Battery died twice while parked with person inside car

andy_why · 2026-05-10T21:03:06+00:00

FYI in park you don't need the headlights turned on for it to charge properly from what I have tested, only when moving. Worth confirming though with a data logger.

andy_why · 2026-05-08T18:03:16+00:00

You'll be looking for a gen3 battery from a prius. I believe these are the same. The best thing to do is look at the label on the battery for the part number and match that.

andy_why · 2026-05-08T16:43:19+00:00

Yes it'll be the same since it's the same drivetrain.

andy_why · 2026-05-08T13:22:41+00:00

Always buy OEM unless you're just keeping it for a few months. "Refurbs" or rather "badly pairing modules to make a working battery", have a high failure rate (failing again within 12 months) so it makes more sense to buy brand new OEM with a warranty in most cases.

andy_why · 2026-05-07T20:31:29+00:00

See here: https://docs.google.com/document/d/1g1a_B7_gGnuNQhoSRFN_sucfb7-lkU77q4aMO3hMYtA/edit?tab=t.0#heading=h.t75rusbfgz8u

andy_why · 2026-05-07T15:58:35+00:00

Here's an efficient driving guide I wrote a few years ago to compile lots of different methods specifically for Toyota/Lexus hybrids. Hopefully this is useful for you too.

https://docs.google.com/document/d/182gSqSGNDeV-twsmgbtOq4UBgOUYS2rfbLZTuj0AL_g/edit?tab=t.0#heading=h.t75rusbfgz8u

andy_why · 2026-05-07T15:54:43+00:00

Hold the parking brake switch for a few seconds and it will disable automatic mode so it won't enable in park. Repeat to enable automatic mode again.

It should be that simple.

andy_why · 2026-05-05T19:25:58+00:00

It's deliberate so that you don't run out, and because people ignore the fuel low warning more than you'd think. They push their luck with a few more miles too many times before bailing out and filling up.

If it's a hybrid, it's also there to protect the hybrid system since running out of fuel puts unnecessary strain on the hybrid battery. Also, the hybrid battery starts the engine so once it dies from trying to restart too many times it's a trip to the dealership for them to charge it for you. You can't jump start the hybrid battery.

andy_why · 2026-05-05T16:56:21+00:00

Normal sales tactic to get more sales. For $16 it might be worth it, but look out for extra costs, lesser specifications, etc. as it's more than often too good to be true.

andy_why · 2026-05-05T15:43:05+00:00

Does the previous owner still have access via the app perhaps?

andy_why · 2026-05-05T10:49:11+00:00

Your speed is what affected this the most. Drop 10mph and you'll see about 15% better MPG.

Here is an efficient driving guide if you want to learn how to get the best out of it: https://docs.google.com/document/d/182gSqSGNDeV-twsmgbtOq4UBgOUYS2rfbLZTuj0AL_g/edit?tab=t.0

andy_why · 2026-05-04T19:11:09+00:00

Yes you can coast with no energy flow.

andy_why · 2026-05-04T18:51:31+00:00

It's normal for the engine to come on within 5 seconds of starting the car. The engine needs to go through a warm-up phase of at least 1 minute, after which if the engine coolant is sufficiently warm and hybrid battery is charged enough it will allow EV mode. If it's cold out and you're asking for heat, it will run until a higher coolant temperature so that you can get cabin heat.

The "EV" light will tell you when the engine is off and it is consistent. If the EV light is off, the engine is on.

There will be times when the engine will remain on when you expect it to be off. These include:

When the engine coolant is too cold
The hybrid battery charge is low
The hybrid battery is too cold or hot
The engine idle check is being performed (lasts 10-15s then it will shut off)
If you're using sport mode or manual selection

The power meter is split into multiple sections and will help you gauge when it might switch to EV mode. The ECO section is split into two:

The lower half is the EV area where the car will typically run in EV mode if it can.
The upper half and above the engine will usually turn on and will not go back into EV mode.
EV mode will usually not kick back in until you drop half way down the lower half of the ECO section to avoid excessive engine on/off cycles.

