It's hard to say what the condition is of the pack. Can you tell us what the currect voltage is? If it's close to 25.6v and assuming $125 is a good price then the 3 or 4 years is not a major problem. Lifepo4 cells drain at a rate of about 1% per month. But most manufactures ship to the suppliers at about 1/2 charge. So if the cells sat for 36 months they self drained about 36%. You do the math if they were on 1/2 charged in the first place. As I said if they are still holding about 25.6 they are in very good shape. You may not want it if they are below 22.4v.

You should actually be able to use the old IZip charger assuming it's also 24v. It likely has a max output of 29.2v whice is exactly what is needed for a 24v lifepo4 pack. Of course I am assuming this pack has a BMS. I would recommend looking on EBay for a female XLR plug that you can use to do a quick temp connection to the pack through the charging port........what ever you do be sure you connect it up correctly.........(Check the polarity). Eventually you may want to look into a new charger but be careful of buying "smart" chargers. Some BMSs will not ****ion correctly with smart chargers.

Bob

PS..The life of lifepo4 is said to be 10 or more if properly maintained and cared for. So as I said it's a matter of how low the cells were allowed to discharge. There is always possible that the pack was charged just before shipping to you. But so what as long as it was holding the charge when you received it..........