Dual Batteries in a 2003 Ford Excursion Diesel

When I bought the DieHard Platinums, they were one of the most highly rated and highest CCA battery available for their size. There are probably very few (if any) retailers that actually manufacture the batteries they sell. The Platinums are actually made by EnerSys. But I digress. This thread was not suppose to be about where we shop or what we buy. I was just trying to find out if there’s a good reason why I should or should not run 2 batteries with different specs. Should I give up 2 years worth of free replacement warranty by prematurely replacing it so I have 2 of the exact same battery? That’s the real question here.

The existing batteries were 2 Die Hard Platinums, one less than 2 yrs old and the other less than 3 yrs old

I’d say you have evidence that not replacing the batteries together shortens the older one’s life.

I think when one battery fails, the other battery will die trying to keep it alive, now a similar anecdote, you can have a 10 watt charger, but if 5 watts is all it needs, that is all it will take, I think that may apply to different cca of the 2 batteries.

So one battery may fail sooner than the other

That is the reason as stated previously by an esteemed collligue for the recommendation for replacing both, but it is not an automatic disaster, my 2 cents

fyi, the current month’s issue of Consumer Reports has the current test results and recommendations for car batteries. The battery make/models that tested best varied quite a bit, depending on the group size. Some of the Sears versions were top rated in certain groups. The Sears batteries in general were a little on the pricier side of the spectrum it seemed.

When I first started driving truck our equipment was 6 volt, Shortly after we were in the process of changing over to 12 Volts. Both the 6 volt and 12 volt tractors used four 6volt batteries. The 6 volt tractors were connected in parallel /series combination and even after the tractors were all 12 volt we had a vary volt box on the back of the tractor so we could pull both 6 v and 12v trailers.
If a road tractor wouldn’t start because of a bad battery, they were all replaced and tested. The good ones were set aside for the city tractors where only the bad batteries were replaced.

If most of your driving is close to home you can treat it like a city tractor. If you mix in long haule, replace them both.