[Neweller]

John, that is always recommended. There should always be caution when matching up age variations of batteries. When they are connected in a bank, they will behave as a single unit. When having old and new batteries hooked to one another usually causes an unbalanced battery bank. Yes, it will technically work but there will be an unevenness which will generally cause an premature failure of the newer batteries and probably the whole entire bank.

If replacing a whole bank you have to ask yourself what type you will replace the with. If you are staying with the same type like 8D wet cells and they are Interstate, you might get a better trade-in through them. I have had Interstate give me either a standard core trade-in or up to double the core on a newer battery that they can recondition and sell for a profit. If you don't mind advertising and selling your older batteries, you can always try selling them on Craigslist.org. People will buy them for there equipment and so forth. Just a thought on offsetting the money. A lot of battery dealers charge a core whether you are buying a used, reconditioned or new battery.