Sorry for your battery issue. In my opinion, battery quality and longevity have both decreased over past 20+ years…especially for common brands of flooded lead acid batteries.
Before I leave the store with a new battery, I check date of manufacture, resting voltage, cold cranking, and load test. This may irritate common auto parts store folks…too bad. These tests are generally more accurate only if the batteries have not been on a charger within past 30 minutes. I make this point because if you call ahead to find out if the store has your type of battery, some locations will slap a battery on a charger (particularly one with an older date sticker) before you arrive and it may pass some tests with the somewhat inflated readings.
Before I install a battery into one of our Vipers, I fully charge it with a real charger…using appropriate settings for battery type. Battery tenders are not meant to do this…though I do use them regularly post installation. Starting and driving a car regularly is generally a good thing…BUT, is the drive of sufficient length and type to offset startup drain and support all accessories? Admittedly, this last point is more of an issue with a Gen I and II Viper where loafing down a highway for a short drive at 1300 rpm and observing speed limit with multiple accessories on may not fully recharge your battery…especially as it ages and/or it lives in a high heat location. Heat kills batteries !!
For multiple reasons, starting over 16 years ago, I began changing our batteries over to AGM batteries instead of flooded lead acid types. My time between battery changes more than doubled…even in a Gen I and a Gen II that live in a non-climate controlled environment with no provision for battery tenders. These cars get charged every month (plus or minus a couple of weeks) either at my house or using a portable generator.
NOTE: A Gen III Viper sitting (in hibernation mode) next to the above two Vipers has a 15 year+old AGM battery in it that still shows at least 50% charge even if the time between is 6-8 weeks.
I do not use hibernation (sleep) mode in the Gen IV’s or V at home since they are on tenders. Therefore. I cannot quote an accurate IOD (Ignition Off Draw) amperage for those beasts with and without hibernation mode. Generally, a stock Gen I or II can draw up to 30 milliamps continously and still be “normal” per Service Manuals. You might want to consider the IOD test to look for an abnormal amperage draw.
Yes, AGM batteries are more expensive, but to me they are a better valve…especially in Gen I and II Vipers where pulling the left rear wheel off to change the battery gets old quickly !!
For what it’s worth, my two favorite AGM battery types are Interstate MTZ and Odyssey…based on personal experiences…including consideration of warranty, availability, ease of return if it suffers premature failure, and service from the personnel.
I hope this helps a bit as you search for a solution to your issue.
Others may chime in with more specific info or differences of opinion. “It’s all good !!”