Small Genset - Can it mate to shore power port?

[jssailem]

You guys talk about it as a "Plug and Play" arrangement. What about the Ground wire in the pig tail? Where does it connect to ground? And is having a Galvanic Isolator on the Green AC ground wire a factor?

 

[jviss]

I'm thinking of getting a small genset for emergencies.

I have often thought this, too. And, I usually have plenty of propane on board. Just make sure you have the right propane hose. A test run would make sense.

But lately I've been thinking that a "spare" LiFePo4 battery would be a much better option for emergencies. Maybe a 50Ah battery, left at 85% capacity. They have very low self-discharge rates, and are not degraded by being left in this condition. And, they can be discharged down to 10% or maybe even less with no damaging effect. No extra fuel to carry or consume. Clean energy, and instantly available.

Do you have a specific idea of what an emergency might be, or just a vague sense that you might find yourself with no stored electrical charge? Just curious. I have been thinking of this myself, and thought that if my problem is a shorted or otherwise faulty main bank, a generator is not going to help. I'd like to be able to make port with my emergency power, and deal with rectifying what caused the emergency once I'm on the hook.

 

[Bob J.]

You guys talk about it as a "Plug and Play" arrangement. What about the Ground wire in the pig tail? Where does it connect to ground? And is having a Galvanic Isolator on the Green AC ground wire a factor?

Interesting point. In the past most folks I know with a suitcase generator on boats or RV's put a jumper between ground & neutral on the pigtail. I believe it had something to do with the earlier Honda's tripping off. I had a jumper on my pigtail because that's what you were supposed to do??
Removed it last year when I was able to connect to earth power while stored on the hard. End of the season used the generator to extend range without the jumper. Go figure....

 

[jssailem]

Here are two posts from the past about the issue.

Earth Grounding Honda Generator

Just heard about this. Wiring the earth ground to the neutral leg of the 110v output on a Honda 2000 generator. Seems to eliminate false polarity indications when feeding power into house panel. If this is a good idea, why didn't honda provide for it?

forums.sailboatowners.com

And the definitive statement I like..

How to test inverter for shore power ELCI failure without ELCI present

Background: My boat has a Xantrex Freedom HF inverter/charger. It was professionally installed. Here is what happens: 1- At my marina when connected to shore: no problem. Shore electrical is many years old. 2- At other marinas with new pedestals (ELCI-style), shore breaker is tripped after a...

forums.sailboatowners.com

 

[Bob J.]

Yea that's right, the issue was reverse polarity. Amazing the stuff we forget...

 

[Head Sail]

I have no interest in the air conditioner. I just want to top off batteries if the solar panels don't keep up.

A start battery will top off your house batteries when you start your engine.

 

[dlochner]

The best solution is to prevent run down batteries. The money spent on a genes for only occasional use is better spent on a good battery and charging monitor like the Balmar SG 200. With a good monitor you won't be surprise that your batteries are run down.

 

[kloudie1]

Looks like an interesting little generator. Since it is propane powered, it can sit without fear of a fouled carburetor, and it will power your battery charger just fine. It probably should be stored in a plastic bag when not in use to keep the corrosion at bay. On some boats, it will turn on the "Reversed Polarity" light as some have stated. Some boats have a breaker that will trip if the reverse polarity light comes on. If it trips on reverse polarity, it seems like bonding the neutral and green will solve the problem with the floating ground. Consult an electrician if you aren't comfortable with doing that.. Looks like it is a good solution to your desire to have a way to charge batts .. I note it does not have the CO cutoff feature of the newest generation of generators but you'll want a good CO detector/alarm down below in any case..

 

[Hello Below]

I have no interest in the air conditioner. I just want to top off batteries if the solar panels don't keep up.

I see that the runtime spec for this charger at 25% load (175w) is 3 hours with a 1lb tank of propane. My question is how much propane will you need to have available to “top off” your batteries? What is the size and type of your batteries and what is the output of your battery charger?

 

[dlochner]

I see that the runtime spec for this charger at 25% load (175w) is 3 hours with a 1lb tank of propane. My question is how much propane will you need to have available to “top off” your batteries? What is the size and type of your batteries and what is the output of your battery charger?

The typical charge time bring a LA battery from 50% SOC to 100% SOC is about 5 to 6 hours. There are a couple of articles on MarineHowTo.com on charging.

 

[Tally Ho]

I think that the short answer is yes, you can use a small portable generator to run the battery charger, maybe even use a 110 appliance, etc.

Maybe the easiest way to connect the generator to the boats AC system is to use one of these adapters. I use one all winter when Tally Ho is on the hard over the winter so I can:
- keep batteries topped off
- run a space heater, shop vac, Kuerig, grinder, etc. I cannot run them all at once, but I have run them all.

https://www.amazon.com/gp/product/B01L2BLRAW/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

A short, heavy duty extension cord between the generator, and this plug should be fine for light duty.

