How much 12v do you really need?

Isn't our battery rated a lot more than that I would kind of think you'd want to be or stay pretty close to at least the factory minimum? The battery has to run all 21 computers the headlights when they're on All that 12 volt stuff and if you got halogen lights and regular bulbs throughout the car That's a pretty decent load any other things that go on in the car charging telephones running refrigerators you name it people are living in these things sometimes so there's a lot of that then that battery has to stand times the car's not driven or sitting in the freezing cold and the extreme heat I would think seriously you'd want to at least be very close to the original sort of ratings of power delivery and amp hour etc but that's just me. I know I'm working on a power chair right now that came with 35 amp hour 12 volt batteries and I want to put lithium batteries in the power chair and they want to sell me these little tiny batteries that still leave half the tray open to fill with foam I want to fill up the battery tray as much as possible with maybe a sliver of foam I don't care about amp hour and all that it's going to go up the more cells I have I'm sure. A few years ago with my Toyota Corolla I wanted to do the same thing they wanted to sell me this little tiny battery that barely fit in the battery tray in the front of the car I told those people the same thing I don't care about matching the amp rating of the car fill the battery tray up It can't be but a good thing It still half the weight of the lead acid type and they gave me a bunch of hoo haha about doing that but they did it.

 

It doesn't need much to get it to the READY mode and run for a while.

But you do need some reserve capacity.
What you propose is too small and "cheap" likely is the key word.
I suggest that you need to stay close to the AH rating of the original.

 

you want to be sure it it will charge properly. idk if any old battery will or won't. some have used lithium successfully

 

Second that advice..

 

I agree. If the original battery is replaced with one of only about one fourth the ampere-hour capacity, it may perform ok initially, or with frequent use of the car, but it will run down in only a fourth the time if the car is parked unused for several days or if a door is left ajar.

 

Id like to see someone install a itjium “12v” battey that has no bms circuit.

 

I wanted to put a 50Ah lithium (LiFePO4) in my Gen 3, but ended up putting in 55ah Full River AGM because I was worried about being stranded if the BMS decided to cut out. It just fit into the battery bracket and had to buy some hard to find JIS terminal adapters.

https://fullriverbattery.com/batteries/part-dc55-12/

It was cheaper than a standard Prius 45ah, but I now wish I’d paid the extra.

 

I put in a Lithium LiFePo4 battery in at last. It’s a 40ah with 400 cold cranking amps so designed for automotive use. The seller describes it a “external cranking battery” presumably because of issues with it. It has JIS battery terminals and is a little smaller I think than the standard AGM for a Prius. It was $US115. It’s this one. (I paid about half price)

https://lanplus.com.au/index.php?route=product/product&product_id=525

i have a 40 amp dc to dc charger connected to it charging 270 ah of LiFePo4 batteries in the space here the spare tire should be. I pressed the starter button once without pressing the brake down and as you know that’s puts a load on the 12v battery but doesn’t charge it. The batteries BMS shut down within a few seconds with that 40 amp load. There is a button on the battery which resets the BMS. I carry a fully charged Noco jump starter in case I have more trouble. I know this will start the Prius at the battery terminals.

It’s saved me about 12 kilos in weight compared to the 55 amp Full River.

 

Well you have to round up the battery with no BMS in it I guess our car would have the BMS for the battery right because it monitors the battery system charges it with a high voltage DC battery system already incorporated into the car so. Doesn't the Prius monitor the 12 volt and handle all that within itself so I wouldn't think you'd want to put a battery in that has its own monitoring system as who would know how that system is supposed to work I would think it would be made for a regular vehicle which might have an alternator and a starter and all that sort of thing where a BMS would be needed. But in the Prius I would think you'd have to hunt down the Dakota type battery with no BMS in it and can that be done easily are they expensive I mean the little battery we already have is well fairly small other people have run universal UB batteries. Without consequence If I'm going to park the car for a long time I'll probably pull the white plug so nothing is going to the car if you will battery is just sitting there. Make sure that space in the battery has ample drain holes opened so that if any water passes through it doesn't freeze and ruin the battery That's what I mostly find in Prius even in the Southeast United States water gets in the battery tray in the winter time it freezes takes out the battery and round and round you go.

