New battery, old battery, it doesn't matter!
Gentlemen, I work in a power house where we use several banks of batteries from 48V to 250V which utilize "cells" linked in series and parallel to raise the capacity and voltage to that which is required for the application. We change out cells frequently when performing periodic maintenance. Electrolyte levels, voltage levels, specific gravity is measured once a week on our critical batteries. Periodically we put the batteries on equalize to correct both individual cell voltages and the total battery voltage. Otherwise, we float a charger on the batteries and allow the charger to carry the load typically. I have worked in the power house for over 20 years and I would bet that some of the cells in a couple of the batteries have been there even before I got there. Life of the battery/cell is dependent upon several things. Maintenance is critical, keeping the water levels at the proper point, maintaing the voltage level within a certain band. Typically, a fully charged battery voltage is not 12 volts (for our boats or vehicles) but is about 13.2 or so volts depending upon the specific gravity of the individual cells. I suggest that everyone obtain a voltage monitoring device and ensure at the end of the day or week, or use of the boat, that the batteries are returned to the fully charged state. One other thing that is done with our batteries is to periodically discharge the battery to a very low level and then return the battery to a fully charged state. My take is that you can parallel any and all batteries you want just use common sense and try to make sure you are using similar rated batteries. Don't connect in series because the voltage will step up. Buy an automatic battery charger and connect it to your batteries and turn it on. Turn it off when you are gone from the boat for extended times just to be safe. Check the water level in your batteries frequently. You never know when the alternator or charger may go goofy and over charge your batteries and boil them dry. That equals heat and possible fire. Bad day at Black Rock!
Gentlemen, I work in a power house where we use several banks of batteries from 48V to 250V which utilize "cells" linked in series and parallel to raise the capacity and voltage to that which is required for the application. We change out cells frequently when performing periodic maintenance. Electrolyte levels, voltage levels, specific gravity is measured once a week on our critical batteries. Periodically we put the batteries on equalize to correct both individual cell voltages and the total battery voltage. Otherwise, we float a charger on the batteries and allow the charger to carry the load typically. I have worked in the power house for over 20 years and I would bet that some of the cells in a couple of the batteries have been there even before I got there. Life of the battery/cell is dependent upon several things. Maintenance is critical, keeping the water levels at the proper point, maintaing the voltage level within a certain band. Typically, a fully charged battery voltage is not 12 volts (for our boats or vehicles) but is about 13.2 or so volts depending upon the specific gravity of the individual cells. I suggest that everyone obtain a voltage monitoring device and ensure at the end of the day or week, or use of the boat, that the batteries are returned to the fully charged state. One other thing that is done with our batteries is to periodically discharge the battery to a very low level and then return the battery to a fully charged state. My take is that you can parallel any and all batteries you want just use common sense and try to make sure you are using similar rated batteries. Don't connect in series because the voltage will step up. Buy an automatic battery charger and connect it to your batteries and turn it on. Turn it off when you are gone from the boat for extended times just to be safe. Check the water level in your batteries frequently. You never know when the alternator or charger may go goofy and over charge your batteries and boil them dry. That equals heat and possible fire. Bad day at Black Rock!
We also had 3 diesel generators at each site, so in practice the battery bank only had to supply the load for a few seconds (if the automatic start worked) to a few minutes (if they had to go out to the gen shed to get one going). Patrick, be careful.... once you admit you don't have a dedicated starting battery, you'll be branded as a heretic. ;D (you're not alone - I don't either!) Cheers, Bob s/y X SAIL R 8