Battery charging issue

[blueshark66]

Went to take the D for a drive the other day and the battery was dead. Enough power to turn on the lights but not crack the engine. It's a new battery I put in this past spring. So I hooked up the charger to the connections in the engine compartment. Checked it the next day and the lights on the charger were blinking like mad which, according to the manual, could indicated a bad battery. So I messed with it for a few minutes and made sure all the connections were good - the charger showed the same thing. Then, just for fun, I unhooked the charging cables and reattached them directly to the battery. Now the charger shows a low battery and that it is charging as normal. Just to make sure I'm not crazy, I moved the charger back to the engine compartment hookups and it shows a bad battery. Move it again back to the battery and everything is ok.

So I'm currently charging the battery directly, but does anyone have any idea what could be causing this? I don't understand how it works on the battery but not on the engine compartment hookups. Any help would be greatly appreciated!

Chris

[Ron]

Sounds like there is something on the car causing it, something left on, shorted, etc. Does the battery spark a little (every time) when you connect the last terminal? I'd start by disconnecting the alternator, then maybe one fuse at a time. See if the charger then likes it between each...


...in case it developed the short while sitting somehow, I'd be careful when re-hooking the battery up fully charged the first time....

[Shep]

Warranty the battery, it sounds suspect. Probably a bad cell or two.

Also, NEVER charge a battery while it is still connected to the car. Getting a jump is one thing, but if it plugs into a wall outlet, disconnect the battery before charging.

My rule of thumb for knowing if a battery is bad: once charged to 100%, load test for 10 seconds. 85% or lower charge level after the load test is my benchmark for immediate replacement. It's a bit harsh for most, but the ones that can't start a car anymore come in at 78% or less.

[Bitsyncmaster]

How long did the car sit (never run)? Three months drains about half the power with the OEM loads.

[David T]

Get the battery recharged and then tested. If the car sat unused for months the battery could just have gone dead from the small standby draw. Or you could have a large drain like the light for the glove box staying on for example.

[Elvis]

I never disconnect the batterie before charging.

never.

never had a problem.


What is your reason for saying this ?

[Bitsyncmaster]

I never disconnect the batterie before charging.

never.

never had a problem.


What is your reason for saying this ?

I agree. I usually just use the cigarette lighter to charge since it remains powered as long as you keep charging current less than 10 amps. If your smart charger is showing a problem, you must have a bad connection somewhere.

[blueshark66]

The car had been sitting for less than a week, so it should have been fine. I have noticed this problem before - I'll drive it to work and need a jump (for no apparent reason) to get it going at the end of the day. There must be something drawing power or a bad circuit somewhere. I'll try working through the fuses and see if I can isolate the issue.

I've never heard of unhooking the battery to charge it either. In fact, all the chargers come with the set of leads that attach to the battery so you don't have to unhook it every time you charge it or keep it on a trickle charge over the winter.

Thanks for the help!

[David T]

The car had been sitting for less than a week, so it should have been fine. I have noticed this problem before - I'll drive it to work and need a jump (for no apparent reason) to get it going at the end of the day. There must be something drawing power or a bad circuit somewhere. I'll try working through the fuses and see if I can isolate the issue.

I've never heard of unhooking the battery to charge it either. In fact, all the chargers come with the set of leads that attach to the battery so you don't have to unhook it every time you charge it or keep it on a trickle charge over the winter.

Thanks for the help!

Best practices now is to remove a dead battery in order to either swap it or recharge it. Especially on newer cars with all of the computers. To just maintain a battery it is OK to charge it (top it off) in the car. If the car only sat for a week either the battery is bad or you have a large draw (or possibly both!).

[Shep]

I always thought charging the battery while connected messes with the "smart" circuitry in the charger itself. Most of the chargers I see warn about this.

Trickle charging is maintenance and is more than okay, but I had assumed voltage spikes and empty/full detection was thrown off if the battery had drain while charging. Any truth to that?

Just remembered too, what about the battery light in the dash? Does it light up?

The battery still sounds faulty to me. Have it tested at an auto parts store, preferably the one you bought it from. Constant dead batteries say it can't hold a charge, which I see a lot of once the battery dies one too many times. Premature failure should be covered under warranty however.