Battery Maintainer Tender OK on 07 Prius during COVID?

With 2007 Prius, you should be more concerned about HV battery than 12V battery.

You could either drive it 5 or so miles every 2-3 days or force charge the traction battery by pressing left foot on brake and then putting it in drive and gently pressing gas pedal with right till battery is top of purple bar or in green. This will keep both HV battery as well as traction battery charged.

 

Well maybe.....but NOT because it is sitting partly discharged.
The HV battery will be just fine with that.

The 12 V won't.
A real automatic tender type charger is fine; a cheap trickle charger, not so much.
The OP said both at different places in his post......and they are NOT the same thing.

 

I would say pretty much the opposite. The hybrid battery is much more impervious to short down times than the 12 volt. And yeah, if the car's gonna sit for protracted times, and only see short drives when you do use it, a smart charger hooked up constantly is good.

For the hybrid battery, according to the Owner's Manual:



That said, for a hybrid battery in borderline health, I would temper the above guideline. Say try to do a good drive every couple of weeks. But don't go nuts.

 

Maybe run the AC a bit too, if you often don't use it. Helps circulate oil in the system, avoids seals drying out. At least so I've heard.

 

My personal experience with my 2005 is after even 3 days of non use the traction battery goes down to 2 pink bars, within a quarter mile. Before parking I make sure HV battery is near full. After a period of non use, the battery initially shows the level it was parked at and rapidly drains down. I assume the initial value is last cached value and does not account for internal discharge.

For 12V battery there is an easy enough option of jump starting, though you have to be careful about the polarity. But for HV battery you need to have Prolong system which I do not have.

I would not trust my car to sit idle for couple weeks or even one week for that matter. 12v batteries can sit idle for a month easily if you turn the smart key off using the dash button, given that OP has a new 12 V battery. All that 12V battery does is to charge brake accumulator once in a while. Prius also does not have any Cold cranking amps requirement from 12 V battery.

I agree that the owners manual states to drive it once every several months. But I doubt how much of it is valid after 13 years. In fact I would say owners manual is much more valid as regards to 12 V battery given that it is new.

 

Absolutely the right idea. I've been using a 3 amp Battery Tender on not only the Prius, I've been rotating it to my wife's 2009 Acura MDX and our daughter's 2007 Toyota Yaris to keep their batteries in shape too. I loaned out my Prolong charger prior to this mess so to keep hybrid pack in shape I'm running the car 20 miles down and 20 miles back on Needles Highway one day a week. It's 45-55 mph all the way with no signals or stop signs.

This is the 3 amp Battery Tender I use but I didn't see it listed on Amazon. I got mine for $30 from a Costco outlet store.
https://www.batterytender.com/Battery-Tender-6V-12V-3A-Selectable-Battery-Charger_7

 

As others have correctly posted, the danger is not to the 12v, but to the hybrid battery and for that, you need to DRIVE the vehicle. One could, if absolutely necessary, allow it to run in the driveway for 20 minutes with the AC on MAX Cold once or twice per week. That would keep the HV pack and 12v charged up. Myself, I would take the long way to the grocery store with it

 

I'll add my affirmation too, absolutely the right thing to do, and as long as it has an automatic function to drop the current and monitor voltage can be left on indefinitely.

Sorry to disagree, but the bigger concern with cars being laid up is the 12 V battery. You may have additional concerns if the HV battery is in poor condition, but generally, an HV battery that is healthy will hold its charge quite well for a long time as the internal discharge is low and it is totally disconnected from the system when the car is OFF. If the HV battery is not in good condition, then doing what is outlined in the post quoted below, might be appropriate.

It sounds like your HV battery is on the way out, so I hope you have a plan for that event.

While it might be a suitable strategy for this situation, I don't think it is necessary for anyone with a healthy HV battery. When starting out, you would also be better to ensure the foot park brake was on, HVAC OFF, P selected and then press the gas pedal until the ICE starts. Wait for the 50 seconds (or so) that ICE runs until it shuts off again. The start driving. This is much kinder on the HV battery and you then won't (or shouldn't) see the battery dip into the purple (or pink) bars as you drive off. This technique will help you get better mileage too.

Yes. Also, if you disconnect the 12 V it defaults to 60% (6 bars) but quickly works out the correct value after a few minutes charging/discharging.

