hello...mmm...as a reference, i go to a large battery store to get my batteries ..they are not new, but they are used, similar to what you are trying to do...
i have paid 15 bucks canadian each for a bunch of batteries(12 of them)..all hold their charge, and i am real happy with them as they are running everything in our remote cabin..refrigerator, lights, and of course stereo
....
thumbnail(from here), has gone to this same store and bought a whole skid of L-16's for 30 bucks each..i believe he said he bought 18 of them!...real good find for sure...tons of amp hours...
my main concern isnt just the price, but the fact that you will need them all to be able to keep the same level of charge...meaning it is real important that you dont buy for instance 3 batteries this week, and 4 next week from a different source, and of a different amp hour rating..and they all dont have the same amount of amp hours..the weakest battery in your battery bank will dictate what kind of amp hour rating you will get so more than the price is important here...making sure they are all very close to being the same strength is as important, if not more important than price..
i guess what i am trying to say is...first before buying batteries, you must be clear on how much energy will you be using, and secondly, you need to buy the batteries all at the same time, regardless if they are new or used...i think you are on the right track by finding some used batteries...15 bucks is a good deal in my opinion...if you are near a city, most larger battery stores sell large back up battery systems to police departments, fire departments, casino's and any other big business...so every couple years these companies trade in their back up systems and in most cases, they are always charged up, they have never been used,.just like the dusty battery on your local store shelf...this kind of a deal is worth the time to check into...5 years old, as another poster has mentioned is a stetch, but it is a good starting point..maybe call another battery store and see what they have..newer the better...usually they take business' used batteries and only give them scrap prices for them...so battery stores cannot understand what we want them for? but this is our little secret in a way, as i believe as soon as these battery stores find there is a market for their used batteries, then scrap prices will no longer be offered, so what they dont know, doesnt hurt them...as a matter of fact., the same store that i buy my used batteries from, and a couple others i have told them about this store,are now starting to have trouble securing used batteries, as their is someone from quebec who will drive down (600 mile trip), to purchase everything this store has ...so, people are starting to know that their is money to be made on used batteries....this guy will come and make 2 trips a week (load right up), so he isnt just buying these batteries for himself, he is reselling them most likely to alternative energy folks like me and you....good luck on your project...pickster