987687 Posted March 1, 2012 Share Posted March 1, 2012 I don't like gel or agm batteries in cars. They have a different charge curve, absorb, and float than a normal lead acid battery. Most importantly, it's a lower voltage than a normal lead acid. The regulator in the alternator doesn't know this, so it overcharges the gel/agm batteries. This ruins them, so they don't last as long as they should. Quote Link to comment Share on other sites More sharing options...
1-3-2-4 Posted March 1, 2012 Author Share Posted March 1, 2012 A fully charged lead-acid battery at rest should be 12.6v. By the time it gets down to 12v it's like 75% discharged. The alternator will try to pull the system voltage up over 14v, but if the battery is discharged it will be a high load on the system so 13v may be normal. Does it go up to 14v if you bring the engine RPM's up to about 2,500? I've had batteries marginal to the point where I had to put the headlights on for a minute to warm the battery up so it would have enough CCA to start the truck. Never had one where the extra load of an accessory was enough to reliably prevent it from cranking. Like I said before reading the voltage from the OBDII port in the program torque was not good since it was almost 1 V off It was showing 13.1 but with my meter it reads 14.3V Quote Link to comment Share on other sites More sharing options...
1-3-2-4 Posted March 1, 2012 Author Share Posted March 1, 2012 I took the battery out of the car to check it and clean it up a little. out of the car about 30 min or so it's reading 13.2 Quote Link to comment Share on other sites More sharing options...
Cougar Posted March 1, 2012 Share Posted March 1, 2012 Before you replace the battery it may be a good idea to have it tested and see what the condition of the battery really is. You may not need to replace it yet. When making voltage measurements it is helpful to know some things about where the test is made and what you are working with to make the test. Voltage measurements taken from the dash area are always going to be somewhat lower than ones taken at the battery due to wire losses. It shouldn't be a lot but it is some small amount. Also the device you are using to make the measurement can effect the results. Using a DVM meter is best since it will have a very high input impedance and place a very small load on the circuit, which will give a more accurate voltage reading. A meter with a low input resistance will cause the reading to drop down some due to loading on the circuit under test. Quote Link to comment Share on other sites More sharing options...
1-3-2-4 Posted March 1, 2012 Author Share Posted March 1, 2012 I will have it tested but it's of an unknown age and was deep cycled many of times.. it was dead when i went to test drive the car.. smart me decided to bring my jump pack with me. as we all know this type is not meant to be deep cycled. Quote Link to comment Share on other sites More sharing options...
1-3-2-4 Posted March 9, 2012 Author Share Posted March 9, 2012 Just wanted to update to say that so far it's been fine must of been the corrosion around the terminals (I picked up some marine) and after I cleaned them off it's been good. Quote Link to comment Share on other sites More sharing options...
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