help me solve this please! 07 HV battery

Your first issue was just due to the age of the battery and sitting for 3 weeks unused.

The HV battery is built using 28 individual modules. The ecu monitors these modules for abnormal conditions like low voltage so it can provide warning if anything abnormal is going on. Over time, some of the 28 modules will develop self discharge characteristics, which will bleed off some of that modules charge. If you use the car frequently, it's not really noticeable. Kind of like refilling a cup of coffee after every sip. If the car sits a long time, that self discharge may cause the module to so low that it now triggers that warning. That's what happened to you. Sometimes this can be resolved by 'force charging' the HV battery by running the engine to charge the battery back up, which puts in back into the state it was prior to the extended shutdown.

Now, since you already swapped the battery, the force charge is no longer an option for you. Now you have a used battery that has additional problems. A P3030 means the wire harness that the ecu uses to monitor the modules has a broken connection somewhere. The 28 modules are monitored in sets of two. Each set is called a block, so there are 14 blocks in your battery. Each block has a sensor wire that goes to the ecu. Typically, where the wire mounts to the module terminal, there is some corrosion that will weaken the crimp connection. Sometimes it's bad enough the crimp connection may crack and the wire falls off. That is what usually gives the P3030. All those sensor wires plug into the ecu using one plug/socket. Sometimes that plug/socket will develop corrosion on a few of the pins, and it may get bad enough that the pin breaks off. This will also give a P3030.

 

Opportunity to rebuild you pack.. TMR-JWAP is a pro! You will notice the corrosion starts on the negative post and spreads. Batts are leaking electrolyte. If the corrosion is bad enough getting in to the ECU sense connector, can trigger a fire as there are no current limiters between the sense wires. good luck