Function of the secondary battery in Start/Stop technology, FCA

Philip Educator California Posted   Latest  
Discussion
Education
2018 Chrysler Pacifica L 3.6L (G ERC Flex) 9-spd (948TE)
C2222
P00FD — Battery "B" State of Charge Performance

Friends,

I'm wondering if anyone has access to training material regarding the FCA Start/Stop technology. I'm particularly interested in the function/purpose of the second small 12v battery. I expect that replacing it will solve the two codes in question but I'm curious as to what the little 12v battery does.

Thanks!

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Dmitriy Analyst
Ontario
Dmitriy
 

Scott Shotton presented a case study on AesWave‘s blog, and explains the details of operation near the bottom of the post. Hope this is helpful, even if not from FCA itself… aeswave​.​com/blog/Parasitic…

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Thanks
Interesting
Philip Educator
California
Philip
 

That was very helpful; thank you for the link.

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Robert Technical Support Specialist
New York
Robert
 

Second battery to to provide power to functions of the vehicle during a stop start event to preserve the main battery for restart.

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Paul Owner/Technician
California
Paul
 

Hey Phil! I know nothing about Chrysler of course, but on the short lived original Subaru Crosstrek hybrid, the little battery was for engine staring only and was charged by the belt driven alternator/starter. The other battery (a regular group 35) was used to power 12V systems and was charged with the DC-DC converter. When the little battery fails, you can see low voltage on the start battery…

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Robert Technical Support Specialist
New York
Robert
 

It is not a hybrid the little battery is about the size of a powersports battery.

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Paul Owner/Technician
California
Paul
 

Thanks for the clarification, but the Subaru Crosstrek hybrid does have a similar system though. There are two 12V batteries and one “high voltage” battery (high voltage in quotes because it's only 100V). Because of the design, the high voltage battery can't crank the gas engine, so the starting battery does that job with a starter/alternator. The starting battery is a tiny battery with tiny…

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Joseph Diagnostician
Texas
Joseph
 

Oh the Subaru first gen hybrid…. When the main battery starts dying ($180 installed), it leans on the start stop battery (950 installed); and if further ignored takes out the ISG (integrated starter generator).

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Richard Instructor
Florida
Richard
 

On those vehicles, the small battery powers up all of the vehicle accessories only during an auto start event. The main battery is isolated to only power the starter. There’s also an isolation relay that controls which battery is connected.

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Erik Diagnostician
Florida
Erik
 

I keep forgetting some manufacturers do this. When I was with Toyota we have one main battery and if the vehicle had heavy accessories the vehicle had a boost inverter to aid. I think we had only the Highlander and they have put it in the RAV4 and Camry by now. Granted it is not perfect and the main battery is almost $450 last I checked. I guess knowing how it fails and what the vehicle does…

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Jason Owner/Technician
North Carolina
Jason
 

Hello guys, Just my 1.012cents worth.. The Chrysler Pacifica is basically a rebranded R-Class Benz. I service a lot of Mercedes . The “Secondary” battery is there to maintain accessories that are equipped on certain vehicles to isolate power from the primary battery during start up and assist as backup during long or extended periods of ”Engine Off” accessory functions such as the “REST”…

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Robert Technical Support Specialist
New York
Robert
 

The CS body or older Pacifica only has a single 12v battery, the current Pacifica after 17 has 2 batteries and is a FIAT based vehicle.

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