Charging the 12V Battery??

This is normal! Beginning with the 2016 Gen 4 Hatchback models, Prius added "smart" charging logic to the 12V charging system that lowers the charging voltage when the 12V is brought back to "full" charge state.

 

A 12 volt battery is 100% charged when it reaches 13.6 volts.

You will never see that volt level in an installed car battery without an external charge. Because in a car there is always a Load on it on it while it’s charging it.

Most car battery’s live at 12.6

It’s is very healthy to periodically charge the 12 volt battery with a battery charger to its maximum 13.6 volts. On a Prius it’s very handy as they all have front front jump points.

Periodic charging is a great way to check on the health of the 12 volt battery. Over time it takes longer and longer to reach that 13.6 volts as the battery ages. Sometimes it can’t be reached then you know the battery is getting sketchy and won’t take a full charge.

I recommend a CTEK MUS 4.3 battery charger. Works great does multiple types of battery’s and has recondition mode for sketchy battery’s.

I try to charge my cars every few months noticing the time it takes to get to 13.6 and if it can get to 13.6

Amazon.com

 

I should have been clearer, was thumbing away on a phone.

Yeah, I meant charging the 12 volt, and by "not possible", I meant if you're parked somewhere where there's no 120 volt plug-in available, or it's not secure, vulnerable to theft.

If you're in a garage with power, I would keep the 12 volt on a smart charger.

I'm using a CTEK 4.3 fwiw, but there's lots of options.

 

Here is a flooded lead acid battery chart for state of charge. It takes more than 12.7 volts to force the charge into the battery. My high quality Xantrex TRUECharge charger, set for warm ambient temperature, does the initial absorption charge at 14.4 volts and the float charge at 13.5 volts. (Cold 14.8/13.9, hot 14.0/13.1.)

 

Which was the voltage range I saw on the Scangauge2 when I had the HHR. It could spike over 15 volts briefly. Cars use 'smart' alternators that vary output, as it helps with fuel efficiency.

Hybrids have DC to DC convertor to step down the voltage coming off the traction battery to run accessories and recharge the starter battery back up. When off,the big battery is physically disconnected from the rest of the systems. So when any car is parked, the parasite load is draining the 12v battery. that load has only increased in years with things like SKS being added to cars. Check the manual, there could be things that could be shut off to reduce the car off drain.

A plug in may or may not maintain the 12 volt when charging. I'd assume not for most. Again, check the manual.

 

I tried to jump in my 4 month old Prime today and it was reporting 12V problems and wouldn't start. Eventually it just went dark. I haven't been driving it much with the quarantine and it's been all battery when I have. I have a remote jump battery. Can I use that to 'jump' it or do I need another car? It's stuck in my garage and not easy to get another car into place to jump it.

 

Try the jump starter, should do the trick. Then hie thee to a automotive retailer, pick up a smart charger. Bring the jump pack along.

 

I learned the hard way that you can't leave your car months without a battery maintainer as two different dealerships recommended.

 

or disconnect the 12v neg

 

Though you should only do that with a battery fully charged to avoid sulphation, and even then it can self discharge on its own.

"The warmer the environment while a battery is in storage, the faster the rate of self-discharge. For example, a battery being stored at an average temperature of 80℉ will discharge at a rate of 4% per week. Whereas a lead acid battery being stored at 65℉ will only discharge at a rate of approximately 3% per month."
Battery 101: 3 Useful Facts On Lead Acid Batteries | Northeast Battery

 

yeah, mine is in the cold. i charge the golf cart batteries before leaving, and upon returning

 

Sure you can.
But it depends on how MANY months, how fully charged it is to start with and how healthy it is overall.
A healthy fully charged battery should last several months.
An old weak one, maybe only a couple of weeks; maybe less.

 

NOPE.

Based on recent Prius Prime 12v battery testing, this is not accurate information.

New Thread Coming Soon...


Rob43

 

You can believe whatever you please but.............
50 years of experience with automotive batteries says that it IS "accurate information"......in general.
Of course, some specific situations might be a bit different.

Exactly which part of what I said do you believe it "not accurate" ?

 

This has been my experience on older vehicles without the electronic parasitic draw. Some modern cars have an excessive parasitic draw even compared to identical make/model/year. If the draw it too excessive it's a dealer warranty claim item...I know of other brands where new cars have been lemon law buy-backs just from pulling down a good new battery in a few days.

So...the amount of excessive draw needs to be quantified. Anyone with a digital voltmeter can do it. Take a voltage measurement of the battery every idle day. Record how much the voltage drops off just from sitting with nothing running, no doors open, no interior lights on, nothing. If it's excessive and the car won't start after a few days, now you've got something to show to the dealership service folks for a warranty claim. They'll first blame the battery and replace it. That is a possible cause. If the second battery is drawn down the same way, and daily records kept of the diminishing voltage, now there's the chance for a warranty claim for some electronic problem. (Do any of the Prime models have a light inside the glove box? If so, just take the bulb out and see how the battery holds up for a few days.)

 

Yap, that what I have been doing on my almost brand new 2020 PRIME.
This thread: 12v Battery Is Discharging, Re-Charge Now ! | PriusChat

So far, for a new healthy 12v battery, as long as the car is driven once a week for ~1 hour, there is no problem keeping the 12v battery charged enough to start the car. Yes, the voltage drops a small amount every day, but not enough to cause the battery to be depleted. But I don't know how low the battery gets in several months of inactivity.

 

What do you guys think about this product? Will it be overkill to jumpstart a Prius Prime? Should it be used to charge the car's 12V battery?

TrekPow G22 1500A Auto Battery Booster Jump Starter

 

It's a jump starter, not a charger. A jump starter is purely for emergency, when you've got a dead battery but must use the car.

My 2 cents, a jump starter should be more for the other guy, so if someone's stuck, you don't need to use your Prius battery. My pref is Clore JNC660, but it's pretty old school now.

 

I saw a video review of it, and it says it outputs about 16V when there is no load. So my question is, will this be an issue if trying to jumpstart a Prime?

 

There's nothing special about the Prius batteries, so I would expect it'd be fine.