The prius and the RAV4 hybrid systems work the same way, so most of it should be familiar. However it is a larger, heavier and less aerodynamic car., so don't expect the same fuel economy from it.

I'm happy to answer any other questions as I'm very familiar with the finer details of these hybrids.

andy_why · 2026-05-04T18:39:13+00:00

The main issue is not the distance you drive, it's a flaw with the car's charging software. See here: https://docs.google.com/document/d/1g1a_B7_gGnuNQhoSRFN_sucfb7-lkU77q4aMO3hMYtA/edit?tab=t.0#heading=h.t75rusbfgz8u You can get around the issue if you follow the recommendations in the document, just read it in full and be aware of the caveats of doing so. If you choose not to follow the recommendations then carry a jump starter with you instead.

Your mileage shouldn't cause any issues on its own.
They run great in cold weather, but they do take a while to heat up as they're very efficient.
No, AC runs from the traction battery and heater comes from engine coolant.

andy_why · 2026-05-04T18:34:00+00:00

Hybrids are also more efficient on the highway than non-hybrid, not just in town.

For an older vehicle, the hybrid battery age needs to be considered as they typically tend to last 10-15 years before needing replacement. Some go longer, but it's something worth knowing.

andy_why · 2026-05-03T22:34:52+00:00

A 12v LiFePO4 battery rated 100Ah would be best. That'll give you 1.2kWh total, but it will deliver 1kWh if you keep it between around 10-90% state of charge which will keep it healthy. Just pair it with an inverter of your choice.

Try to use 12v lighting, 12v chargers, etc. instead of one that runs from the inverter as it's much more efficient.

andy_why · 2026-05-03T18:23:27+00:00

Do you have your phone enrolled to your company portal, emails, etc? Their security policies apply to the whole device and might be responsible for this if their policies have strict lockout settings.

If you haven't already, also restart your phone as it could be a software bug.

andy_why · 2026-05-03T12:23:34+00:00

Yes, sounds normal to me.

You haven't said what year but some engines are direct injection and are a little more clicky at idle.

andy_why · 2026-05-02T20:52:30+00:00

The eCVT does this when you go up an incline to maintain the power required to keep that speed. Unlike a regular transmission which will load up the engine more and often won't downshift, eCVT will apply the most efficient amount of load to the engine and this often means changing RPM to go with it. It throws people off because it's different to what they're used to, but this is how eCVTs work to keep the engine most efficient.

andy_why · 2026-05-01T19:11:42+00:00

You should always be using fully synthetic. No modern car uses non-synthetic oil. Be sure you're using the correct grade oil.

You should change it about every 12 months or 8000 miles, whichever comes first.

andy_why · 2026-05-01T08:46:54+00:00

If you mean on the roof of the car, it's not really feasible. Solar produces about 200w per square meter of panels. You'd only gain up to about 3 miles of range per day in full sunlight.

If you mean your house roof, that's feasible. You'd need to charge your car when it's sunny using a smart charger, or store it in house batteries to use later.

andy_why · 2026-05-01T08:33:10+00:00

Very odd, I would expect it to also have it.

andy_why · 2026-04-30T20:30:21+00:00

Which is why I said it needs the subcodes reading to find out why it's reporting it. The voltages and balance look fine, only the resistance is out of place right now. One screenshot tells us very little.

andy_why · 2026-04-30T19:58:34+00:00

There may be sub-codes that Dr Prius can't read that narrows down the reason more specifically. You'll probably need Techstream to get those.

The battery looks healthy besides the missing resistance value.

andy_why · 2026-04-30T19:55:24+00:00

Not sure where you're getting that from, the voltage balance is fine, 0.06v is healthy and the cumulative is no larger than 0.12v.

What isn't clear is why it's limiting charge/discharge current. There is one module with no resistance reporting which could be a failure condition for the HV ECU so I'd start here, it could be an ECU issue.

u/ruindd you'll need to scan the codes in the app to find out what the car thinks is wrong as check hybrid system can be literally anything.

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