 

A lot of people dont understand batteries or how voltage or amps work. Most car batteries are rated in CCA. Cold cranking amps is the amount of amps the battery can physically put out when the starter demands it to start. Some starters that are bigger require more. On diesel, starters are 24V, so they have TWO 12v batteries connected in series to make it a 24V system. If you double the voltage of anything, the electric motor will spin twice as fast. You can try it at home with any house appliance and any battery.
But anyways, CCA are irrelevant to the prius as the prius has no starter and replies on hybrid battery to roll the engine. The prius battery is rated in amp hours and not cranking amps.

Any car battery would realistically work. Just because a battery is capable of delivering a huge load of amps in a short timespan doesnt mean anything as far as the electronic components of the prius go. It will only demand the amount of amps needed to run them and no more over. You wont fry anything or risk your battery dying. Its only pulling enough amps that it needs. Only thing that matters is its 12V, as anything more can realistically overheat the electronics and anything less will not run them. If you ever have a dead battery, on the multimeter it will read 11V or less. 11V means its depleted. And thats why it wont start your car.

Get the biggest 12V battery you can fit and put that sucker in. The computer charges it based on the voltage it reads. Thats the only way to know how charged a battery is, by reading the flow of electrons passing from + to -. Its impossible to know exactly how many electrons are inside (amps) but we know exactly the limits of how many can fit inside due to battery chemistry and when we charge the battery at a little above its capacity, lets say 14V, it will stop charging itself because once the battery is at 14V itself, it is at equilibrium as far as the flow of electrons go. All cars alternators are limited to around 14V. If you hook up some live wires from a 120V house plug straight to a battery, itll overcharge it causing gas to be released and catch on fire or blow up depending on the chemistry of it.

 

….and all AGM batteries for a Prius will be rated for cold cranking amps. Even my 55ah Full River was rated at 400cca.

 

Regardless of of lack of cranking demand, CCA is a useful metric of a battery’s condition. “The Prius battery” is just a battery, has both CCA and amp hour specs.

A battery with specs similar to the factory battery is best bet. Dimensionally identical too.

 

Raytheagle did that, and man people here pounced in him left and right. Said it was overkill and unnecessary and waste of money.

 

The Toyota-design battery hold-down bracket is intolerant of even the slightest variation in battery height.

 

I made a mistake. I believe most 12v car batteries, lead, gel, sealed, will have a CCA spec listed on the sticker. Rarely you might buy a brand that does not have it listed (my case), but that does not mean its CCA perimeters dont exist. Its just hidden and requires real world testing to find out.

I imagine the factory battery of the prius was chosen to be just enough power to power all the start up functions, but since no real load demand was needed, they could get away with a small compact battery that has a low CCA which some batteries dont even bother listing in CCA. Like lawnmower batteries, as their application purposes dont require large amp draw.

The problem you see is always a cost factor. I tried to get it replaced but a prius battery for some reason is 3x the cost of whatever battery i can find at a local walmart. And they do not have any in their inventory that is a direct fit, size or amperage.

The solution is just go to a bigger amp capacity one for cheaper. Granted, you want one that will fit unless you wanna do some DIY metal working inside your trunk to force it to fit. Bigger amp capacity last longer anyway, because their use and discharge rate isnt proportioned to their size. So theyll stay topped off longer thus longer lifespan.

 

some people have used lawn tractor and wheelchair batteries

 

Up here Canadian Tire is pretty reliable. Searched for battery for 2010 Prius (applicable for any third gen):

General PDP Template | Canadian Tire

The battery size, post diameters and specs are very similar to the stock Yuasa.

Price keeps climbing though.

 

strangely, someone just reported getting an oem for $179. where i paid $210. in 2019

 

FYI, Walmart started selling the correct size AGM battery for the Gen3 Prius in April of this year for about $160 to $180. Check the Walmart website.

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