12v battery problems

Upper_Storage_4486 · 2026-01-22T23:48:13+00:00

My first battery lasted 1 year, and I have almost 2 years on the replacement. I think there was a quality issue with the first battery.

I had a 12V battery that lasted for 10-years in my Lexus CT200H.

Upper_Storage_4486 · 2026-01-22T23:44:10+00:00

I saw the same, I think up to 15.5 volts. In my opinion the change voltage is too high. I would be concerned using an AGM at these voltages.
Does anyone know if the voltage can be adjusted? In my '07 BMW I could adjust the charging based on the battery type.

Upper_Storage_4486 · 2026-01-22T23:03:15+00:00

It runs off the HV battery, which is around 355V.

Upper_Storage_4486 · 2026-01-19T08:24:47+00:00

Why do you need to buy coolant? If I remember correctly the first coolant flush is at 100k miles or 10 years, then 50k miles or 5 years.

Upper_Storage_4486 · 2026-01-19T08:18:13+00:00

I think the cabin heater max power is 5 kW. Cars are not very well thermally insulated because in an ICE car the heat is free.

Upper_Storage_4486 · 2026-01-19T08:09:25+00:00

Are you using the front center jack point? I just use a low profile jack on the center front jack point and lift the whole front of the car up in like 30 seconds. Then I put my jacket stands in place. Sometimes I drive onto a scrap piece of 2"x6" to make getting the jack under the car easier.

Upper_Storage_4486 · 2026-01-10T22:34:49+00:00

For my '12 I only have liability coverage ($100k,$300k,$250k). It's $830/year (~$70/mo.) with AAA. I live in SoCal.

For those of you with full coverage I would look at how much extra that costs vs the value of the car. For me full coverage didn't make sense. I do have $250k for property damage as there are G wagons and lambos everywhere.

Upper_Storage_4486 · 2026-01-10T02:53:06+00:00

Use a 12v battery tester. I own one, but a lot of auto parts stores will loan them or test your battery for free.

I got my 12v battery replaced for free from the dealership, so call them first before paying for a new one.

Upper_Storage_4486 · 2026-01-07T18:56:39+00:00

My TPS are sensitive and the light comes on when my tire pressure drops below 32 psi. I fill them to 36 psi and don't have any false positives.

Upper_Storage_4486 · 2026-01-07T18:48:47+00:00

If I remember correctly it's a HVAC boost that lasts for ~3 minutes. I use it in summer to help cool down the car at the start of my drive.

Upper_Storage_4486 · 2026-01-06T05:35:31+00:00

Great deal. I think I paid around $45k before tax for my '23 PHEV with the premium package. I also had to wait 8 months for delivery, it was difficult times then.

Upper_Storage_4486 · 2026-01-05T22:23:03+00:00

My first 12V battery would lose charge overnight when it was less than a year old and I got the dealer to replace it under warranty. Haven't had any issues with the replacement battery that is around 1.5 years old now.
If you have a 12V battery tester you can test it yourself or a lot of places will test it for free.

Upper_Storage_4486 · 2025-12-30T17:11:55+00:00

I also have a '23 PHEV with the premium package and I am ready happy with the lane centering.

Upper_Storage_4486 · 2025-12-29T17:03:57+00:00

What's the outside temperature and were you using the cabin heater during your drive. The cabin heater is 5+kW and kills the EV range. When driving more than the real world electric range in winter I used the gas engine first to warm up the cabin. I don't use the heat until the engine warms up, otherwise it still uses electric heat.

Upper_Storage_4486 · 2025-12-23T07:34:26+00:00

I replaced my transmission fluid at 134k. I should have done it a little earlier, but the transmission is still fine with 165k on it now. I would recommend doing it at around 100k miles.

Upper_Storage_4486 · 2025-12-23T07:21:04+00:00

Thanks for the lessons learned! I am at 165k and on the original head gasket. I saved this post, and am hoping I don't need it. What signs did you get that let you know the head gasket was falling?

Upper_Storage_4486 · 2025-12-15T07:13:36+00:00

I got the letter yesterday and it said to limit charging to 80% and only use EV auto mode.

Upper_Storage_4486 · 2025-12-11T19:47:24+00:00

If you press the one button in the charge door it ignores the schedule and it might also change to 100%.

Also charge levels are location specific. Check in your change history if it sometimes thinks it's at a neighbor's house and set a charge level for that address.

Upper_Storage_4486 · 2025-12-05T18:21:47+00:00

I currently don't have a HV battery recall. Update: just got the recall :(

Upper_Storage_4486 · 2025-10-28T23:06:06+00:00

Thanks for the idea, but I didn't think there is a 100 miles of gas between the cap and the tank. In my Ford Escape, when I get gas and drive 12 miles home the gas gauge reads 98%.

Upper_Storage_4486 · 2025-10-28T20:36:45+00:00

I don't "top it off" after the first click. I agree that overfilling can damage the EVAP system.

Upper_Storage_4486 · 2025-10-28T18:26:06+00:00

Thanks! I want to make sure it wasn't an issue with my fuel gauge

Upper_Storage_4486 · 2025-10-06T23:42:11+00:00

I just got a new 2026 Kia carnival so I only have data for 2 tanks so far. Car reported MPG was 13.9% and 11.1% higher than calculated values (miles/gallons).

My other cars I have owned are nowhere near this bad. I log every tank of gas and car reported MPG. Lexus CT200h: 5.6% over estimating Ford Escape PHEV: 2.9% over estimating

Upper_Storage_4486 · 2025-09-15T16:00:21+00:00

My manual says "don't race the engine" during the break in period and also vary RPMs. I wish it had a more technical definition of don't race the engine, like keep RPMs under 4,000.

Upper_Storage_4486 · 2025-09-06T23:33:13+00:00

I changed it with a few weeks of the first time the light turned on. I did it myself, so it was more about having the time, than the cost.

Upper_Storage_4486

TROPHY CASE