Hi guys!I figured the folks here could explain to me what's going on with the batteries under the hood of my truck.I have a 2006 Dodge Ram diesel 4x4 short bed truck. It has 70,000 miles on it and mostly used to haul my camper in it's bed. The camper has 200+ watts of solar panels controlled with a Morningstar Pro Star PS-30 PWM controller. There's a Blue Sea battery isolator so that my truck's batteries are charged after my camper's batteries reach full charge. It also allows my truck's alternator to charge my camper's batteries. So, with all that said, my truck's batteries are currently 4 years old and they measure 12.4 volts after sitting overnight. Voltage during driving or solar charging is 14.4 volts. Right after shutting off, with the camper off the truck, the batteries are around 13.6 to 13.8 volts. Over night, they drop to 12.4 and stay there for days.Specific gravity of all the cells, this truck has two Group 65 FLA batteries, is between 1.25 and 1.26. I've taken the batteries out and placed on a bench with a voltage controlled power supply. Current draw drops to zero at 14.4 volts, so I can't boost the specific gravity unless I put a higher voltage in. If I put 15.2 volts into the battery I can get a current draw of 4 or 5 amps. Not sure that's what is good though for the battery, just info for you experts. Anyways, battery resting voltage is 12.4 volts, specific gravity of electrolyte is 1.26 across the cells. I have a load bank, 100amps. Hooked up, it states green/good as I throw the switch and hold it. I only hold it for 15 or 20 seconds, but the needle stays in the green zone. I suspect my battery is starting to sulfate and these readings indicate it's starting to just get old and wear out. Any thoughts?

Should be ok for another year or so IMO. I would equalize them if you have the chance, to help with that.You also have parasitic loads in the truck drawing down the "resting" voltage. Could use a maintenance charger on them if sitting a long time between trips or taking many short trips in town so they never get recharged.

Do the batteries drop to 12.4v sitting on the bench overnight, or only if in the camper? Also when sitting on the bench make sure you don't have the batteries connected to each other while sitting overnight. You don't want a failing battery to drag the other battery down with it.

The way I look at it, batteries start truck they are good!Batteries fail to start truck they are bad time to replace both!

BFL13 wrote:Should be ok for another year or so IMO. I would equalize them if you have the chance, to help with that.You also have parasitic loads in the truck drawing down the "resting" voltage. Could use a maintenance charger on them if sitting a long time between trips or taking many short trips in town so they never get recharged.I agree, I probably have a year or so left in the batteries, but I got these from Costco back when they sold the Kirkland branded car batteries. Warranty is for full refund up to 4 years and 100 months prorated. I'm right at the point where I can replace them virtually for free, but since Costco now only carries the Interstate brand, the 100 month prorated goes away, just 42 months full refund. I don't have parasitic loads. Based on Dodge truck forums, there should be 30ma of current draw when the truck is off. I measure mine and sure enough; 30ma after about a minute or so after shutting off the key. that's .03amps. Since the truck normally has the camper and solar charging things, I'm pretty sure they are fully charged. But just to be sure, I did leave it on a charger for over 48 hours trickle. Nothing changed after I disconnected the charger; next morning, batteries at 12.4 volts.

opnspaces wrote:Do the batteries drop to 12.4v sitting on the bench overnight, or only if in the camper? Also when sitting on the bench make sure you don't have the batteries connected to each other while sitting overnight. You don't want a failing battery to drag the other battery down with it.I have a mechanical disconnect and disconnected, still drops to 12.4. Both do the same.

Truck battery eval | Good Sam Community

time2roll
Nomad
Feb 06, 2017
100 amp load is a bit light for testing. Need to be closer to CCA unless the indicator adjusts for this.

I thought I read MEX said these 65s were often acid starved and that may account for the low voltage and specific gravity.

I would just keep running them. Test in 12 months to see if the numbers keep dropping.

For a superior replacement consider Bosch or Odyssey AGM.
Ski_Pro_3
Explorer
Feb 06, 2017
Decided to go ahead and change out the batteries now, while they are only starting to go south. These are group 65 batteries at 850cca and a reserve capacity of 150.

I got Group 31 batteries. They are commercial ones built by East Penn/DEKA. They are rated at 950CA and 175RC. I have to modify my battery trays slightly to get them to fit, but they are quite a bit heavier and as commercial batteries, designed for semis, agricultural and earth moving equipment, should be more rugged and last longer than just 4 years. That's my hope anyways.

Plus, they are the same price as group 65 batteries.
Ski_Pro_3
Explorer
Feb 06, 2017
rhagfo wrote:
The way I look at it, batteries start truck they are good!

Batteries fail to start truck they are bad time to replace both!

Normally, I'd say the same. However, the other day, my truck threw an engine code. Can't remember what it was, but based on truck forums, the problem was low battery voltage sensed at the ECM. Fix was to replace the batteries or poor battery connection.
My connections are fine, but the code is indicative of a weak battery, even though they test good with a 100amp load.

I think the batteries are just getting sulfated. I just had never seen voltage at 12.4 and specific gravity so out of whack with each other. conflicting each other.
Ski_Pro_3
Explorer
Feb 06, 2017
opnspaces wrote:
Do the batteries drop to 12.4v sitting on the bench overnight, or only if in the camper?

Also when sitting on the bench make sure you don't have the batteries connected to each other while sitting overnight. You don't want a failing battery to drag the other battery down with it.

I have a mechanical disconnect and disconnected, still drops to 12.4. Both do the same.
Ski_Pro_3
Explorer
Feb 06, 2017
BFL13 wrote:
Should be ok for another year or so IMO. I would equalize them if you have the chance, to help with that.

You also have parasitic loads in the truck drawing down the "resting" voltage. Could use a maintenance charger on them if sitting a long time between trips or taking many short trips in town so they never get recharged.

I agree, I probably have a year or so left in the batteries, but I got these from Costco back when they sold the Kirkland branded car batteries. Warranty is for full refund up to 4 years and 100 months prorated. I'm right at the point where I can replace them virtually for free, but since Costco now only carries the Interstate brand, the 100 month prorated goes away, just 42 months full refund.

I don't have parasitic loads. Based on Dodge truck forums, there should be 30ma of current draw when the truck is off. I measure mine and sure enough; 30ma after about a minute or so after shutting off the key. that's .03amps.

Since the truck normally has the camper and solar charging things, I'm pretty sure they are fully charged. But just to be sure, I did leave it on a charger for over 48 hours trickle. Nothing changed after I disconnected the charger; next morning, batteries at 12.4 volts.
rhagfo
Explorer III
Feb 06, 2017
The way I look at it, batteries start truck they are good!

Batteries fail to start truck they are bad time to replace both!
opnspaces
Navigator II
Feb 06, 2017
Do the batteries drop to 12.4v sitting on the bench overnight, or only if in the camper?

Also when sitting on the bench make sure you don't have the batteries connected to each other while sitting overnight. You don't want a failing battery to drag the other battery down with it.
BFL13
Explorer II
Feb 06, 2017
Should be ok for another year or so IMO. I would equalize them if you have the chance, to help with that.

You also have parasitic loads in the truck drawing down the "resting" voltage. Could use a maintenance charger on them if sitting a long time between trips or taking many short trips in town so they never get recharged.

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