Battery charged, suddenly no start.

[ParadiseMJ]

My MJ has been sitting for a couple weeks, so I went to take it for a ride.  Started up a little slow, but started and ran fine for 50 or so miles.  Got home and parked it overnight.  In the morning it started slow again.  So I put it on a charger this morning and left it on for 8-10 hours.  Get in, "click", then nothing. 

So I clean off the terminals extra shiny, then I get the clicking relay.  Then I put the 50 amp START charger on it...here's the main thing I see.  When I turn the key to ON, the tach jumps up to 2k or so, all the lights and buzzers are working, but all I get is the clicking relay.  The battery is now fully charged.

 

Can anyone help me?

[Jeep Driver]

Time for a new battery. 

[rokinn]

I've used this thing to test whether my 12v car/rv batteries are good or not.  The voltmeter can read proper voltage but the battery can still be bad.

 

https://www.homedepot.com/p/Commercial-Electric-Electric-Battery-Tester-MS602H/202353291

 

[HOrnbrod]

I don't know if the above meter load tests an automotive 12VDC battery under load or not; I suspect it does not looking at the rotary switch positions. And yes, a battery can read 12-14 DC at rest and still fail under a start load because it can not deliver sufficient amperage due to battery calcification. Calcification can cause one or more internally shorted cells or plates depending on it's construction and the battery fails to deliver it's rated CCA (Cold Cranking Amps) to overcome the load when starting. Sometimes you can "boil" a calcified battery free, but it requires at least a 20A constant current charge HD hooked up overnight with the cell caps pulled for better gas venting and disconnected from it's load. And always when charging the battery overnight with any charger, disco the negative cable.

[Gene]

If you have a helper, then put the voltmeter on the battery  posts, a fully charged battery should read about 12.5 V or higher. Then have someone turn the ignition key to start. If the voltage goes way low, perhaps five or six volts, then the battery is defective. If the battery voltage stays high, not really dropping below 12, then look elsewhere. Bad starter solenoid would be one possibility.

Gene

[ParadiseMJ]

Well, it might just be the battery but, I went out a little later and checked the voltage at the post...the post itself, got 13.2v and then on the terminal clamp, and got 2.5v.  I thought it could just be a cheap fix, bad contact from the post to the cable clamp.  I'll probably bite the bullet and get a battery and new clamps.

 

Thanks

[Gene]

Hi Paradise,

 

That voltage difference goes along with a high resistance connection. I would try changing the terminal (or whole cable) first.

 

Gene

[ParadiseMJ]

I bought a new battery, New terminals, Found a sketchy starter relay connection.  Fixed ground to block. Go figure, my voltmeter finally sticks straight up, not to 11, my radio works, my outlet works, lights don't dim when accy's turned on. First trip to the mountains since January, starts like new.

 

Thanks for the tips.