Battery tender for not driving car for 1.5 months

That means the charger is satisfied it's done all it can, run through a cycle, and the battery is "ok". Maybe. Butyit's not a tester.

Test it with an electronic load tester, if you want to really see it's viability. They test Cold Cranking Amps (or a few similar parameters), and deliver a verdict.

 

Many auto parts stores will test your 12v battery for free. It may be a good idea to test if it was that low.

 

Pre-pandemic we often cruised 60 days at a time twice a year. I have been using two Deltran Battery Tender Junior automatic battery chargers for my PP and the wife's Lexus. Mine are model 021-0123 with an output of 12VDC at 750mA. They have always worked fine; just attach them to the + and - terminals, plug them in and shut the hood.

 

Just checked...our 5 year old original battery reads 11.970 volts. The car gets driven every day and plugged in every day. The build date on the car is 10/16, so the battery was made in September or October, 2016. The voltage is about the same every time I've checked it over the years. I am watching the condition.

 

How far / long does it get driven every day ?
11.97 if read directly from the battery and not from an interface item on the screen, indicates that it is a little LESS that half charged and that is NOT good.
Either it is not being charged properly OR it is about worn out.

 

PT Guy's comment made me go out in the garage and check mine. Similar car and environment; mine was built 03/2017. It reads 12.72V.
However, it was being charged after a 20 mile trip a couple of hours ago. Not sure if that makes any difference.

 

Check it again after it has been sitting unused for 12 hours or more.
If it loses more than a couple of tenths over 24 hours of no use, it probably is nearly worn out.
That also applies if it loses a couple of tenths every day that it sits idle.

 

Guess you are right. Just checked it and it reads 12.16V. Probably wouldn't be a bad idea to start looking for a new battery just to have on hand when I need it.

 

You'll need it soon.

 

I have a CTEK MUS 4.3. Do I need a separate battery tender?

I left my 2017 (original battery) plugged in for 11 days, and the battery wouldn't start the car upon returning home. I charged with the CTEK and it went through all 7 steps, so I assume the battery is still good. I topped off the water in the battery, but it was only a little low and no plates were exposed. I guess I should have left the car unplugged, as I read somewhere that it could drain the battery faster.

Any thoughts here?

 

By “battery tender” you mean a charger that can be used long term? What you have is fine for that; it’s what I’m using.

 

Have you used the RECOND mode?

 

Once in a blue moon. I have an optima yellow top in there, installed September 2015, use the “snowflake” setting, slightly higher voltage IIRC, manual recommends for the “spiral-wound” style of battery (looks like a six pack).

with our low use of the car these days I have the charger connected near constantly.

for your battery, I’d get it tested, see where it’s CCA is. If it’s dropped lower than spec, I’d replace.

you can get such testers for $50-70, DIY level. I’m using a Solar BA5, but there’s lots of choices. Konnwei KW208 looks interesting. Or Topdon BT100.

 

Thanks. Just ordered the KW208.

 

Regardless of the make or model, a "reconditioning" mode is largely just marketing hype.
You can't really recondition a wet cell battery by any combination of voltages applied externally.
Once it's gone, it's gone.

 

What's the spec for the OEM battery? Wouldn't an older (but still good) battery be expected to have a lower CCA than new anyway?

The replacement battery sold by Napa Auto Parts says 445 CCA.

 

Might be on the label. They tend to be lowish, 325 CCA?

A brand new battery usually tests well above spec'd CCA, and I've found a battery testing at or below spec'd CCA is usually on it's way out. The new electronic testers seem to concur, give thumbs down verdict when CCA has dropped significantly.

High spec'd CCA (Cold Cranking Amps) is not necessarily the best either. I'm fuzzy on it, but I understand higher CCA comes at expense of lower Amp Hours, and the latter is equally if not more important. The Toyota Prius OEM batteries tend to be a balance, average CCA and pretty good Amp Hours as well.

 

After using the car yesterday, I measured the battery voltage. 12.27v. What do you think or wait for the tester to arrive?

 

It'll survive till the tester comes, and it'd be nice to have a "patient" to test it on. But yeah, that doesn't sound good: any time a battery is chronically around 12.4 or lower it's days are numbered.

On the flip side, I can recall an instance, let the grandkids out of the car, noticed about 18 hours later there was a door ajar. Didn't have a 12 volt "tester" as yet, but checked with a mulitmeter the voltage was 11.9. I put it on a CTEK 3300 charger, let it run to completion, which took about 12 hours. It did last a year or so after that, before I swapped to an Optima Yellow Top.

The Yellow Tops are not necessarily the best though; I'm likely going with OEM Yuasa spec'd for 3rd gen, next time around.

 

I live in a warm climate with the car garaged, so my battery has a pretty easy life. Summers are hot though.

What do I lose besides radio preset stations when I disconnect the battery?