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Discussion Starter #1
Early this summer, my battery died.
(batt did not have enough juice to crank after a 2 hour drive).
So I replaced it with a nice AGM, size 27F.
Went to a few show & shine, then back in the garage.
Well, after about 3 weeks, dead battery again.
Fully recharge and drove an hour.
Back in the garage, I decided to check the current the car draws when sleeping.

I measured 27 mA between body and neg post.

I would like to have numbers from others MK2.

I will be doing investigation next winter, but am curious of what a non-issue car takes / what am I targeting to.

PS: you will most probably loose time & radio station doing so.

Thanks in advance.
 

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I will be doing work on my '83 tomorrow and I have to disconnect the battery so I will get a reading for you.

Having said that, a 27F battery, not AGM should be rated at 66-110 Ah.
3 weeks is 504 hours.
27 mA is 0.027 A
504 h * 0.027 A
Total draw for this time period should be about 13.6 Ah so there should be oodles of capacity left in three weeks.

Something sounds off.

Dale
 

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Please be aware that lead-acid batteries SELF discharge. A maintainer is a great idea.2 A is fine.
Your alternator should provide 14 volts AT the battery.13.7 is good.
Your discharge leaks may be caused by multiple electronic devices.
Alarm systems and KEEP ALIVE memory in other things.
If you remove the negative terminal,you will loose your radio pre-sets and possibly confuse the ECU.
NEVER do that to a late model automobile.Mercedes,BMW and more.

(To find the current draw,start pulling fuses to everything.)
First,use a test light and connect the lead terminal to the disconnected negative post and see if it lights up. If not,you are good to go.
If it lights up,start pulling fuses,until the test light goes OUT.

I had a Corvette in the shop and the door locking solenoid was causing the draw!:rolleyes:
 

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I recently had to replace my alternator because the rectifier diodes were leaking BADLY. I would take my battery charger off the battery and I could see the battery voltage drop by 0.1 volts in a minute! The battery would drop to 6 V overnight. I replaced the alternator and the problem went away immediately.

I would assume that leaky diodes allow current to flow from the battery through the diodes in the alternator to ground.

I was lucky because the problem was so obvious I could spot it. If it was more subtle I wouldn't think of this.

I don't think that you will see current from battery negative to ground show up on this path. I think you WOULD spot it if you measured from battery positive to the wiring harness. The alternator is an alternate ground if the diodes are leaking.

Just a thought.
 

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If you don't drive your car a lot you should spend the money and buy a CTEK charger. They come with a wire harness and you connect it to the battery and run it down to the grille somewhere. Then just plug the car in every time you park it. I have one on my car and you can let it sit for months and it will fire up everytime. They're a little pricey, but well worth the money IMO.
 

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If you don't drive your car a lot you should spend the money and buy a CTEK charger. They come with a wire harness and you connect it to the battery and run it down to the grille somewhere. Then just plug the car in every time you park it. I have one on my car and you can let it sit for months and it will fire up everytime. They're a little pricey, but well worth the money IMO.
I use a charger with clothes pin type connections to keep my cars charged, but using a permanently attached connector that is a simple plug in connection would be a lot easier.
Where do you have the connector located so that you can plug it in easily without opening the hood and yet not have it stick out like a sore thumb?

If you have pictures, I would love to see it.

Dale
 

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Not quite on topic, but in my experience, AGM batteries don't play well with older cars because their alternators don't put out enough voltage to fully charge the AGM. Running around on a partially charged battery all the time seems to shorten their lifespan really quickly. Look at most modern cars with an AGM and you'll see charging voltages between 15-16v. Even my 07 FJ can't handle the AGM without me keeping it topped off via charger pretty often. Tried a number of them on previous 85 Celicas with horrible results when not charged via AGM-specific charger regularly.
 

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I use a charger with clothes pin type connections to keep my cars charged, but using a permanently attached connector that is a simple plug in connection would be a lot easier.
Where do you have the connector located so that you can plug it in easily without opening the hood and yet not have it stick out like a sore thumb?

If you have pictures, I would love to see it.

Dale
I don't have any pics, but it runs thru the gap around the radiator and over to the drivers side of the lower opening. With a zip tie or two along the way. It hangs down a little bit, but typically gets blown inside the opening once you start driving it. I think they also make one that plugs into the lighter socket if you don't mind going inside the car.
 

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Back in the garage, I decided to check the current the car draws when sleeping.

I measured 27 mA between body and neg post.

I would like to have numbers from others MK2.

