries. – david Jan 15 at 6:52