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Old 07-12-2015, 08:42 PM   #1
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Portable Generators

Hi Everyone

Was hoping to find out your thoughts and clarify my thinking also.

I have researched other posts and I know a few of you use small portable gensets either to save fuel or because you do not have a large gen or to save your big gen from not loading up fully.

My situation is this.

I have two large 20kw Northern Lights gensets in separate engine rooms. Both run perfectly well. I also have a 400amp hour 24 volt inerter bank which powers everything except hot water system and Air Con. We never use Air Con when away from dock. I also have a 12 volt system for lights (LED) and head pumps. Not much demand on these batteries.

The inverter bank will last 24 hours but that draws it down to 50%. It powers a very efficient domestic fridge a separate chest freezer, the mains water pressure and TV's, sound system. I have the inverter running from the moment we leave the dock as I have the PORT motor charging this bank via a 100amp alternator.

After sitting at anchor over night, we need to recharge the inverter bank via a 30amp 24 volt Victron Charger. SO this charger is powered by the big genset. At the same time I switch all electrical loads to Genset and leave this on for about 6 hours for the day.

When on the dock, my boat and the loads (not including air con) are run on one 15amp power cord and dock supply.

So my question is can I just get a 2500 watt portable genset to charge the inverter bank, 12 volt bank and run the basic fridge and freezer loads instead of needing the big generator.

The big genset will use about 5 litres an hour. over 6 hours this is 30 + litres. A portable genset will use about 6 litres.

Seems like the way to go for me.

Can you tell me your thoughts and also if you use a portable genset, where do you put it and do you just plug your shore power cord into it.

Thanks for your comments.

Bo
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Old 07-12-2015, 09:19 PM   #2
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First, I think a bigger charger is in order. A 30 amp charger is just too small for an inverter bank. It seems like an 80 to 100 amp charger would cut your generator time to 2 hours or less each day.

Since your generator capacity is too high, you could add a third smaller generator. It would have to be large enough to carry the extra load of the charger. You didn't say what size and type the battery bank is. If AGM you can charge at about 25% of rated capacity. It will take a little calculating to figure the size of the charger and generator needed.
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Old 07-12-2015, 10:31 PM   #3
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My batteries are brand new (last week) Gels. Each are 220 amp hours.

I know the charger is a bit small, but that is not going to change. I am right on the edge according to Victron. 50amp would be better, but not going to happen.

I estimate I can run most major vital loads with 2000 watts of power.
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Old 07-12-2015, 11:59 PM   #4
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I don't have any 240v AC on board when out, but would have thought if you have 2 x 20kw diesel gennys already, why complicate things by adding in a third and petrol powered genny, which you would have to place outside somewhere for safety, and which would probably make more outside noise than your permanently installed, and presumably sound-proofed diesel gennys. After all, diesel is still probably the cheapest part of our boating, even here in Aus, and the cost of a 2500 kw portable would pay for a heck of a lot of diesel. Just sayin'.
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Old 07-13-2015, 05:35 AM   #5
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"So my question is can I just get a 2500 watt portable genset to charge the inverter bank, 12 volt bank and run the basic fridge and freezer loads instead of needing the big generator."

Your 20KW is able to operate the charger at full output , a smaller std diesel might not , except for a few min after start up. Their sine wave output does not have the power to produce the energy a charger needs (under the sine).

Weather a modern gas unit that uses its inverter to create electric has the required power is a great question. I would simply borrow a unit and see if it can recharge the house bank in the time a 20KW can.

For my money I think rolling your own , a simple gas or diesel hooked to a truck 135A hot rated alt would be fine for charging , as well as operating much of the house current items.

I doubt your home grown unit would be anywhere as quiet as the Honda., although it too could operate at slow speeds when full output is not required.
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Old 07-13-2015, 07:32 AM   #6
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We use a Honda 2000 and have a 40amp battery charger that works just fine with the Honda with lots of power to spare. If I use the battery charger I switch the fridge over to 120 as well since the genny is running anyway. Obviously there are some limitations of what combination of things you can run at the same time but it does not take long to figure it out. Microwave and water heater, no. Battery charger and water heater, yes. The biggest fly in the onitment is the micro, it wants to be run alone. Most other combinations work fine.

The Honda for 6 hours will use about 3 liters.
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Old 07-13-2015, 09:00 AM   #7
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Sell one of the 20kW units and install a smaller say 5kW. If this imbalances boat, add or move batteries to make up for removed weight.
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Old 07-13-2015, 09:12 AM   #8
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Sell one of the 20kW units and install a smaller say 5kW. If this imbalances boat, add or move batteries to make up for removed weight.
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Old 07-13-2015, 10:03 AM   #9
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I would add two more batteries to your 24 volt system and put a 100 amp smart charger. In this way you would have longer quiet time on inverter, charge with the already installed 20 kw generator with half the current fuel burn. This would be the best way to go. Without the gas household genny air cooled noise and CO risk to worry about. You also would not have to handle a 2500 watt gas portable generator. If you hadn't noticed they weigh a more than the Honda 2000 by a bunch.
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Old 07-13-2015, 10:06 AM   #10
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Sell one of the 20kW units and install a smaller say 5kW. If this imbalances boat, add or move batteries to make up for removed weight.
If the OP isn't willing to upgrade a battery charger, then I'm guessing he'd be much less interested in replacing the generator. Heck, just the thought of trying to remove a 1,000+ pound object from deep in the bowels of a boat makes we want to run in the other direction.
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Old 07-13-2015, 10:14 AM   #11
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If the OP isn't willing to upgrade a battery charger, then I'm guessing he'd be much less interested in replacing the generator. Heck, just the thought of trying to remove a 1,000+ pound object from deep in the bowels of a boat makes we want to run in the other direction.
Some boats are a nightmare to remove a gennie, others are pretty easy. If machine is in good shape and not too elderly, it could be worth what a new little one costs.

