2002 Camry Electrical / Battery problem

Have you checked the trunk light if so equipped?

While car batteries are capable of massive storage of electrical power, they can be drained drastically over-night by just one lamp. The maths is simple, ie a typical battery is 50 ampere-hour. This means it can supply 50A for 1 hour or any equal ratio of this ie 25 A for 2 hours or 10 A for 5 hours or 1 A for 50 hours etc, etc.

The above is assuming the battery is operating at as-new capacity and has been fully charged. In practice, this is not allways so. Age especially, alternator performance, nightime driving with hi-beam, all can leave the battery with much less than 50 amp-hour capability overnight.

It has been estimated that the average car battery after a years use, has only 1/3 to 1/2 of its original capacity.

Now consider how much capacity an engine starting exercise takes from the battery: The initial lock-torque current peak is huge. This is due to the inertia of making the engine start turning and can be a high as 600A for up to a second or two, then there is the cranking current which is roughly in the range of 150- 180 amps plus the added current of the ignition, fuel-pump etc. A fully charged new battery should allow cranking for 15 mins or so, but a deteriorated battery is more likely with repeated starting current-peaks, allow only a few minutes.

Effect of a standard interior lamp on battery drain:

A typical interior lamp is 15W. The formulae for current in terms of power and volts is I = P/V where P = 15 and V = 12. Current is therefore 1.25 A (amperes). Now assuming our battery is running at 50% of new and fully charged capacity ie 25A-hour, this load will flatten it completely in 20 hours and will render it incapable of supplying the initial lock-torque current peak in *much* less time.

If you suspect something is draining your battery overnight, the best way to ascertain this, is to connect a multimeter on its DC current range in between the +ve battery clamp and the battery post it was on. Make sure the meter is on a current range of at least one Amp or more. Total current drain should not be more than 30-50ma (ma = 1/1000 amp), and is usually drawn by the dash clock and security systems . Any readings above 100ma should be investigated.

Jason

Thanks Art, no I've not checked it -- assume you just mean to check if it's staying on... By the way, I've also just discovered that neither of the rear brake lights is working, just the high center one. Would that be a clue? Thanks again.

Thanks for the information. Hate to admit it, REALLY stupid, but I think I've figured it out, and it's not at all complicated. I surf at least a couple of times a week, and I load my surfboard through the trunk & tie the trunk lid down. You know the rest. Weekdays, typically pick the board up from home at lunch time, then it sits in my office parking lot with the trunk lid tied down (but open), so the trunk light burns the entire time. Stupid me, never thought about having the trunk light on for hours & hours at a time. Couple of days ago I had to abort the surfing, so it sat that way for about 8-9 hours.

Regards,

Sounds likly to me. I would check the connections. Could be loose and intermittently touch metal and shorting out. Anyone change a bulb for you. That would be the fixture I look at first.

Glad you found it. Next time just unplug the lamp!

Jason

Some car makers, like Chyrsler, have battery protectors which turn off your lights if the battery is getting too low to start the car.

they

simple,

or 1

has

has

the

the

up

in

fuel-pump

so,

power

running

flatten

way to

the

your

says

ignition

have

way

power,

for

hours

especially,

the

for

roughly

the

sure

current

usually

Cute but domestic car makers have improved while Toyota and Nissan quality have gone down hill. We will be keeping our 99 300M but trading the rattle box 2001 Avalon very soon.

Take it to a good Sparky (Independent) Have them check the drain on the battery. They will know where to look if need be. Good Luck.