Auxiliary battery

I originally started carrying a 12V electric drinks cooler in my car in 2024, as the weather turned warmer. I enjoy having a cool drink in the drink holder, particularly on long drives. But I could see that the smallish, 33 Ah 12V battery was not going to keep the cooler running for long, once I parked, so I looked for a 12V battery with higher capacity. I found a 100Ah lithium battery that I thought I could make fit, but I was wrong. Another reason is that the stock Toyota battery has additional terminals, which I believe are for temperature sensors.

So then I decided to install the new battery as an auxiliary, to run the cooler while the car was off. To prevent draining the stock 12V battery, I installed a battery isolator, which disconnected from the main 12V source at a fixed level. It reconnected when the system voltage rose to a preset level when the car was running again and charging the system.

Unfortunately, I discovered that in warmer weather, the 12V system voltage is lowered to the point where it fails to trigger the battery isolator, and the auxiliary battery never gets a charge. I discovered this on a long road trip, where I discovered that the cooler was no longer working, and the auxiliary battery was dead, after a long day of driving.

The answer was to upgrade to a programmable battery isolator. It allows me to adjust the cut-in voltage lower than the 12.6V the system maintains in warm weather. I also set the upper limit to 13.6, which protects the lithium battery from over-charging. So far, everything is performing perfectly.

 

The only problem is that ice melts, and tends to be quite expensive on the road. Besides, it keeps things chilled, even if I'm not driving the car for a few days. I have a 5A battery charger connected to the aux battery when I'm parked and plugged in.

 

There is a spot on the left side, directly opposite the stock battery on the right side, that has adequate space for it. It doesn't sit level, but that doesn't matter with a lithium battery.

I'm not worried about keeping it chilled in the cup holder. It's cold enough coming out of the cooler.

 

You seem to be delusional. What is it that you think is your goal?

 

I'll always welcome being held accountable for what I say, but you seem to take it a whole new level.
Maybe relax and shift your focus elsewhere for a bit.

 

Well, call in the mod to give me another thrashing, I guess.

 

Just trying to be accurate. Save the lecture. He's been trying to goad me all along.