If you did not have 3 children, I would try to talk you into giving up the washing machine. A lot of the introductory “fun” of getting to a new village/town is looking for the resident who does laundry and sitting around, talking with and meeting others in doing so. And if you plan your route well, your clothes will be bathing suits and t shirts.
I would continue to discourage as, in the repertoire of cruising skipper’s headaches, washing machines are not at the top (generators take that prize), but they are not at the bottom either. And support, once you leave home territory, is hard to come by.
That said, three children….
First, A suggestion: wash only in cold water. Heating water is a huge power-sink and the clothes will get clean, but may not be quite as “bright”. It was a cruising mantra when I started out in Central America to not have white underwear and white shirts etc. as they would come back clean, but a bit dingy as the small villages often used recycled water and the water was certainly not heated.
Some invertors have a hard time with fluctuating power demands. When I run my microwave, with its on-off cycles, I need to have an AC night-light (very low power demand, but enough to keep the invertor active) going to keep the invertor from going to sleep. In this way, when the microwave cycles, the invertor stays “on line” and power is available when the microwave calls for it again.
I would be surprised if your invertor cabling was too small a gauge: it is too easy to determine (4.5 kw at 24v for ?? meters = such and such gauge for ex.). It is also easy to check. Now the connections may need cleaning, but your issues sound different from voltage drop.
It sounds like you are depending on your invertor far more than most (frig/freezer, toaster, microwave, washing machine), especially when about to set off on a cn. I would urge you to think about redundancy and back-ups.
It is great to be using power generators such as solar and wind, but I would suggest that diesel generators will have a place well into the 21st century.
And, yes, you do not wish to hammer the batteries into a 18-20v level (24v bank). Gels are pretty robust and accommodating, but they will sulfate and have their life shortened. I would in no way describe them as “old tech” there still remains no proven and safe alternative to the AGMs, Gels, and flooded batteries which have powered us for so long. Lithium batteries have come a long way, but their use is still restricted to those “early adapters” and field reports, much positive, are still rolling in. I would very much discourage, at present, a couple with 3 small children from setting off on a cn with lithium.
The gel cell battery bank should be able to do the work demanded with out any trouble: the crunch will be how long the high load demand is needed. That is one of the benefits of a generator: lots of power for the period you need it. Solar and wind power cover this by big battery banks or the battery banks get hammered when large and sustained demands occur.
Enough for now: Come back with questions/comments etc.
My best, Dick Stevenson, s/v Alchemy
Another random thought: I have seen solar panels on biminis and very seldom have I felt that the job was well done. Two things stand out. One is that to tolerate the loads of weight up high on a bimini, the bimini support structure must be very well engineered and robust (think bashing to wind in a swell and waves for a few days at 15-20 degrees of heel and how that structure will manage. Second is that the bimini and solar panels must be fairly easily field removable to prepare for storms at sea or at anchor.