Inverter Sizing A big one or multiple smaller ones?
I did it the other way around. I opened my checkbook and bought the biggest inverter I could afford then sized my load accordingly.
I used this approach on my old boat and suspect it may apply to most. I bought my first inverter back in 1991. Back then the bigest and best seemed to be a 2000W Trace. Unfortunately it didn't fit my budget. I bought a 1500W Vigel. It served my needs (Microwave, toaster, coffee maker, fans, TV etc) well until early in the 2000's when it caught fire. It was only running a fan at the time. I woke up thinking I was hearing an electrical arcing sound. I was. Fortunately I was on the boat and no harm was done except the inverter. But it did get my attention. I replaced it with a much cheaper 1750W. That still works, but I am a bit hesitant to install it in the trawler due it's age The burning inverter is still a clear memory. I need a bit more capacity and I want an inverter/charger to take better advantage of Genset time and shore power than I get with my 40 amp charger. I am wondering about the use of a single large inverter/charger vs. using two or three smaller units.
Here is my logic for multiple units, I welcome comments and opinions, my mind is not made up yet.
My AC needs are too light to run the 7.7KW genset unless the Air Conditioners, electric stove and/or hot water heater are being used. And even then I've got excess power that could be used to charge the batteries faster than the 40A. can. My 840 AH battery capacity could utilyze a 100A to 150A charger. But I need the ability to turn down the charge rate if I am stuck with only a single 30Amp shorepower connection.
My AC inverter loads would be refrigerator, currently running nicely off a cheap 1000W inveter. Occasional use of the microwave, coffee maker, vacumn cleaner, fans, a 1HP 120V AC washdown pump. and the Admiral's CPAP machine.
Inverters seem to be more efficient when running near their capacity as compared to running a very light load. So my reasoning is to continue to run the fridge off a dedicated inverter with no charger just slightly bigger than the minimum. The admiral's CPAP can run off a portable unit plugged into a 12Vdc outlet. It pulls very little juice. The other stuff could run (not at the same time) off a 1500W to 2000W inverter/charger. To run with a single inverter, I think I would need a 2500W to 3000W. I think I can go the multiple inveter route cheaper. This is because the fridge doesn't seem to care if it's fed a modified sine wave. The 12V supply wires can be significantly lighter. And I like the added redundancy if one of the beasts misbehaves. The idea of a 3000W inverter running all th time seems wastefull of battery energy.
Your thoughts??
Craig