Hello there ! I have a problem with my Prius 2021 LE. Bought it used a year ago. Mileage 64k. A month ago, the aux (12v) battery died twice in a month. I was able to start it with a jump starter. This month, the temperature dropped from 80 to 59 and the car began to ask me for a jump start almost daily. I looked at the battery. It is an "FB" brand (an unknown brand for me) 20HR 45Ah CCA battery. I measured the voltage on the battery a couple of times 12.3-12.6V (once it was even 9V). I wanted to measure the parasitic drain. But here something interesting happened. After having studied dozens of videos about how people measure this, I armed myself with a multimeter in the 10A position, plugging the wires into COM and 10A. I disconnected the negative terminal and connected the multimeter to the negative terminal and the negative pole of the battery. Aaand…nothing… On the multimeter 0.01 And it feels like it doesn't measure at all. In all the videos i watched there was always a quick surge in current at the beginning. After this, people blocked the cars and waited for the car to fall asleep. And here is the problem. I don't understand why, but when I connect the wires to the battery through a multimeter, the car does not wake up. There is no reaction. It refuses to be powered. I can't use the keys. I can't open or close the car via remote. It is still dead, although it is connected through a multimeter. This is the second multimeter and the third set of wires. I tried copper and aluminum. Copper/alluminum clamps. All the same. No result. I don't know what to do. Of course I can buy a new battery. But what drives me crazy is the fact that the car refuses to be powered through a multimeter. And where is the guarantee that the problem is in dead battery? It will be very sad if the car kills the new battery. Need your help guys. I will be glad to receive any information. Thank you!
.01 amps that your multimeter shows is 100 milliamps. I think you need a higher level of precision to properly analyze your problem. .01 amps could be the rounded value of as little as 51 milliamps or as much as 149 milliamps. A parasitic draw of 51 milliamps would be nothing concerning, but a draw of 149 milliamps would be about 3 times as high as it should be (if none of the car's start up systems were powered on when you were taking the measurement). Now that you know the draw is less than an amp, it should be safe to plug your positive probe into the milliamp terminal on your multimeter. That will give you a truer picture of whether you have a problem or not. I would guess that your car will not power on with the multimeter between the battery and the cable end either because it does not have a good enough connection to draw the power it needs or else the battery is dead. The 12.3 Volts that you measured at one point is low enough that there is no guarantee it can fire up the computers on the car. If the car is not driven on a daily basis, it is not surprising that the battery is discharged. A battery maintainer would be a good investment if the car is not driven regularly.
That looks correct, though clamps would work better. You should be able to turn on a dome light or something to see if it's working/reading. IF YOU EXCEED 10A, you'll pop the the meter fuse. So if the car's self diagnostic fires the ABS motor or fuel pump, you'll likely pop the fuse. Did you check the electrolyte levels in the battery? That one looks like the original battery. My OEM battery is a GS Yuasa. It's that time of year to check the electrolytes levels again, now that it's cooling back down. FYI; I had to top mine off last year - plates showing. Why not just pull the battery and take it to an auto parts store to check it out? Sorry, forgot to mention: on a Fluke meter, there's an independent amperage fuse within. If you popped that internal fuse; you'll get nothing - The meter will appear to work, but the amperage settings won't. The open circuit is your meter. You can get a clamp-on amp meter that'll read down to 25mA. That's about where it should be when it's asleep. Still pulsing for your key fob.
Thank you for your answer ! 1. 0.01 A = 10 mA (not 100) you can use any converter to check it ✌ So i agree with you about 51-149 interval, but in this case that means 5-15 mA interval (it’s nothing). 2. I’ve tried to use copper clamps instead of 2 aluminum feeler gauges from the kit — same result. 3. I agree 12.3 V is too low, but it’s enough to boot car computer (i can turn on my engine with this voltage). But car is still dead if i use copper clamps and multimeter. Sooo idk.
I have a 2020 Prime and have to charge the battery frequently to keep it good. .01 amps is 10 milliamps. Once the neg cable is off your car the emissions monitors have to reset through a drive cycle. If you get a parasitic draw value, then what? It doesn’t mean anything is wrong.
Your assuming that meter reading is accurate and it isn't a rounding error. OP couldn't get the car to respond to anything - Like there was an open in the circuit. Unless I could turn on a dome light or something and watch the meter move - I'd assume that isn't an accurate reading. Just my two-cents....
If that was for me, I wasn’t assuming anything, but you are. I was correcting the statement in the thread .01 amps is 100 ma, which it isn’t. I know about rounding errors. It’s a pet peeve actually.
