Original factory 12V battery dead with zero warning

Yes. Most of them have a simple quick disconnect to make using it easy especially if you don't drive every day.

 

Consider hooking up a cable with SAE connector to 12v battery and then route it to behind the tail light cover for easy access to charge. While you're at it. Attach yourself an AirTag or Smart Tag 2 (Samsung) so you can track your car if lost or stolen Sometimes your car might get towed way when you think it was stolen.

 

I use CTEK battery conditioners on ‘the fleet’, with LED battery condition indicators integral to quick connects.

 

We’re currently putting about 3k kms yearly on our 2010, typical usage a 20~50 km drive, once a week on average. Keeps the engine healthy, but not good for 12 volt battery longevity. I’ve wired in a CTEK quick-connect harness (sim to the pic @Air_Boss posted, but no LED indicators), at the under-the-hood fuse box. Have a CTEK charger connected pretty much ALL the time: if we drive one day, I pop the hood when we get get home, connect charger the next morning, leave it thus till we next use the car. Current battery was installed over a decade back.

 

'I see these gadgets as helping me to avoid asking my neighbor to jump me, but otherwise I'm not so clear on the reason for this.'

What are convenience and reliability worth, especially on infrequently-used equipment?

We use them on 'the fleet', the standby inverter generator, and other 12V devices.

 

Yes because of two reasons that make sense and were already mentioned.

One is the battery has no high current starter load. In conventional cars this is essentially a serious load test every time you crank it. Capacity is checked by electronics (sometimes) but certainly the driver can tell when it is cranking slow meaning low charge. Prius has no high load.

A second is there are a couple of battery discharging mechanisms that get you. The obvious map light. The obvious headlight turned on manually after shutdown. The less obvious hatch not closed 100% but still latched. The far less obvious and less problematic key fob in range of the car (of which is technically only a problem over many days). Aftermarket radios, obd2 readers, gps, etc sometimes fail to go into sleep mode.

The real problem is an unloaded 12v battery that is many years old can suddenly fail 20 minutes after being driven to the store. You have a fairly new battery but each discharge takes an extra chunk of life off the expensive agm 12v (which incidentally takes discharges pretty well).

My recommendation is carry a 12v lithium jump starter with polarity protection. You won't get stranded and the real killer, reverse polarity jumps won't happen. That can and does cause weeks of downtime and frustration that will make a dash light discharge seem like the good ol days.

Lead a horse to water


PS. 500,000 miles of Toyota hybrids since 2008 (355,000 miles on the v) and I never had a "maintenance" charger hooked up. Never. I have jumped my Prii (x3) and my Rav4 Hybrid as a test a few times but only once because it was needed. I have instructions shown above printed out for the wife and friends and customers with Prii. I make them open the car with the mechanical fob key, open the hood and remove the fuse box cover to give them skills a tow truck driver may not have. They can leave hatches slightly open, sit in the shutdown car with the headlights on. etc and ruin both of our days.

I have jumped many pickup trucks with their gigantic batteries, usually in a parking lot where "they suddenly" failed.

Good luck on my hybrids? No. Its understanding what you have and typically drive it several times a week. Its being prepared (mostly for the other guy's problem) and NEVER jumping a Prius to or from.

With that said, I have left a Prius in an airport parking lot for three weeks many times. Jumped it once.

 

My 12v battery kept draining and I found out why. I accidentally pressed the car seat heater on and left it on. Until one day I noticed it. Also my car drains because it came with a TheftPatrol tracker which was free for 3 years and then they charge you monthly. I think my AirTag or Smart Tag 2 will do just fine.

I understand you. I was even thinking of setting up a converter that I can manually switch to charge from HV (200v) to 12v so I can jump start the 12v using just a switch. It would not overload the 12v, just enough to power up the car and then switch it off. But I'm not going to bother or take the risk. My new Sodium Ion car jumper will give me some peace of mind for now. I can also charge my 12v using solar or a portable power station using the plug I installed.

 

You can buy a lithium 12v battery with a built in jump starter operated by a key fob. Maybe $1,000 but will work unlike the many attempts to tap into the 201v battery.

We are in a high cost of gas period where people panic and buy used Prii. I was shaking my head last week when a woman traded her truck and Subaru for two gen3 Prii because of the mpg and reports of Toyota reliability. One "suddenly" started overheating. Stop leak wore off.

 

If you go the Lithium jump pack route, just realize that if the jump pack is left in the car at sub-zero temperatures it will not perform well, or at all.

 

That's probably the real culprit. I doubt the seat heater operates when the car is off.