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Battery Runs Down After 1-2 Days Of Non-Use


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I have had a dead battery 3 times now. Water level is good. Had a friend chack the volts without and with load. All checked ok. As far as I know there is nothing on (interior light, etc.) that would be draining it. It's a 1.5 year old 8 year battery from Toyota that is right for my model.

Actually, I don't know if it's the battery when it won't start (I don't check voltage then) but it must be since a jump from another battery makes it start right up.

Any ideas what to look for or check?

Thanks in advance!

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It sounds like a load drain on the battery. Typically, a trunk light or glove box light will be on and drain the battery after a day or so. You need to disconnect the negative terminal on the battery and insert an ammeter in series with the terminal and battery post. Make sure all doors are closed and car is as quiescent (nothing running, everything closed) as possible. Check the current reading. If it shows around 500 to 600 milliamp of drain, then a light is probably on. To trace it down further, you then go around disconnecting fuses or bulbs until the current reading drops way down. Then you deal with the offending circuit. Usually it is a switch that is stuck on.

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Can't I just go out in the total darkness and look around and see? Could there be anything else that would draw current that wouldn't be a light?

Yes, you can look around in the dark. That's actually a good idea, but it may not be conclusive. And yes, it may be something other than a light that is causing the current draw. Assuming a drain is the problem.

Putting an ammeter on the battery will confirm that diagnosis.

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With the way the roads are now a battery gets bounced around a lot. Although it is unusual for that new a battery to go bad it certainly is not unheard of as they are just a thing. The LS400 engine draws a lot of juice to start. An internal short in the battery might not show up on a voltage test but might on a load test. I'd take the battery back and ask for a new one.

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I have had a dead battery 3 times now. Water level is good. Had a friend chack the volts without and with load. All checked ok. As far as I know there is nothing on (interior light, etc.) that would be draining it. It's a 1.5 year old 8 year battery from Toyota that is right for my model.

Well a cold engine will draw the most cranking current from battery. So if terminals or at all loose or corroded it may not start. You'll hear the click/clicking sound. Yet when engine is warm it will magically start fine.

Could also be a good battery and bad alternator. In this case the jump start gets engine going but with alternator not charging enough battery never gets topped up. Measure battery voltage at the positive and negative terminals with the engine running (be careful around running engine) and as many electrical items turned on as you can (high beams, AC, blower full speed, rear window defrost, audio, bun warmers, ...). If battery is reading less than 13.3 VDC then alternator isn't putting out enough power.

Could also be a rogue leakage current. Also referred to as high key off current drain. You need to put an ammeter in series with battery and negative terminal. Then wait 30 minutes for all electronics to revert to low power sleep mode. If current draw is much above 50mA something is drawing too much. You have to remove one fuse at a time until you find the offending circuit. Tedious work but these problems can be quite subtle to track down. Possible culprits are leaking diodes in rectifier plate of alternator (replace alternator), leaky electrolytic capacitors in virtually any electronics device in the car (radio, ECU, ...), faulty door closed switch, ...

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if you lock it at night and it's in a garage leave the alarm off and see if it makes a difference. If not go to your local autostore and buy an optima battery they're the best batteries created. I've had one in my car and the alternator is bad because my power steering pump has been leaking. i also have a heavy banging audio system in my car and my car still starts every time. Best battery created. you get what you pay for.

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buy an optima battery they're the best batteries created.

Maybe (the best battery) but if alternator isn't charging no battery in the world will solve that. Also if there is leakage current then a new battery won't fix that either. You need to understand the cause for the dead battery before you start swapping parts. Your alternator must be OK because batteries aren't self charging so the recharge is coming from somewhere.

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I had a similar problem on my '92 this spring. Hooked up an ammeter and started pulling fuses. After the first time through, (after pulling every fuse and no results) I realized that it had to be a non-switched feature that was causing the unnecessary load. I went through all of lights again and still got nothing. I then remembered that you can still roll up the window after removing the key (for a little while, at least). I removed the master window switch and received the desired result. I figured rain may have dripped into the switch an corroded the contacts. I sprayed some wd-40 in there and blew it out with some compressed air. (wd40 is volatile enough to remove some corrosion) Replaced switch and problem solved! Haven't had a problem since. That's my little story and my little redneck fix--best of luck!

