Battery dies every few weeks

Hi, in the last six months my honda battery has gone dead three times out of the blue. My mechanic keeps telling me I must have left something on because after I get a jump start the battery tests at 50% which he says is good. I can not believe that suddenly I am inadvertently leaving lights on every couple of months. is there anything else that could make the battery periodically die, then when charged last a couple of months and then suddenly die again?

What does your mechanic mean when they say that the battery tests at 50%?


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Sounds like testing battery and alternator would be a good thing to do. Frankly I would have someone else do it because tests at 50% to me means the battery is have gone.

Absolutely need to test alternator.

Do not forget to check serpentine belt: if it is loose, even good alternator will not give you enough charge.

You might also want to test if car has any discharge current when tuned off: easy to do if you have a basic multimeter tool:

  • open hood
  • close doors and make sure to turn off any electric consumers like headlights or dome light
  • loosen negative lead on batter, but DO NOT disconnect it
  • put multimeter into current mode (DC), highest range
  • keeping one multimeter lead on negative battery terminal and another lead connected to vehicle ground, remove negative wire from the battery
  • read what multimeter says, should be ZERO

if you happen to disconnect any leads, next reconnection will start process of car recalibrating its circuits, resulting in current spike and likely burning fuse in your multimeter, so if you happen to get one of wires off, then reconnect the battery and start over

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need to know year, model, engine. that will most likely solve the problem.

You might find this an interesting read.

According to this website and others I found, testing at 50% means it tested at about 12.24 volts.

it’s a 2009 Honda Accord EX. I do not know what kind of engine it has

If the battery is original, it’s time to replace it.

I bought the car in 2014 from Honda and apparently they did not give me a new batter, I don’t know how old the battery is

That doesn’t mean anything to me. Does that mean the battery is gone?

That means the battery is half charged. The mechanic may have meant that the state of charge is 50%.

When a vehicle comes in with a half charged battery after being dead and jump started the battery and charging system are normally tested, if no problem is found the vehicle is tested for unusual draws. Sometimes the problem is very intermittent and challenging to replicate.

I agree. If original, it’s 8 years old, and it’s lived a full life.
I assume the mechanic tested the charging system?

I also find myself wondering about your driving habits. If you make only short local trips, your battery may not be fully recharging after you start the car, slowly becoming weaker over the weeks. Can you describe your driving habits?

Ask a shop to do a battery load test. that’s the only way to test a battery. It needs to first be fully charged to get an accurate reading. Use a abattery charger overnight if necessary to fully charge it.

If the battery is over 3 years old in a hot climate, probably makes more sense to skip the testing and just replace it. Over 5 years old in a mild or cold climate, same thing.

Here’s some of my own recent battery experience, fyi. My Corolla’s battery is about 4 years old, and since I live in a mild climate I expect it is still good. Due to the colder weather the past month it has been a little slow to crank. So I topped off the battery once a week with a battery charger for an hour or two and that almost fixed the slow crank problem. But still sometimes seemed a little slow to crank. So then I removed the battery connectors, cleaned them and the posts nice and shiny with a battery post tool, and removed the caps & topped off the battery fluid with distilled water. One cell in particular was definitely low, but they all needed some topping off. Next I carefully cleaned the top of the battery to prevent any surface contaminates from forming a circuit on the surface of the battery. Which would allow it to partially discharge overnight. That all completely solved the problem, and no need to top off the battery charge with a battery charger any more either.

I think he only tested the battery and did not test the alternator. I can’t imagine what could be drawing on the system. When I tried to start it the dome lights did go on, and the remote worked to open the door. It just wouldn’t start. I had it jumped and now it starts. If I bring it to my mechanic, he’s going to insist I left a light on. If I go to Honda, I’m concerned that they will sell me things I don’t need - like a new alternator even if it’s really only the battery. The guy who gave me a jump said it was the battery because he said if it was the alternator the battery light would have gone on on the dashboard when the lights came on, and it didn’t.

[quote=“its_still_a_honda, post:15, topic:98081”]
if it was the alternator the battery light would have gone on on the dashboard when the lights came on, [/quote]

That’s correct for the most part. Unlikely to be an alternator problem. But there’s no need to guess on either. A battery and charging system test is easy enough for most any shop to do, and usually doesn’t cost much. Some places do those test for free, in hope they can sell you a battery if the battery test doesn’t pass.

Right, so then the question is what is a pass? He says 50% does not mean it needs to be replaced. I think he would go down to 25% before replacing. I think he tries to save money by not replacing what he sees as a good battery. Is 50% good enough - I’m in NYC where I can expect temps between 10 and 40 for the next few months

A battery with 50% of its rated power when fully charged should be replaced. However he may have been telling you the battery’s state of charge is 50% because it was recently discharged and has not been fully recharged.

The delivery date can be found on replacement batteries, if you are uncertain of the age of the battery have it replaced.

I agree with the above statements. But it could be some subtle battery drain.

I had a problem with a Jetta years ago, with the battery dying every 6 months or so. Took me a while do determine that the dome light was staying on occasionally. When that was combined with my not using the car for 3-4 days, it drained the battery.

Only determined the problem by trial and error. Tried turning the dome light off permanently, and no more problem.

Take it to an auto parts store. Most of them will perform tests on the battery and charging system for free. That will give you a second opinion. They may also be able to find a date code on it. If they say it’s ok, then you may need to look at your driving pattern. Short trips don’t charge the battery enough to keep it sustained.