Adding secondary battery for 12v outlets

I'm not sure you would have to take a careful look at where the relay is for the outlets. But as an alternative I might suggest putting the 2 outlets or other outlets off that new battery with a battery isolator. It's a device commonly used in RV'ing and is available at a few places. It will allow the new battery to charge but not draw off the existing battery when it's not charging. 2-battery System Battery Isolators - JCWhitney is an example of one. I might also suggest a deep cycle battery for the aux too.

 

I have constant power source for my GPS, Cell Phone Charger, Radar Control remote control unit, Bluetooth headset charger, and Laptop charger.

When they are not charging devices they consume less then 50mA. This would take over a year to drain the batttery in the car. Here is a pic of the wires I connected to.

 

If you are referring to the original equipment 12V auxiliary battery, that has an Ah rating in the mid-30s.

Using simple arithmetic: 0.05A x 24 hours/day x 14 days = 16.8 Ah. Usually you don't want to drain the battery more than 50% if you are interested in long battery life.

Or if you don't care about long battery life, you can see that the battery will be completely depleted after one month.

 

Using simple logic: Drive car, alternator charges battery. It will never sit more than a week. If it does I will unplug the chargers.

 

Patrick's comment was simply correcting the error in your earlier post, where you stated it would take over a year to drain the battery. Those small loads add up over time.

Another small correction: the Prius does not have an alternator.

Tom

 

Looking at the big picture. My chargers that are directly connected to the AUX battery will not drain the battery if I drive the car more than once a week. The regenerative system in the Prius will charge the AUX battery. I am simply pointing out that the battery gets charged and it will not be depleted after one month as Patrick Wong stated.

I drive my car 30,000 miles a year. This config will work perfect for me and many others.

 

Just a quick correction -- The Prius does not have an alternator, the 12v battery is charged by the dc to dc converter whenever the car is in the ready mode. Also, regeneration helps charge the traction battery, not the 12v battery.

 

Do you really belive the 12V AUX battery never gets charged by the car?

The Prius has a permanent magnet AC electric motor. This motor functions as a motor and a generator (AKA alternator). The AC output goes to a bridge rectifier and converts it to DC. The DC output uses a DC to DC converter to output 12-15V to drive components in the car and charge the AUX battery.

 

The MG1 and MG2 are never called alternator.
In your theory, your Prius only charges the aux battery on regeneratiing, but it is not correct. Also, there is no bridge rectifier.
The aux battery is charged anytime in ready mode using HV battery power via DC-DC converter.

Ken@Japan

 

An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current. That is exactly what MG1 and MG2 does. They are one in the same.

Those Diodes in your pictures are a bridge rectifier.

 

When generating, an MG does indeed operate as an alternator, but no one would ever refer to it as such. It's simply a matter of terminology, much as one would never call a concert violinist a fiddle player.

Ken is an excellent engineer. I'm sure he recognizes the bridge rectifier in the schematic.

As long as we are splitting hairs over terminology, the MGs on the Prius are not permanent magnet MGs, but are hybrid synchronous MGs. They do have a permanent magnetic field, but they also use an induced field at higher power levels. This means they run as efficient permanent magnet motors at low power levels, but transition to more powerful but less efficient induction motors at high power.

No one is trying to beat you up over a simple term like alternator. It's simply a matter of clarification. People come onto this forum and read the term alternator and assume the Prius has a conventional automotive alternator hanging on a belt somewhere. It doesn't, so we want to avoid the confusion.

Tom

 

MG1 and MG2 are not alternators, given your definition above. MG1 and MG2 will also convert electrical energy to mechanical energy. Alternators typically do not perform that conversion.

Two examples of electrical to mechanical energy conversion:

- MG2 is directly coupled to the transaxle output shaft, and powers the car when the gasoline engine is not operating.

- MG1 starts the gasoline engine.

Regarding the diodes in Ken's schematic, it appears that the purpose of those diodes is to protect the IGBTs by limiting the reverse voltage that would otherwise appear across the emitter - collector junction?

 

Again, in your theory, your Prius only charges the aux battery on regeneratiing.

Place your voltmeter on the 12V line.
In READY mode, you'll see consistent approx 14V even in neutral at standstill.
In ACC or IG-ON mode, you'll see less than 12.5V, and it shows the the DC-DC converter is disconnected from HV battery.
That's the evidence that the aux 12V battery is charged by the HV battery power via DC-DC converter.

Ken@Japan

 

That is splitting hairs. The motor type is Permanent magnet AC synchronous motor. I am sure it is enhanced, but its still a Permanent magnet AC motor.

Why would he post this? With a picture of a bridge rectifier?

 

That is what I said a few posts back

 

Getting back to my original post. It is ok to connect devices to constant power as long as they do not consume to much energy. The vehicle will always keep the Aux battery charged.

I was trying to make a simple point and you guys went down an odd path. I am an Electrical Eng. and I work with motor control applications.

 

What they are trying to point out, if I understand it, is that the MGs (through the inverter) charge the HV battery, and the HV battery supplies the power to the DC to DC converter (and thus the 12 volt) in Ready mode whether the MGs are turning or not. Also, that the MGs never send power to the 12 volt or to the converter, except through the inverter/HV steps.

But I am not even an engineer, so not claiming to know anything.

 

I read that there is concern over battery life among those with short trips, due to the conservative rate of 12V charging, so at the margin, these small extra loads could make matters somewhat worse. Does adding a 2nd 12V battery to the recharge scenario reduce the charging of the primary 12V? Are BMS isssues a concern with 2 12V's?