Prius 12V battery system to 115v thru inverter

good topic. ill like to know this too.

 

It should be ok to take power from jumper terminal. It is connected to inverter so voltage will be slightly higher than 12V battery when Prius is in ready. 1500w is bit too much to take from Prius but it should be ok as long as you don’t use more than 1000w of power from inverter for long time.

 

Actually you need to limit your 115 v load to 800 watts. The inverter does dissipate some energy due to not being 100% efficient (about 85% usually for a good inverter). That puts your DC (12v) load at about 80 amps which is where the 12v bus starts to sag in voltage.

JeffD

 

Is this 80amp limit known? I couldn’t find actual measurements or facts anywhere. Is this actual power of 12V charger or power after what car uses with or without lights fan etc?

 

There is a 100A fuse in the line between the car's DC-DC converter and the 12V battery. If you blow this fuse it's a major pain to replace, so Jeff is allowing a small safety margin by recommending no more than 800 watts load on the inverter, which, as he notes, should then pull no more than about 80A through the fused circuit.

 

i would go directly from the battery terminals. there are some threads here with very attractive set ups.

 

If you connect inverter to jump start terminal all power doesn’t have to go through 100A DC/DC fuse. Power goes from Prius 12V “battery charger” through 100A DC/DC fuse to jump start terminal and there to 110v inverter and if something is left over it goes through 120A MAIN fuse to battery. And if 110v inverter is using more than what Prius 12V “battery charger” can provide rest of it will get from battery through 120A MAIN fuse.


So safe peak load (ONLY FOR FUSES) from that jump start terminal can be 120A+ Prius 12V “battery charger”-What Prius itself is using. Average load can be Prius 12V “battery charger”-What Prius itself is using.


So does anybody know Prius 12V “battery charger” output current? Only thing we know from fuses is that it has less than 100A.

 

i just don't like the connection point.

 

How do we limit to 800 watts? By size of inverter or by keeping tack of what you plug-in?

 

If you use an 80 amp fuse on the DC input to the inverter, you are protected.

JeffD

 

If you connect inverter to jump start terminal all power doesn’t have to go through 100A DC/DC fuse. Power goes from Prius 12V “battery charger” through 100A DC/DC fuse to jump start terminal and there to 110v inverter and if something is left over it goes through 120A MAIN fuse to battery. And if 110v inverter is using more than what Prius 12V “battery charger” can provide rest of it will get from battery through 120A MAIN fuse.

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This shows a lack of understanding of how electrical systems work. The 12 volt battery will draw whatever current it needs depending on it's state of charge, it's internal resistance, and the voltage applied. It does not take whatever is left in current terms after the inverter's needs. For the system to work well with an inverter installed the inverter should be connected through a suitably sized fuse "I agree 80 amps" directly to the 12 volt battery with as short length cables as is reasonably possible.

John (Britprius)

 

You don’t really need that 80a fuse. It will bring you extra safety for 110v inverter failure and stop you from running your 12V battery down (at least running down quickly). But if you don’t use 80A fuse you can put more and/or more powerful devices on. Depending on loads, inverter and battery just don’t use them for more than 15min to hour.

 

I did use bit incorrect terms in there. I should have written that maximum amount that battery can take is the amount that is left after what inverter takes from maximum that Prius 12V charging system can produce.


I have designed electrical devices. Work at electrical repair shop and I’m almost electrical engineer so I think I know basics of electricity. And I did look this up from wiring diagram of Prius.

 

The fuse is there to protect both the car and the inverter. No electrical engineer would install a devise without suitable fuse or breaker protection. A short circuit, or fault in the inverter could easily draw current in excess of 1000 amps depending on the battery fitted in the car. This would result in a burnt out car very quickly.
The high current fuses in the Prius are there for a reason and that is not to feed an inverter that should have it's own fused supply. The Prius DC to DC supply was designed to run the Prius systems not an inverter with an output of 1500 watts. While I agree it is capable of running an inverter, 1500 watts is 125 amps plus any inefficiency in the inverter. This could be reasonably another 15 amps making a load of 140 amps something it was not designed for.

John (Britprius)

 

I did use bit incorrect terms in there. I should have written that maximum amount that battery can take is the amount that is left after what inverter takes from maximum that Prius 12V charging system can produce.

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This is still not true. Overloading the "charging system" Dc to DC converter will do one of two things:-
Overheat the converter, shutting it down followed by a discharged 12 volt battery. Or the converter will fail needing an expensive replacement.
The converter cannot prioritize what piece of equipment uses what current it just sees one electrical load. The total of the inverter load, and the 12 volt battery charging load plus any other running load on the car.
The DC to DC converter has a sense wire connected directly to the 12 volt battery. This wire measures the voltage at that point
and the output of the converter is then adjusted to maintain the battery. This wire could be much shorter if it were connected to the jump point, but then it would not take into consideration the voltage drop along the aluminium main supply cable from the battery to the jump point. This is why the inverter should be connected at the battery.

John (Britprius)

 

Although it’s not good to use Prius fuses to protect 110v inverter circuit it will work. With 1500w 110v inverter fuses are about correctly sized also.


Let’s say charging system can deliver 80A (at this specific voltage) and 110v inverter that is connected to jump terminal will draw 140A then 80A of that will come from charging system through 100A DC-DC fuse 60A will come from battery through 120A MAIN fuse.

DC-DC converter will be current limited. And besides current would be as high if you had empty battery or even one shorted sell in the battery and DC-DC converters don’t broke with batterys.

Of course but rest of power can come battery through 120A main fuse.

This will only make jump starter point voltage higher but not much since lots of stuff including headlights use that voltage directly (I think)

 

There is the electrical load of the car running systems to take into consideration. The ECU's, MFD, Speedo display and ignition systems use about 20 amps continuous. Then add another 15 amps if the cooling fans come on to keep the engine cool because the car is stationary.
The DC to DC converter is rated at 100 amps maximum so drawing 140 amps (1500 watts) plus the minimum of 20 amps for the Prius systems give a load of 160 amps, so the little Prius 12 volt battery "the small version rated at 35 AH large version 45 AH at 20 HR rate" will be supplying a steady 60 amps.
Now a battery in good condition with a full charge may be able to keep this up for 30 minutes before it is discharged. If after 15 minutes of running at 1500 watts you lower the load to 850 watts that's 80 amps with the inverter losses plus the running load of the Prius 20 amps there is nothing left to recharge the 12 volt battery. This without charging losses would need another 30 amps for 15 minutes to recharge.
The Prius battery is supposed to be limited "according to the label on the top" to a maximum charge rate of 4.5 amps.
I am not saying this will not work for a very short period, but if you want a reliable safe system using the 12 volt bus the current must be limited to something under 80 amps.

John (Britprius)

 

That’s exactly what I did say couple of post ago.

 

What you said (quote) was "just don't use them for more than 15 minutes to an hour" and what I was trying to convey is that even 15 minutes is to long.

John (Britprius)