Hello! I'm new to this forum. I was wondering if any fellow Mazda owners have some tips regarding battery charging problems I am having with my Mazda Tribute 2005.

A little background:

Mazda Tribute 2005, 115,000 miles. I take very good care, diligently maintain following owners manual every 5,000 miles, and drive easy. I don't have any fancy equipment, additions or modifications.

For the last 2 years my commute is only 10 minutes or less. And during weekends I may drive longer (a couple hours total)

Back in April the battery died and I bought a new one. Usually batteries have lasted me 3-4 years. However this time, after just 7 months (in November) I started noticing that it was taking longer for the car to start. Normally it takes 2-3 seconds, now it was taking maybe 5-6 seconds instead. I thought it was just the cold weather. One day the battery was completely dead. No turning of the engine at all.

I went to the store where I bought the battery and I got it checked. They charged and the tested showed the battery charging and holding the charge. The car started perfectly. They later tested the alternator and diagnosed that it needed to be changed.

Since changing the alternator will cost me several hundred dollars I decided to do a little more in-depth investigation on my own. I bought a battery charger and charged the battery. I have been using the car without problems for a few days, but I have been keeping an eye on maintaining the load low (not using radio, A/C, heating). Then I bought a voltmeter that I plug to the cigarette lighter socket. Here is what I have found:

Battery, before starting the car in the morning (around 40F / 5C): 12.1V
Alternator:
Right after start: about 12.0V
After about a minute in idle it raises to 13.3V
After driving for a minutes it is stable at around 13.5V. There is very difference whether stopping at the light (~750rpm), or going (~1,500-2,500rpm)
After 10-15 minutes driving the voltage seems to be slowly increasing some times reaching 13.9V
I have not yet driven longer than 10-15 minutes
Battery right after turning off is at 12.6V, and after a few minutes is around 12.5V

The readings above are for driving with minimal load, meaning no headlights, no a/c, no heating, no radio.
In the evening, when I turn on the headlights the voltage drops. Instead of 13.5V it is about 13.2V. If I turn on the a/c or heating it goes down to 12.6V.

Some conclusions:

• It is clear that the battery will not charge on these conditions. If I am driving with headlights, heating, and radio, the battery will never fully charge at best will only stay partially charged.
• From what I have read, the alternator should be producing a higher voltage when engine is spinning at 2,000 rpm, closer to 14V
• There is a very clear drop in voltage when load is added

So my questions to this forum are:

• Can this be caused by old or faulty cabling? From my understanding, bad cabling can produce this kind of voltage drop as current increases.
• Is it possible to test the alternator directly on its output?
• Besides cabling, are there other components that can be checked/replaced? Like voltage regulator?
• Do you have any videos or links I can use for guiding me to get under the hood and find the necessary cables/connectors?

Thank you very much for your help!

 

Your short commute simply isn't able to replace the energy used to start the car with the alternator as it is. With major power drains all turned off you should be getting over 14V assuming healthy battery and alternator. I'd suspect the regulator is bad/failing, if integrated with the alternator then yes, you need the alt replaced IMHO.

Bad wiring/connections CAN fool a good regulator into not giving enough current though but such diagnosis probably needs an auto-electrician to safely find and rectify due to the diodes involved. A simple check though would be to check and confirm the battery cables have good connections at both battery and the battery earth point to the chassis.

With such short commutes though

 

Thanks for the suggestion!

 

Regulator is integral with alternator and yes the out put is down but exaggerated by your short trips not giving the alternator time to replenish the energy used in the cold start

 

Thanks peedee

 

Common issue with tributes is corrosion on the main power cable where it bolts onto the Alternator. Check that out first, & measure what the output is directly from the alternator.

 

I have the same issue as you and I bought a trickle charger. I know that this is solving the symptom and not the root cause but I have found this work around to be acceptable and I no longer have dead battery problems.

I drive my car maybe 2-4 miles at a time about 2-3 times a week. I have a 2002 and less than 90000 miles! but it looks and runs practically brand new except for the battery issue :-)

 

Thanks for the suggestions. I have an appointment at the garage to get it all checked. Hopefully I will not need to replace the alternator.

 

Those voltages sound good to me considering the the age/miles of the car. Sure a brand new alternator would give you more output, but the problem is more with your short run times.

As stated, it takes a lot of power to start the car and you're probably not driving it enough to fully recharge the battery.

Example of what may be happening:
Day 1: Battery 100%, start drains it to 90%, short drive charges back to 95%
Day 2: Battery 95%, start then 85%, charge back to 90%
Day 7: Battery 65%, start then 55%, charge back to 60%
Day 8: "dead battery" car won't start.

I would charge the battery every night and see if the problem goes away, then you know it's your short trips that are causing the problem.

 

Updates:

I had all the cabling and belt checked so it looks like the alternator is confirmed damaged needing replacement.

In the last week I have continued to observe the voltage. Without load it was ranging between 13.0 and 13.5v, and with load (headlights, heater) it would range 11.9 and 12.6v.

I have been able to manage by not turning on headlights and heater. It has been working ok even with my usual 10-minute short drives. If I have them running the battery won't charge, or would even get discharged during driving.

One weird situation is that in a few occasions while driving the alternator would suddenly start working perfectly: 14.0v+ without load and 13.9v with full load. But that would only last for a few minutes. This would be completely random with no relation to speed, engine rpms, temperature, etc.

Thank you all for your responses!