New Bidirectional EVSE

[Rpgonzalez]

when the 'buffer battery' is depleted (or sagging from heavy load) to around 12.0v, and the MME dcdc is trying to maintain 14.4v, the current I measured in jumpers peaked at 40amps breifly, but settled to about 30a and dropped as the voltage came up in the buffer battery.

I didn't need to put it thru a charge controller... the current is self limiting given the voltage difference between MME system and buffer battery.

Interesting. So what happens if you sustain the heavy load and the buffer battery keeps sagging... wont you start drawing more current from the mach-e connection points?

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[dtbaker61]

Interesting. So what happens if you sustain the heavy load and the buffer battery keeps sagging... wont you start drawing more current from the mach-e connection points?

I'd guess 'yes'
... but this whole solution with a 1500watt inverter is based on the understanding that is the PEAK output the dcdc can keep up with thru the LVB connection points.

so yes, if you intend to run 1500 watt loads 'continuously', the cables from 12v connection points to inverter should be sized to withstand 160a in free air.... probably 2/0

If you anticipate usual loads around 100-200 watts for a laptop and a few lights, or a cordless tool charger, then the draw will be less than 40amps, easily handled by 10awg, or certainly safer with 4awg or 2awg to handle occasional peak loads.

If I were going to permanently hardwire a 1500w inverter in the Frunk, I'd probably use 2AWG and put a 150amp circuit breaker on the positive lead.

With the alternative 'portable' unit with it's own buffer battery, the MME is really just a 'fast charger' and self limits to about 40amps and then drops as battery is charged.