Not an electrickity guy so if this thread sounds basic, I apologize in advance. I've read most of the threads regarding batteries, what brands etc. and I still have some questions. I haven't driven my SD long enough to tell if the cranking power is up where it should be but I suspect it is not as the truck seems to labor a bit to get started. The starter would be slower turning over after a couple of days of sitting idle and if left for a week, the truck wouldn't start at all. So, I had both batteries tested ... both are Motorcraft.

The "first/black" battery is rated at 750 CCA according to the top label. It had no other labels on it ... not even the little round date sticker. It has a "check eye" but it looked both faintly red and green ... almost split half in half if that makes sense. Fully charged, it tested at 13.03 v and only 363 CCA with a recommendation to replace it. This seems like a no brainer as the load test CCA's are very low.

The "second/red" battery had no info labels left on it at all. It did have what looks like the date sticker on the side reading J/2 - 10/2. When I had it tested, the technician programmed in 700 CCA's as the original "factory" rating ... a best guess approach. In hindsight, I'm thinking it too was originally rated at 750 CCA's. Fully charged it tested at 12.59 v and 652 CCA. It passed the test (remember the parameter was set at 700 CCA's ... not the 750 it probably is). Does the 652 test number still mean the battery is OK?

My questions:

1. Does the J/2 - 10/2 sticker mean it was made in October of 2002 or does this sticker mean something else?
2. Is the "second/red" battery still OK to use at 652 CCA's?
3. If not, could I use it in my cargo trailer to light up some LED lights etc. I'd use it with a solar panel maintainer.
4. If it is safe and worthwhile to do so, could I use the "first/black" battery for my cargo trailer even though it's now rated at 363 CCA's instaed of the original 750 CCA's.
5. Is there a "percentage rule" to follow regarding the factory rating i.e. 750 CCA and the "as tested" rating i.e. 80% of factory ... that tells you when to keep using/give up on a battery?

I'm testing my two Motorcraft RV batteries tomorrow ... the group 65 one is rated at 750 CCA and the group 50 one is rated at 600 CCA's. Depending on what happens to the RV's battery tests, I'll probably end of buying a pair of 850 CCA rated batteries for the SD, and then use the other(s) in the cargo trailer or maybe the RV if the group 65 battery needs replacing. Does this sound reasonable?

Sorry for the long post. Your opinions are sought and welcomed. ~ Bugjr ~

 

The weak battery will always pull the good battery(s) down in a multi battery system.

Turn the questionable battery in for the core on the new batteries and put the best new pair you can buy in the truck.

 

I'll probably end of doing just ... and I'm assuming that I can't/shouldn't use the weakest battery to run the LED's in my cargo trailer. Right?

What about the RV using two batteries with two different CCA ratings i.e. 750 & 600. Is the 600 CCA rated battery considered "weaker" than the 750 CCA rated battery and if so, does it draw down the the stronger 750 CCA battery?

 

Yes, any system that runs multiple batteries should have them all match.

And I guess you could use the bad battery for a non-critical system but it is dying so even there it probably won't last long.

 

I agree especially in the truck there should be a matching pair of batteries. The TT may be ok with a mismatched set (I have a mismatched set of marine batteries in mine).

 

Closing the loop on my situation here. This battery situation was really bugging me. The first place I had them load tested (a Canadian Tire dealer ... like Pep Boys) said 3 of 4 batteries were toast. The 4th one tested at 653 CCA vs. 750. I didn't accept I had 3 bad batteries.

The second place (another Canadian Tire dealer) also said I had 3 bad batteries out of 4. Not the same three however!!!! In between tests, I put all 4 batteries on a trickle charge with at least one full day between testing.

One day later, I found a battery wholesaler that would test for free too. The batts were on the trickle charger again overnight. So, their verdict was 2 bad batteries and, 1 rated at 725/750 CCA and another testing at 653/750.

I bought 2 new Costco batteries for my SD (what a cranking difference) will put the strongest old battery back in my RV and will buy a new group 50 battery (600CCA) for my RV. I'll keep the weakest group 65 battery (653 CCA tested) to use in my cargo trailer. Case closed ... at least until I need a new battery .

 

Good outcome, good plan, good deal! Thanks for the follow up post.