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Discussion Starter #1
I remember a discussion while back about draining the battery.
I thought car this advance would at least stop the drain in ACC mode before battery was dead but I was wrong!

Few weeks ago I was trying to copy CD to HDD in my 19 MDX.
I had the car in ACC mode and key fob inside (Not sure headlights were on or not).
I kept swapping CDs (4 or 5) over 2 hour period.
I inserted new CD and came back hour later to find car dead.
Break press and power button just flashes all lights dim and clicking sound.
I jump started it and everything was fine except warning about break module.
I took it to dealer and first time they gave me back I saw the warning as soon as I left dealership.
Turned right around and they kept car overnight and cleared all codes.
Everything is good now but just a warning that ACC can drain battery completely.
 

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There is nothing surprising here. Accessory mode for 3 or 4 hours with headlights on is going to drain the battery.
 

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Two hours in accessory mode on a marginal size 48 battery and it doesn't dawn on you that it will be flat after that? The fact that more and more people lack a basic understanding of auto mechanics and the inability to apply critical thinking skills to the machines we operate will ultimately make self-driving cars a necessity.
 

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Discussion Starter #4
Two hours in accessory mode on a marginal size 48 battery and it doesn't dawn on you that it will be flat after that? The fact that more and more people lack a basic understanding of auto mechanics and the inability to apply critical thinking skills to the machines we operate will ultimately make self-driving cars a necessity.
I know a lot about MDX repairs, go read my posts on this forum.
Why would car allow battery to drain that low?
I can understand if it was a electrical problem etc.
 

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Mainly because no mfg that I know of has ever installed a battery minder. Cars are pretty dumb whenmit comes to batteries. It charges and discharges the battery it can read a state of charge when the engine is running and feed voa the alternator juice to charge. But it cannot read a state or rate of discharge.
 

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I remember a discussion while back about draining the battery.
I thought car this advance would at least stop the drain in ACC mode before battery was dead but I was wrong!
This might be the discussion you were talking about:

I think the MDX does have some measures in place to help keep the battery from draining, but they don't account for every single scenario. If the car is off and you leave the door or tailgate open, I think the interior lights turn off after 15-20 min of door inactivity. But if the car is in accessory mode, I think Honda/Acura assumes that the driver is actively doing something to leave the car in that mode. So in that case I don't think the car will shut things off automatically.
 

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You also assume that battery is fully charged.The AGM battery does not charge to 100% with the two stage charging system of Honda.(Depending on outside temperature) I have been studying My 2018.I charged to 98% yesterday.Drove 1 hour today,checked charge at 25 degrees.58 % charge.I had battery checked by Acura dealer last month.They said battery is good.My tester says it is good but needs to be recharged.So, depending on the level of charge,You may discharge Your battery faster than You think in accessory mode.
 

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Discussion Starter #8
Emmet, right and I think I wrote there that once I was copying CDs and somehow car shut off so I thought it must have automatic shut off but apparently not :(

Normally I would never leave a car in ACC that long but is there a way to copy lots of CDs without driving around?
That's the kind of project I would do un-distracted at home...
 

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I know a lot about MDX repairs, go read my posts on this forum.
Why would car allow battery to drain that low?
I can understand if it was a electrical problem etc.
It is pretty easy to think about scenarios where someone in a car would still need accessory mode even though the battery is too low to start the car.
 

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Emmet, right and I think I wrote there that once I was copying CDs and somehow car shut off so I thought it must have automatic shut off but apparently not :(

Normally I would never leave a car in ACC that long but is there a way to copy lots of CDs without driving around?
That's the kind of project I would do un-distracted at home...
LoL Can you charge the car with battery charger while doing this?

Or on a serious note do 1 CD at a time.
 

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Or just leave the car running. gas is cheap
 

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The problem is so prevalent that my dealer installs a battery minder on all new Acuras they sell. A friend of mine left his MDX in the garage during summer months for 8 days with everything shut off, and came home to a dead battery. He immediately had the dealer replace his battery, and install a battery minder. I just picked up a new 2020 ASpec, and the dealer installed the battery minder as part of the predelivey package.
 

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Mainly because no mfg that I know of has ever installed a battery minder. Cars are pretty dumb whenmit comes to batteries. It charges and discharges the battery it can read a state of charge when the engine is running and feed voa the alternator juice to charge. But it cannot read a state or rate of discharge.
I didn't think my TL, or any other car for that matter, came with a minder, but the other day my wife left the lights on when she accidently hit the rotary switch and put the lights on on instead of auto, when I went to out to start the car I couldn't figure out why the car was dinging when I opened the door, after searching around I found out the lights were on over night, but the battery wasn't dead, the car started up, so the car had to shut the power off by itself.

HOWEVER, I'm not sure if the car came from the factory with a built in battery minder, or as one of the posters mentioned a dealer was installing them in every single new Acura and maybe my dealer did the same thing? Either way I'm glad it's there. So I think if leaving something on that will drain the battery to dead you should have a minder installed.
 

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The battery minder I refer to is plug in unit that charges the battery as it is needed. If I was going away say for 2 weeks and the car would be sitting, I will plug in the battery minder which would automatically maintain the charge of the battery. The unit was not installed at the factory, but by my local dealer.
I didn't think my TL, or any other car for that matter, came with a minder, but the other day my wife left the lights on when she accidently hit the rotary switch and put the lights on on instead of auto, when I went to out to start the car I couldn't figure out why the car was dinging when I opened the door, after searching around I found out the lights were on over night, but the battery wasn't dead, the car started up, so the car had to shut the power off by itself.

HOWEVER, I'm not sure if the car came from the factory with a built in battery minder, or as one of the posters mentioned a dealer was installing them in every single new Acura and maybe my dealer did the same thing? Either way I'm glad it's there. So I think if leaving something on that will drain the battery to dead you should have a minder installed.
 

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The battery minder I refer to was installed by my dealer, and not at the factory. It is a plug in unit that I would use if say I was away for an extended period of time where when plugged in, the unit would charge the battery when required.
 

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I know a lot about MDX repairs, go read my posts on this forum.
Why would car allow battery to drain that low?
I can understand if it was a electrical problem etc.
YOU left the key on!

Understand the reserve capacity of your car battery:

I'm going to guess your vehicle has a size 27 ...

The reserve minute rating is the number of minutes that a battery can run a 25A load until dropping to 10.5V, just like with starting batteries. A Group 27 deep cycle battery with a rating of 180 reserve minutes will run a 25A load for three hours
Plus, with doing that in colder weather, it's reduced even further...
 

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When I went to pick up the MDX when new I told the salesman I wanted to spend some time with the settings and controls before leaving. He told me to be sure to run the engine while I did that. Needless to say I was a bit surprised that he thought I needed to keep the engine running. The truth is there is a large electric load and a small battery, so be careful drawing power without the engine.
 

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With each newer vehicles with computer controlled electronic gadgets, I'm noticing more models are going to the agm style batteries for a bit more longevity...

I'm trying this for an older mdx just to see; the champion brand I got has a 4 year FREE replacement warranty, not a pro rated one
 

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I use a battery minder if I am going to park any car for over a week or two, say for vacation. I also have a lithium jump starter in all my cars for safety's sake. I have stranded myself several times accidentally leaving something on or plugged into the car (radar detector, charger, etc). I might go ahead and hook up one to my battery (semi-permanent) on the MDX after reading these posts. I've had several vehicles that use a constant 2-6 amp drain even when the key is not in the car or the car is completely off.
 
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