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I have had a dead battery 3 times now. Water level is good. Had a friend chack the volts without and with load. All checked ok. As far as I know there is nothing on (interior light, etc.) that would be draining it. It's a 1.5 year old 8 year battery from Toyota that is right for my model.

Actually, I don't know if it's the battery when it won't start (I don't check voltage then) but it must be since a jump from another battery makes it start right up.

Any ideas what to look for or check?

Thanks in advance!

Could possibly be a dead cell in the battery. The best way to tell is, after you had it jumped and ran it for a while, is to (with a DVM) meter the battery across the post as soon as you cut the engine off. Don't just check the voltage for a second, leave the leads on the battery for about 30 seconds to see if there is drainage happening. Usually it will be 1/100 of a volt decrementing every few seconds or so if it is a dead cell. If there is a light on someplace it will drain faster than that. Since it seems like the car runs good after it has been jumped, this should rule out the alternator being a problem.

Another thing to look for is when you go to start it after a few days, look at the voltage before you start your car. If it is a dead cell, the voltage will remain close to 12 VDC or a little above. Again read with a digital volt meter. ( A DEAD giveaway)

Also, my battery went dead in my 2001 LS430, I called Lexus to see how much a new one was. They asked for my VIN and told me mine was still under warranty. It wasn't a full warranty but saved me 50% and then the new one took on another warranty. Doesn't hurt to ask. Hope this helps.

JZ

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I have had a dead battery 3 times now. Water level is good. Had a friend chack the volts without and with load. All checked ok. As far as I know there is nothing on (interior light, etc.) that would be draining it. It's a 1.5 year old 8 year battery from Toyota that is right for my model.

Actually, I don't know if it's the battery when it won't start (I don't check voltage then) but it must be since a jump from another battery makes it start right up.

Any ideas what to look for or check?

Thanks in advance!

Hello I had the same problem with my LS400. The problem was the radio. Really weird but that m-f'er was draining my battery every night in the garage.

Don't know exactly why, but I removed it for a week and it never happened again. I replaced it with an aftermarket jvc and the battery has never died.

Let me know if this works!!!

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I have had a dead battery 3 times now. Water level is good. Had a friend chack the volts without and with load. All checked ok. As far as I know there is nothing on (interior light, etc.) that would be draining it. It's a 1.5 year old 8 year battery from Toyota that is right for my model.

Actually, I don't know if it's the battery when it won't start (I don't check voltage then) but it must be since a jump from another battery makes it start right up.

Any ideas what to look for or check?

Thanks in advance!

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After you shut the engine off and take out the key, now wait two minutes.

Now, connect an Amp Meter that measures milliamps (small) in series with the negative OR positive terminal.

Anything over 30 milliamps is too much and needs to be isolated by removing fuses and relays until the draw is below 30 milliamps.

If you are drawing less than 30 milliamps and still cannot start the engine, check for 13.5v to 14.3v when the engine IS running. You're confirming your Alternator is working well.

If the Alternator is not working well, (or even if it is!) clean the two flat terminals that mount just beneath the 12mm socket head nut, beside the + Positive battery Clamp.

Use 80 grit sand paper and really clean the upper and lower surfaces of these two flat terminals. Now reconnect them and see how your Alternator output is at idle.

If your alternator is putting out above 13.5v AT THE CENTER OF THE POSITIVE LEAD POST OF THE BATTERY, not the clamp, and you are less than a 30 milliamp draw after two minutes, then replace the battery.

Let us know how it goes?

Thanks!

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  • 3 years later...

I had the same problem and while talking to a Lexus dealer I mentioned it. He directly spotted the problem to the phone! I had removed the phone computer in the boot (under the mat to the right). But what drained the battery was that I had still the actual phone in the center console. I removed that (without cutting any wires) and the problem was sorted.

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