Posted: May 19, 2020
GMC Sierra 2500HD Battery
If you have a GMC Sierra 2500HD from the early to mid-2000s, especially one equipped with a Duramax engine and dual batteries, you know battery replacement is not an inexpensive endeavor. However, did you know any vehicle equipped with multiple batteries should always have all the batteries replaced at the same time? The reason is that as batteries age, the way they work changes. Internal resistance begins to form inside a battery, which can make an older battery with more internal resistance have less reserve capacity and take longer to charge.
So if you have a GMC Sierra 2500HD that is equipped with two batteries and you know one had gone bad, you should really replace both batteries. If you don't, you'll end up with a new battery with low internal resistance and and older battery with higher internal resistance. The old battery will take longer to get fully-charged (and may not ever get fully-charged), while the new battery may get fully-charged right away and then overcharged, as the alternator or battery charger attempts to fully-charge the older battery. That can shorten the lifespan of both batteries and lead to a regular cycle of replacing batteries far more often, than if you just replaced them both at the same time.
So what do you do with the other battery in a two-battery application, if you know it is still good and even passes a load test? If it fits, you can continue using it in another application or you can recycle it and receive a core credit when you buy your new batteries. So which battery will fit in your GMC Sierra 2500HD? That depends on the year of your truck and the engine in it.
For example, if you have a 2000 GMC Sierra 2500 with a 6.0-liter gas engine, you have five different OPTIMA batteries to choose from in both REDTOP and YELLOWTOP options. Which should you choose? If your truck is basically stock and doesn't have significant electrical demands, then a REDTOP is a great option. If your truck has significant electrical accessories, like an aftermarket stereo, car alarm, auxiliary lights, a winch, snowplow or other such accessories, then a YELLOWTOP designed for both starting and deep-cycle use is a better choice.
However, move just a few years later to a 2007 GMC Sierra 2500HD with a 6.6-liter Duramax diesel engine and your battery choices are reduced to just the H6 OPTIMA YELLOWTOP. You can find the exact battery fitment for your GMC Sierra 2500 or 2500HD here. Regardless of whether you end up with one or two batteries in either REDTOP or YELLOWTOP sizes, the key to maximizing battery lifespan and performance is keeping your battery fully-charged whenever possible.
REDTOP batteries are fully-charged at about 12.6-12.8 volts, while YELLOWTOP batteries are fully-charged at about 13.0-13.2 volts. Accessories like OnStar, that stay active even when your truck isn't running can slowly (or quickly) discharge your battery. When any battery gets discharged below 12.4 volts, sulfation starts forming, which is what increases that internal resistance in a battery and diminishes lifespan and capacity.
That makes a quality battery charger an excellent investment for any vehicle. We believe in that so much, that we'll add a year of warranty coverage to your new battery purchase, if you buy your battery and Digital 1200 battery charger from us at the same time!