I will be doing investigation next winter, but am curious of what a non-issue car takes / what am I targeting to.

PS: you will most probably loose time & radio station doing so.

Thanks in advance.
10.1 mA between negative post and body. The same between the positive post and the wiring harness.
 

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Not quite on topic, but in my experience, AGM batteries don't play well with older cars because their alternators don't put out enough voltage to fully charge the AGM. Running around on a partially charged battery all the time seems to shorten their lifespan really quickly. Look at most modern cars with an AGM and you'll see charging voltages between 15-16v. Even my 07 FJ can't handle the AGM without me keeping it topped off via charger pretty often. Tried a number of them on previous 85 Celicas with horrible results when not charged via AGM-specific charger regularly.
This is absolutely true. It's also another one of the benefits of upgrading to the 92 Camry alternator. It's charging voltage is about 14.5 vs about 13.8 with our original alternators. There are ways to increase the charging voltage of (older) alternators by using certain pairs of diodes in the reference voltage line to make the voltage regulator think that the system voltage is lower than it really is. Each set of parallel diodes in series with the reference lead increases the charging voltage by about 0.6 volts. This mod isn't hard, but it's not something to be undertaken unless you really understand exactly which components to use and how to properly connect and protect them. If anyone is interested in doing this, a Google search should provide a source for device specs and complete directions.
 

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Discussion Starter #11
Thanks everyone.
Dale, 7-10mA is pretty much what I would have guess, given the '80s electronics. We have ECU, radio, clock and a couple of modules drawing continuously.
I do have a batt tender ready to be plugged-in. I just have to pop the hook, and my charger is attached to the garage door opener, so the mating plug is always near by.
I did not know about AGM may be asking a bit more for charging.
As per TSRM, (page CH-4) we should have 13.5 to 15.1V.
I have 14.4V above Idle speed.
I will be chasing my 27mA later this winter, plug it for now.
I would not be surprise to find corrosion somewhere in a door (a door connector game me issues in my first Supra) or in the main junction block, as I have had a leaky windsheild couple years ago.

I'm interested If anbody else have a value for me, as it would confirm a good car condition mA draw.

Thanks
 

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I wired in a "battery tender" to an orange plug below the bumper.
Yes,I have driven out of my drive way,without unplugging it.

On my old Ford,I had a plug at the REAR of my car.
On a Supra,the wire to the electric antenna is always HOT.That would work.


I have a block heater connected to that plug also!
 

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I wired in a "battery tender" to an orange plug below the bumper.
Yes,I have driven out of my drive way,without unplugging it.
Hahaha,

You'd look natural in Edmonton Alberta in January!
EVERYONE has block heaters to keep the engine warm enough to turnover. There's usually a 6' extension cord plugged in. The other end gets tied around the rear view mirror.

I'm sure it's really common to forget to unplug those suckers!

I suppose that it could be the real man's way of running an EV. No "less than manly" batteries for you!

Dale
 

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14.4V still might be marginal with an AGM battery. What's important here is not the spec for our cars, but what todays batteries need to stay properly charged. Batteries have changed significantly in the 3 - 4 decades since our cars were designed and built. That being said, I think that installing a battery tender may be all that's required to keep your battery topped up. If not, as I stated earlier, there are ways to increase the charge voltage in 0.6V increments and it looks like 1 would get you to 15.0V which was stated as the minimum charge voltage todays vehicles have. The higher charge voltage recharges the battery significantly faster than a lower one would so it would also likely solve your problem.
But I share your concern about corrosion due to the windshield leaking. In the past, I had a similar problem and after having the windshield replaced, finally tore the car apart trying to get to the bottom of a few intermittent issues that had become more than annoying. What I found was that the connection to the door harness as well as a few others behind the main fuse box had mostly a greenish corrosion and in a few places there was some that was whitish. I don't have any idea if these were due to 2 different issues or if the difference in the color was simply due to a time difference of how long they.d been corroding.
The corrosion creates two different issues. In some cases, the corrosion creates poor or no contact between 2 interconnecting terminals. In others, it creates partial to complete shorts between adjacent terminals because it's conductive. This could be the source of your increased current draw. In any event, after thoroughly cleaning both halves of every connector in that area, everything has been problem free for years. The only cleaner that really works is DeOxIt. It's been highly recommended forever by myself as well as quite a few others.
 

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Discussion Starter #15
Thanks Ray, I'll give a look at that mod to the regulator.
My Mitsu Lancer also have a 24F battery (lead-acid), so I might swap.
But 27mA sounds a bit high to me for standby, so I'll investigate anyway were it goes.

