need help please , hybrid battery low

If the Prius will not become READY, then towing the car with the wheels on the ground will do nothing with regards to charging the traction battery. The original battery may be near-dead after 1-1/2 years of non-use.

The engine no-start may be due to other problems besides a bad traction battery but you will need to have the DTC read to determine whether that is the case.

A used battery from a salvage yard is a potential low-cost alternative to new, if you need a replacement traction battery.

 

Replacing your battery before knowing what is wrong seems like good money after bad, but here are some batteries.

prius battery | eBay

 

The HV battery cranks the engine, so if it starts then the hybrid battery (while low) is probably not the actual problem. I'd say there must be another reason why the engine wont run.

 

What's the condition of the +12 volt battery? If that is shot due to 1 1/2 year storage time, that would explain some of your problems. I would drain the gas, put some fresh gas in. Why did you let it sit for a year and a half, if I might ask?

 

This is a good example of why you can't let these cars sit for more than a few months. I'd say it is more likely that the ICE has a problem. Valves tend to stick, fuel is stangant, etc, etc.

You had maybe 2-3 chances to get the car started with a hybrid battery that sat that long. Probably by now the hybrid battery state of charge is too low to crank the engine.

The 12V battery is easy, just put a regular car battery in there for the moment.

The hybrid battery may need to be charged up. There are a few people out there with the equipment to do it, me included, but you may have to go to a dealership and have them fly in the special charger.

You really need some sort of diagnostic tool to read codes and things like hybrid battery voltages and state of charge. Techstream would be preferable but even a ScanGauge would work. Do not buy a generic OBDII scanner at an auto parts store because it will not give you the information that you need.

 

The inverter has a DC converter which performs the function of the alternator. It is powered by the hybrid battery.

The sequence of events is a follows:
1. The 12V battery must have sufficient state of charge (SOC) to boot up the computers. Sagging below 10.5V will cause failure to become ready.
2. If all computers boot successfully and there are no dire problems, then the car will become Ready, and the Ready light on the dash will be lit.
3. The car will try to turn on the gas engine a few seconds after the ready light comes on. The hybrid battery will send power through the inverter to MG1 (as motor) to crank the engine. After the engine starts running, then the engine will start turning MG1 (as generator) to create power to charge the hybrid battery via the inverter.