12v batteries bad from sitting; worth replacing if the cars will still sit?

1. You can keep the 12v batteries charged by getting a battery maintainer
2. If you don't plan on driving the car much, you should sell the hybrids and get a regular car. The hybrid battery does not like sitting for long periods (especially when it's old). The modules will all discharge at different rates and you'll be left with a battery that's out of balance.

 

"Regular cars" will have the same problem; maybe even worse.

Are they parked where there is 120 V AC power available........even via an extension cord ?
You can solve the problem for about $35 (after getting new batteries) with an automatic tender type battery charger......even if it could be plugged in only for 12 hours on each car every couple of weeks.
Then each should be driven every 90 days or so. That does NOT mean starting without moving.

P.S. Searching the forums here would have given you maybe HUNDREDS of similar answers.

 

If you continue to be real low use, as in the car will sit for weeks:

Replace the batteries, with new and fully charged, then maybe disconnect the neg cable. Battery deterioration is largely due to low but constant background demands of the car.

Or as previously mentioned: smart chargers.

 

Something like CTEK 4.3 will do better than hobble along.

 

And after THAT answer, it's obvious that you are well versed on being rude.

I gave you my considered opinion......which is shared by most people.
To summarize: A new battery will last a LONG time if you put a tender on it, or hook a charger to it for a few hours every two weeks or so.

And your situation or "twist" is not really different than most everybody else's.
So the answer is basically the same.

 

I've had a similar problem with my 2004 Prius and the 12v battery since I got the car 4 years ago in 2016 because I am an infrequent driver (~2000 miles/year). My 12v batteries have died literally dozens of times. It is important with any of these batteries to never let them die because when they do, there is sulfation build-up inside which decreases battery capacity and maximum state-of-charge voltage (when that gets too bad, you need to replace the battery). I've gone through all the iterations to address this issue. Here's my suggestions:

(1) CHECK CURRENT BATTERY. Disconnect your 12v battery and take into an autoparts store to have them check the health (capacity and maximum voltage). If they say it's bad, then it probably should be replaced. [You might try using something like a $70 Noco5 Battery Maintainer/Desulfator, which might resuscitate it by removing sulfation.]
(2) USE A PLUG-IN MAINTAINER: If you can use an extension cord with a battery charger/maintainer, that will be a good way to keep the battery charged when you're not using it for long periods of time. I use a 3T3B Black & Decker maintainer occasionally for mine but not ideal when parked in a driveway.
(3) USE A SOLAR MAINTAINER: The advantage of a solar charger over plug-in version is that the solar panel can be kept in the car and will charge the battery daily. I use a 20W 1.3amp TP Solar Trickle Charger (available on Amazon) but depending on the parasitic draw, this might not be enough to keep the battery fully charged each day, especially in winter (less sun). In general, this is a great solution though and works for me combined with using the plug-in maintainer every few weeks.
(4) DISCONNECT BATTERY: When you know you're not going to use the car for a long time, disconnect it. The disadvantage is you'll need to access it in the back, and each time you disconnect you'll reset radio settings, tripmeter, and some other things. I used to do this a lot but not anymore with the maintainers.
(5) GET A PORTABLE JUMP STARTER: I keep in the car and have used a Suaoki 12.8 amp-hour portable charger to jump it if the 12v battery happens to go dead. I haven't used this at all since getting the maintainers.
(6) CHECK FOR PARASITIC DRAWS: Your circuitry may be draining the battery at more than the expected ~20 ma (milli-amp) level when the car is off, parked and in a resting state with fob far away. You'll need a multimeter to check this. Good to have a multimeter to monitor your battery voltage as well. [I actually posted something on this yesterday but my post is still waiting for a "moderator" to approve so it can go public].

 

Go low cost and try this.
Amazon has it in stock.

[NOCO - 1-Amp Smart Battery Charger - GENIUS1

If it doesn't work you send it back.

 

Too much dialog about the $200 12v battery and not enough about the $2000 hv battery. Both will go bad. Yes a battery charger made for maintaining the 12v should be used on any car not driven at least weekly. Worse is the hv battery which will die as well.

So the best thing is using a made for purpose charger (which is very small and has a quick connect cable you leave on the battery), plus crank it up and drive five miles or more every week.

You also should use a bottle of gas stabilizer in the tank or use no ethanol gas if you can find it.

 

While technically true, that statement is a bit misleading.
The HV battery is a whole different situation. With it's different chemistry, it is NOT affected so much by just sitting for a long time.
Unless maybe it was on the way out to begin with.

 

I am good with technically true. Plus several recent posts have identified the hv battery as failed after long periods of no use.

 

More than likely these several reports involved old batteries so ...

It is important to remember that with this chemistry as the battery gets older it is more affected (negatively) by sitting than when new. Therefore it is important to qualify any advice given.