So I've noticed lately the locks are a little 'sluggish', and it's kinda slow to crank at startup (still starts in just a few cranks tho).
SO I get out my volt meter & across the batt it reads 11.5. Running its 14.5ish (so seems alt is providing a good charge right?)
Shortly after turning off it's 12.3ish.
Now a few days latter batt is back down to 11.5 (yes I don't drive it that often) yet my falcon batt, that hasn't been started in over a month still reads 12.5v.

The current battery is a warrenty replacement that's only 13mos old, prior to that the battery was less than 24months old. Both replacments are from Sam's Club, I think they're Interstates.

So think it's the batteries, or something else? I need to have a load test done to it.

Does a battery replaced undery warrenty recieve a new date for replacmemnt? ie the newer batt is only 13mos into 18mo gurantee, or does it go back to original purchase date?

Thanks
Bryan

 

How long had the battery been sitting when it read 11.5 ?

How long did the truck run ?

How many days later did it read 11.5 again ?

If you are starting the truck, checking the voltage while running, and then shut it off in 5 min, I would suspect the battery to read 12.3.'

If you want to check if the battery is holding a charge you can try do a uick test.

Quick go / no go test at home if you have a charger and meter :

Have the battery stand alone ( at the very least have it disconnected from the truck's system ).
1. Charge the battery on a 2A setting until fully charged.

2. Once charged, take a voltage reading and record it.
2.1. This should be in the 13.n range.
2.1.1. on the low side, 12.9 / 12.8.
2.1.2. 12.6 could be acceptable for a battery that is getting to its last legs.
2.1.3. The charger should have the battery up in the high 12 / low 13 range.

3. Let the battery sit for 3 to 4 hours and take another reading
3.1. Should be within 0.2 / 0.3 VDC of the 1st reading.
3.2. This should have the battery at 12.6 to 12.8 range.

4. Let the battery sit overnight and take another reading
4.1. should be what the 2nd reading was +/- 0.10 / 0.20 VDC of the 2nd reading.

This should put the overnight ( unhooked ) reading within ~0.4 VDC of the fully charged reading.
If the battery is 1.0 VDC + off the 1st reading, the battery is not holding a charge on its own, and should be replaced.
If the truck is only used a few times per month, it could be normal loss, or a parasitic loss.
If it is a normal loss, a trickle charger on it that auto shuts off / changes the charge rate depending on the battery charge might be in order to keep the battery at peak, without 'boiling' it.

BatterMinder has a nice wall wart for maintaining batteries that get used infrequently.
It also has a desulfate function in it ( auto turns on and off ) as well as modified the charge rate depending on the battery voltage ( not the old school charge at a given rate until unplugged ).

Other wall wart chargers that have 3 levels of charging, but will only ID a sulfated battery ( at least when I did the research back then it was the case, products might have evolved since then ).
The 2 of the 3 levels are full voltage, and either high or low current until 100%, then it drops to low voltage / low current. This means unless the battery holds at 12.6 or higher, the charger will always be pounding the battery at the high constant voltage charge rate.

 

Thanks, I'll try those tips.

The first time I measured it, I had a coleman solar trickle charger pluged into the cig. lighter. Thinking maybe it was somehow not working/shorting therfore draining the batt, I unplugged it before the next reading. Both times I think it was reading about 11.5ish.

I'll have to get my AC trickle charger out & give it a good recharge; altho the last drive was over an hour long, so that should have brought it back up to full charge?

 

Read these captions:

. .

 

OK, I was out & Sam's was close by, so I just had them 'check the battery'

They said it was just low & needed a charge, so they charged it for about an hour.

Got home, measured 12.28v. 4hrs later 12.24v, but24hrs later is 11.95v.

Think they're just trying to delay so they don't have to replace it under warenty?

It's still factory excpet the air shocks have been removed, air pump dis connected, and the radio has been replaced; but with factory harness (so no power slicing was done)

 

It was charged for 1 hour, and you drove home, and it was already at 12.28 VDC, something is not right.

did you check all your cables for damage / corrosion ?

Take the battery and the alternator in to be tested.

Either the battery is not holding a charge or the alternator is not charging it.