But we don't know the boat. Could be in the nightmare category.

20kW is a big machine to run for OP's duty cycle with minimal AC use. And to have two of them.
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Old 07-13-2015, 10:42 AM   #12
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Sell one of the 20s and put in an 8kw.
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Old 07-13-2015, 11:37 AM   #13
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Talking

Oh Oh portable Gennies......

Oh this isn't the Sea Ray forum, so you are safe....
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Old 07-13-2015, 11:48 AM   #14
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Bohans,

One piece of info that would be handy is to know how much you anchor out. Do you anchor 3 days a month, one week a month, or most of the time? Also long range plans for the boat such as keeping her for life or plan on trading in a year or two. I don't think good advise can be given without taking those things into consideration.

My $ .02
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Old 07-13-2015, 04:56 PM   #15
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Thanks everyone for the replies. I do appreciate your thoughts.

I was really just looking to reduce my fuel costs for the genset which is underutilized. And thought the small gen was a simple solution.

Removing a 20kw genset is not an option. The expense is not worth it.

A larger battery charger up to 100amp whilst initially I thought would not happen, may be the best option. Thank you for that suggestion. It makes sense that the best way to load the genset and reduce run time would be to upgrade the charger size. I shall start looking for one and maybe sell the Victron to fund the cost.

Whilst I am not trying to be boating on a bare budget, I also do not want to be throwing money into redundancies and additional items all the time.

It was also a good question to ask of my long term plans for the boat. This boat is potentially my last as it is 70ft long and big enough for the whole family of which we live aboard. So it is a keeper for the long term future. This makes sense then to deal with the marginal charger at some near stage in the future.

Take care everyone and thanks again.

Bo
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Old 07-13-2015, 07:36 PM   #16
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With a couple of more batteries

With a couple of more batteries to carry your inverter load you will probably increase battery life and of course the 100 or 120 charger load will run longer and harder. should save fuel and the generator. I have 120 amp charger on my boat maintaining 4 8D 12 volt batteries. Takes about 2.5 hrs to bring them back to float charge.
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Old 07-13-2015, 08:23 PM   #17
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What about this option...

What if I put an additional 24 volt 100amp alternator on the Genset. It is big enough genset to turn this and would provide a rapid charging of the inverter bank.

Has anyone upped the size of their genset alt in this way and if so how.

I think the northern lights gens can have an additional pto on the front end.

Is it possible to use the existing wiring from the main engine's 24 volt alternator to supply current to inverter bank, as this would mean not having to run all new wires. These two motors are right next to each other in the same engine room.

Thanks again...

bo
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Old 07-13-2015, 09:35 PM   #18
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Here's an affordable, reliable 12V 90A charger that will improve your charging at minimal cost.

IOTA DLS-90 AC/DC Power Converter and Battery Charger

If you need a 24V charger, Iota makes them up to 40A. The IQ4 feature provides the smart charging capability.

I run a DLS-55/IQ4 55A charger on my Honda 2000. That's the max the Honda 2000 (1600W continuous) can handle at max charger load of 13A. A DLS-90 can be powered by a Honda 3000 (2500W continuous) but I'd also vote for sticking with your current, under-utilized diesel gensets. Hondas are much noisier than built-in marine gensets and while you might carry gasoline now for a dinghy OB, it takes a lot more gasoline for the Honda gens if you'll be out for a week or more.
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Old 07-13-2015, 10:20 PM   #19
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What about throwing 200 or 300 watts of solar up? I have a 15kw, and instead of adding a smaller diesel or gas I am going to put 200 watts of solar on.
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Old 07-14-2015, 05:51 AM   #20
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What about this option...

What if I put an additional 24 volt 100amp alternator on the Genset. It is big enough genset to turn this and would provide a rapid charging of the inverter bank.

Has anyone upped the size of their genset alt in this way and if so how.

I think the northern lights gens can have an additional pto on the front end.

Is it possible to use the existing wiring from the main engine's 24 volt alternator to supply current to inverter bank, as this would mean not having to run all new wires. These two motors are right next to each other in the same engine room.

Thanks again...

bo
You can certainly add a second alternator to your generator or replace the existing one with a higher output, but you will find that if you're not doing the fabrication work yourself, the cost will far exceed a new 110ac battery charger. My vote would be to double the battery size, get the biggest 110ac charger the bank can handle, and make sure the engine alternator can recharge the bank in a reasonable days' s cruise. In my refit project, the goal was to have 2 to 3 days worth of battery and be able to recharge completely on the next cruise day avoiding having to run the generator solely to recharge batteries. Obviously any use of the generator such as ac or cooking, would also help recharge the battery bank.

Ted
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