2016 Prius c 12 V battery dead, how do I recharge it?

You can use the underhood terminals to charge the 12v battery. You should look for a smaller one, or one whose output can be turned down to 2-3 amps.

Harbor Freight sells a decent one for $29. 2A rating and has reverse polarity protection.

 

Battery Tender Jr is about $35 and has an easy to use permanent cable that attaches to your battery and enables quick connects.

Use for storage situations of ten days or longer even though a new battery can last three weeks.

 

I don't consider that charger from Harbor Freight to be "decent".

While Battery Tender is a good brand, 800 MA max. capacity isn't
very versatile; it is made mostly for small batteries like motorcycles and
lawn mowers.

Something with a 2 to 4 amp capacity is a better choice, in my opinion.

IF.......you get a good automatic tender type charger......and the car is near a power
outlet when not being used, then leaving it connected while you are gone would
be a better plan than what you have been doing.

 

Where was the car for these hiatus, at the airport, at home, and if the latter, what's your parking situation?

If at all practical, connect a smart charger, rated around 4 amps or less, before your trips.

I'm using a CTEK 4.3 (believe current itteration is CTEK 5); it's been very dependable. Our usage is very spotty now, as little as one drive per week, albeit decent length, and we try to consolidate shopping/chores with those uses. Yearly usage around 3000 kms.

Our battery's just past 8 years old now, tests like new. It's on the charger 'round the clock, not detrimental: it runs a charging session, then subsides to light "trickle charge".

 

All you have to is supply more than the 30ma the car continuously consumes. Once the car goes to Ready the inverter’s dc to dc does all the 12v heavy lifting up to 100 or more amps.

 

Actually the first step is to measure your battery voltage. If it is very low (say, below 9V), many of the smart charger with limited capacity (a few amperes) may not be able to revive it. You may need a stronger charger to start with, or parallel connect your battery with another fully charged battery, then charge it with a smarter charger.

 

What will it take to get you to STOP using that incorrect terminology ??

It does NOT "trickle charge".

It does drop to the "float" voltage step in the automatic routine or stop charging completely
as it monitors the need for additional charge.....depending on the model of smart charger.

 

When do we get to vote?​

 

Sorry Sam.

 

did you try the other fob?

 

So trickle is banned? Noted!

I once had a Pastor who was very old-fashioned and hated the word "sexy" so I was sure to use it around him at every opportunity! (It's just how I roll.....maybe I'm trickle charged!)

 

One of the (thankfully few) common failure points in the Prius c are the electromechanical door lock actuators. It is quite possible that your key fob is transmitting a good signal, the car is receiving the signal and putting some voltage down the door wires to flip the lock, but the actuator at the end of the chain simply isn't doing anything.

Check that out before spending money on new keys.

You might try using the double-click unlock on the fob to unlock all doors, then try them all. Fairly unlikely that all actuators will have died at the same time.

 

even a mediocre 12 volt can be a problem, or the replacement fob battery could be bad.

 

You can check them using the door lock/unlock button on the door itself. Roll down your window ahead of time, reach in to push the door lock button. Test the doors to see if they locked. Then hit the unlock button, and see if they all unlock correctly.

You can also test your transmitter- some locksmiths and hardware stores have radio frequency field strength meters, usually right next to the replacement coin battery rack.

They aren't terribly specific tests, all they do is light up when there's a sufficiently strong radio transmitter active near them. The idea is that if you hold your key up close and push the button, you should see the lights blink on the tester. The tester has no way of knowing if the radio codes being sent are accurate, on the correct frequency or anything like that, but it's a simple test that you can generally access for free.