Have a 2016 F150 with original battery. I left my rear auxiliary lights on last night accidentally (yes I know I’m an idiot) and the battery was completely dead. Tried leaving it tied to my wife’s for a few minutes and nothing. Local auto parts store measured it at 8 volts. Left it on charger for two hours and it measured 11.6 volts. They said I needed a new battery. Does this sound right?

TIA
Chris

 

It's probably an AGM battery which requires it's own charging procedure, they use a high current charger. They only way to load test a battery is to have it at full charge, 11.6 V isn't full. All that being said it's not uncommon for these batteries to have a seemingly early death. Long idle periods at discharge and deep discharges like you did hasten their end. I hope that helps.

 

What does "tied to my wife’s" mean?

What kind of charger did you leave it on for 2 hrs.?...fast charger, trickle charger, etc.
Is it an AGM battery?

Generally when a 3 yr.old OEM battery is completely drained dead, its probably time for a new battery.

 

I would leave it on a charger overnight. If it starts the truck then use it until it fails. I wouldn't replace it unless the overnight charge doesn't work.

 

It was on whatever charger Autozone uses. What you said helps. It makes it sound reasonable.

😂 Connected my dead battery to her good one and let her car run. Kind of like in real life. 😞. Your explanation also makes me feel better. Just wanted to make sure I was getting ripped off.

Thanks guys.

 

The attached might be useful even if it refers to specific Ford testers.

If its an AGM battery it is maintenance free. They are essentially sealed except for a vent.

If it is a FLA battery, even if it says "Maintenance Free", it is not really maintenance free. They all have one or two covers that can usually be removed with a little firm prying. Once off, you will see the six cell ports and can check the electrolyte level. If the electrolyte is below the top of the plates then just adding fluid may or may not help to recover your battery health. Before adding water you should get a battery electrolyte tester (a hydrometer) and check the strength of the acid. The actual hydrometer reading which tells you whether your acid strong is correct or not is dependent on the charge level of the battery. If you only need to add water (which is very likely the case) only add de-ionized or distilled water. Tap water is bad because it contains chlorides.

If the battery has been heavily discharged several times, the lead plates could be sulfated which drastically reduces the performance of the battery. Several companies make smart chargers which work with AGM and FLA batteries and often have a desulfating setting. Running a desulfating cycle may recover the battery's performance.

Note that the Battery Management System (BMS) needs the charger to be connected properly or it will not "know" the actual charge state of the battery. Charger positive (+) connected to the positive (+) of the battery; Charger negative (-) to chassis ground (not to the negative terminal of the battery).

Caution: Be careful around the electrolyte. It is sulfuric acid, highly corrosive and if it gets into your eyes can cause blindness.

 

Sounds too damn complicated. Why not just a simple battery? Buying a new one seems easier and cheaper than having to buy a bunch of testing equipment.

 

Hydrometer - $10
Digital volt-ohm-amp meter - $50 (you don't need a Fluke)
Good smart battery charger - $50-75 (I have a NOCO 7200)
Battery post cleaner - $3

Most quick tests can be performed with the multi-meter.

Don't need a battery tester. Use NAPA's, etc.

Batteries aren't cheap these days and why add one more battery which needs to be recycled (hopefully not going to a landfill).

 

Charging it to 11.6 is only useful if we know the size of the charger. On a 100A charger, that's horrible... on a 4A charger, that's expected. That said, it's entirely possible to destroy (usually by reversing a cell) a lead-acid battery with one very deep discharge.

 

Im surprised that the batt monitor in the truck didnt shut everything off before the battery died. Isnt it supposed to do that?