fix or replace?

It would be best if you could the car drive more often than twice a week. If you cannot fit three or more drives in this vehicle of 20 minutes or more for each drive into your normal daily schedule, then you should consider obtaining and using an automatic multi-stage 12 V battery charger and use it when the car is not in use for 3 days or more to maintain your 12 v battery in a healthy condition.

 

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it is possible that something is draining the 12v while the car is off. but hopefully it is just the lack of driving.
determining which it is would take some testing. if you can't find a private hybrid mech, you might be better off selling and buying a non hybrid. it sounds like your dealer is clueless.

 

If this means you got a “new” reconditioned hybrid battery somewhere you really bought a used battery spit shined to look good for a short time.

There is a constant 12v draw on a car even when off but it’s is so small that a good 12v battery should not need a battery maintainer if driven once a week. However there can be abnormal drains like lights, aftermarket gps or radio or even an obd2 reader left plugged into its port. Or something more serious, eg an excessive “parasitic drain”. A decent mechanic or a good diy’er can measure that drain with a $3.99 Harbor Freight meter. If an excessive draw is there the skill comes in to pinpoint the location and fix it.

Unfortunately a standard Corolla or Camry 10 or 15 years old would be far more reliable and much less costly to fix than one of the most complex cars ever made, eg a Prius.

If most of the current problems turn out to be battery related (maybe both batteries) then fix the 12v drain and or get a new Toyota OEM hybrid battery, often available for $2k-$2.5k.

 

Noco chargers are good, but I'd go for one with a 4 A output rather than that 1 A. The advantage of the 4 A charger is it will charge faster (4 x) than the 1 A.

 

i only use mine as a maintainer. it should keep the battery full for people who don't drive much unless there is a serious drain when off.

 

True enough but a higher amperage unit will charge a low battery faster and will trickle charge when full so it is the best of both worlds.

 

Beware...

Harbor Freight sells a nice little charger which is advertised as a 4A charger:

4Amp Fully Automatic Microprocessor-Controlled Battery Charger/Maintainer

Well, it is apparently 4A at 6V but 2A at 12V, or at least that's how it looks to me, since I have never seen it put out more than 2A at 12V. (It may vary from unit to unit, I'm not convinced that the part number at that store always corresponds to the same exact part.) The only other problem I have had with this unit is that it gets confused by surface charge and will not always charge the battery. Other chargers might have this issue too. I suggest turning on the headlights for a minute or so, then turning them off, then turning on the charger. When I have done that it always charges.

 

I can't predict the condition of your car but assuming it's typical for that mileage i'd definitely put a new hybrid pack in it and happily keep driving it another 200k miles.

My own belief system is that a cars value is not wholly dependent upon a book statement of value....but mostly based on its predicted life remaining. Since I believe it has another 200k of usable life, and I don't care about modern tech in a car, it's worth a lot more than book.....

If you value a car that looks good then it's not worth much. I personally don't mind some scratches and peeling paint. Occasionally I notice new scuffs from other cars that apparently hit mine in a parking lot. It rolls off of me because mine is already scratched. My Toyotas are commuter cars. Appearance isn't important. Money saved is...