Inverter Size and Possible Transfer Switch

[rslifkin]

Originally Posted by mitiempo

With a good inverter/charger there is no reason to have a stand alone charger, and if it is a legacy install, turn off the breaker to it. Keep it for emergency only.

Does remind me of the fellow who used his inverter to power his battery charger thinking he had perpetual power though,

That's basically what I did when I put in my inverter/charger. I tripped the breaker between the existing 3 bank charger and the house bank, so it can be reconnected in an emergency, but normally it just charges the 2 engine start batteries.

[mvweebles]

Originally Posted by mitiempo

With a good inverter/charger there is no reason to have a stand alone charger, and if it is a legacy install, turn off the breaker to it. Keep it for emergency only.

Does remind me of the fellow who used his inverter to power his battery charger thinking he had perpetual power though,

Agreed, but the OP specifically asked about a standalone inverter with transfer switch. There are some very simple ways to add limited inverter functionality. But the moment a x-fer switch to emulate the shore-power use-case, the complexity goes up quite a bit.

Re: inverter/charger power loop. I have a conversion camper van with a power-station. RVs frequently have all-in-one power stations that include AC circuits, DC circuits, and a battery charger (45-amp in my case). Most people who add an inverter just power a couple outlets with the inverter. In my case, I wanted to power the entire AC panel. There is no practical way to isolate the charger, so it's on a separate breaker that is normally off. I have occasionally forgotten and had it turned-on with the inverter on. Far from a perpetual energy machine - energy to convert/de-convert energy wasted about 3-amps continuous which would likely increase as the batteries decline and charger increases output. I originally said it was not dangerous, but in all candor, I am not sure what would happen when battery voltage drops very low - not sure the charger has a low-voltage cut-out as this is not a normal scenario.

Good luck - Peter

[mitiempo]

Originally Posted by mvweebles

Agreed, but the OP specifically asked about a standalone inverter with transfer switch. There are some very simple ways to add limited inverter functionality. But the moment a x-fer switch to emulate the shore-power use-case, the complexity goes up quite a bit.

Re: inverter/charger power loop. I have a conversion camper van with a power-station. RVs frequently have all-in-one power stations that include AC circuits, DC circuits, and a battery charger (45-amp in my case). Most people who add an inverter just power a couple outlets with the inverter. In my case, I wanted to power the entire AC panel. There is no practical way to isolate the charger, so it's on a separate breaker that is normally off. I have occasionally forgotten and had it turned-on with the inverter on. Far from a perpetual energy machine - energy to convert/de-convert energy wasted about 3-amps continuous which would likely increase as the batteries decline and charger increases output. I originally said it was not dangerous, but in all candor, I am not sure what would happen when battery voltage drops very low - not sure the charger has a low-voltage cut-out as this is not a normal scenario.

Good luck - Peter

The charger would not have a low voltage cutout - it will be charging. The inverter will have a low voltage cutout as any I have seen do.

RV manufacturers could learn a bit from the marine industry as their all in one power stations leave a lot to be desired.

[mvweebles]

Originally Posted by mitiempo

The charger would not have a low voltage cutout - it will be charging. The inverter will have a low voltage cutout as any I have seen do.

RV manufacturers could learn a bit from the marine industry as their all in one power stations leave a lot to be desired.

Agreed. But the cost for marine-quality/Blue Sea components is 5x comparable RV quality. As more RVs add solar and hi-output alternators to run AC and such, Blue Sea systems are becoming common. The old-school RV power stations get the job done and are very reasonably priced.

Peter

[AKA-None]

Originally Posted by s/v Jedi

Exactly, the microwave will run, just a little rougher (you can actually hear that the power isn’t clean) and the power is reduced. This is easy to see by comparing the time it takes to bring a cup of water to a boil on inverter vs shore power or genset.



I remember in Panama, the shore power was very dirty (distorted sine wave) and the A/C made a lot of noise. When shore power went out and we run on genset, the A/C went quiet with the cleaner power (good inverter is cleaner than a genset).

If your genset has dirty power (spikes&dropouts) then I’d check your brushes

A generator doesn’t produce non sine wave power if the brushes and commutator are good. It’s inherent in the physics of a coil moving through a magnetic field

The frequency is related to how often the coils move through the magnetic field which is why a generator runs at a fixed speed

[goboatingnow]

Easy enough to wire a contactor powered by the shore power feed only to pull in to connect in the battery charger , relying on a manual switch , you will forget !!

[sailingharry]

Originally Posted by AKA-None

If your genset has dirty power (spikes&dropouts) then I’d check your brushes

A generator doesn’t produce non sine wave power if the brushes and commutator are good. It’s inherent in the physics of a coil moving through a magnetic field

The frequency is related to how often the coils move through the magnetic field which is why a generator runs at a fixed speed

I think you read Jedi's post backwards. It was shore power that was dirty, and the generator that was clean.

[botanybay]

Originally Posted by mvweebles

Presumably, the standalone charger turns on when boat is plugged into shore power. If, when shore power is removed the inverter takes over (the transfer switch), inverter will be powering the battery charger which charges the batteries that feed the inverter. An energy loop. There are workarounds (remember to manually turn off charger being one), but if you want auto transfer, a combined charger/inverter is the easiest and simplest.

Peter

The easy solution is that the multi plus has two outputs. One is when inverting or on shore power/generator the other is only active when shore power or generator providing power. This second output immediately turns off when the shore power/generator goes away

[AKA-None]

Originally Posted by sailingharry

I think you read Jedi's post backwards. It was shore power that was dirty, and the generator that was clean.

Oppps sorry
But the above applies if your generator is supplying dirty power

My bad