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Old 01-06-2015, 06:02 AM   #1
Mutad0r
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[SOLVED] Electrical proglems - Battery keeps draining

I have a toyota corolla '89. I recently returned from a 12 day trip to find my battery dead. I've been on longer trips this year, but the battery has so far never drained. Before removing the battery for charging I measured the current drawn by my car. It was 150mA. It's not extremely high (depending on your point of view) but it's not quite low either. I calculated that my 60Ah battery shouldn't have drained completely in 12 days, but I figured that since it's cold it could have or 'whatever'.

Before charging the battery I measured the voltage. It was about 10V, which troubled me, since in my knowledge, an empty battery would read a lot closer to 12V. I decided not to buy a new battery quite yet, so I charged it. It charged and got to the desired voltages, I put the battery back and the car worked and everything was juuust peachy!!

Then, a day later I tried to start my car and it had real trouble cranking the engine. But it started. The day after that, the battery was completely drained and the starter wouldn't even click (just as when I returned from my trip).

SO. I'm starting to think that my battery is dead, however it does charge to normal voltages. my evidence for it being dead is that a full battery drained in just 48 hours at a drain of 150 mA. I could just buy a new battery, but I wouldn't drive a corolla '89 if I was ready to start with replacing the most expensive component.

My current plan is to let the battery sit indoors and see if the voltage drops, then test the current drain again and start pulling fuses and relays, to try and find what takes all that current. I read online that the drain should be under 30mA. Buying a new battery is a last resort at this ponit.

THE MOST IMPORTANT PART: What I really want to know from YOU, is whether 150mA drain is okayish, but not good (or worse). And whether you think I do have a dead battery, irrelevent of whether the drain is too big or not.

TL;DR: Read paragraphs 2, 3, 4
still TL;DR: I forgive you!

Last edited by Mutad0r; 01-08-2015 at 06:20 AM. Reason: Added 'solved' to title
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Old 01-06-2015, 06:59 AM   #2
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Re: Electrical proglems - Battery keeps draining

I'm not all that familiar with the electronics in an '89 Corolla, but they probably don't go fully in to standby until after several minutes (might take as long as 45 minutes). The 150 mA draw doesn't seem all that high if the measurement is before the car is completely in standby. Also, there is no way the 150 mA draw should drain a healthy battery after just a day.

It sounds to me like your battery has very low capacity. How old is it? If it's more than 3 years old, there's a good chance it's tired, especially if you don't desulfate it regularly and generally make short trips.

You could either take the battery to a parts store or automotive battery store to have them perform a load test, or you can perform the load test yourself. Since you have a meter to measure the current draw, I'm guessing you also have a meter to measure the battery voltage. Charge the battery using the charger, then disconnect the charger, install a volt meter to measure the battery voltage, then start the engine with the meter still applied. Monitor for the minimum voltage while the start is engaged. If it drops below 10.5 volts when cranking, that battery has low capacity. Continue to monitor the voltage once the engine starts. If the alternator is working, you should read a voltage of somewhere between 13.5 and 14.4 volts with the engine running.

Voltage potential and capacity are different with a battery. Just because it will take a charge and measure over 12 volts does not mean it can maintain that voltage when there is a significant current drawing (from the starter motor) on it.

My bet is on a weak battery and I think you'd be wasting your time pulling fuses to locate the 150 mA draw at this point.

-Rod
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Old 01-06-2015, 10:36 AM   #3
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Re: Electrical proglems - Battery keeps draining

That's what I was hoping to hear actually
I'll try the load test tomorrow and maybe wait to see if the current draw goes down after some time. I have already tested the alternator and it gives out a healthy 14,4V when the engine is on.
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Old 01-07-2015, 07:34 AM   #4
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Re: Electrical proglems - Battery keeps draining

Right, so I did a load test and maybe it's because the engine turned on almost instantly and the voltmeter couldnt react to it fast enough, but the lowest voltage I saw was about 11,2V ....

