As of late, my truck has been getting harder to start. I could start it by using a battery charger or jumping it the first time, and then it was good for the rest of the day. Keep in mind it hasd only been about 5 times that I have done this. I used a meter to test them yesterday and with the ignition off, 12.4v, ignition on, dropped to 10.4v then back up slowly to 11+v. Now the cool part, I had my 6 year old daughter turn the key over to start and the meter would drop to between 5v and 6v. I searched through the forum and read some differing opinions on brands and where to purchase, but didn't really find what I am curious to know. So now to the question I have. What cranking amps would be best to try and purchase? Thanks

 

These are the stock battery specs: 7.3L Diesel Dual 750 cold cranking amps 78 amp hour. I try to use batteries of higher ratings. IIRC, mine are 850 CCA and 150 minutes reserve capacity. I try to get one with the longest reserve minutes for the CCA I'm looking for.

Battery Storage Capacity Ratings
Two standard ratings are used to measure a battery's storage capacity.

Amp Hours

The Amp Hour rating tells you how much amperage is available when discharged evenly over a 20 hour period. The amp hour rating is cumulative, so in order to know how many constant amps the battery will output for 20 hours, you have to divide the amp hour rating by 20. Example: If a battery has an amp hour rating of 75, dividing by 20 = 3.75. Such a battery can carry a 3.75 amp load for 20 hours before dropping to 10.5 volts. (10.5 volts is the fully discharged level, at which point the battery needs to be recharged.) A battery with an amp hour rating of 55 will carry a 2.75 amp load for 20 hours before dropping to 10.5 volts.

Reserve Minutes

Reserve minutes is the number of minutes a battery will carry a 25 amp load before dropping to 10.5 volts. (10.5 volts is the fully discharged level, at which point the battery needs to be recharged.)

 

Thanks Roland! My truck usually sits around a week before I drive out to the farm. I was thinking 850 would be the magical number.

 

Hey David.

Make sure the connections to the battery are clean, if you hadn't already done this. Take another reading putting the meter on the battery post only, then on the battery clamp. I had this problem with mine before.

 

i had a similiar issue ^, cables would show 12v but on the post 10v. i found my battery clamp bolts were erroding away in the center.

 

Thanks all. The batteries are Interstate brand and were in the truck when I bought it. The receipts from the po show 1 replaced before, and they are both out of warranty. I plan to have them tested, but I am pretty sure 1 is old enough to be done. I try to keep up on the connections because from prior reading on here about the issues that can cause. When I tested them I'm pretty sure I was on the post when I tested, but didn't test from the cables.

 

I think that should be stated the other way around. Anyway, always check for differences between post and clamp; indicator of a connection problem.

 

Went to Sam's and had the batt's tested. 1 tested low, needs charged. 1 tested replace. bought 2 @ Sam's, kapt the one that needed charged since I had 2 old cores. Appreciate the posts from you all.

 

Good for you. It is always best to replace them both at the same time. One weak batt will always draw the other one down.

 

trying to keep post short, i should of mention one battery showed 12v at both cable and post, the other battery showed 12v at cable, 10v at post, engine off, key off. i clean my connections regulary and use spray can corrision preventer, so i was a little suprised to find a bad connection until i discovered the battery bolt. to the op hope the new batteries fix your problems, for peace of mind i would check and clean the grounds and power wire and snug the starter bolts.

 

I follow you now! I usually remove a cable from one battery to isolate them and test them individually. I can see now how you were getting those volt readings.

 

New batts in, clean cables, connect, fired up strong! Thanks for the input and preventative advice.