As I detail below, 60 min once a week would be sufficient with HVAC off.

To all those saying you need to drive your car, this, too, is unnecessary, if you don't need to go anywhere, don't. If you have a 12 V charger use it. If you don't have a 12 V charger and your car has sat (or will sit) for a week without starting, then at a week's end, turn off all accessories, including the HVAC, radio, chargers, dash cams, OBDII dongles (or remove), etc, are switched off, ensure the foot parking brake is set on, then put the car in READY. Ensure the car is in P, and leave it to do its thing for 60 minutes. This will exercise both batteries and ensure the 12 V gets a good charge and the HV battery will cycle between 2 and 3 bars with the ICE coming on as required to achieve this. The car should not be left unsupervised and this should take place in a well-ventilated situation, so not inside your closed garage or enclosed parking structure. At the end of this time, you can force-charge to 6 bars, if this makes you happier or more comfortable, but it is not necessary for a car with a healthy HV battery.

 

Yep, like the earlier responses to your post, you're doing the right thing. Check the charger user manual to see if once at the fully charge green light, whether it drops to doing a maintenance (or trickle) charge.

Some of the other information was directed at other posters who jumped on your thread.

Stay safe and keep well.

 

Asked and answered.

TL;DR....

1. Battery Tender is fine. Trickle chargers to be avoided.
2. 10 mile drive every month or so is better!

Good Luck!

 

@dolj,

While you are certainly entitled to your considered opinion, I know from TONS of experience with GenII Prii in TX, that the HV pack is for absolutely 100% certain the larger concern. Think and profess what you will, it will not change the facts that: 1) the 12v discharge rate parked is near zero, unless there are non-factory add-ons and no one can account for that, 2) 12v is NOT required to start the car in traditional terms, just power up the computers, 3) the HV packs HATE being "stored", 4) HEAT is the primary enemy of Ni-Mh cells, especially when in storage and 5) You ain't maintaining the HV unless the car is running.

Reason to set the AC to high cool is to ensure the ICE runs, for no other reason.

 

@05PreeUs

I respect the knowledge you have acquired from TONS of experience with Gen 2 Prii in TX, but you may need to allow for the fact that, while TX is a big state, the world is larger. I think you may have hit on something with your point 4.

I definitely agree with that and if I lived in TX I don't think I leave my Prius outside to bake in the sun.

We'll agree to disagree about the 12 V. The Gen 2 might draw little, but it is not nothing and if you start out with a poorly charged 12 V, it won't do well, not to mention the damage caused by it being low to flat. We see enough threads on here to know it is a problem for a lot of people, especially the ones who drive infrequently and/or short distances.

You ain't maintaining the HV even with the car is running. Under the control of the hybrid system, the HV battery will be kept in the 40 - 80% band and will not be exercised, at least not in the way I understand. Therefore keeping the ICE running is only wasting gas.

I doubt I can sway you, so we should leave it there.

Respect and peace.

 

Conflating infrequent driving where the HV system has inadequate opportunity to recharge the 12v is not the same as the 12v needing to be maintained while parked for a week or two. The DC-Dc is designed to be the PRIMARY 12v power source, o the ability to top off the 12v is limited, therefore longer run time is needed as compared to a non-hybrid.

The goal of running the ICE is not to exercise the HV pack, but to make SURE it is in the 50%-80% SOC range. If it falls much below 40%, you may not be able to start the car and that can happen just from self-discharge over a window of more than a week. Especially in hot weather.

Since the HV pack is thousands, and few people can recharge it at home (no one should try) without very specialized equipment, it IS the bigger risk.

 

WHAT ??
All the answers I've seen say exactly the OPPOSITE.
What exactly are you seeing ??

 

And you are 1000% wrong.
Unless maybe the pack is old enough that it is on the way out anyway.
In that case the "Gen 2" part of this discussion is critical......but nobody has really emphasized that.

For Prii in general, it is MUCH more likely that the 12 V is near the end of it's life and will cause a problem.

 

You have a good method for maintaining the batteries without actually driving. Being fortunate enough to live where I do I will still be driving my car. It gets me out of the house and into some beautiful desert scenery without seeing more than a half-dozen other vehicles on the road. Another nice reprieve from the boredom of being around the house 24/7.