Inverter inefficiencies

[Thedude]

Has anyone else tracked how much power is drawn from the HV battery compared to what is actually powered when using the onboard 120v inverter? I have used my truck several times to power my trailer but never tracked the usage of power between what the truck shows and what is used by the trailer until today.

I have a Victron shunt on the trailer so I know exactly how much 12v power is being drawn from or input to the battery and have previously measured and recorded the draw for all the 12v systems in the trailer. This evening I plugged into the truck for six hours using 0.8kwh to top off the trailer lithium batteries and 1.2kwh to power my Starlink, TV, chrome cast and some lights for a total 2kwh of 12v draw. The fridge is spec’d at 2.5amps/120vac which accounts for somewhere around another 1.8kwh of energy.

The truck shows a usage of 6kwh for a total energy lost to conversions of 2.2kwh or a 37% loss. Half of this energy was converted from DC to AC and back to DC which definitely doesn’t help. Truck
started at 49%/143mi and ended at 44%/128mi.

Sponsored

 

[Zoidz]

As you may know, inverter efficiency specs have no standards regarding measurement methods, so the manufacturer is free to cherry pick. For example, most inverters are most efficient when close to fully loaded, so the manufacturer will quote that - say 93%. But run it at a lower load and the efficiency drops to maybe 80% or less. As you point out, your dual conversion potentially doubles the losses. Two stacked inverters not running at optimum load could easily be running at 80% each, for total loss of 40%.

I also suspect that Rivian's built in inverter was cost sensitive and therefore may not be optimized for efficiency.

https://marinehowto.com/a-look-at-inverter-inefficiencies/

 

[Dark-Fx]

I'm planning on getting better access to mine once the weather warms up a bit. I'm fairly certain it's under the passenger seat in the front. Will be doing some measurements then.

 

[MReda]

On a much older software version, I recorded 2% battery SOC loss in a 24 hour period, and then turned the outlets on with no load, and recorded around 8% in the next 24 hour period. I can't remember the version when I did it, but it would have been late spring or early summer last year.

Sponsored