12 V Battery

AGM, Battery Tender Jr maintainer ($30) with battery in vehicle. Leaving it in vehicle without a charger almost guarantees a ruined battery. Leaving it disconnected might work but I would keep it healthy by maintaining a charge.

You could take the battery out and charge it seperately but the smart move is to drive the car every two to four weeks to ensure no hv battery capacity is lost and to circulate fluids and mechanicals. Therefore maintaining the 12v battery in the vehicle would be my choice.

 

Yes. The car imposes a low-level but constant drain on the battery. If it's regularly sitting for multiple days, then only seeing short usage, you will run the battery down.

Toyota doesn't say much, except page 563 of North American Owner's Manual stipulation "Charging rates: 4.2 A(mps) MAX". I'm using a CTEK 4.3 smart charger, works fine. It has a quick connect wire I've installed.

I've also looked into installing a similar spec but on-board charger. That way everything's in the car, and with a typical install you just have a male 120 volt plug at the front grill, which you can plug into an extension cord.

Not quite sure what you mean. If it's "go away for a long time, and then try to charge the car when I get back", that's not a good idea.

Our garage queen often sits upwards (or more than) a week between uses, and this is how it spends that time:

 

Hi Mendel,
Just curious as to why the battery tender is you are using is connected at the front rather than in the rear battery area? Just thinking it might have less voltage drop if directly connected to the battery. And on a side note, since installing the Lithium 12 volt from Ohmmu, I have noticed that even when our "Carport Queen" is not used for a week or so, the charge seems to stay the same.

 

You could connect directly at the battery, but not sure there's an electrical advantage. Under the hood is more convenient for me mainly. I wired the CTEK quick-connect to the 12 volt lead where it heads into the fuse box. Accessing that point is described in this @NutzAboutBolts video:

here’s a pic. Pos (red) lead going into fuse box, and for neg, aka ground (black) lead I found a threaded hole nearby, and scrounged up a metric bolt (M6?). Near middle of pic, with gold-colored head:


(For ground, you can also piggy back on any existing locator bolt, going into car body.)

Sounds like it's more robust than a regular lead-acid battery. With our low usage, and a regular AGM style lead-acid battery, I don't want to have gotta-use-the-car hanging over my head, and using a smart charger, it's just "ticking over" once the main charge session is complete.

 

Charging under the hood at the jump point allows you to keep the car doors locked and all windows closed. You can gently rest the hood down and leave the car for days. If you want to charge at the actual battery, you'd have to at least have a window cracked to allow for the wire. It's just easier to connect and disconnect if you charge under the hood, especially if is something you're doing frequently.

 

I leave the hood ajar, but we are secure garage parked. For something like a carport with a power outlet, and on-board smart charger would be more secure, and just sneak the extension cord into the engine bay at a corner of the hood, then gently close the hood completely on it, should be doable.

 

I put my Ctek MUS 4.3A pigtail right on the battery terminals and fished the plug-in up onto the rear deck. Then I just run a long extension cord into the back and and close the hatch on it. The gaskets in the hatch are plenty thick to accommodate the AWG 12 cord. I'm in the same boat (so to say) as Mendel and use the care fairly infrequently.

 

The current involved is so small that any voltage drop would be tiny and insignificant.

Then, yes of course. That is one of the advantages of LI batteries.