Thoughts on inverters

[ranger58sb]

TT what is your opinion on electric 110 stoves, invert or not.

Looking to see if cooking from inverter, other than battery capacity is a concern.

We have an electric resistance cooktop, so we didn't set up our inverter to power that. Had it been an induction cooktop, we might have. That'd probably be pushing capacity of our available batteries, though.

As it is, we can use the microwave/convection/air fryer unit, and/or an Instant Pot or Crockpot on the inverter. Haven't taxed the system yet, though, so dunno how long batteries would last. (If I had a nifty space to add batteries, I'd consider that, but I don't see that space easily... and I've got other fish to fry in the meantime...)

-Chris

 

[Jeff F]

Get an inverter/charger, not just an inverter. When wired correctly, the inverter/charger will automatically detect the presence of shore or gen power, switch the loads over to that power source, and start charging the batteries. It's super convenient, and transparently hands loads off between inverter and shore power.

I didn't quite understand the wisdom of this until recently when I replaced my old inverter with a Victron Multiplex.

For me the power sharing feature is really useful. My main panel is 30a. I have a 3kw hydronic heater wired directly to the service and all other loads including the stove going through the inverter, with the inverter set to draw a max of 5.5a from the 30a service. That eliminates the need to manually manage loads. When the house load exceeds 5.5a the inverter supplies the excess from batteries, and when less than 5.5a it charges with the available power.

I haven't had any need for this, but it also has a 'ramp up' feature which buffers sudden loads when using a generator. My understanding is that this negates the need for soft start type devices.

 

[Phyrcooler]

Like the ABYC LFP thread TT started, this has developed into an informative thread. A comment I might add for the long distance cruisers:

Once you've got your wiring, switches, battery bank and type, inverter/charger, charging systems, genset, solar panels and monitoring devices all to a pro's liking -- buy an identical inverter and store it onboard.

Why?
- Inverters are cheap,
- not easily available in far off ports or anchorages,
- prone to failure,
- of limited lifespan,
- abused and
- the lifeblood of most up to date electrical systems.

Redundancy is oft talked about for parts such as bolt on engine equipment, plumbing, toilet etc. Likewise, backup (work around) parts and systems should be the same for mission critical electrical gear. If your cruising grounds are near a well-stocked port or two, a tow boat service or you're a dock sitter redundancy becomes of lesser importance.

And they DO fail….

<snip>
Install a bypass switch that will pass shore or generator power around the inverter and power your loads. It's an important backup in case the inverter has issues, plus a convenient and safe way to have power onboard while working on the inverter.


Rather than picking a few things that you want to be inverter powered, pick the few things that you absolutely do NOT want to be inverter powered. This list probably includes nothing more than 1) electric hot water heater, 2) HVAC, 3) shore charger(s). I would put EVERYTHING else on the inverter. Now this will be influenced by how your boat is wired, and you will need to find a happy median. For example, it's common for HVAC to be on a separate shore power circuit, so that's easy to keep off the inverter. A hot water heater and shore chargers may be more difficult. In some cases you may want to leave the hot water heater on the inverter, but remember to turn it off when not on shore or gen power.


Get an inverter/charger, not just an inverter. When wired correctly, the inverter/charger will automatically detect the presence of shore or gen power, switch the loads over to that power source, and start charging the batteries. It's super convenient, and transparently hands loads off between inverter and shore power.


Once you have an inverter, you will need to keep an eye on your batteries because you will be using them more. And as you use more and more AC power through the inverter, you are likely going to want to grow you battery bank size, increase charging capability, etc.

A lot of great comments and advice here. I am not an expert, but will share a couple of my thoughts, based on my own experience. I had a Magnum inverter/charger on my last boat. And had a multitude of issues. The suggestion of a bypass switch is excellent advice. Nothing like showing up late one Friday night for a long holiday weekend to discover everything shut down due to a glitch. I not only had flat dead batteries, but because everything on the 120v side ran THROUGH the now failed inverter, even though on shore power, I had zero working outlets (or anything else!). I had my electrician install a big rotary bypass switch after that. And swore I’d never have a combo unit again! :lol: I’ve since modified my stance as the pain of dealing with that unit has faded. I’m sure I’ll have to revisit this issue someday when I return to trawler life. But if anything, I’m now a dedicated KISS proponent. The simpler the systems the better. I’d probably still keep them separate.

