Had to replace my battery (under warranty) today. Couple of questions about it.

1. I was getting 13.2 MPG's before the swap. New battery bumped my MPG's to 18.5. Is this a "reset" type thing or was the voltage on the old battery causing the low MPG's? Thought vehicles ran off the alternator and used the batter just at the start.
2. Could the use of my winch drain the battery to the point it dies? Only used my winch twice this summer and the jeep was running each time.
3. Could it be the constant use of my air compressor all summer? I wheeled A LOT this summer.

Trying to be proactive this time around with battery care. Might even concider a dual set up.

Thanks in advance.

 

i would guess it reset your mpg calculator when you were swapping the battery. Itd be like if you tooks the button on the dash and reset it while driving on the highway itll go highes but once you get the city driving and all calculated back in itll go down..again thats just a guess.

2. ive used my winch to the point where even reving the engine it almost died.

3. as for the air compressor i have no idea i dont have one...

 

using any accessory excessively will kill your battery. If you continually cycle the battery real low from using your air compressor or winch or any other power hungry accessory eventually you will kill the battery.

 

Just get a good deep cycle battery. The stock battery is not up to the task

 

Maertz hit it on the head. Resetting the MPG clears out the previous data and the computer begins calculating Miles Per Gallon based on current miles and fuel usage since last reset.

In regards to the battery issue. Lead acid batteries do NOT like to be discharged lower than 10.5 to 10 volts. Doing so will severely decrease the life of the battery. Deep cycle batteries have thicker plates to better accommodate discharges but will still have their battery life impacted if discharged below their comfort level. It is easy to deplete a battery. For example, most automobile batteries are rated at around 45 amp hours. This means that the battery will theoretically run a load of 4.5 amps for ten hours or a load of 2.25 amps for 20 hours. Many devices such as a winch or compressor will require a HUGE load and will drain a battery very quickly. It is a good idea to keep the engine running while running such devices. That way the alternator will share in supplying the current draw while the device is running and will charge the battery when the device is idle. Since your engine is already running you will not have to worry about having the voltage be too low to start your vehicle when it is time to go home. However, be aware that larger current draws will not be sustained according to the above stated rate. For example, draining a battery at the rate of 45 amps will not result in the battery lasting one hour. It will be depleted in SUBSTANTIALLY less time.

It's possible your battery was discharged beyond it's comfort level and failed "prematurely".

KG6SLC aka Eugene

 

Batteries give out because of time or charge cycles. An automotive battery doesn't usually go through a lot of full charge cycles because the alternator is always there providing power, so it eventually dies due to time. A charge cycle is when the battery is discharged from 100% (12.8 volts) to 50% (12 volts) and then recharged.

An OEM battery that goes through a lot of charge cycles can be done in a couple years because there are only so many cycles in a battery. Cheap OEM batteries that are not deep cycle have the least number of cycles available.

Any battery that gets discharged more than 50% loses a chunk of its life. A battery that is allowed to go completely dead loses way more life, and replacement should be considered before heading into the back country.

A deep-cycle Absorbed Glass Mat (AGM) battery has the most available cycles before failure. A modern AGM battery also has enough cranking power to start an engine. The Optima battery is an example, but there are others. All AGM batteries tend to be top-of-the-line batteries.

A top-of-the-line deep cycle flooded cell battery will also give great service. The don't have as many cycles-before-failure as the AGM but the cycles per dollar are about the same. Interstate makes good flooded-cell deep-cycle batteries but they aren't found at the gas station.

Next are the crappy "marine-RV" multi-purpose batteries sold to people who don't know the difference by stores that don't care about the difference.

OEM non-deep-cycle batteries and bargain-priced batteries are here at the bottom of the list where they belong.

 

Great post! This reply is to to part I kept above.

The computer in these JKs will tell everything to shut down if the voltage drops too low. (That's why it won't run at all when a battery post is pulled like old cars would.)

So, if a heavy winch load pulls so much power from the battery/alternator combination that the voltage drops below JK's low-voltage threshold, the computer may shut the engine down.

There are ways to deal with this. Some dual battery setups may protect enough re-start power in one of the batteries. Another Jeep and jumper cables pretty much always works. But if a person is out there alone with one battery, care should be taken when winching.

 

Well said Freewill!

KG6SLC aka Eugene

 

x2 this is exactly why i said even while winching and revving the engine my vehicle almost died. i would have been screwed... got to be prepared

 

What about caring a spare battery and using jumper cables to start, if there is ever a need?