Install your positive eyelet on battery terminal nut (underneath red cover).

Corolla 12th Gen - Hybrid (2020+) | Toyota Nation Forum

 

Crap, thought I posted it in there. Not sure if it's good practice to copy and paste and x-thread this there now that this is up........... Crap.

Also, as you can see in the second pic, I did have the eyelet installed directly to the positive cathode.

Appreciate it.

 

Maybe your eyelet cables aren’t making a good connection where it connects to the ctek main cable.

 

They're flush fit, no gaps or bends, nothing is off. So it can't be that.

No... Try grounding on a chassis bolt or nut such as on or near strut tower.

Interesting, i'll give that a shot. Was avoiding strut tower due to paint, was avoiding sanding paint off. I'll see if I can find another chassis ground, but it's also odd that the left location (in the photo) is a literal grounded wire, and failed to work.

 

Have you tried the eyelet here, where I circled in yellow?

This is my setup on my ’20 corolla hybrid. The negative assembly is a little different, but has the same basic setup. I didn’t use the eyelets that come with my battery tender… I alligator clamp directly to where the posts are secured — they have a firm grip where they are and won’t slip by themselves. I keep the hood open for venting and clearance with those wood blocks (they’re screwed and glued together so there’s no risk of them shifting).

 

Have you tried the eyelet here, where I circled in yellow?

This is my setup on my ’20 corolla hybrid. The negative assembly is a little different, but has the same basic setup. I didn’t use the eyelets that come with my battery tender… I alligator clamp directly to where the posts are secured — they have a firm grip where they are and won’t slip by themselves. I keep the hood open for venting and clearance with those wood blocks (they’re screwed and glued together so there’s no risk of them shifting).

Unfortunately, I tried to use first, but it's affixed to that arch lock (Not sure what it's called), kind of like a rivet.

I tried using the alligator clamps directly over the terminal connectors before I ultimately pulled the battery to see if the battery was just extremely dead, or it was a faulty charger/maintainer. So I couldn't even use the alligator clamps with the battery in the engine bay successfully either, exactly as you have applied.

 

Not sure about the entire effort.
12V is charged off the traction battery when vehicle moves. Keeping battery tender on, will not protect traction battery.
Vehicle needs to be driven for 30 min ever so often, Toyota has specific guideline on that. Questions about stowing a hybrid for long time in a summer house, for example, were answered in TCH/THA forums ad nauseam. Basic search should give all the info.
You have 2 points:
1. official one is under the hood. Large center nut in the fuse box is your positive. Negative is any known good negative under the hood, normally, engine.
2. direct connect to the battery terminals. Like you have in your pic. Clean, lubricate with dielectric grease, connect, spray over with battery sealant.
Have beer, done.
The entire OP is really overblown for something that simple.
And, free but friendly advice.
Stop disconnecting 12V. hybrids do not like that. Yes, it is not 100% but, you don't want to be one of the few chosen ones, that did that and ended with array of error lights in the dash and hefty dealer bill to reset the system
I spoke.

 

Not trying to protect the traction battery. The car was dead, sat a week unused. Trying to keep the 12v battery alive, so the car can be driven, in the rare case.

Just picked this car up in October, driven it maybe 5 times, with a month or so between trips. This is the first time it's died within a week. Car has less than a 1000 miles on it.

I'll relocate the positive eyelet to the fuse box, try that out. You've seen the pics where the attempts to ground it are, one was an engine block ground, did not work.

Direct connection to the cathodes did not work, until it removed from the car.

If the car lights up like a Christmas tree, it still has warranty.

 

TL;DR: 2023 Corolla Hybrid SE. Battery dead. CTEK MXS 5.0 (Eyelet and Alligator clamps) and Battery Tender (alligator clamps) failed to detect the battery, even when connected directly to the harness pigtails on the cathodes. However the battery is detected just fine when the entire battery is pulled. Why?

___

Hi there, I have a 2023 Corolla Hybrid SE. The battery went dead after sitting for a week. This happened in a 2017 Camry Hybrid we previously owned, had it towed to the dealership, but I wanted to fix this myself this time.

I purchased a CTEK MXS 5.0 to retire the old Battery Tender. It came with a permanent pigtail connector, which was a big selling point since this car will sit for weeks on end and apparently the newer Corolla Hybrids (ICE versions too supposedly) will kill the 12v after a bit over a week of sitting. Wanted to route the plug to the tow hook cover.

This should've been straight forward, but was not.

Below are the two points of grounding where I tried. The first on the far left, since I tried to go away from the battery as recommended. The next, closer to the negative cathode. The positive pigtail was secured directly to the positive cathode.

