I'm looking to install a Diehard Platinum / Odyssey in my Xterra soon, but I'm confused on which is best. My uses will be hardly demanding at first, but sometime in the future (as in well before this battery dies) I hope to mount a winch. I have no immediate plans to install a dual battery setup, it's in the back of my mind, but I'm waiting for more need to arise before making that happen.
According to their website, I only have 3 DieHards I can choose from, which is also what I can pick up locally. Group 35, 65, or 34/78
Group 35 supposedly fits stock without mods. It has 850CCA @ 130 minutes reserve. Weight, 50lbs.
Group 34/78 will fit with minimal mods (longer cables). It has 740CCA @ 135 minutes reserve. Weight, 53lbs.
Group 65 is unknown to me if I can fit it. I'll throw it in for giggles in the event I could make it fit. 930CCA @ 135 minutes reserve. Weight, 60lbs.
Now, information I read in the past indicated that Group 34/78 had a significantly better reserve (Amp Hour I suppose) than the stock fit Group 35, making it preferred and Xterra owners were extending their cables left and right. The numbers I see only indicate a 5 minute difference, and this seems to be a negligible to me. My thoughts are why bother if it is so miniscule. Perhaps the designs have changed recently bringing them closer in specs?
Any advice would be appreciated. I'm looking to the best battery that I hope I'll be living with for a LONG time.
All batteries have specs; CA - cranking amps, CCA - cold cranking amps, RC - reserve capacity, AH - amp*hours.
Batteries designed and sold for cranking over an engine, generally don't do well when repeatedly deeply drained. Those will list CA, CCA and RC in the specs.
Batteries designed and sold for deep cycle use can crank over an engine, but generally have a bit lower CA and CCA numbers. Those will list AH in the specs.
The difference in RC and AH is in how they measure it. To get RC, they put a 25 amp load on the battery and measure how many minutes it takes (at 80 degrees F) to run the battery down to 10.5 volts (that's dead for a 12v battery).
To get AH, they figure out what load it will take to drain the battery dead in X hours. Generally, amp*hours are specced at "the 20 hour rate", meaning that from full to dead over a 20 hour period, it will supply a total of X amp hours. For instance, a battery which can supply a 5 amp load for 20 hours would be a 100 amp*hour battery, or "100ah @ 20 hour rate". Sometimes though, the specs will list the 10 hour rate.
Generally, you can tell which purpose the battery is designed for by which specs they list.
Odyssey however (and presumably Diehard Platinum) are a different sort of animal. They are designed to be used for either cranking or deep cycle use.
For a which, which can draw anywhere from 50 amps to 250 amps depending on load, the RC and AH numbers are pretty much useless.
CA and CCA numbers are how much max current the battery can supply for a short time (to run a starter). Unless you do a lot of winching for many minutes, you can ignore the RC and AH numbers and just get the most CA/CCA you can fit in your truck.