Toyoto prius 2010 car battery draining

You just have to buy a new battery, don’t over think it

 

Here we go again with a new thread for the same issue that you have had with the 12v battery for many, many months. https://priuschat.com/index.php?threads/246683/

Answer two questions:
1. Did you buy a new 12v battery in the last two to three weeks?
2. If not, then completely charge the 12v battery. With the car turned off, turn on the headlights for one minute and measure the voltage of the 12v battery with a volt meter. What was the voltage?

 

My friend the guy running the AutoZone battery tester or the one in advance Auto doesn't care about selling you a battery He really doesn't He doesn't get enough commission or anything like that He works in America in 2023 He gets nothing That's why these employees have bad attitudes don't really give a crap so on and so forth because well nobody else does either. So he doesn't really care about selling you a battery that little fancy machine that he brings out to measure your battery that thing is about $9,000 believe it or not or some insane price like that and they generally are pretty accurate they put a battery through its paces in 15 minutes or whatever it is and give you back a basic yay or nay type of condition thing. And generally that little machine is not incorrect and you're still having problems and so on and so forth but you don't want to believe it for whatever reason and that is your prerogative. What you do want to find is what's keeping the car draining the battery all the time as a way to hook your voltmeter up across the terminals and so on and see what kind of amps whatever is pulling The brake pump running every so often should not do this to a relatively decent battery the inverter cooling pump same thing the coolant heat storage tank system if your vehicle has this only comes on once after a 5-hour shut down for a few seconds so most of these things the car knows why it's turning them on quickly turning them off etc so unless your battery is just garbage these things shouldn't affect the 12 volt status so don't worry about having your battery checked that the big box store the big box store spends a lot of money on those battery checkers and they're pretty accurate You don't have to buy a battery right then because they're checking your battery but don't disbelieve what they're telling you because you don't want to buy a battery that's not good use of data.

 

Unfortunately, you’ll have to go through every fuse to find the circuit that is draining the battery

 

Or if there is an abnormal drain. Around 20 milliamperes is normal, fwiw.

That sounds like a battery in need of replacement.

If practical, keep the new one on a good quality, smart charger, constantly between uses. If not practical, consider installing a battery disconnect device.

 

First you describe two different situations - does it drain in thirty minutes (easiest to diagnose) OR does it take overnight (requires more skill to test).

1. Thirty minutes - either a huge amp draw larger than headlights on or a very bad battery.

2. Overnight - a small amp draw like a hatch or map light or an obd2 adapter or aftermarket accessory or a weak battery.

For number one, get a dc amp clamp meter (most are AC only) and measure the negative battery cable. Also take the battery in for a load test, best done with a full charge on it.

For number two you need a series connected amp meter with the hatch latch manually closed with a screwdriver. It is two position - close the latch mechanism completely with the actual hatch open.

Hook up like this and wait at least ten minutes. Amp draw should be 15-30 ma (thousands of amp).



Either way, if you measure excessive parasitic draw, you then have to get more skilled. The best approach is to measure mv (thousands of a volt) across each fuse and fusible link. A fuse drawing current will have more mv.

Another way is to pull fuses one at a time while monitoring ma in the back. Cautions include do one at a time and replace each before going to the next. Otherwise they will get mixed up.

Another caution about pulling fuses is you restart ecu loads when replacing them in many cases. This causes a temporary increase in ma or amps as they start up and finally shutdown in sleep mode.

Since it is 90% your battery and that is easiest, do that testing first.

 

Took a crack at the step-by-step of the above:

1. Connect jumper
2. Disconnect battery neg cable from car body
3. Connect ammeter between car body and battery neg cable
4. Disconnect jumper
5. Wait at least 10 minutes, then take readings. Start with manual scaling meter, start in amperage scale, then go down through milliamper scales.
6. Reconnect jumper.
7. Disconnect ammeter
8. Reconnect battery neg cable to car body
9. Disconnect jumper

The jumper is employed to preserve the car's memories. If you don't care, it can be eliminated.

 

It also prevents ecu startup delays when initially measuring ma. In some meters the initial startup could exceed the meter’s fuse.

 

Voltage is low but is not definitive. A load tester and or age is recommended.

Remember an old Prius battery will fool you into thinking 20% capacity is good because it starts.

 

Yeah you seem to be thinking when your charger says "full" that your battery is good. A fully charged healthy battery would read close to or over 13 volts.

I wouldn't even bother with a load test; that battery is toast.

If you do want to load test, many automotive stores, in particular those selling batteries, have the modern load testers. For DIY, something like Solar BA9 is one example.

 

Canadian Tire has had a battery compatible with 3rd gen Prius, maybe just not in stock right now. IIRC it was getting up around $260~280 CDN. < Yeah checked, nothing right now.

What's the dealership asking these days? Last time I checked it was close to $400 CDN.

Even you don't have excessive phantom draw, driving 20 miles once a week, you will continue to have dead batteries, until you start doing something, either keeping it on a charger constantly or disconnecting it between uses. That's just not enough use. Any modern car has a low but constant background need for electrons, to retain memories.

You might try emailing SaskBattery. They had one when I checked a few months back, for low to mid $200's IIRC.

 

You need a S46B24R battery for a Prius. Often the dealer is the best value since their battery will typically last 8 years or longer.

Don’t buy a Yellow Top, they are not great and don’t last nearly as long but still get a dealers price.

The S46B24R battery is vented with a special port and the terminals are small. Trying to jam in the wrong battery can ‘doom’ you if it is installed with reversed polarity. It happens.

In the US, Walmart and every auto supply has a S46B24R equivalent, usually less than $200 US.

 

Here's current link to saskbattery option:

S46B24R (FP-AGM51JIS) - SaskBattery

Last time I used them they ship cross Canada for free, and only charged GST. (poetic)

Regarding how much driving is needed, my 2 cents: one or two stretches of protracted downtime your battery will be ok. But if you keep your battery on a steady diet of 20 miles once a week, it'll die pretty quick.

 

Nothing wrong with a battery maintainer for a garage queen. But a good battery takes care of you as does the car’s charging system which can do high rate charging when needed.

 

if you can't plug in, disconnect the battery when not using

 

If they have a top line battery for a 2009 or 2008 that'll fit your 2010 I regularly move the batteries from the three to the two all the time and back and forth without any problem at all I'm using the I think it's the Sears Gold AGM