dead batteries

You my have something draining your batteries. Unhook all your grounds and jumpers. Put a test light between the ground wire where it hooks to battery and negetive post on battery. With all doors closed and all lights off if the test light lights up bright your elecrical system is pulling to much current. If so start pulling fuses until you find the circuit pulling. Remember if you open the door it is going to turn on your interior lights. Also your am fm radio is going to dimmly light test light. I pull the fuse for radio mem. And fuse for interior lamps if the test light is still lit pull fuses to find circuit responsible. Ive fixed alot of trucks killing batties this way'.

 

Because if he has two batteries that are less than a month old he has had a dead (or dying) battery problem very recently. The new batteries may only have masked an underlying problem for a month. And there is no guaranty that one of the new batteries hasn't failed early.

There are other things that can look like a battery failure. A weak alternator that is putting out less than 13.8 volts. A starter that is verging on failure. A poor electrical connection at the batteries. An my own personal favorite (headache), corrosion at the disconnect switch on the frame.

I prefer knowledge over guesswork.

 

http://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html

To cell test a battery, you need to pop the cell covers off. (Yes, even "maintenance free" batteries have cell covers)

Put your probes in the cell holes next to each other, you should have 2.1 V per cell. If you don't, that's your dead cell.

You should have had each battery load tested separately prior to replacing ANY battery. Same with checking your specific gravity.

You can try to put isolators in, but that might not solve your problem.


Run a full electrical system eval. Start with the batteries. If you got junk batteries, replace the set.

From there, make sure you have a strong starter.

Then your alternator. My favorite move here is to turn every accessory on the vehicle on, then disconnect the batteries. Weak alternators jump out at that point with a high electrical load. And I do mean turn every thing on.

The batteries are a "buffer" for the alternator, no buffer with a load, it kills the power. No power for the computer, it kills the engine.

Starters need to be tested for starter draw. It can be tricky without a clamp on Amp meter. You can do other tests too on the solenoid as well for voltage drop if you have to.

 

I use clamp meter to check for drain

Other way - after the errand deisconnect all batteries and check its voltage next morning with DVOM. Remove battery with lowers voltage and run truck on 3 batt.s /

If thiings go better - change this battery later

 

Ooooohhh not good! Voltage spikes can kill sensitive electronics.


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Specific gravity testers are cheap.

 

The problem with older batts is that they calcify. You can remove the calcium from the plates by charging them at a higher than normal charge rate, but this high charge rate can build too much heat, attack the plates and ruin the battery.

 

It's common to have a 2 amp draw sometimes bouncing to 3 amps when using a digital meter with a clamp pickup/probe. Beyond that, you got a problem.

 

Good find tx.
Like bender said earlier, if one or two need replacing, replace the set. The others are not far behind. It will be a long and hard winter if everything isnt 100%.