Mystery battery drain on 2005 Honda Civic

Hey all, first post here - kind of a classic Car Talk dilemma: my wife now drives what was originally my 2005 Honda Civic from '05-'10. In the last 3 or so years since she’s been driving it, the Civic has developed a tendency to die on her at inopportune times. A quick jump always fixes the problem but I never, ever had this problem myself when I was driving it and I’ve had the battery tested at AutoZone twice with both techs telling me the battery was in great shape with cranking amps well above its rating. I’ve offered to just buy a new battery and eliminate the issue but the “it’s fine” report from AZ has me puzzled.

I have noticed that corrosion tends to build up on her positive battery terminal very quickly and I suspect she’s getting some drain due to that but I’m stymied as to why it happens. The only thing (and its a stretch) that I can think of is she has a habit that her father taught her of cranking the heat, the defroster AND the A/C in her car when it’s cold out. Normally I wouldn’t think this would make a difference but I wonder if there is somehow condensation developing in that tiny little Civic engine bay as a result?

I’ve asked her not to do it and see if the situation improves but old habits die hard. The battery does tend to come up dead (of course) more in the winter but it’s not an exclusively cold weather situation. Anyway, after jumping her car in single digits this morning before dawn I am ready to admit defeat and just get a new battery but figured I’d throw it out to the many voices here.

Thanks in advance!

How old is the battery? Has the alternator been properly checked? If the battery is a few years old…it needs to be replaced in all probability. I don’t put much faith in checking a battery with a multi-meter because the battery needs to be load checked. If the alternator is not up to the task of keeping your battery charged then you are fighting a losing battle.

The battery is a couple years old but I figured I’d get 5 out of it easily - perhaps that’s my mistake. The car is up for it’s timing belt service, so I need to take it in and I’ll have the alternator tested then, too.

The thing that I’m really puzzled about is all the corrosion on the battery terminals. I will scrub them to death, clean and then coat in petroleum jelly and two weeks later there’ll be a heavy coat of bright green all around it.

Here’s a recent thread on chronic & rapid battery terminal corrosion:

I would add to it that charging system or cable problems can also play in it. You might want to think about the condition of the main cables.

I would also check for a parasitic battery draw. This is something that keeps drawing too much power when the car is off and could be as simple as a failed switch for a glove box light or a short or something on one of the other systems. If it was me I would do this before anything else.

I suppose the battery could have an intermittent connection problem internally. This is kind of unlikely but it has happened to some folks. There is a much more better chance that the battery connections are causing the trouble and hopefully cleaning them will solve the trouble. Many people have been stranded due to this simple and avoidable problem. Another possible problem for this issue could be due to a faulty connection to power on the wire that connects the battery to the main power distribution panel under the hood. Check the battery to ground connections also.

As for the battery acid issue make sure the charging system isn’t over charging the battery. Charging voltage shouldn’t exceed 15 volts. Also make sure the AC ripple voltage is under .1 volt while the engine is running around 1,500 RPM. If you do that yourself make sure the meter you use blocks DC voltage while in the AC volts mode. You should measure zero volts across a battery if the meter blocks DC. You will need to add a .2 microfarad capacitor in series with one of the probe leads if the meter doesn’t block DC.

I think your wife’s habit may be the problem, especially if she gets stuck in city traffic or has a lot of stop signs/lights in her path. At low RPM’s, the alternator does not put out a lot of current. Its enough to keep a battery charged under low load situations, but if she is driving slow or stopped a lot, the fan is on high and the lights are on, the battery is discharging.

If she meets these conditions before parking at night, she will come out to a dead battery in the morning. After initial warm up, she should turn the fan down to a lower setting, at least one notch below high, it really cuts down on the current drawn by the fan and it can make a big difference. The fan will last a lot longer too. The fan is the biggest load here unless you are also running a mega watt sub amp in the trunk.

Stop using petroleum jelly or any kind of grease on your terminals. While agree with the others that you have a crack between the case and the terminal, the grease is trapping the outgasses in the terminal to post connection increasing the corrosion. You might use a little dielectric grease around the base of the post, but keep it off the post or terminal itself. Leave that junction dry and do not coat so that any moisture that gets on it can evaporate.

You will still have to clean the posts periodically, but not as often. The little red and green pads help too, but they are not a cureall, they just help.

Thanks for the great diagnosis / suggestions, all. Will try to troubleshoot accordingly and let you know how it turns out. Unfortunately, I don’t have a way to measure the battery draw myself but since it has to go in for service for the timing belt anyway, I am going to present all these questions/points to the mechanic to make sure we address.

I am of the mind that it has SOMETHING to do with the use of A/C like she does because it just happened so immediately after I stopped being the daily driver.

Good to know about the petroleum jelly, never thought of that!

A lot of short trip driving will also drain the battery especially in an economy car where they don’t size the alternator for a lot of extras.

Good comments above. I’ll add this could also be a starter problem. A starter on the fritz might crank ok when jumped, but not when just using the car’s own battery, esp when it is cold. Starters on the fritz get more demanding about the battery voltage during cranking. Too low and it won’t crank. When jumping you have two batteries in parallel to pull the load, so the voltage during cranking is higher. And this is especially true if the jumping car is running, as then the voltage will be what comes out of the alternator, which is typically near 14 volts. That can easily put a starter on the fritz over the top voltage-wise and it will crank w/out problem.

Any good inde shop should be able to run a suite of charging/battery/starter diagnostic tests and figure out what exactly is wrong straight away. I think that is your best bet.

If the prior load tests show this two year old battery to be good, I’d shy away from buying a new battery. I might temporarily put a battery in from another car though if one – known to be good-- were available, as a test.

Nobody in the business load tests batteries anymore. We use a battery conductance tester.

This allows us to test the battery condition without recharging the battery as you have to do with a load test.

It sounds like there’s a parastic current draw on the battery as the vehicle sits. And on todays modern vehicles where modules/computers can fail to go to sleep after the vehicle is turned off which can draw the battery down, you need to find someone who can detect a parasitic current draw without disconnecting the battery.


Yeah, I’d not only like to fix it but actually understand what is going on and why it’s happening. A full diagnostic test of the starter, battery, drain, etc is definitely in the works.