[Kaliuzhkin]

Is there any possible explanation other than that the battery is going bad?

This is a 2006 Elise which I bought new in 2007. The battery seems nonstandard - it is NAPA SureStart 65.

After driving the car, the battery measured 12.65 Volts. I think I turned off the alarm and immobiliser, total current was 1.6 microvolts. 24 hours later, the battery measured 12.05 Volts. Another 24 hours later, it measured 11.96 Volts.

I think the charging circuit is good. While running the engine at idle, the battery measures 13.5 Volts.

If a load test is called for, am I better off buying a tester, anywhere from $50 to $1,000 or paying a repair shop to test it?

 

[SirLotus]

Definitely sounds like a bad battery to me, you got typical results. After driving, the voltage reading would give a false indication because of the surface charge. Waiting for 24 hours will give a realistic reading. If it's more than a couple of years old I would just replace it, but any decent auto parts store will test it for you. Not sure your reading of 1.5 micro volts is true, more than likely, 15 ma. Charging voltage of 13.5v seems OK. http://www.lotustalk.com/forums/f129/battery-choices-information-64071/
Cheers,
Michael

Is there any possible explanation other than that the battery is going bad?

This is a 2006 Elise which I bought new in 2007. The battery seems nonstandard - it is NAPA SureStart 65.

After driving the car, the battery measured 12.65 Volts. I think I turned off the alarm and immobiliser, total current was 1.6 microvolts. 24 hours later, the battery measured 12.05 Volts. Another 24 hours later, it measured 11.96 Volts.

I think the charging circuit is good. While running the engine at idle, the battery measures 13.5 Volts.

If a load test is called for, am I better off buying a tester, anywhere from $50 to $1,000 or paying a repair shop to test it?

 

[Kaliuzhkin]

Definitely sounds like a bad battery to me, you got typical results. After driving, the voltage reading would give a false indication because of the surface charge. Waiting for 24 hours will give a realistic reading. If it's more than a couple of years old I would just replace it, but any decent auto parts store will test it for you. Not sure your reading of 1.5 micro volts is true, more than likely, 15 ma. Charging voltage of 13.5v seems OK. http://www.lotustalk.com/forums/f129/battery-choices-information-64071/
Cheers,
Michael

I used a multimeter with which I'm not very familiar. The dial was turned to "200 microamps" and the reading was 1.6. Remember, this is with the alarm and immobiliser turned off, so the current reading should be significantly less than 20mA.

Why would this battery be in a new car? Replaced by dealer/seller?

 

[SirLotus]

Are you sure it was not on "Milli" (1000th "ma") and not "Micro" (1,000,000th "ua"). My guess is your reading was 16ma. Cobra state that disarmed the system takes 9ma and to that you have to include the radio and ECU. The parasitic load on my car is 20.5ma with the alarm/immobilizer OFF, but also includes the Radio & ECU. You car is, what, 3 years old, the battery was probably replaced due to it sitting for so long before you purchased it.
Michael

I used a multimeter with which I'm not very familiar. The dial was turned to "200 microamps" and the reading was 1.6. Remember, this is with the alarm and immobiliser turned off, so the current reading should be significantly less than 20mA.

Why would this battery be in a new car? Replaced by dealer/seller?

 

[ads_green]

the problem is that even a new battery can be trashed if it's allowed to go completely flat. Once this happens you get little crystals on the metal plates that reduce it's ability to hold amps. It'll still show a good voltage but as you show above, it's cranking ability and storage time will be drastically reduced.

You could get a battery conditioner/charger that'll break down the crystals may bring the battery back to a reasonable standard.
To be honest, I don't think it's worth getting the battery load tested - you've already shown it's compromised and the current being drained isn't that much to cause that kind of drop. So battery definately the most likely culprit.

 

[Kaliuzhkin]

the problem is that even a new battery can be trashed if it's allowed to go completely flat. Once this happens you get little crystals on the metal plates that reduce it's ability to hold amps. It'll still show a good voltage but as you show above, it's cranking ability and storage time will be drastically reduced.

You could get a battery conditioner/charger that'll break down the crystals may bring the battery back to a reasonable standard.
To be honest, I don't think it's worth getting the battery load tested - you've already shown it's compromised and the current being drained isn't that much to cause that kind of drop. So battery definately the most likely culprit.

One thing that might have an effect - I don't think the battery every gets fully charged. Most of my driving is local. I don't go on 50 mile trips twice a day anymore.

As you suggest, this battery might have been compromised before I even got the car.

I'll measure the battery drain with alarm and immobiliser on. My neighbors will hate me for the noise.

The first time the battery went dead, I bought a second battery, an Exide Platinum. I switch batteries when the battery goes dead. Then I charge it in my kitchen with a Battery Minder, using anti-sulfuration. So this battery has gone through that process. It's time to replace the battery again, and I'll test it in my kitchen.

I wonder how much more I can squeeze out of this battery. :shrug:

 

[SirLotus]

I'll measure the battery drain with alarm and immobiliser on. My neighbors will hate me for the noise.
I wonder how much more I can squeeze out of this battery. :shrug:

I measured 42.5ma on my car with the alarm & immobilizer armed 20.5ma disarmed. No need to set the alarm off. Don't take chances with a suspect battery, we all know how much trouble that causes on this car, replace it.
Michael

 

[TimMullen]

Then I charge it in my kitchen with a Battery Minder, using anti-sulfuration. So this battery has gone through that process.

I have my Battery MINDer plugged into the wall in my garage, with an "extension cord" routed along the ceiling and dangling near the rear of the Elise. Whenever I park it for a couple of days, or whenever I figure the battery hasn't gotten fully re-charged, I simply plug the dangling cord into the leads that are permanently attached to the battery. So far, my original battery is still going strong, after almost 5 years. :shrug:

I like my Battery MINDer...