Greg

 

[Hello Below]

I’m just trying to wrap my head around how much propane is needed to satisfy the OP’s “top off” requirement.
For lack of better data, let’s us my boat as an example.
Trojan T-125 plus GC batteries x 4 totalling 480Ah (@ a 20hr rate). To get from 50% to 100% SOC will require 240A to be replaced. To do that in 6 hours the charger must output 40A/hr not including any inefficiencies in the charger or battery charge efficiencies or power usage other than the charging of the batteries. Thus no fridge, no radio, no . . .
So the propane generator spec shows that it in conjunction with the boat’s charger would produce approx 13 amps/hr @25% load. And uses 1/3lb of propane to do that. We need 3 times that to satisfy our requirement, thus 75%. So using a straight line fuel consumption we would use 1 lb(of propane)/h for 6 hours for a total of 6 lb of propane to produce the needed 240amps. Seems a reasonable amount. Does the OP normally carry that amount dedicated to charge batteries when needed?
Unfortunately there are many bad assumptions in the above, such as:
- charger is not 100% efficient (more like 80%).
- fuel curves are not linear but . . . well curved. So at 75% load (40A o/p) I would expect more like 2 lbs per hour burn rate rather than 1 lb. Maybe 3lbs per hour
- during the 6 hours of charging other devices will be sharing the output of the charger (generator) with the batteries.
Of course, there is no need to get back to 100% SOC, 90% would be enough.

 

[dlochner]

I’m just trying to wrap my head around how much propane is needed to satisfy the OP’s “top off” requirement.
For lack of better data, let’s us my boat as an example.
Trojan T-125 plus GC batteries x 4 totalling 480Ah (@ a 20hr rate). To get from 50% to 100% SOC will require 240A to be replaced. To do that in 6 hours the charger must output 40A/hr not including any inefficiencies in the charger or battery charge efficiencies or power usage other than the charging of the batteries. Thus no fridge, no radio, no . . .
So the propane generator spec shows that it in conjunction with the boat’s charger would produce approx 13 amps/hr @25% load. And uses 1/3lb of propane to do that. We need 3 times that to satisfy our requirement, thus 75%. So using a straight line fuel consumption we would use 1 lb(of propane)/h for 6 hours for a total of 6 lb of propane to produce the needed 240amps. Seems a reasonable amount. Does the OP normally carry that amount dedicated to charge batteries when needed?
Unfortunately there are many bad assumptions in the above, such as:
- charger is not 100% efficient (more like 80%).
- fuel curves are not linear but . . . well curved. So at 75% load (40A o/p) I would expect more like 2 lbs per hour burn rate rather than 1 lb. Maybe 3lbs per hour
- during the 6 hours of charging other devices will be sharing the output of the charger (generator) with the batteries.
Of course, there is no need to get back to 100% SOC, 90% would be enough.

Charge curves are also not linear. The closer the battery gets to 100% SOC the more resistant it is to accepting a charge. As a rough estimate the battery will require 15 to 20% more energy to reach 100% than was taken out before the losses due to the charger itself. In this example it would be necessary to put back 275-290 ah to restore the battery to 100%. That’s before accounting for any losses due to the charger itself. This amounts to about 3,300 watt hours, a run time of about 5 hours at full output for the genset.

The numbers just don’t add up for this device, especially when the price of 1lb bottles of propane are considered. Right now they are running at $5-6 a bottle.

In the long run the money spent on this genset would be better spent on a good battery monitoring system and an externally regulated high out put alternator.

 

[jssailem]

For me it is similar to the question, Electric Power or Diesel auxiliary. For economics and power per pound of reliable energy on a sailboat, diesel pencils out financially better than tossing the installed system and repowering with Electric.

 

[Tally Ho]

The OP just wanted to know if he can plug a generator into his shore power port…

I don’t know if he cares about our opinion of whether or not he should

Greg

 

[Hello Below]

The OP just wanted to know if he can plug a generator into his shore power port…

I don’t know if he cares about our opinion of whether or not he should

Greg

Late Sunday afternoon, no football, baseball in spring training only, boat not ready for cruising and you want us to stick to the OP’s original question?

 

[Benny17441]

Yes, you can run a battery charger with a 1000 Watts inverter. Some generators like a Honda 2000 have a connector for direct 12V output, but I can tell you from experience that it takes an extremely long time to charge a battery that way. What people usually do is connect a pigtail adapter to the 30A shorepower inlet of the boat and utilize the inboard battery charger. Just be careful that if you are running other appliances simultaneously that you do not exceed the output capacity of the generator.

 

[jviss]

I didn't think he was planning on charging the house bank up from empty to 100% regularly with this thing, he said "for emergencies," which I took to mean a way of putting enough charge in to start the engine.

 

[Ken13559]

If you have decided to use a portable generator onboard, a Honda 2200 can run any appliance, power a 40 watt charger, and run a 12000btu air conditioner. Honda has become become the standard for portables. I am sure that you have already investigated the merits/ dangers of portable generator use on boats.

That's exactly what I carry onboard. Honda EU22i Genset mainly to run my Aircon when at anchor. Now having fitted a Micro-Air EasyStart to the 12000btu unit, I power Aircon and battery charger same time with Genset on Eco mode.

Ken Y

 

[Tally Ho]

Late Sunday afternoon, no football, baseball in spring training only, boat not ready for cruising and you want us to stick to the OP’s original question?

Sorry…what was I thinking

I was also uncharacteristically short with my note…sorry.

But hey, aren’t you a NCAA basketball fan? Or is your bracket so broken you have given up watching ? (you are not alone!)

Greg