Low Bars on Battery Guage after Idling a While

No offence, but sitting in a cosy car with the radio playing seems like a pretty slack watchman gig.

 

no need to panic, the engine will recharge the battery. but sitting in a car is not good for health. get out, stretch and walk some.

 

Sounds like a cushy gig! (Just remember to have the system in READY mode, so the ICE comes on when necessary, else you'll flatten the battery(s)!)

 

congrats and welcome! no worries, that is exactly how the car is programmed to work. it's the most efficient use of the gasoline. to ease any possible future fears, you may want to leave it on at home, and check it periodically to see what it does exactly. all the best!

 

It depends on what you have running. Keep in mind the Prius traction battery only has the equivalent 12V capacity of one big deep cycle marine battery at 108Ah... and it only uses 40% of that.

When it warms up, I recommend you run the discharge test in my signature to check your battery state of health. i expect you'll find it significantly deteriorated.

Computations for above claim:

6.5Ah battery * 200V = 1300Wh
1300Wh / 12V = 108Ah

And technically, 40% of 108Ah is 43Ah, which is equivalent to a relatively small standard auto battery.

 

Hi Rory. Just make sure that you leave the Prius in P (park) and not in N (neutral), and it will automatically start the engine and charge the battery when it gets too low. Never leave it in "N" or it can't charge.

 

Thanks, uart! I knew my post didn't look quite right, I (obviously) meant "PARK" - ("READY" goes without saying!) - Well spotted!!!

 

One thing that surprised me with the Prius is that when it is on, all of the ECUs (computers) in the Prius are drawing more than 200W of power (IIRC, I remember seeing it measured as 250-350W). So if you're sitting with it on in "Ready" mode (mode you drive it in), it will drain the hybrid pack in a surprisingly short amount of time. It's normal behavior for the Prius to turn off the engine until the battery drops to two bars, then it will turn on the engine to charge the battery. However if you're in "ON" (from everything off, keep foot off break and push start button twice), the engine will not start to charge the hybrid battery. If you just want to use the radio, I'd recommend putting it in "ACC" mode (from everything off, keep foot off break and push start button once). Then you can play the radio without power being drawn for all of engine ECUs. However don't stay in this mode for too long or you will drain your 12V battery.

 

It shouldn't surprise you if you think about it, and not if it's healthy and you understand how little usable capacity is actually in the hybrid battery.

On a 220V battery pack, 1A isn't much of a drain, and it's probably closer to 2A. Keep in mind the Prius is powering the inverter coolant pump, ABS actuator, etc., all 12V systems, etc. There are like a dozen ECU's in it.

A perfect pack has 2.6Ah of capacity from 80% SoC to 40%. Assuming you start at the 60% SoC level, a 2A current will go through 1.3Ah of capacity in about 39 minutes.