Looking for aftermarket 12v battery

The aftermarket battery is just fine. I have used Autozone batteries for many years with no problem. Their highest warranted battery is probably between 80-100 dollars. You get the correct model battery for your car and it is a simple disconnect and reconnect.

 

Because of the venting of the Prius 12v battery, your aftermarket choices are very limited. The aftermarket battery, along with the terminal mod kit will cost at least as much as the Toyota battery.

 

There is no off-the-shelf replacement 12 vdc battery that is a direct swap, especially the post size and the venting requirement

For about the same price as the Toyota battery, you can get an Optima that was originally intended for a Mazda Miata.

12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008 and 2009 with installation kit and free shipping

It comes with adapters to match the Prius post size. Hobbit and others have posted on their adventures of putting in the elearnaid kit

 

I inquired at my Toyota Dealer, and they recommended a 'Dynacell" battery, costing about $160 plus installation.

It is a "silver calcium alloy", and carries a 72 month free replacement (no pro-rate) warranty. Does any one have a comment on this battery?

BTW, the Optima battery certainly looks expensive, unless I misread the page, about $180 on sale?

 

The Toyota battery has a tube that vents to the outside. Because the battery is in the cabin, the vent prevents dangerous gasses from building up.

 

Does anyone happen to know the acceptable voltage range and CCA for a second gen battery? I know that they are rated somewhere around 300 CCA. The dealer tried to talk me into replacing the battery in my girlfriend's prius today. The specs on the battery were 200 CCA and 12.5 volts. I know that CCA is illusory to begin with, and a worthless measurement when the battery isn't even used to start the engine. I have plenty of experience with cars, but the prius is a little intimidating. I as a rule avoid the dealerships, but the girlfriend insists with the prius.

12.5 volts and 2/3 of the "rated" CCA doesn't sound that bad to me. It wouldn't concern me at all on my non-hybrid cars. The dealer did the usual song and dance about filling my tires with nitrogen, flushing the brake fluid and the urgency of paying $75 for a new cabin air filter, so I took his battery warnings with a grain of salt. He then threatened that I would be voiding the warranty by not heeding his warning. That if the battery went dead I would be in BIG trouble. The users manual says jumping it isn't that complicated. Any thoughts? TIA

 

The correct low-cost option is to use the same Toyota battery. Then you know that the clamps will fit the terminals and that the car's vent tube will fit the battery. (The apparent craftsmanship of the Toyota battery is amazing. It looks like a watch, not a piece of industrial equipment.)

The Optima/eLearnaid solution is more expensive, but the battery construction should give it longer life, and the eLearnaid kit makes it a perfect fit. If you do this, note that you will need every tool they list and, if you don't have a bench vise, considerable hand strength to take apart the Toyota positive clamp assembly.

 

Uhh, why does a dealer want to replace it with something other than the correct Toyota battery?

Do you know that it needs replacing? Use your voltmeter. If you don't have a voltmeter use the built-in self test procedure given by jdenenberg here:
http://tinyurl.com/927877

Nitrogen is fine if it's free, flushing the brake fluid as a regular maintenance item is rubbish, and you can get the Toyota filter for $25 and replace it yourself in five minutes (or usually, just vacuum off the old one, put it back facing the same way, and pay nothing). Find another dealer.

 

I still think you could easily and safely replace the battery with a sealed motorcycle battery. I haven't had to try this yet though.

Regards,
Dave

 

If you find an aftermarket battery that fits perfectly we'd love to hear about it. The difficulty is finding one whose terminals will fit the clamps, and that will fit the vent tube.

 

No, I agree you'll have to rig up the connection. My suggestion is not a job for someone expecting to remove a nut and put it back on. For that, stick with a battery made for the Prius. I just can't make myself pay $150 for a little battery.

Regards,
Dave

 

Hi Dave,



Although you might "easily" replace the 12V auxiliary battery with a motorcycle battery of lower capacity, I question the assertion that this is necessarily a safe alternative. The battery serves three functions:

1. Provide ~30A current upon startup to power up the various ECUs
2. Provide emergency backup power in the event that the DC to DC converter fails. Note that the steering assist and brake systems require 12V power, as well as all of the ECUs.
3. Satisfy quiescent current demand when the Prius is IG-OFF. This is around 30 mA, so each 24 hour day that the Prius is IG-OFF requires 0.72 AH. In two weeks, this requires 10 AH. Usually it is not wise to discharge the battery to more than 50% if you want long life, and the capacity deteriorates over time; hence Toyota's suggestion that the car needs to be made READY for 30 minutes every two weeks when in storage, if the battery is not disconnected.

If you install a battery of lower capacity, and over time that capacity degrades even further, then you may find in an emergency situation that you will lose 12V power before you can safely stop the car at the side of the road.

Imagine a winter night when you have all lights on, the rear defroster running, and the cabin heater system running, so the vehicle requires a sizable 12V current demand, maybe 70A or more. Then the DC to DC converter fails while you are at freeway speeds in heavy traffic.

It will take a while for you to change lanes and find a safe place to stop, then gracefully power down. Maybe you might run out of 12V juice before this can happen. Suppose you need 10 minutes (0.167 hour). 70 A x .167 H = 12 AH. This would discharge a fully-charged base Prius battery in new condition by almost 50%.

If you start to run out of 12V power it would be quite difficult to manually steer and manually brake the vehicle, while the brake failure warning horn is blasting away and the instrument panel looks like a Christmas tree.

Therefore I would suggest that if a non-Toyota battery is chosen, that it should be AGM, vented, and of the correct AH capacity or greater: 36 AH for Smart-equipped vehicles, and 28 AH for base vehicles.

Definitely. I believe that the owner's manual suggests that the fob should be stored at least 15 feet away from the vehicle and that the fob should also be stored away from sources of RF energy (such as florescent lighting.) While the fob is in close proximity to the Prius, a two-way communication remains in effect which will drain the fob battery as well as the Prius 12V battery.

 

OK, you got my interest. I am going to try to find an alternative that meets the requirements you listed, but costs less than $100. I'll report back later.

Regards,
Dave

 

No

That vent you're referring to - the ductwork - is part of the NiMH traction battery cooling system. It has nothing whatsoever to do with "venting gasses" away from the battery

The factory 12 vdc battery is completely sealed, with provision for a vent tube. Look at this photo, the vent tube is outlined with a squiggley blue line



The Mazda Miata also has a battery located where it needs to be externally vented. Thus, the Optima battery for the Miata works in the Prius, with slight modification

 

I suspect if you try to meet those objectives (Matches Prius post size, sealed, with vent tube provision, under $100) then we'll never hear from you

Nothing is stopping a creative person from jury-rigging something up to work. Just don't expect it to be safe

 

If you're curious how the NiMH battery cooling system works, this photo explains it



I am unsure who originally provided this photo on PriusChat. Apologies in advance