I don't drive much. How can I keep my 2013 Prius c 12v battery in good shape?

The outlet style gauge will work fine- the trick is to use it in accessory mode, without turning the key to the READY position.

 

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For simple voltage check, you can run some sort of quick-connect wiring to the battery. Primarily for convenient charger connection, but also good to check voltage.

A word of caution when doing the latter: the positive and negative pins in a quick connect are typically quite close together, and if putting both volt meter probes into the connector, you might touch them together, create a short. Better to just contact the positive side, and connect your meter's neg lead to bare metal on the car body.

More important than reading voltage though, is keeping it charged. Get a decent smart charger, and a quick connect harness (for convenient connection, use them whenever the car's idle for mutiple days, and you won't have problems.

Again, CTEK 5 would be my recommendation, and I believe it comes bundled with a quick-connect harness.

 

Agreed, either way is okay, and it wouldn’t take much to open the battery area one time to hook up a pigtail

 

Yes it will. The wiring leading to the pins is likely red and black? Connect volt meter positive lead to red pin, and negative lead to bare metal, and there you go. That's how I check voltage all the time. With the car off.

 

A battery monitor shows the voltage and soc on a phone. It would be a one time deal to do the work, put one in, plus why not a maintainer on permanent hookup in there too? They make them to mount somewhere and have the ring connectors. Then figure out a place to have the ac plug and after that it makes it easy, monitor, when needed get the extension cord and charge.
I just put monitors on both vehicles makes it very nice to see what’s going on even while driving, about $15.

 

You'd have to allow for some losses due to loading because by the time the key is in accessory position there are at least a few lamps and computers already drawing power. In other words, testing this way is less precise, but it can still be useful.

I'd hope to see 12.5 or so, but I'd probably accept anything over 12.2 at least until I had an opportunity to correlate what I found on that meter to a test done the real way. After that I'd have a lot more confidence in the readings from the outlet gadget.

 

You can’t touch a volt meter positive probe to a pin in the connector?

 

I got a couple different ones. I just ordered this one. There are others too. Should be able to loosen nuts on battery and slide the leads in without losing battery connection if hold down on the battery terminal. At least that what I did.

 

just touch the two metal connectors with the volt meter leads

 

That's an SAE "bullet" connector. Would not be hard to get another connector and permanently wire it onto a cheap voltmter. You'd then just plug it in the same way as you would the charger to get an instant, no-guesswork reading.

 

Figure out which is positive, touch the voltmeter positive probe to it, and connect voltmeter negative probe to engine or car body. I’d avoid connecting both probes at the connector, way too easy to create a short.

I was just checking volts on mine yesterday morning, thought to snap a pic (attached). Obviously a different car, but same principle.