Big battery concerns

drash · Mar 8, 2012

My 12v aux battery finally started going bad after it hit the 7 year mark. FYI you could conceivable start the car with 2 9V batteries like I did, In a pinch. The 12v battery drives ALL the 12v accessories, like the taillights, headlights, radio, normal car stuff. And yes it is kind of babied because it's not in the engine compartment. However, because it is small in mass it may not last as long as a bigger battery. As with all lead acid batteries it has a finite lifetime irregardless of it's cozy life and life is dramatically shortened if discharged more than 50% without immediately recharging it.

andyprius · Mar 8, 2012

jadziasman said: ↑

Okay aux battery worshippers! I surrender. It seems it's impossible to free you from your unshakable faith in the omnipotence of your beloved. Hey, you've something to believe in! I'm happy for you. I won't ever question your faith again even though I am a heretic in this regard.

All right, I confess that I was technically incorrect in stating that the traction battery never charges the aux battery when the Prius is not in motion. That in and of itself is not a serious misjudgment in the big hybrid picture though. Ultimately it's still the ICE that charges the aux battery, not the traction battery. I spend most of the time in my Prius driving at a serene 70 mph. Not a lot of serious traffic jams here in my neck of the woods.

Sure, the aux battery is being supplied with 14V from the DC/DC converter while the other electrical systems are being supplied with power from the traction battery at the same time. I just don't consider this as the traction battery charging the aux battery. From what I can see from the wiring diagram, the aux battery isn't doing anything at this point and it shouldn't be. It's the traction battery that needs the constant replenishment from the ICE via MG1 and MG2. The traction battery is providing power to the ECUs, the headlights, the radio, the AC, the heater, etc while the car is standing still and in the READY mode. The aux battery is on standby at this point. And when the SOC reaches a certain point, presto the ICE automatically fires up again. A worn out traction battery is the real problem for the HSD while in READY mode, the aux battery has no active role to play.

Correct me if I'm wrong - I know someone will speak up. Please tell me what, if anything, the aux battery is supplying power to when the Prius is in READY mode. Or why it would draw a lot of power when having nothing to do.

And if the aux battery is near the end of its life, it just won't be able to start the HSD reliably. And if, for whatever reason, it was possible to start the hybrid systems with a weak aux battery, well, the worst outcome from that would be that the ICE would run more often but I can't see how that half pint aux battery can be so demanding as to upset the apple cart. Makes no sense because where is the electric load on the aux battery at this time when the HSD is running other systems. Sure the aux battery has internal resistance but is it enough to cause the havoc that have sent so many of you into a tizzy?

My '05 has 166,700 miles, turns 7 years old this month, and STILL has the original aux battery that was installed at the factory in Japan. I've owned many cars in the past 36 years and I can't remember a 12V battery lasting that long in any of my non-hybrid cars. That tells me the Prius aux battery has a limited, easy job to do. I will replace it only when it needs replacement and that will be just like any other car, I'll know it's shot if it needs to be jump started (which I'll be afraid to do when the time comes).

I have had no problems at all with my '05 after the 33K miles I've driven it thus far and have never experienced any of the bizarre behaviors that many swear up and down must be caused by that pesky aux battery. The power door locks work every time, the interior lights seem to shine brightly, etc. I don't see any issues with the OEM aux battery whatsoever.

The Optima company must ADORE Priuschat because of all the unnecessary 12V battery replacements that they have sold the past few years since the early adopters have sent out their clarion calls to Prius owners everywhere. Some even claim that the OEM battery is garbage. Again, that's great publicity for the Optima people they just can't buy.

I have never, ever heard of anyone (until now) replacing a perfectly sound 12V OEM battery as a preemptive strike against the unfathomable possibility of being stranded by a dead battery - GASP! What is this world coming to????

If you wanna go and take a ride wit me
We three-wheelin in the fo' with the gold D's
Oh why do I live this way? (Hey, must be the money!)

I enjoy Priuschat and visit it every day.
Click to expand...

