Wire inverter to EV battery

Careful where you tap - while the Li-ION is "ONLY" 207 volts - I believe that the MG1/MG2 run off 600 volts.

 

I'm not sure if you're referring to the "memory effect" that some types of rechargeable batteries suffer from to one extent of another, so I apologise if this is not what you meant. But this point is worth discussing here as it's relevant.

You don't say if your Prius has Li-Ion or NiMH batteries, but either way you absolutely do not need to worry about the memory effect of these batteries. This belief is a relic from the day of NiCd batteries that were common in the 1980s.

NiCd batteries had a very memory-prone cadmium anode, which readily formed crystals on its surface during use. These were were the main cause of this issue. By comparison, the nickel plate, shared by both NiCd and NiMH can also suffer from crystalline formation, but only at relatively deep (under 20%) and repeated (several tens to hundreds) of discharges to those low levels. NiCd could suffer from the memory effect at all levels of charge and due to the nature of the chemistry involved it did so very easily.

If you don't want a memory effect with NiMH, don't discharge it below 20% of its true capacity (this is different from what a battery %age charge display may read, more on that later).

With Li-Ion batteries, the deeper you discharge them the more you reduce the number of times they can be recharged and the more you reduce their capacity. If you could keep a Li-Ion battery between 45% and 55% it would last a human lifetime. Pretty much any device worthy of a Li-Ion battery will have appropriate charging/discharging logic built in to prevent it going below, say, 20% of it's actual charge capacity or over 80% of its maximum, as this is where damage starts to happen quickly. These values are chosen by the manufacturers to align with the life expectancy they wish their products to have. For example, a mobile phone battery may have true maximum charge/discharge levels chosen so that they typically last 2-4 years. The charge state display (such as the battery %age on your phone) will be calibrated so that the real life 20%-80% charge range reads as 0% to 100% respectively. In other words, when your phone reads 100% it's actually (for example) at 80% and 0% is actually 20%, 50% is still 50% of course.

The whole reason a Gen4 battery, be it NiMH or Li-Ion, has a 10 year warranty in many countries, including mine, is because the charging logic limits the charge/discharge to conservative (low damage) levels. In fact, if I recall correctly it was more like 30% to 70% true values on a Prius Gen 4.

So, in short, don't go treating your battery like a NiCd battery from the 1980s. You'll shorten the life of the battery.

Why? The battery charges most efficiently and fastest when its close to its middle charge range of charge level. So by waiting longer to charge it, you not only waste more fuel as the charging is less efficient, but those energy losses end up turning into heat in the battery, shortening its lifespan. By doing it your way, you will have to run the combustion engine for longer overall to achieve a given amount of battery time.

Then there's the risk of discharging your battery too low if you go too far. The car uses the high voltage battery to start the combustion engine. If it's too low, it won't even try to start and there is no at-home way to recover from this. You will need to have your car transported back to Toyota, where they may be able to use their HV battery charger to recover your battery. However, due to the damage caused by such deep discharges, it's also possible you'll need a very expensive replacement.

If you do go down this route, you MUST have a low-voltage cutoff that is set to some value higher than whatever Toyota considers to be the minimum if you're going to do this without the car being in Ready Mode. If you only use the HV battery while in Ready Mode the car will figure out when it needs to charge the battery.

 

Here you go.

 

Quick answer already given in the link posted by @Leadfoot J. McCoalroller.

"Memory?" As @The Professor said, neither Li-Ion or NiMH have memory issues like NiCad. But you absolutely do NOT want to over discharge a Prius traction battery. Toyota keeps it to the charge and discharge levels it has in order to keep the battery healthy for at least 10 years and 150,000 miles. If you go draining it under that, you'll soon be needing to buy another battery.

Quite a few, but they don't step it down to 12V. The convert it to 240/120 VAC. Read the thread Leadfoot posted for more info.

Gen 3 has an inverter in the back??? Not unless someone put one there themselves.

2016 Prius 2 ECO only comes with Li-Ion.

Edit to add: The only reason to use an inverter on the traction battery rather than the 12V battery is that you can draw more power from it. The car will still insist on keeping the traction battery within it programmed parameters as long as you keep it in ready mode. If you try pulling juice from the traction battery with the car off, you might as well just shoot that battery with a rifle. You're gonna kill it just the same.

 

This topic comes up over and over, and part of the reason is threads in all the different model/year-specific forums, even though most of the idea isn't model/year-specific. I started a thread in the non-model-specific "Knowledge Base" forum and tried to collect a bunch of the existing links there.

Electric power from a hybrid, connecting inverter to the high-voltage system | PriusChat