Alternator / Charging Issues

Hi all,

I've got a 2014 Tacoma DCSB 4L/V6, and I'm encountering some odd issues with the alternator and battery charge.

Last month, I had a few hard morning starts, and within 2-3 more days, it wouldn't crank at all. The battery was 7 years old and only reading about 11.2 VDC, so I replaced it. The next week, the same thing happened--a few hard starts, then click-click. I put the battery on a charger, and it came up to 12.3 VDC without issue. At engine idle, I was seeing ~12.5 VDC at the battery, so I replaced the alternator and serpentine belt. Unfortunately, a week later, I'm right back where I started, and I have to trickle charge the battery every 3-4 days.

With the new alternator, at engine idle, the voltage at the battery is ~13.2 VDC, but will go as high as 14.6 VDC when the engine RPM goes up, then immediately level back off. This holds true with lights, stereo, and AC going full tilt. I thought maybe something was draining the battery, but with the engine off and doors closed, I'm only seeing ~23mA parasitic draw. I've checked the wiring and fuses, and cleaned all connectors.

This seems to be an intermittent issue, but I can never catch it happening. Is it possible this could be an ECU problem?

Follow up: It appears the new alternator had a faulty diode. Argh.

 

Getting a battery to last 7 years is unusual. If I get 3 I’m happy, beyond 5 I feel I’ve done well and start shopping for a replacement so I’m not left stranded.

A good way to test a battery’s health is a starter voltage drop test. Look it up if you don’t know how. Having a meter with peak low hold is best.

 

Did you use an amp clamp or multimeter to do your parasitic draw test? also did you road test the vehicle and utilize every function prior to doing the test? Sometimes you have the drive the vehicle and work a function before the draw comes up. The battery dying could of "unlatched" something and cause it to appear okay because it wasn't used again.

also to clarify when you say you had ~23ma that read on the meter as 0.023 amps or 0.23 amps? The general rule is 0.05 amps

 

Agreed, the mom-and-pop NAPA down the road tell me the alternator and battery are good.

 

23mA, so 0.023A. I'm using a DMM to do the current testing with. I've checked it immediately after a drive, and after the truck had been sitting for a few hours.

 

My local NAPA tested the battery for me, but that's a great tip. My DMM does do low/high volt holds, so I'll keep that one in my back pocket.

 

I do, but they've all been disconnected since this started happening, they were my first suspects. I pulled the fusible link for the powered subwoofers at the battery, and unplugged the Sony XAV-AX7000 / Metra unit. I did power-up everything while doing voltage testing (no discernible difference), but it's all disabled at the moment.

BTW, I borrowed an OBD2 reader from a friend this afternoon, it came back with a generic P1604 error, but that was it. I'm thinking this is probably a wiring or connector issue, nothing near as exotic as I'm making it out to be (like the ECU).

 

1. What kind of battery did you replace it with? AGM or flooded?
2. Has your commute changed at all? How far do you drive daily?
3. When you trickle charge, are you removing the battery from the truck or just throwing the charger on?

I had a similar issue with a 1 year old interstate AGM battery. It wouldn't start one morning. No indicators that it was dying. I pulled the battery out and put it on a battery tender until it went green. I haven't had any issues since. I realized that I changed my commute route. I no longer drove on the highway and only took city roads. It shortened my commute to about 15 minutes and also I'm not running my engine hard anymore. I emailed with Interstate engineer and they said that their agm battery is ok to charge at 13.2.

 

It's flooded, and no, my routine hasn't changed. Admittedly, my commute is only about 2.5 miles, but only I crank it in the morning and again in the evening--it's never been a problem before. I usually put 30-50 miles on it every weekend as well. I usually clip the charger on with the battery in place.

 

2.5 miles is pretty short. Does your truck even get to operating temp? Maybe try removing your battery connections and only have the tender on it until it reaches a fully charged state and see if that helps.

