Parasitic drain - is 55 milliamps ok?

You have discovered that the easily replaceable fuses don't cover everything since your parasitic draw remains the same. The moderate capacity loss of your battery has nothing to do with causing the draw. If anything it is the result of the draw.

The current is likely coming from the fusible links or the 5 amp fuse at the battery, assuming all normal fuses were removed. See attached where most of the fusible links are shown as triple fuse elements. They are actually single links, primarily in one big module.

For example, one member found the eps electric power steering was a cause of parasitic draw. It has a fusible link.

 

This CTEK charger is roughly equivalent to what I'm using, near-constantly. Has worked well for me.

 

FBC1207D 12V 7amp &-stage Smart Battery Charger. I use it on Moto setting - meant for small, motorbike bats. Amazon doesn't yield any results by model number. They are about $25 or less.

 

if you'd rather not buy a charger, letting it sit in ready for 12 hours will work fine

 

Parasitic draws can be easy or they can be the most difficult of all auto diagnostics.

Certainly 50ma should last several days and could be mitigated by constant use of a standby staged battery charger or by using a battery disconnect for longer durations. I would not like those solutions.

An advanced method is to measure millivolts (mv) across individual fuses or fusible links. A draw will cause a very small mv voltage drop across the protection device. It requires a quality meter with high impedance. Not an analog (dial) meter or some cheap meter like the $3.99 Harbor Fright (Freight) or its clone. The fusible link module in gen2 is basically hardwired in but the plastic cover can be removed.

Otherwise pulling connectors on the fusible link loads is the next order of business. This method requires good drawings from Alldata or the Toyota Information System (TIS). Both have costs and learning curves.

Push come to shove, Pine Hollow Diagnostics in State College, PA might be worth a trip. He is one of the best specialists and has a youtube channel where advanced techniques are demonstrated. Sometimes he does road trips as well.

In his latest video he runs down a similar draw using a custom wifi logger and mv tests. Other videos explain the mv method in more detail. He also hacks a solution for this customer without buying an $800 module.

Be sure to wait for Bonus Footage he almost always includes after he signs off.

While not exactly your issue, he sells a custom cylinder pressure sensor and in other videos, demonstrates logging starter current for electronic "virtual compression" tests. He also uses a pc based scope (picoscope) where he diagnoses variable valve and other timing or networking issues. He will use the wifi parasitic draw sensor to monitor intermittent draws over time. Sometimes he opens a bad module and repairs it.

TIS
https://techinfo.toyota.com/techInfoPortal/appmanager/t3/ti?_nfpb=true&_pageLabel=ti_home_page&goto=https%3A%2F%2Ftechinfo.toyota.com%3A443%2Fagent%2Fcustom-login-response%3Fstate%3DLTLZ0D3OC77sBJT4SwcvSOXlqHI&original_request_url=https%3A%2F%2Ftechinfo.toyota.com%3A443%2F

 

Also remember to try unplugging the brake related box which is right next to the battery. Several members have mentioned that it is often a source of parasitic loads.

Regarding battery chargers - whichever model you get, be sure that when charging an OEM Prius 12V battery, the current in never exceeds 4A.

 

12. 6 is fine. measure again in the morning to see how much it's losing per 24 hour period.

btw, 12.6 doesn't tell the whole story. only a load test can tell you if the battery is good or bad.

you can try turning on the high beams and watching the voltage drop over 15 minutes, but that's a very simple test and not always enough load

 

12.6 is fine. The question is how long does it last? For battery validation it requires a load test, free at most auto supplies. But you are working the symptom and not the root cause.

 

Yes but it is supplied by the 15a ABS fuse you probably already pulled.

 

That module has constant-on power, solely to remember HVAC settings. In the "just have to vent" thread, I've been bemoaning the lack of ergonomic HVAC controls, which are typically mechanical. By default they "remember" what's set, basically because when you turn a dial or shift a slider, it stays where you left it, due to inertia, which doesn't require volatile memory, lol.

Yeah interesting video, by revising the power to be ignition-on only, you have a system that goes back to (reasonable) defaults, a slight setback, but doesn't draw down the 12 volt.

 

Tens of mA currents are on the hairy low edge for what can be measured by a DC clamp meter. They are more often employed to measure much more substantial currents, which would burn up most inline ammeters. In order to measure a current that low accurately a clamp ammeter must be zeroed right next to the wire, with the jaws closed, and then the wire moved into the clamp, ideally without the meter moving at all. I could never do that with one of these battery cables, too thick, so had to move the meter. Anyway, since the newer meter returned the expected value, we should suspect inaccuracy in the older one. If you have access to a small battery and some resistors it isn't difficult to set up a wire with ~20mA flowing through it (measure the voltage on the battery and the resistance first so you know exactly what it should find) to test its accuracy. 1.5V and 75 Ohms would work for this test.

 

Looks like the first meter was on ac amps rather than dc. But the second meter was using the 10 amp setting while plugged into the ma jack. So both have operator error.

 

Yeah 17 milliamperes is good, normal.

 

Good catch. It wasn't "on" AC amps, that model only does AC amps, and it only does it with the clamp, not the probes. There is no wire within the clamp in the photo. Relatively few clamp ammeters can also do DC amps. I use a UNI-T UT210E, which is about as low cost as it gets for a meter with this capability. Despite the reasonable cost, the UT201E is a pretty good meter with solid construction.

Here is a review:
https://lygte-info.dk/review/DMMUNI-TUT210E%20UK.html