HELP! Prius 2010 does not start with a new aux battery

Maybe a loose or corroded connection somewhere? Where were you measuring the voltage? I hope the 2v from a new battery, and the 40V are typos, because neither makes any sense.

 

When the battery is new and not connected, it should read around 12v - 13v. If this battery had that reading when new, then it shouldn't have any issues starting the car when it's connected. A fully charged battery should be around 12.7v-12.9v when it's connected

When the car is in READY mode, the battery voltage should be around 14.1v. It should not read above that voltage, even after 10 hours of leaving it in READY mode.

Your battery readings are all over the place, a new battery should not have that big of fluctuations. I would check to make sure all your connections are tight

 

Sounds like a bad 12v... What's the voltage reading on it when the car is off?

This is the one that is highest quality for lowest price in my opinion: https://ebay.us/5n8222

I can explain batter terminal for it if you decided to go with this option.

 

are you checking with the car 'ready'? if so, that is the inverter charging voltage.

you should check the voltage at the battery and at the jump point under the hood after the car has been off a few hours.

that will also tell you if there is a wiring problem.

 

You may have a defective battery or you have defective equipment reading the battery voltage.

If you are charging the battery, the car battery (agm) is designed to be charged using 4 amps to 10 amps only. No high powered 20 amp or higher chargers

 

Your meter is bad. Buy a digital meter.

Not likely unless the car had a direct positive to negative short. You would get sparks like an arc welder.

This is an invalid test. You can't accurately measure voltage with a meter in series to the circuit.

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However, you could have an excessive parasitic draw running down the 12v battery. To check that you insert an amp meter in series (not a voltmeter which is a separate instrument in your old school world of analog meters). A parasitic test checks amp draw when the car is off. It should be less than 30 ma. A hatch light left on will drain the battery overnight. Other parasitic drains can be worse. I would not attempt this test without help.

The fact you have jumped it successfully a couple of times says all you need is a charged battery. Do not repeat the overnight Ready trick. Not good at all. What if the car overheated? Burned up engine.

You need a Battery Tender Jr, about $35 at Walmart or Amazon to charge the battery overnight.

But the FIRST thing you should do is take the battery back to the supplier and have them do a "Load Test" on the battery. Also have them charge it up. Usually free. I would suggest finding a mechanic or a friend to help you with this problem based on the steps taken so far.

 

I hate to muddy the water (well maybe not), but bad things happen if the car is jumped with reversed polarity. Meaning the plus on one car is hooked to the minus on the other. Even for a second.

At that point the car won't go to Ready and many things are not powered up anymore including everything served by the driver's side interior fuse box. For example the interior lights.

An inadvertent reversed polarity jump will blow the 125 amp fusible link buried inside the driver's side engine fuse box. A few more fuses in that box will also blow. Getting to the 125 amp fusible link requires removal of the engine fuse box, a difficult task.

There is a small visual access port that can be checked to see if the 125 amp is blown. Use a flashlight. Again if the interior lights work, you are ok. Obviously a discharged battery can also kill lots of things including the interior lights.

All of which is the reason to avoid jumping the Prius especially with another car. A lithium jump box like the Noco GD40 (an ultrasafe polarity checking jump pack $100) is the way to go.

Finally, while reverse polarity jumps have taken out many 125 amp fusible links and other more accessible fuses, "usually" the vehicle is otherwise undamaged by some miracle of Toyota engineering. In your case hopefully a blown 125 amp is not the problem. Get your new battery checked.

Visual of 125 amp fusible link (fuse):

 

Sure its not your remote-key's battery? The car simply doesn't detect the key hence the no-start? Also, get optima battery or oem toyota from dealer.

 

sounds defective. a load test at the place of purchase will confirm it

 

Autozone is the bottom of the barrel auto supply. Their corporate management has no desire to be good. Go elsewhere.

This is a decent meter for $37. It includes a dc amp clamp which is rare under $300. I would also buy a $5 "beater" digital meter at Harbor Freight which actually is decent for series parasitic testing and around the house quick checks.

 

Technically the battery label says 4.2 A max +/- 0.1A if I recall correctly...

REVVL V+ 5G ?

 

I don't think autozone sold you a known defective battery. It happens.
I've worked at various dealerships and have come across defective parts.

If you think of the probably hundreds of thousands of each part they make, sooner
or later some won't be up to par. That's why there are warranties!

Did you check the voltage of the replacement battery? And it still may need to be charged.
2 weeks ago I replaced my battery. It was at 11.9 volts, right from Toyota. I kinda expected it.
And of course it didn't have enough juice to get the electronics up and running. I put it on a 3 amp
charger for about 3.5 hours. It was enough to get it going. Then drove for an hour. It sat for 3 hours.
And started right up. After I got home I put it on the charger for 10 hours. Haven't had a problem since.

You volt meter may be fine. Hard to judge it against a bad battery. Harbor frieght sells the cheapest of
the cheapest chinese junk. It's "good enough" for simple things. Don't expect it to last.

Autozone sells junk too, but they also have the better stuff. It will just cost more.

Sadly, almost every place is having there stuff made in china....

 

That rule is for unregulated chargers. Staged chargers including the car can go 60-80 amps for short periods.