 

What replacement alternator did you put in? The replacement belt is correct and tight? You used a battery brush on the new terminals and posts? It’s unclear, you still have the 7 year old battery in?

If you have a aftermarket alternator that could be the problem. An old battery can lose its ability to hold a charge. Putting the charger on it can mask this problem. Disconnect, drive away, turn off, an hour later it slow cranks.

Your 12.3 static voltage reading isn’t as good as you think. Here’s a chart I use. It’s all per cell, a 12v battery has 6 cells. So 12.3 calculates to 50%. When you do the starter voltage drop test, loaded, the % will probably be even lower.

 

@mepage. Any follow up?

 

That was going to be my very first question. Some aftermarket alternators (O'Reilly to name just one) are just plain junk. A surprising percentage are actually DOA right out of the box.

 

Double shifts this week, I apologize for the silence. I threw together a simple datalogger with a Pi and an INA226 I2C breakout and I'm going let it run for a few days with my regular drive.

Just from what I've seen over the past 30+ hours, there's very little parasitic draw. It also appears that the battery charges to about 12.22 VDC, and that's it. I'm seeing a steady 13.52 to 14.31 VDC while driving or idling.

 

At 7 years, you got your moneys worth out of that battery, replace it.

 

OP indicated that he already did.

 

When all else fails do a voltage drop measurement on the battery cables themselves, they can deteriorate creating higher resistance and resistance consumes some of the available power in both directions, which means less available for cranking and less is making it back to the battery for charging. The alternator charges to a specific voltage, typically that entire amount can be measured across the battery terminals but when there's excessive resistance in the cabling some of that amount is the voltage drop in the cable itself. To put it simply, if your alt charges to 13.5 and the wiring has a 1v drop in it the battery's state of charge will be less because the alt sees the entire circuit and not just the battery. In extreme situations you'll actually feel the cable getting warm when the truck is cranked.

Edit: The way toyota does their cables with short runs to the alt and ground the culprit (if that's it) will likely be a connection of cable very near to the battery

 

Above is a good idea. I had one that kept eating starters. I think it was something like 3 starters in 2 years. I did my starter voltage drop test at the battery terminals. Second drop test, negative lead on the negative battery terminal, positive lead on the starter post where the fat positive battery cable attaches. The difference was close to 1v. I think it was like .8v or so. I replaced the positive battery cable (from battery positive to the starter). It’s been over 2 years now on the same starter.

 

My 4 cyl taco has 386km on it and until Friday had never let me down since I bought it at 217km running it in cold canadian climate. I was sure it must be the alternator that brought on the battery light that killed my engine in the middle of the night on Friday. After talking to a few shops who really couldn't care less about me on a Saturday I wound up reluctantly taking it to a dealer that has service on Saturday. They told me the alternator is fine confirming what one mechanic said. They tell me I need a new rear differential breather $103, replace alternator belt $170, replace thermostat housing $317. $45 to fix a simple coolant leak and a wopping $1,500 to replace a $20 water bypass pipe. This diagnostic for this information cost me $180. There are videos for all these recommended jobs for the DIY inclined but I don't know what to do now. junk the truck or do the repairs myself or do everything but the bypass with the dealer then trade in. Regardless I feel like the $180 for the dealer to bring me up to date was worth it because I don't know who else will tell you what should be fixed vs what has to be fixed. But once a car fails on me even once I lose trust and faith in the vehicle. I can't afford to be in middle of nowhere with no faith in my vehicle. I love my tacoma and it doesn't owe me anything but it might be time for change. My experience with electrical problems on older vehicles has been catastrophic.

 

The only thing you listed that would "kill" an engine would be the "alternator belt" (serpentine belt) if it was slipping or broke. The other items listed wouldn't stop an engine suddenly. Changing the serpentine belt (and while you have it off, you may want to look at the belt pullies) isn't too hard. Lots of writes up on here on how to do it.