For now, my current vessel (sail), has a standalone charger. I’ve also not run any existing circuits through the inverter, but have kept it separate. It powers a couple dedicated outlets - mostly used for visitors 120v computer chargers. But even that use is seldom. Between iPads/MacBook/iPhones, everything can be charged off the 12v side. While I like the speed and convenience of a microwave and Keurig at dockside, they are not essential. The stove and French press work great at anchor. The less stuff to break and curse, the better. I prefer to deal with the low voltage side. But everyone’s tolerance for frustration and need for conveniences is different.

 

[mvweebles]

Suppose y'all are talking about something like this as a "bypass switch?" Or are you just talking about a jumper across the in/out 120VAC of the inverter?

Peter

 

[SteveK]

On the Bayliner I had three 30 amp inlets with three position switches normal line in, off, connect line 1.
The #3 line in was disconnected when Line 1 went to smartplug so the terminals were sitting empty.
I took the inverter load hot/neutral to line 3 input. Now the switch is Inverter, Off, to Line 1. The inverter feed line is also from what was line 2 inlet so inverter can be isolated at both input and output.

 

[Phyrcooler]

Suppose y'all are talking about something like this as a "bypass switch?" Or are you just talking about a jumper across the in/out 120VAC of the inverter?

Peter View attachment 134583

No… a rotary switch similar to this:

Except mine was labeled “shore - off - inverter”

 

[twistedtree]

Suppose y'all are talking about something like this as a "bypass switch?" Or are you just talking about a jumper across the in/out 120VAC of the inverter?

Peter View attachment 134583

That looks like an set of interlocked breakers to select the power input source for the inverter.


A bypass switch would disconnect the inverter inputs and outputs and bridge them directly to each other. So when bypassed, the inverter is completely isolated from AC power sources and loads, and the loads normally powered by the inverter are directly powered by what would otherwise be the input to the inverter. It can be done with rotary switches, changeover switches, or interlocked breakers similar to your input breakers.

 

[sunchaser]

A bypass switch would disconnect the inverter inputs and outputs and bridge them directly to each other. So when bypassed, the inverter is completely isolated from AC power sources and loads, and the loads normally powered by the inverter are directly powered by what would otherwise be the input to the inverter. It can be done with rotary switches, changeover switches, or interlocked breakers similar to your input breakers.

Our bypass is a Blue Seas rotary switch similar to phyrcooler's picture. Magnum inverters, realizing the need for a potential bypass, have external wiring to facilitate a manual bypass. My two 2812s are equipped this way.

 

[bnoft]

It's been a few years and I don't remember the details (model, size), we installed a Magnum pure sine inverter/charger on our '91 42' GB. This replaced the 2500 Xantrex we had installed 3 years previously. The Xantrex was in the ER, the location was part of the reason for its failure according to the marine electrician who installed the Magnum. I fabricated a shelf in the forward hanging locker, running the wiring thru the bulkhead to the batteries in the ER, maybe 4-5' wire run which matched the wire run of the old Xantrex. The lower temperature in the cabin would provide a better environment for the Magnum. We had about 7 years of quite satisfactory service from the Magnum, as far as I know it is still in the boat which we sold in 2018.
The boat we bought in '18 had a dead inverter in it and I decided not to replace it. This boat would require more generator run time anyway and I felt the cost of the inverter would pay for the additional diesel we would burn.

 

[Slowmo]

Our inverter charger is probably 20 years old and, knock on wood, still working fine. It is a 2500W Xantrax Heart. The interface monitors power in/out which is nice feature. The charger aspect is nice, it is a 150A charger, which is great but also draws a lot of current from shore power. When I first dock I tend to leave the hot water heater off for an hour or so until the the charge rated drops off so that I don't overload the shore power (generally most marinas in our area are 30A).