Glad to hear that you enjoy Priuschat everyday, that is identical with me. I think I am going to stay away from this Technical portion of the discussion leaving it to our more astute members. I am quite sure that the 12V is very important and is not just there for starting. And if consistently below 12V various issues can and do ensue. This has been proved numerous times by removing and replacing with a known good 12V Battery. I will await Patrick, Hobbitt comments on the subject. I am frrankly too lazy to research HSD theory of operations on my Bentley book.

seilerts · Mar 8, 2012

jadziasman said: ↑

...
Some even claim that the OEM battery is garbage. Again, that's great publicity for the Optima people they just can't buy.

I have never, ever heard of anyone (until now) replacing a perfectly sound 12V OEM battery as a preemptive strike against the unfathomable possibility of being stranded by a dead battery - GASP! What is this world coming to????
...
Click to expand...

The battery in the picture below was in good working order, showing no signs of a problem. Less than 30 seconds in Ig-On (for key programming) zapped it, giving it a bad cell. The OEM battery is garbage.

andyprius · Mar 8, 2012

seilerts said: ↑

The battery in the picture below was in good working order, showing no signs of a problem. Less than 30 seconds in Ig-On (for key programming) zapped it, giving it a bad cell. The OEM battery is garbage.

Click to expand...

Seilerts is also one of our astute contributors! NUF SED :cheer2:

Cory151 · Mar 8, 2012

jadziasman said: ↑

Okay aux battery worshippers! I surrender. It seems it's impossible to free you from your unshakable faith in the omnipotence of your beloved. Hey, you've something to believe in! I'm happy for you. I won't ever question your faith again even though I am a heretic in this regard.

All right, I confess that I was technically incorrect in stating that the traction battery never charges the aux battery when the Prius is not in motion. That in and of itself is not a serious misjudgment in the big hybrid picture though. Ultimately it's still the ICE that charges the aux battery, not the traction battery. I spend most of the time in my Prius driving at a serene 70 mph. Not a lot of serious traffic jams here in my neck of the woods.

Sure, the aux battery is being supplied with 14V from the DC/DC converter while the other electrical systems are being supplied with power from the traction battery at the same time. I just don't consider this as the traction battery charging the aux battery. From what I can see from the wiring diagram, the aux battery isn't doing anything at this point and it shouldn't be. It's the traction battery that needs the constant replenishment from the ICE via MG1 and MG2. The traction battery is providing power to the ECUs, the headlights, the radio, the AC, the heater, etc while the car is standing still and in the READY mode. The aux battery is on standby at this point. And when the SOC reaches a certain point, presto the ICE automatically fires up again. A worn out traction battery is the real problem for the HSD while in READY mode, the aux battery has no active role to play.

Correct me if I'm wrong - I know someone will speak up. Please tell me what, if anything, the aux battery is supplying power to when the Prius is in READY mode. Or why it would draw a lot of power when having nothing to do.

And if the aux battery is near the end of its life, it just won't be able to start the HSD reliably. And if, for whatever reason, it was possible to start the hybrid systems with a weak aux battery, well, the worst outcome from that would be that the ICE would run more often but I can't see how that half pint aux battery can be so demanding as to upset the apple cart. Makes no sense because where is the electric load on the aux battery at this time when the HSD is running other systems. Sure the aux battery has internal resistance but is it enough to cause the havoc that have sent so many of you into a tizzy?

My '05 has 166,700 miles, turns 7 years old this month, and STILL has the original aux battery that was installed at the factory in Japan. I've owned many cars in the past 36 years and I can't remember a 12V battery lasting that long in any of my non-hybrid cars. That tells me the Prius aux battery has a limited, easy job to do. I will replace it only when it needs replacement and that will be just like any other car, I'll know it's shot if it needs to be jump started (which I'll be afraid to do when the time comes).

I have had no problems at all with my '05 after the 33K miles I've driven it thus far and have never experienced any of the bizarre behaviors that many swear up and down must be caused by that pesky aux battery. The power door locks work every time, the interior lights seem to shine brightly, etc. I don't see any issues with the OEM aux battery whatsoever.

The Optima company must ADORE Priuschat because of all the unnecessary 12V battery replacements that they have sold the past few years since the early adopters have sent out their clarion calls to Prius owners everywhere. Some even claim that the OEM battery is garbage. Again, that's great publicity for the Optima people they just can't buy.

