Can cigarette lighter outlet handle 7 to 8 amps draw ?

It should be OK. I think it can take up to slightly over 15 V. It would have a heat-sinked voltage-regulator IC inside.

 

Good info. The convertor voltage output would be IC-regulated, but it could be load regulation (decrease of the voltage with increasing load) what you are seeing, as load regulation is never perfect even with an IC.

 

voltage = energy per charge (joule/coulomb)
current = charge per second (coulomb/second)
voltage × current = energy per second (joule/second = watt) = power

For DC, it is simply the power, but for sinusoidal AC, you need to multiply by the the phase factor, which is the cosine of the phase-difference angle between the voltage and current as a function of time, as for purely capacitive and inductive loads, there is no power delivered when averaged over time.

 

So you might think, but there's more to the story. The voltage regulation is done in the converter, but the power management control ECU tells it what voltage to produce. It calls for different voltages at different times, depending on various conditions including the 12 volt battery charge state (estimated at start-up), whether you are driving or parked, temperature, etc. Toyota hasn't published all the rules, but others have collected data on the output voltage changes under different conditions; you can find threads on it here.

... which is why for AC systems, there is this perplexing other unit, the VA (volt-ampere)—hey, isn't a volt-ampere just a watt? Well, yes, if the power factor is 1. But VA is just the raw product of volts and amps, not yet adjusted for the power factor, and then that times the power factor gives you watts.

Sometimes both matter. For example, I was able to use a purely-capacitive load one time when I needed to calibrate an inverter and I needed to draw a good amp or two from it, which would be 120 to 240 watts, but I was just running the inverter off a 50-watt bench supply. So I used the inverter to "power" a 40 µF motor-run capacitor, which drew 1.8 amps, therefore 216 VA, but zero actual watts.

The VA mattered inside the inverter though. It's around 90% efficient, so to supply 216 VA it needed to consume 240 VA, and the difference (24 VA) were real watts being used up in the inverter, which, on top of the 25 watts it just always uses when powered on, was just about exactly all the 50-watt bench supply I had it hooked up to could provide.

 

Ah, I found it. The IC-regulated voltage is varied around 14 V according to the battery temperature in order to extend the life of the 12-V battery (auxiliary battery). I should have thought about that.

(l) DC–DC Converter Control

(1) The DC–DC converter steps down the HV battery nominal voltage of DC 351.5 V to approximately DC 14 V in order to supply
electricity to the electrical components, as well as to recharge the auxiliary battery.

(2) In order to regulate the output voltage from the DC–DC converter, the hybrid vehicle control ECU transmits an output
voltage request signal to the DC–DC converter in response to auxiliary battery temperature sensor signals.

Yes, VA rating is very important. That's why many systems use capacitors to balance out inductive loads. You don't want a high VA; otherwise, the power company could come knocking at your door. Even though it doesn't show on your utility bill, high currents will strain the system, overheat the wires, and increase resistive losses in the wires and transmission lines, increasing the energy consumption indirectly.

 

As I said, Toyota hasn't published all of the rules they programmed into the power management control ECU to determine what voltage requests it sends to the converter. The aux battery temperature is one factor. Others have been seen in action and reported in other threads here.

Most of what I've seen has been Gen 3-related, rather than Prime. Gen 4 has a more elaborate "battery state sensor" assembly than earlier generations, so it's possible the charge voltage rules are different too.