Anyone ever open the main junction block of the driver kick panel?
It's a major puzzle of criss-cross multi-layer folded steel multi-finger spider legs!
I did open one up on my first Supra to clean the many connectors that were covered by this greenish stuff Ray talked above. A serious challenge!
 

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This is absolutely true. It's also another one of the benefits of upgrading to the 92 Camry alternator. It's charging voltage is about 14.5 vs about 13.8 with our original alternators. There are ways to increase the charging voltage of (older) alternators by using certain pairs of diodes in the reference voltage line to make the voltage regulator think that the system voltage is lower than it really is. Each set of parallel diodes in series with the reference lead increases the charging voltage by about 0.6 volts. This mod isn't hard, but it's not something to be undertaken unless you really understand exactly which components to use and how to properly connect and protect them. If anyone is interested in doing this, a Google search should provide a source for device specs and complete directions.
That same technique of "raising" the ground the regulator uses as a reference has a solid base-of-use in many electronic applications, so it's not some snake-oil magic. As Ray says, you must do it correctly to get it to work properly, but it does work, and I've used the basic priciple many times in different circuits.

The color of the corrosion is a way of gauging approximately how long the connection has been subjected to "unexpected" conditions. It starts out white as the tin plating on the terminals sacrifices itself as tin oxide, and then progresses to the green color as the underlying copper begins to corrode. ANY amount of salt in the air or water will greatly accelerate the corrosion. I've seen two-year old connections that weren't properly sealed against the elements literally melt away back in Illinois where they dump salt on the roads at the first sign of a snowflake.
 

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Not quite on topic, but in my experience, AGM batteries don't play well with older cars because their alternators don't put out enough voltage to fully charge the AGM. Running around on a partially charged battery all the time seems to shorten their lifespan really quickly. Look at most modern cars with an AGM and you'll see charging voltages between 15-16v. Even my 07 FJ can't handle the AGM without me keeping it topped off via charger pretty often. Tried a number of them on previous 85 Celicas with horrible results when not charged via AGM-specific charger regularly.
Interesting. I had not read anything about that, rather I had read somewhere that the AGM lasted better in storage for classic cars. I purchased an AGM battery for my 69 Corvette a couple years ago. The "reproduction" Delco batteries are in fact, modern AGM batteries wrapped in a case that looks like its from the 1960s. The manufacturer recommends keeping it plugged in when not in use and specifically they recommend a certain unit of Battery Minder brand, though I already had CTEKs. I found at first my CTEK would sometimes stop and blink an error. I eventually figured out that it seemed to be associated with the CTEK extension cable. It doesn't error out when instead of the CTEK extension, I ran a regular AC extension cord from the outlet across the shop floor and plug the unit to the battery directly. Hopefully no more than the Corvette gets driven it'll last. Its 99.999% on the CTEK in "snowflake" mode (there's a setting for cold weather and AGM batteries that's supposed to increase the charge voltage.) I also bought an AGM battery for my truck because it too sits probably 80% of the time plugged into a CTEK, but its a 2007. I hope I don't wind up regretting spending the extra money for AGMs.
 

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I'm surprised that the Absorbed Glass Mat batteries are not always the best solution for older cars that cannot charge at the recommended voltage! Mine cannot do better than 13. 8 VOLTS. (Stock alternator,so far.)
I'll assume that the "jelly roll" ones are the same issue.
The best battery for older cars are NOT AGM's.

I use the snow flake setting on my solar systems AGM's with my # 7002 CTEK. It gets WARM,charging 6 of them. I use an external fan.I'll guess that is why they fail: overheating.

I trust my "battery tender" wired into my Supra.2 AMP setting.
No,I don't have one. I got one from Sears,when I worked there. Ching Tau brand.
http://products.batterytender.com/Chargers/
 

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Yes, getting at the connections on the back of fuse box in the drivers side kick panel is a PITA. But it can be done without that much difficulty. The first thing I do is remove the seat and then the trim panels in that area so that I don't have to "stand on my head" to access it easily. The fuse box then can be unbolted and pulled out some and turned some to get at the connectors on the back side. Cleaning these connectors thoroughly as well as the one to the passenger side door in the passenger side kick panel has fixed many problems and intermittent issues over the years. And by using DeOxIt, I've never had to redo any of it again.
 

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Agree 100% with Ray.....DeOxit is "The Kind"!

Been using that stuff for well over 25 years, and it's never let me down. I've even had it bring back controls that I thought I was going to have to replace.
 
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