12v charging system

Discussion in 'Gen 2 Prius Technical Discussion' started by Recian, Jun 19, 2026 at 5:31 PM.

  1. Recian

    Recian Junior Member

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    So im looking for in depth info on how the HV battery charges the 12v in our cars. Im working on an altima hybrid for someone and they use the same toyota hybrid system from gen2 prius and early camry. Wiring schematics are very similar in terminals pins and terminology. Im basically not getting any charge to the 12v battery. Nissan side ESM indicates DC/DC converter charges it (otherwise theres very little info) which is typical in HEV/EV but they call it the EPS DC/DC and it is bolted above the battery separately from it. Its putting out 44v on its output circuit. The traction battery has a 2 gauge wire 12v lead that comes from a module on the main relays board goes to the 120a fuse under the hood then directly back to the 12v battery in trunk. Is there another DC/DC built into the battery that charges the auxiliary 12v? In our systems?
     
  2. PriusCamper

    PriusCamper Senior Member

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    Not sure what the 44v signal is used for in a Nissan? Are you sure about that? I can't imagine a Toyota Hybrid system where the DC/DC converter does below high voltage at anything other than 14.1volts.