kanonen

I can't seem to find a logic to this:

So my car battery isn't that new. But every time I start the car 1st thing in the morning even in below zero temps, it starts right away.

The problem is after i drive for a relatively long time then I shut the car to start it, say 5mn or 10 mn later, I happens often that the battery feels like almost dead. I have to crank it a second time and hit the throttle a bit.

Any ideas why is this?

kanonen

i think I'll just call cartalk

curls

Odds are your battery is not charging enough in the 5-10 minute period to make up for the juice it took to start the car the first time. Could be a dying alternator, battery, or just normal behaviour, but its hard to tell. If you can get your electrical system load-tested at a garage, it'd tell a lot.

JimHolloman

If you can get a voltmeter (I recently bought one at Harbor Freight for $2.00 -- and it is accurate), check the voltage at the battery terminals with the engine running. It should be between 13.0 and 13.5 volts. If low, it is likely your alternator -- but it can also, in rare cases, be a battery with a shorted cell -- but such a battery would not start the car.

Then, check the voltage with the engine off. It should be between 12.0 and 12.5 volts. If it is lower than 12.0 volts, then it is most likely the battery not holding a charge.

With the engine not running, pull one battery cable, put the meter on DC current, put one lead on the naked battery terminal and the other lead on the battery cable to measure the current drain. I don't know what normal would be for the TSX, but I would be suspicious of anything over 500 milliamps (1/2 amp). A high reading indicates that something in the car is drawing too much current. But, that would normally mean the battery would be the weakest in the morning.

In any case, try to find a multimeter and check your battery voltage with the engine running and with the engine not running. Check the voltage at night and then the first thing in the morning -- and see how they compare.

Radio Shack, stores that sell auto parts, and electrical supply stores sell small multimeters. You might even find one at Lowe's, Home Depot, or Ace Hardware. You need DC voltage and DC current in the appropriate ranges.

kanonen

ok, thanks. I will get a voltmeter and post results. It just didn't make sense to me why it starts 1rst thing in the morning, then sometimes after hours of driving I need to crank it twice.

will post later.

JimHolloman

In rare cases, a shorted diode in the alternator can cause reverse current flow. In other words, rather than charging the battery, the alternator is actually draining the battery. But, the voltage readings ought to point this out.

Another, more involved, way to check this would be to loosen one terminal (the negative terminal would keep you from causing an accidental short with the car body), crank the car, and then pull the cable off the battery and check the current (expect several amps of current). Assuming you disconnect the negative lead, place the negative (black) lead of the meter on the black cable and the red lead of the meter on the battery connector. Is the current flowing in a positive (correct) direction? If the engine dies when you pull the cable from the battery, it suggests a bad alternator that is not putting out enough current to supply the ignition system. Although, I have seen cases where the system would not charge if disconnected from a battery.

So, another good way to test the system is to swap out the battery with a known good one that is fully charged. Then, monitor the voltages.

Good batteries are available for $55-$60 -- so if your battery is around two years old, you could consider going ahead and replacing the battery -- even if the alternator will also need replacing. And, if the alternator does need replacing, try to get a rebuilt one rather than a new one. If is not uncommon for rebuilt alternators to have diodes with higher current capacity than OEM alternators. And, it will be about half the cost.

Another thing you might consider is buying a 12 volt smart charger ($15-$20). Get one with an output of at least 900 ma. It can charge a week battery overnight with sufficient charge to start the car. You can leave it on overnight and then in the morning, you know that you are starting with a full charge (assuming that the charger switches to trickle mode -- as indicated by an LED).

kanonen

Ok, so I did part of the tests, first thing in the morning:

engine off: 12.40V
engine on: 14.50V

I didn't didn't do any current measurements as I have to understand your suggestions a bit. Plus I think I got a bit of a complicated digital multimeter so i don't wanna blow it. I'll do some readings then post some other measurements.

As I reflect on when the battery seems dead, it only happends after I try to start the car again after a relatively long drive and a short rest. Last time it happened, was when i drove for 4h or so, then stopped to buy a coffee for 4 mn or so, then the battery acted dead and I had to crank it twice.

The only thing i can think of is some heat issues that might impact battery or alternator!

kanonen

well..heat issues (speaking out of my a##) or a shorted diode in alternator as u suggested.

JimHolloman

The voltages suggest that both the battery and the alternator are functioning. I just checked mine and got 12.75 volts and 14.5 volts.

However, the battery has not been tested under load. The dealership can do it, or many places that sell batteries can do it such as Autozone (of course, if the battery test weak, then they expect you to buy a replacement from them).

You can emulate a load test by holding the meter on the battery terminals and have someone else crank the car (especially at times when it is hard to start). The voltage should not drop below 11.0 volts. A battery can develop a high internal resistance and maintain good no load voltage while been unable to produce ample current for starting.

Is the engine temperature normal (about 1/3 up the gauge, I believe)? An overheated engine can be more difficult to start (turn). A remote possibility is that the starter is dragging when it gets hot. A hot starter that suffers any distortion can sometimes allow the rotor, that turns, to touch the stator (the outer case) and cause a serious drag.

But, if it was me, my next step would be to swap out the battery. If you are near a junk yard or a battery recycling operation, you can probably pick up a battery that tests good (under load) for less than $20.00. Or, you could go ahead and spring for a new one. If a good battery doesn't do it, then the starter moves up on the suspect list.

Fortunately, we have a battery that is very accessible.

P.S. A shorted diode would not allow the alternator to charge and you wouldn't see the 14.5 volts -- something no higher than the battery voltage of 12.5 volts -- or perhaps even less.

curls

Actually now that I re-read your original post, I have a VERY similar "problem" with my car, and it happened before and after a new battery.

When starting a 'warm' car (had just been running, as in getting a coffee as you suggested), the car cranks a bit longer and definitely seems to need a short tap of the gas pedal to finally catch. Once it does, its great and is like nothing ever happened.

It seems normal, to me anyhow, that this occurs in the TSX. Might be emissions-related (a car that's off and then cranked to "START" will assume a cold catalytic converter and would use a typical cold-start A/F ratio to start the car. Once the ECU realizes the catalytic is hot [ie: once the A/F ratio sensor detects a difference in emissions than expected from a cold started car], it adjusts, probably by cutting fuel by an amount that makes the car "stumble". It eventually catches itself and keeps running - I don't think the tap of the gas pedal helps, but it is a mental thing that I do it almost subconsciously.)

Now, that's completely talking outta my arse as to the "why", but its my theory and frankly I'm not concerned with it in my car as it's always done that (even before the new engine was put in about 70K km ago).

kanonen

hum interesting. I am not that concerned either actually...at least now. But now that I remember, it did have a slight difficulty cranking on other occasions. In super high temps: 95 and plus when the car was sitting in the sun. (JimHollman: engine is always in normal range, less than half the gauge)
So I think the cold start a/f ratio does make sense. From your suggestions, I am ruling out the battery though.