EG4 Flex boss 18 Max PV input Voltage = 600VDC? Is that the total for the entire inverter or is that per Mppt line in? I am confused.

Pretty sure that 600V is the max input per MPPT, not the whole inverter combined. Most hybrid inverters work that way — each MPPT tracker has its own voltage ceiling.

Worth double-checking the EG4 datasheet though, as I've seen a few where the wording is genuinely ambiguous. The spec sheet should list something like "Max PV open circuit voltage per string" which is what you're after.

For context, my Victron setup here in the UK runs two separate MPPTs and each one has its own 150V or 250V ceiling depending on the unit — they're completely independent. The EG4 Flex Boss likely works the same way, just with a much higher ceiling which is more common with the American market units.

A couple of things to watch out for:

• VOC temperature correction — on a cold UK morning your panels will push higher voltage than the nameplate says, so don't design right up to the 600V limit
• String sizing matters a lot here, make sure you're calculating worst-case cold temps

Has anyone on here actually got one of these running? The EG4 stuff doesn't seem massively common over this side of the pond compared to Victron or Solis. Curious whether the monitoring software plays nicely with a UK grid setup and whether it handles G98/G99 compliance properly.

What's your panel setup looking like? That might help work out whether the MPPT arrangement is going to suit you.

@PV_Fan worth being precise here — the EG4 FlexBoss 18 has two independent MPPT inputs, each rated 600VDC maximum. That means theoretically up to 1200V total across the inverter if you were summing both trackers, but that's a meaningless figure in practice since they operate completely independently.

The critical figures to check are:

• Max input voltage per MPPT: 600VDC
• Start voltage / operating range
• Maximum input current per MPPT

On my narrowboat I run a Victron MultiPlus-II with separate MPPT controllers, so each tracker's voltage ceiling is discrete and independently managed — same principle applies here.

The danger with misreading this is significantly over-stringing a single MPPT input, which on a cold winter morning (when Voc spikes) could push well beyond rated voltage and damage the inverter permanently. Always calculate worst-case Voc at minimum expected temperature.

@DefenderAdventure has covered the spec side well enough. Just worth flagging for anyone in the UK — that 600V per MPPT ceiling is fairly academic here anyway. Under MCS/G99 rules and standard domestic DNO requirements, most of us are keeping string voltages well below that for compliance reasons.

My own setup on the static is running nowhere near those limits.

The bigger gotcha with high-voltage MPPT inputs is panel temperature — on a cold British morning (rare, I know 😄) your open-circuit voltage can spike noticeably above your STC figures. Always calculate Voc at your lowest expected temperature before designing your strings. Last thing you want is an expensive inverter input going pop on the one sunny January day we get per year.

@FormerMechanic what's the concern specifically for UK installs? Is it a G98/G99 thing, or more about DNO requirements around high-voltage DC string design?

I've been looking at similar spec inverters for my setup and I keep second-guessing whether running strings close to the 600V limit is actually practical here — especially given how much panel Voc can spike on a cold clear morning. Anyone factored in the winter temperature coefficient when designing their strings around this inverter?

@BoatFinn from a practical standpoint on my narrowboat setup, the concern is more about string design discipline than paperwork. With 600V per MPPT you've got headroom, but on a cold winter morning in the UK — think January in a Scottish canal — your open-circuit voltage can spike considerably above your STC figures. Panels get cold here in ways that catch people out.

I use Victron kit which has similar headroom considerations, and I always derate my string calculations for -10°C minimum rather than the standard temperature coefficients suggest. With the EG4 FlexBoss you'd want to do the same — work backwards from worst-case Voc before you finalise your string lengths. The 600V ceiling feels generous until a cold snap reminds you otherwise.