However, turning on the charger/maintainer, it would not detect a battery connected. I even tried the alligator clamps on the two 12mm nuts directly on the cathodes and that failed to work.

I pulled the entire battery to attempt to use the alligator clamps directly on the cathodes and that worked perfectly. Not sure why.

However, this is not a very plausible way to charge the battery "on the go".

I'm curious if there's a way or any way to get this to work. I was thinking that there may be eyelets that are the diameter of the cathodes that I can secure under the harness pigtails, but I don't want to just shoot in the dark, but I think that should work?

Far left was first attempt to ground, as seen, a ground even exists there. Top Right is where I ultimately tried to secure an eyelet.
View attachment 421236

Horrible pic after pulling battery, of where I had the positive eyelet installed, you can sort of see the negative eyelet installed at the top. This did not work.
View attachment 421237

Ultimately this worked, but as mentioned, not a good solution when my wife needs to take the car.
View attachment 421239 View attachment 421238

More information, that may be redundant:

If you notice, the maintainer reads on Step 4. Step 4 is "Ready to go" whereas Steps 5 - 8 are topping-off to charge and further maintenance. After connecting the battery, it went to step 4 after 7 minutes or so.

View attachment 421244 View attachment 421245

Cathode is positive. Anode is negative. Jump the battery, then drive the car for an hour. What did the dealer do for you the first time you got this fixed?

 

What did the dealer do for you the first time you got this fixed?

They replaced the 12v. I just hated having the car dragged up on the ramp. I practically disowned that Camry after they did that. I drove it maybe twice over a duration of a year before selling it for profit/refund.

Your CTEK MXS 5.0 charger may have not recognized the connected 12V battery at first if it was excessively discharged.

This was the case, the battery was just too dead. Still weird that the clamps didn't work over the terminal connectors though....

Wait? Wtf? So if I have to take a week+ trip and leave the car at the airport I should expect it to be dead when I return?

There's also a fuse that can be removed which does the same purpose as popping a terminal off. I'm not sure where it is though.

 

Your CTEK MXS 5.0 charger may have not recognized the connected 12V battery at first if it was excessively discharged.

 

I purchased a CTEK MXS 5.0 to retire the old Battery Tender. It came with a permanent pigtail connector, which was a big selling point since this car will sit for weeks on end and apparently the newer Corolla Hybrids (ICE versions too supposedly) will kill the 12v after a bit over a week of sitting. Wanted to route the plug to the tow hook cover.

Wait? Wtf? So if I have to take a week+ trip and leave the car at the airport I should expect it to be dead when I return?

 

Simply disconnect 12V battery when leaving car at airport... It will then also be harder to steal while left unattended.

 

Cathode -
Anode +

 

You may well consider upgrading from your original and already compromised GS Yuasa battery of only 360 CCA, to a 660 CCA AGM battery, which the Hybrid should already have.

ACDELCO EVLN2AGM Silver / Advantage; AGM; BCI Group 47 (H5); CCA 660; RC 105

$143.79 Electrical > Battery > Battery | RockAuto

EXIDE MXH5L247 AGM; BCI Group 47; CCA 680; RC 100

$203.79 Electrical > Battery > Battery | RockAuto

 

You may well consider upgrading from your original and already compromised GS Yuasa battery of only 360 CCA, to a 660 CCA AGM battery, which the Hybrid should already have.
…

High CCA isn’t needed for these hybrids since the 12V doesn’t start the engine. The 12V is for starting the computer and accessory use. The car isn’t drive-able if the computer doesn’t boot up, which is why the 12V is still needed to “start” the car. The engine starts up by using one of the electric motors (I believe the MG1) getting power from the inverter via the traction battery, and all that is dictated by the computer.

Though I agree… may want to replace it sooner than later since it reached a dead state.

 

(Deleted. Accidental post)

 

With out something being 'broken', there is no reason for the 12V battery to go flat after just a week of sitting.

Things to suspect:

1. Faulty body control module (BCM() computer that refuses to 'go to sleep' when it's supposed to. The fault may be software - so a dealer update can cure it.
2. Faulty battery that self-discharges or has a 'weak' cell that can't maintain voltage.
3. Faulty switch keeping a circuit 'on', e.g. trunk light. Most of that should be managed by the body control computer 'battery saver' but...
4. Aftermarket alarm or accessory wired into 'always on' instead of 'car on' circuit.

The dealer ought to be able to diagnose the excessive draw and determine the circuit responsible - it just may take a bit to re-create the exact conditions. Worst case scenario here is where a BCM software update is needed - that may take a while.