I have a 2001 Dodge Ram 2500 with a Cummins Diesel Engine and it has two (count 'em), two 750 Amp Batteries. One on each side of the engine Left and Right. Years ago, they could be bought with a 5-years warranty, now only a 3-year warranty is offered.
The factory installed batteries died in year 3 and year 4, so every three years I stop by an auto parts store (usually more than one for all the aforementioned reasons… ie: Advance, Auto Zone, Pep Boys, and O’Reilly’s) and have the batteries checked.
My gripe is that most parts store employees think that I do not need to unbolt the ground off one of the batteries to get a valid check of each battery separately. These folk tried to convince me that they can check each battery separately, when they are still connected. I’ve tried to convince then that if they did that, they would only get the reading of the strongest battery and one could be stone cold dead and they would not know…
But hey, we are now paying them $15 an hour for what, “Attendance…”
I don’t do that. When checking batteries on diesels with dual batteries I test both simultaneously at the combined CCA rating. So I would test yours at 1500CCA and if the available CCA were less than 1200 (80%) I would replace both batteries.
I’m surprised the two batteries are connected directly in parallel like that. Seldomm are two batteries exactly matched, so it seems like they would fight with each other. I’d have expected there to be battery isolation circuitry.
By connecting in parallel verses series, the voltage stays at 12-volts but doubles the amps the two batteries (each 750 Amp) combine to generate up to 1500 Amps. If they were connected in series, they would put out 24 volts, but only 750 Amps.
Think about a simple flashlight, when you stack batteries, Positive to Negative, the voltage doubles with two batteries, triples with three, (when connected in series…).
We’ve all seen the remarks that there are no longer any true mechanics and you are probably proof that previous statement is wrong. I am reading your user name, ASEMaster, to mean that you are an ASE Master Technician, and that Certification is not granted, but earned through demonstrated knowledge and skill.
And I bet you do not work in a parts store, dispensing useless and idiotic information like: windshield washing fluid makes a good car wash it you run out shampoo, or that a water injector increases gas mileage, or if you disconnect a vacuum hose your engine develops more power with the increases air, because the idle goes up when the hose is disconnected.
I believe your method has merit but as I wrote earlier, when my truck was new, the 5-year batteries that it came with did not last that long. One died at 3-years and the second went at 4-years. If a battery is marginal and the other is in excellent shape, you could still get your 80% reading, with the strong battery making up for the weak one.
Can’t you avoid that conversation by disconnecting one battery before you enter the building to request the battery test? Why are your batteries so dirty? Have you been adding water?
Wow, I guess some of you never heard of “don’t shoot the messenger…”
First off, I know my posting might have been misleading, but that is not my truck. I wanted a photo to accompany the notes I was writing about having two batteries… When I posted that topic and photo, it was “0-dark-thirty…” and I really did not feel like going out into the garage and trying to photograph my batteries at night. I Googled “2001 Ram Truck Engine” and that photo came up and it showed both batteries, so I used it (next time, I’ll post ‘googled photo’…"
I have included a current photo of my 22-year old, 2001 Dodge Ram’s Engine Compartment, showing the very clean condition of my batteries (both are almost 2-1/2 years old…
When I take the truck in to have the batteries tested, I always loosen the ground cable on the “slave battery” (passenger side…) so the batteries can be easily tested individually…
Cute, I like it…
As I wrote, the factory installed batteries were originally warranted 5-year. The dealership only replaced the bad batteries as needed, not as a matched pair. I replace batteries in pairs, I know a weak battery can bring a good one down. I learned that back in the '50s with my battery operated toys and those batteries often leaked just by looking at them too hard… (LoL)
As you could see in the photo above, the batteries are NAPA, and I replaced them as a pair, and even though they cost over $280 ($140 each), they are only warranted for 18-months… Receipt below…
Hydrometers can only be used to estimate the state of charge. I prefer to have not only the voltage but also a load test performed, “it just feels good…”
I had a cat years ago that liked to help me with my golf-swing practice. I’d hit a whiffle golf ball, and the cat would bring it right back to me for my next swing. This would go on for an hour or longer, cat never tired
