Batteries & parasitic draw...?

[chrisinkanata]

Having cold start troubles again after the truck sits for several days. Frequently have to boost the truck after it's sat for a few days. Extended crack times as well, but that another issue. During my diagnosis of this, I see that my parasitc draw with everything off, (hood lamp, doors shut, no key, no accessories plugged in or on) varies between 68 and 75 milliamps. That seems a fairly high to me. Pulling fuses results in zero amps when the 10A TBC fuse in the engine compartment fusebox is pulled. With the TBC fuse in (68 - 75 mA) the removal of the radio fuse results in 60 mA and 10 mA or so seems normal for the radio. I need to figure out the other 50 - 65 mA.

The TBC fuse is power to the Body Control Module (BCM). No other fuses effect the current draw. I'm obviously wanting to first confirm that 75 mA is in fact too high please. Any thoughts on that?

Assuming it is, does the BCM control the trailer plug wiring? Based on the exposure to elements (salt water etc) that would seem a logical place to start. May as well go with the obvious. I've had to replace a badly corroded trailer plug under the rear bumper several years ago...maybe it's time again if it's connected to the BCM.

BTW....batteries are 2.5 years old, AC Delcos.

Thanks a lot guys!

Chris

[JohnC]

I think there was a discussion about parasitic draw a while back. If you have Onstar, it'll start of "big" and taper off with time. That said, a pair of good batteries should be able to sustain a 65ma draw for at least 1000 hours (more than a month) without failing to start the engine.

[DmaxMaverick]

As John said, 65ma isn't anything to worry about. I'm surprised it isn't more. The BCM draws power for several things, including Onstar, the security system (both always on), and radio (also part of the security system). One thing I have noticed, is later models use more, and the later they are, the more they use.

[More Power]

To blend some of what has been posted here... 65ma is .065 amps. After sitting 1000 hours, the system will have consumed 65 amps. Not enough to prevent starting. Each of these batteries has an RC (reserve capacity) of 110 amps - and you have two of them.

My project truck has sat for as long as 4 months without charging or starting. It cranked a little slower than normal, but still started. Nowadays, I routinely use a Battery Tender Junior (www.batterytender.com (http://www.batterytender.com)) to keep the batteries topped off. This can be left on for as long as you want.

Check the condition of your battery terminals and battery cables. A local battery store can perform a load test of each battery to determine their condition.

Jim

[chrisinkanata]

After a long drive today, I disconnected the passenger side battery. It checks out at 12.78 volts and the driver's side is only at 11.4v. I'm going to get them both tested on Wednesday. If this is bad batteries again though, I'll be some pissed. This will be the fifth set of batteries since new.

[Kennedy]

Check the alternator too just to be sure it's not running a bit high on voltage.

I'll second teh Battery Tender, but I prefer their Waterproof 800 series as it plugs to wall with a cord rather than potentially blocking with a wall wart and gets you more cord, plus it can be used outdoors. My Harley has the wall wart style connected.

[chrisinkanata]

Well, another bad battery it was. On the upside, GM replaced it under full warranty which is great. But geez, in 250k kilometers and 10 years, that's the 5th new left battery and 4th right battery. That right battery has been carrying the load so to speak for a while now, but GM would not replace it as it tests good. I fully expect it to expire soon as well though. I was really hopping that after I replaced the pinched, severed positive battery cable a while ago, that would address all the wonky electrical things, including batteries.

The extended crank times are rectified as well. Thought for sure I had some bad glow plugs but I'd have to say that a fast, steady cranking speed is vital for cold starts. Two good batteries will of course give you that.

Oh well, it is what it is I guess.

Chris

[JohnC]

I bought my 2006 in the fall of 2005. I'd tell you how old the original batteries are today, but if I did, they'd probably quit tomorrow! ;)

[Dinkie Diesel]

I am having a problems too with abnormal amount of battery replacements. 2001 and I think I'm on my 4th set. First set were replaced under warranty by dealer. Next set I bought were also Delco's highest rated. I think they were replaced once under warranty. And now I have Interstate batteries about 1 year old and I feel sure one of them is going bad.

I can almost tell now when the battery(s) are headed downhill by watching the voltmeter. After sitting for two or three days I see the OEM voltmeter dip to just above 9 volts at crank. I can hear a slightly slower crank speed. Engine starts but static voltage remains below 12 while glow plugs/heater are kicked in. Once the glow plugs turn off the voltage jumps to around 12v. Then I see a slight increase and then it spikes to 14.78 using my digital voltmeter.

I took it to the shop I bought the batteries from. He did a load test after isolating the two batteries. Both checked out okay at a rock steady 10+ volts under load. He also got a 14.78 reading while running. He then did a hydrometer test. I saw some fluctuation on the hyd test but he claims it is within spec. He also claims his data states that any voltage up to 16v is considered normal.

I can see a slight amount of dark seepage coming from under one of the battery filler lids as if the battery may be cooking a bit.

What happened to the old days of 13.8-14.2v? I think 14.78 is too much. Ironically, after replacing the batteries in the past the voltage did stay around 14.2 or 14.3. It is my contention that the charging system must be very sensitive and can see something going bad in the battery(s) hence the higher output.

This is not related but I have found too that during that period between starting the engine and the alternator kicking in, sometimes it will not go into gear until it reaches 13 or 14 volts. I used to think this was due to converter leak down but it can't be after just one or two nights. What allows this delay before charging starts once the engine is running?


Thanks,


Jeff

[JohnC]

I expect the "delay" has more to do with the intake heater and glow plugs being on than the alternator not charging. It just can't charge enough to make up the difference.

[gimpyhauler]

I am about to replace my batteries. The "old ones are about 2 years old. My truck isn't always used every week. The batteries I bought were high quality from PepBoys. I bought them because of a referral from a friend. He just had his replaced as they were leaking. Now it appears mine have started to leak. The real problem is I move to Oregon where there are no PepBoys stores.

So my question is: Will the Battery Tender keep both batteries fresh by hooking the battery tender leads to the center red box and Neg ground attachment point? Will using the cigarette receptacle attachment keep both batteries fresh?

Thanks in advance.

[rapidoxidationman]

The batteries are connected in parallel, so connecting the tender to the red box behind the power steering reservoir or to your cigarette outlet (assuming it is always on and doesn't turn off when the ignition is off) will keep both batteries topped off - IF all the electrical connections are good.

[gimpyhauler]

Thank you. It seemed obvious but I didn't want to screw it up so I asked. Thanks for the validation.