I have never, ever heard of anyone (until now) replacing a perfectly sound 12V OEM battery as a preemptive strike against the unfathomable possibility of being stranded by a dead battery - GASP! What is this world coming to????

If you wanna go and take a ride wit me
We three-wheelin in the fo' with the gold D's
Oh why do I live this way? (Hey, must be the money!)

I enjoy Priuschat and visit it every day.
Click to expand...

Well apparently you've never been an owner of Ford Powerstroke Diesel, because they have not one but two 12v batteries (biggest you can fit) and if they are not replaced annually the truck will leave you stranded, or do some really odd things.

The injectors on the 7.3s uses high voltage to actuate an electromagnetic fuel injectors that spray out at pressures of about 12-18,000psi. Im on my second Superduty and they've always been this way. Running high voltage injectors, high amperage glow plugs and just plane old turning over a 444ci diesel makes battery change an annual tune up item.

Just because "you've" never seen it doesn't mean it doesn't happen.

efusco · Mar 9, 2012

jadziasman said: ↑

Okay aux battery worshippers! I surrender. It seems it's impossible to free you from your unshakable faith in the omnipotence of your beloved. Hey, you've something to believe in! I'm happy for you. I won't ever question your faith again even though I am a heretic in this regard.

All right, I confess that I was technically incorrect in stating that the traction battery never charges the aux battery when the Prius is not in motion. That in and of itself is not a serious misjudgment in the big hybrid picture though. Ultimately it's still the ICE that charges the aux battery, not the traction battery. I spend most of the time in my Prius driving at a serene 70 mph. Not a lot of serious traffic jams here in my neck of the woods.

Sure, the aux battery is being supplied with 14V from the DC/DC converter while the other electrical systems are being supplied with power from the traction battery at the same time. I just don't consider this as the traction battery charging the aux battery. From what I can see from the wiring diagram, the aux battery isn't doing anything at this point and it shouldn't be. It's the traction battery that needs the constant replenishment from the ICE via MG1 and MG2. The traction battery is providing power to the ECUs, the headlights, the radio, the AC, the heater, etc while the car is standing still and in the READY mode. The aux battery is on standby at this point. And when the SOC reaches a certain point, presto the ICE automatically fires up again. A worn out traction battery is the real problem for the HSD while in READY mode, the aux battery has no active role to play.

Correct me if I'm wrong - I know someone will speak up. Please tell me what, if anything, the aux battery is supplying power to when the Prius is in READY mode. Or why it would draw a lot of power when having nothing to do.

And if the aux battery is near the end of its life, it just won't be able to start the HSD reliably. And if, for whatever reason, it was possible to start the hybrid systems with a weak aux battery, well, the worst outcome from that would be that the ICE would run more often but I can't see how that half pint aux battery can be so demanding as to upset the apple cart. Makes no sense because where is the electric load on the aux battery at this time when the HSD is running other systems. Sure the aux battery has internal resistance but is it enough to cause the havoc that have sent so many of you into a tizzy?

My '05 has 166,700 miles, turns 7 years old this month, and STILL has the original aux battery that was installed at the factory in Japan. I've owned many cars in the past 36 years and I can't remember a 12V battery lasting that long in any of my non-hybrid cars. That tells me the Prius aux battery has a limited, easy job to do. I will replace it only when it needs replacement and that will be just like any other car, I'll know it's shot if it needs to be jump started (which I'll be afraid to do when the time comes).

I have had no problems at all with my '05 after the 33K miles I've driven it thus far and have never experienced any of the bizarre behaviors that many swear up and down must be caused by that pesky aux battery. The power door locks work every time, the interior lights seem to shine brightly, etc. I don't see any issues with the OEM aux battery whatsoever.

The Optima company must ADORE Priuschat because of all the unnecessary 12V battery replacements that they have sold the past few years since the early adopters have sent out their clarion calls to Prius owners everywhere. Some even claim that the OEM battery is garbage. Again, that's great publicity for the Optima people they just can't buy.

