2016 Prius Battery Isolation

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sbfoster777 asked Sep 3, '23

2016 Prius Battery Isolation

Hi,

My sincerest thanks if you are familiar with the Prius charging system and can answer this question:

I have a 2016 Toyota Prius with an added 12v AGM battery that is installed in parallel with the OEM AGM starting battery. They both are charged with the cars charging system and both feed an installed 2000w AC inverter. I'd like to install the simplest isolator that Victron makes between the parallel batteries and the inverter to ensure that neither battery falls below a voltage level that will damage them if the inverter is in use and the car is turned off. Since the car does not use a conventional alternator, I need a guide on the right way to connect the isolator to the proper connection points in the charging system.

Again, many thanks to whomever would like to tackle this problem.

-Steve

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Answer 1 · 2023-09-03T03:26:03Z

Fundamentally, this is no different than a standard car charging system, electric-wise.

First, since the batteries are in parallel, they will always be at the same voltage.

Second, while not consistent with general best practices, I recommend the inverter feed from the spare battery such that it takes the brunt of the load and will be charged a little less than the car's 12V.

The Prius AGM is high quality but relatively fragile due to its limited demand application.

I don't know the 2016 system specifically, but the 04-09 have a 70A DC-DC converter that provides charging and 12V power from the HV system - HV battery and . I expect the 2016 is highly similar. This means you really only have about 600-700W of sustainable output as the car consumes about 20A when running.

Victron does not make an isolator approved for use as a direct interrupt for an inverter. The surge associated with cap charging will blow one out once it reconnects the inverter. The only way a battery protect can be used is to signal a remote off switch on the inverter, i.e., the inverter must have this function - usually in the form of a relay or jumper that forces the unit off when a signal is received.

Ideally, you get a quality inverter that you can simply set the cut off to something like 11.9V. The Prius 12V does almost nothing during start up and only needs to supply 20-30A for a couple of seconds until the HV relays are closed and the HV battery/DC-DC converter are powering the car/starting the engine.

Something worth noting... the USABLE capacity of the HV battery (40-80% utilization) is almost identical to the TOTAL capacity of the 12V.

Lastly, get yourself a decent lithium jump starter for $50. Keep you from ever getting stranded.

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