Here's another thing.. I did another drain test. I disconnected the battery and put a seperate wire between the ground terminal and ground wire that had a switch in the middle. left it like that for an hour and then I attached my ampmeter to the ground terminal and the wire and then disconnected the switch. It showed 1A of current and I was like WHAAAAAAAAT. I have no idea how I got the 150mA prefiously. Its getting dark outside so I'll wait untill tomorrow and make another drain test, this time I'll hook the ampmeter up directly and wait in the car for some time, no matter how cold it is outside.
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Old 01-07-2015, 12:09 PM   #5
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Re: Electrical proglems - Battery keeps draining

Yeah, if you determine you do have a 1A draw on the battery even after sitting for an hour, that would be excessive and you should spend some time searching for that.

How long had your car been sitting when you tried the starter load measurement? As quickly as it started, it almost sounds like the engine may have still been warm even.

-Rod
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Old 01-08-2015, 06:18 AM   #6
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Re: Electrical proglems - Battery keeps draining

The car had been sitting for over 24 hours, it wasnt THAT cold outside either, I think it was just below freezing.

Anyway, I think I've solved the problem... And everything is my fault.

The reason I got different current drain results is that the first time I tested the 3 ground wires seperately ( car, alarm, amp) and the second time I had them all together. So I tried the ground wires in combination of 2 and found out that it's the amplifier that drains 1A, but only when the car main ground is also connected to the battery. I traced the problem to the amps kill-switch wire that was supposed to go to the ACC in the ignition.

That's when I remembered what had REALLY happened. When I came back from the trip, the car started and I drove to the store on a very bumpy road. When I had done my shopping, I left and found out that my alarm wouldn't disengage when I turned the ignition to ACC (it would automatically lock the doors if the car isn't started after a certain amount of time), the wire to ACC had shaken loose.

So I re-connected the wire to ACC, but when I initially removed the wire, another wire came away too. I thought that it had come from the wire next to ACC, but I was wrong. That wire that had come loose was the amplifiers killswitch, and the one I wired it to was the main 12v from the battery. So instead of the amp being turned on only when the car was started ( or atleast the ignition at acc ), it was always turned on, and apparently the amplifier drains 1A of current even if no music is playing.

With all the wiring done correctly the car drains 240mA initially and I'm currently waiting to see if that goes down.

Moral of the story is: always check what you wire to what. (my excuse is that I had to do it in the dark at the stores parking lot with nothing but a screwdriver and some tape)
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Old 01-08-2015, 06:45 AM   #7
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Re: Electrical proglems - Battery keeps draining

Thank you for the follow-up with what you've found.

You have the ground wires for the alarm and amplifier running all the way to the battery? Do you have issues with noise through the amp, such as alternator "whine"?

-Rod
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Old 01-08-2015, 08:56 AM   #8
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Re: Electrical proglems - Battery keeps draining

Quote:
Originally Posted by shorod View Post
Thank you for the follow-up with what you've found.

You have the ground wires for the alarm and amplifier running all the way to the battery? Do you have issues with noise through the amp, such as alternator "whine"?

-Rod
Why yes, yes I do, I'm hoping you're about to lay out a neat trick of how to fix that?

Also, the current fell to approximately 20-30mA (The 200mA only showed with a 10mA precision)
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Old 01-08-2015, 10:45 PM   #9
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Re: Electrical proglems - Battery keeps draining

By running your ground wires all the way to the battery you're no only spending money on extra wire, you're also making basically large antennas that will pick up noise and, in the case of the amplifier, bring this noise in on the ground and play it over the speakers. Your Corolla should be just like probably 99.99% of the other cars on the road and uses a common ground. Especially with audio equipment, you want to keep the ground wire as short as possible and bond it securely to a night, clean ground. It will also help to use or make a clean ground that is not shared with something prone to noise such as the fuel pump or alternator. That will help minimize the noise you hear over the amplifier.

On a typical car there's really no reason to run a ground all the way to the battery for any device.

-Rod
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