|09-19-2012 09:08 AM|
Also, charging the battery with the alternator will not get enough capacity back into a battery to return it's original performance... even a couple hours at idle wouldn't do much. Alternators don't typically give their full output until the engine reaches around 1,500-2,000 RPM. A battery charger is a much better option for this type of thing, set it to a 2 amp trickle, and leave it on all night... then you may get a good charge on the batteryrge on the battery, unless it's been deep cycled too many times.
|09-19-2012 06:36 AM|
This would pretty much eliminate the possibility of parasitic current as it has run for 30 minutes (more than enough to put a substantial charge in the battery) and it is dead immediately. That would mean that either there is a problem in the charging circuit, the main battery connections, or the activation system for when you turn the key on. Starting with a jumper battery would pretty much eliminate the activation system, leaving the probable cause in the main battery system.
|09-18-2012 02:01 PM|
The jeep stays running once it's started, right? It's most likely not the alternator if so. Sparky sounds like he's on the right track, you probably have excessive parasitic current draw; this could be shorted wiring, a stuck relay, or a device that isn't powering down. Once the draw drains the battery once, the battery can't ever hold the same capacity it once did - the more it dies, the worse it gets. I would get a multi-meter and check for current draw, it's fairly simple.
First, disconnect the negative battery wire from the battery post. Close all doors, and make sure all electrical components are off. Place the multi-meter's black lead in the "COM" jack, and the red lead in the "A" jack, and turn it on to the DC AMP setting. Connect one lead (doesn't matter which one) to the negative battery post, and the other to the negative battery cable. Check the reading on your multi-meter while holding the leads in place; they will be high at first (a couple amps), but drop down within a couple minutes. After the vehicle "shuts down", the draw should measure around 35-40 milli amps, or .035 amps. If you are getting a higher reading, you have excessive parasitic current draw. The first steps would be to disconnect any aftermarket devices or wiring that has been installed and take the reading again. If it hasn't improved, start to pull fuses in the fuseboxes one at a time until the draw drops back down to .035 amps or so. Once you see the drop, you can determine which fuse or component is causing the draw.
Even if the second battery is nearly dead, but still holding 12 volts, it could help "jump" your Jeep when you wire it together with another nearly dead battery. If you hook them up in parallel like jumper cables would, you are keeping the voltage constant, but increasing the capacity, or amps it puts out. Alone, the batteries probably don't have enough capacity to crank the starter. I recently had to replace my battery, and just before I did, I had very similar issues to what you are describing. My volt meter would jump around to about 16 volts or so as well. A weak battery will not help to equalize the voltage the alternator is putting out, so you get a higher voltage.
|09-18-2012 01:42 PM|
Check the battery cables
Be sure to check the battery cables themselves. They could be corroded inside the insulation. If you have a voltmeter, check the voltage across the battery terminals themselves. Then, when trying to start check from the vehicle ground to the various parts of the circuit (battery negative, battery positive, starter hot lead, etc.). Try to see where there is a break in the voltage readings to see just where you are losing the voltage.
My guess is it is in the ground side.
|09-18-2012 12:41 PM|
|sparky||Sounds like a short draining the battery.|
|09-18-2012 06:12 AM|
|Wattapunk||CLean/tightened the battery connections along with others suggestion regarding checking for fray wires.|
|09-17-2012 08:40 PM|
|09-17-2012 08:22 PM|
|c_goodnow||Try checking the ground side of the battery? might be a bit loose either at the battery or on the block. Make sure its all cleaned up too|
|09-17-2012 08:05 PM|
Wont start unless I connect to two batteries?!
Hey Guys, hope everyone had a great weekend wherever they were. So I had a little Marine reunion over the weekend and my 04 Wrangler Sport 4.0 with the Inline 6 worked when I picked up my buddies at the airport and all the way home, went to hit the bars and wouldnt start, gotta jump and hit up walmart for a battery, replace it and it starts right up. Next day its back to being dead, the speedometer and tackometer needles start twitching. Figure "hell if its dead again then it has to be the alternator", hour later I get my new alternator in and starts right up. It works over the weekend and now its dead again, and by dead I mean that when I open my doors the lights wont even come on. I still had the battery I had just replaced sitting on the floor and tried to jump it using that since nobody was around for a jump, and I'll be damned it worked. Let it run for about half an hour thinking it might charge the battery, thinking about the easiest and cheapest solution of course, and 30 minutes later I turn it off and same thing, wont start and seems like there is no battery connected at all. I jump it again with the allegedly dead battery and it works, switch the batteries out and repeat the jumping process and it works, so both batteries work. I took it for a short drive and realized that the voltage goes up and down when I give it more gas, about 12 at idle and up to 16 or so when its running at 4,000 rpms. Any ideas on what it could be? Going to school on the GI Bill which hasnt hit yet so money is tight but at the same time I need the rig to be running. Any help would be appreciated! Thanks again guys