I have never, ever heard of anyone (until now) replacing a perfectly sound 12V OEM battery as a preemptive strike against the unfathomable possibility of being stranded by a dead battery - GASP! What is this world coming to????

If you wanna go and take a ride wit me
We three-wheelin in the fo' with the gold D's
Oh why do I live this way? (Hey, must be the money!)

I enjoy Priuschat and visit it every day.
Click to expand...

Well, the ICE provides all the power for everything in the car, so yes, that is ultimately the thing charging the 12v, but it first must go through the traction battery, then the inverter, then to the 12v. so if you prefer to think of it as the ICE charging the 12v, then so be it, I won't fight you on it.

The 12v does NOT sit idle during normal operation. It supplies power for all of the accessories (perhaps not the headlights--I seem to remember they have their on inverter so that may come from the traction, but I don't think so b/c you can have the headlights on even when the car is in ACC mode and the traction battery is not active). You are right that the relative amount of drain to the 12v is very small.

I also agree with you that the OEM 12v is not that bad of a battery. I kept my original for 5 years before preemtively changing it. My reasoning was that the new one would last me another 5 years--the amount of time I expected to keep the car. Why wait until it dies and inconveniences me? I know it will have to be replaced at some point and I can do it when I need to be somewhere or I can do it at my convenience and not have it end up stranding me or making me late for something and/or needing to inconvenience someone else to run me to the dealership to buy a new battery. I won't criticize you for waiting and getting every drop of life out of your battery if that's they way you choose to do it. But for me I need my car to be reliable, and after seeing enough reports of that 12v dying unexpectedly at around the 5 year mark, it made sense for me to do it preemtively. But look, to each their own.

qbee42 · Mar 9, 2012

jadziasman said: ↑

<snip>

Sure, the aux battery is being supplied with 14V from the DC/DC converter while the other electrical systems are being supplied with power from the traction battery at the same time. I just don't consider this as the traction battery charging the aux battery. From what I can see from the wiring diagram, the aux battery isn't doing anything at this point and it shouldn't be. It's the traction battery that needs the constant replenishment from the ICE via MG1 and MG2. The traction battery is providing power to the ECUs, the headlights, the radio, the AC, the heater, etc while the car is standing still and in the READY mode. The aux battery is on standby at this point. And when the SOC reaches a certain point, presto the ICE automatically fires up again. A worn out traction battery is the real problem for the HSD while in READY mode, the aux battery has no active role to play.

<snip>
Click to expand...

There are two voltage buses on the Prius: HV and 12V. The HV bus is attached to the HV (traction) battery, the low side of the inverter, and the input to the DC to DC converter. All charging of the HV battery is done through the inverter, and the high side of the inverter is powered by MG1 or MG2.

During normal operation in Ready, all power to the 12V bus is supplied from the DC to DC converter, which itself is supplied by the HV bus. This power to the high side of the DC to DC converter might come from the HV battery or one of the MGs; it all depends on the mode of operation. If the ICE is charging the HV battery, the power is coming from MG1. If regenerative braking is charging the HV battery, power comes from MG2. If the Prius is running in EV, the power comes from the HV battery.

The standard operating voltage on the 12V bus is higher than the quiescent voltage of the 12V battery. This means that the 12V battery charges continuously when the Prius is in Ready. The only exception would be during a high current draw situation exceeding the 100A capability of the DC to DC converter. This would not be normal.

Once charged, the 12V battery draws very little power to remain charged. Essentially it is just sitting there waiting to be used again once the Prius is out of Ready mode. However, a problem can occur when the 12V battery is failing and refuses to charge. Once failure mode causes the 12V battery to become a load, drawing power from the 12V bus. This will hurt mileage, and if severe, it can drag down the voltage of the 12V bus. If it does this, weird things will start to happen with the ECUs and MFD.

Tom

Big battery concerns

drash Senior Member

andyprius Senior Member

seilerts Battery Curmudgeon

andyprius Senior Member

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efusco Moderator Emeritus
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qbee42 My other car is a boat

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Big battery concerns

drash Senior Member

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seilerts Battery Curmudgeon

andyprius Senior Member

Cory151 Member

efusco Moderator Emeritus Staff Member

qbee42 My other car is a boat

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