I have a slow battery leak on my '03 S2k. After leaving my car parked over the weekend, I have about a 75% of starting the car without a jump. If I don't drive it for 3 days, it's about a 10% chance. There is no problem with starting the car within 24 hours of driving it. I have a trickle charger that I use if I am not driving it for long periods of time. It confirms that the battery is losing charge over time. AAA has tested the battery and says it is good.

What could be causing the leak? My mechanic said it might be the aftermarket Viper alarm. Or that my Optima battery might be crap. Could it be anything else? An electrical engineer told me it might be a leaky diode, which would;t be uncommon for such an old car. Anyone have experience this? I'd hate to have to remove the alarm since it seems like it would take a really long time (and I wouldn't have an alarm).


I'd appreciate any help.

 

Optima batteries ARE crap but it's not the entire problem. The small amp hour capacity of these batteries is being sucked dry by the parasitic draws of things like the car radio memory, key-less locks, alarm, etc especially aftermarket. Google how to check this draw from your battery. You need a amp meter but it need not be exotic since the draw should be under a couple of amps.

Once you damage a starting battery by discharging it low enough that you need a jump start several times it may not recover and the battery capacity will have even less amp hours available. Will test good but that's just the surface charge. A constant low amperage discharge will discharge a battery much deeper than it ever gets starting the car. Motorboats typically have two batteries: starting and deep-discharge (house).

-- Chuck

 

Thanks for this information. I googled how to measure the parasitic draw and got my multimeter. I hooked it up in series between the negative terminal of the battery of the disconnected battery cable. I measured between 50 to 60 milliamps. I read that this was at the top end of parasitic draw for an S2000. So it seems like my battery is crap. That sound right?

 

60ma for 24 hours is 0.06 x 24 = 1.44 amp-hours which shouldn't bother the car for a couple of weeks. If the battery is good. Your's appears to be "not good." There are some changers that will de-sulfate batteries but the Optima construction may prevent this.

Starting batteries need not be exotic. Flooded cells work fine if their electrolyte is kept topped up with de-ionized water (preferred).

Optima batteries excel in physically rough service like Baja.

-- Chuck