Matt Andrews

Kind of dumb question, because I feel like I know the answer. I think I've got a bad battery. but...

Several of you know I bought a new to me car a couple mos ago. I've been using the kill switch when the car sits. I've found that if I don't, and I don't drive it for 2 days, the car won't start. My DeWalt battery charger throws an error saying there is something wrong with the battery. Battery was new August of 2016. Car maybe recieved 200 miles in that 3 year period. I'm told it sat with the battery disconnected most of that time. So what are the chances the battery is bad, and it isn't something else draining the battery when its not disconnected?

FWIW, its "dry battery" : 999-611-036-20 which appears to be discontinued? (doesn't look that dry to me as fluid seems to slosh in it...)

Matt

911PERVY

Only 2 days its done I would guess, "dry" means shipped dry then acid added at installation. Moll batteries arent very good

Stephen Koch

You could also have a drain. My front trunk switch causes a drain as it keeps windows powered as it thinks trunk is open when it is closed and this drains a fresh battery in a couple of days. Only way you can tell is check for drain or lock car with window down, wait 5 mins and then reach inaide see if window switch works (it shouldn't).

Earlydays

If the trunk switch is open, it would mean that the trunk light is also on and this will drain the battery over time. Easy to check - close trunk and wait a few minutes, if it is on you will feel the warmth from the light on the outside of the trunk lid.

Stephen Koch

In my case the front trunk light is off, you can see the switch turning off the trunk light but the car still thinks the front trunk is open and keeps the window switches live. In a dark garage you can easily see the light go off through the shutline. I dont know why it does this but it does!

Stephen

Antigravity

If you battery even sat one year or less, it would be over-discharged and taking on some damage.... if it sat 2 years... its DUST, a GONER.

Any battery chemistry drained below roughly 9.5 is OVER-DISCHARGED. Over discharging and letting is sit for a few month below the 8v range is damaging the battery cell... and as it gets lower it getting more damaged... as as the time goes on it ruining it. At a minimum your battery should not be seeing below 10.5 EVER to keep it healthy. Batteries operate in a very small voltage range and as I mention are over discharge going below 9.5. Even at 11v that is not enough voltage to start the car. So optimally you keep the battery charged and are driving enough to do that.

Just get a new battery and move forward... you don't even have to chase checking it out or trying to charge it anymore.

Railmaster.

Or start the camera in your phone and film inside the frunk and look at the film if the light goes out or not.

Kappi2907

Buy a trickle charger with test function (e.g scheduled decharge), this Will extend the live of your battery. Average life span of a A brand is at least 6 years!

Matt Andrews

so I must have a drain. with the windows down, I cut off the car and remove the key. then lock the doors. 30 mins later, the windows still go up and down.

I don't have an underhood light. I've never noticed before, but I guess they weren't installed on carrera cup cars. What other switches should I be investigating that may be keeping power running in the car?

Kappi2907

Disconnect the battery cable on the negative pole, remove fuse by fuse while measuring current with a multimeter connected between the negative pole and the disconnected battery cable. Start with the usual suspect like alarm, door switches, etc

Deserion

Wonder if your power window relay is sticking. I recently discovered that mine was (temperature difference after sitting a few days). Removed the cover, cleaned with electronics cleaner, and it's been going good so far though I plan on replacing it, still.

Problem is that this method will effectively mask any real power draws with the removal of fuses. Testing with the fuses in-place can prevent that.

Matt Andrews

I will google this, but if anyone has a diagram or instructions on testing the relay, I'd appreciate it. I've pulled the relay and have it on my desk now with my multimeter

Kappi2907

Well it worked for me and a lot of other P drivers. Fastes way to find an issue with 'leaking' current. I guess my grandpa was wrong learning me this method (45y experienced mechanic).

Matt Andrews

Kappi-
Your suggestion is a method for testing the relays, right? Meaning pulling the fuse that leverages the relay, and seeing if you can complete a circuit with a tester?

Matt Andrews

I cleaned the relay and put it back in. When you remove the key and open the door, the relay opens cutting power to the windows. but if you don't open the door, the relay never opens to "turn off" the windows. Thats not controlled by the relay is it? but even if it is, I open the door every time I get out. How is this causing the battery drain?