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Old 02-19-2019, 04:10 PM   #1
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Generator, replace or not

My northern lights 5kw has died, I like to hear thoughts on replacement vs using the space for battery bank and sizable inverter? If I go the battery option where can I find information on what to buy and install?
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Old 02-19-2019, 04:24 PM   #2
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Depends how is your boat set up? I need my genny to run the boat. A/C, electric stove, HWH etc.
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Old 02-19-2019, 04:35 PM   #3
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Think about how you will keep the enlarged battery bank fed. Especially if staying in one place multiple days,meaning no alternator input. And calculate the loads you need to service, to see how much input you need.

A combination of a large solar array and wind generator to feed the batts may work. All that battery, plus a solar panel set up,and wind generator,will involve expense,so you need to do a cost comparison, new set up vs generator repair/replacement.

Personally, I`d renew the generator. I also have some useful solar but even a big solar system could have trouble with hungry items,like stoves.
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Old 02-19-2019, 04:41 PM   #4
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What killed the 5kW? Very fixable machine in most cases.
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Old 02-19-2019, 05:29 PM   #5
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You are looking at around $12K +/- to replace if it is relatively easy access. I would fix if possible. What happened?
Sure you can go battery/inverter but what are you going to charge the bank with? On my boat with a 8 cu ft refrigerator, one overnight at anchor sucks out about 120 Ah from the bank. Cruising at 1700 rpm will top up the bank in a few hours the next day. Now if you stay put a second night, you need something engine powered or solar to recharge the bank. Running the main in neutral for hours is a bad choice.
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Old 02-19-2019, 05:30 PM   #6
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Don't know what kind of boat you have, but if most like it typically have gensets, I would discount yours about $10,000 in comparing it with other similar boats with gensets.


Listen to Ski's advice. Unless it was trashed by a salt water dunking or threw a rod or similar catastrophe, the NL's can often be rebuilt much cheaper than replacement and a whole lot less than $10,000.



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Old 02-19-2019, 05:41 PM   #7
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As others have noted... unless you can reach out and shake hands with a connecting rod from the engine room, a rebuild would be the best course of action, IMHO.
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Old 02-19-2019, 05:49 PM   #8
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Without more information on the failure, engine or generator end. Major failure such as engine block / crankshaft destroyed vs wonít start using excessive oil, itís hard to give decent advice.
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Old 02-19-2019, 08:08 PM   #9
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Quote:
Originally Posted by captDJ View Post
My northern lights 5kw has died, I like to hear thoughts on replacement vs using the space for battery bank and sizable inverter? If I go the battery option where can I find information on what to buy and install?
I have thought about what I would do if my NL5kw died, and it does look the solution includes bigger batteries and solar. But it also includes changing the heating system to hydronic so as to make hot water. Total = $not cheap.

So when my gen hydrolocked last summer (don't ask), the result was one of the valves becoming stuck open, and after 30 years, it was time to do a top-end overhaul. Head removed, machined, new valves, springs, seats, injectors, head bolts, glow plugs, gaskets/seals, injectors ++.

Total $1500, all labor mine except head work.


Ready for another 30 years
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Old 02-19-2019, 09:07 PM   #10
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Thanks to all, seems to have had a stuck valve which the piston hit and broke the valve rail? Plus soot in the cooling system which could point to a cracked block, estimate was 3-5k to fix.
I was thinking about replacing my a/c with one that requires less amps that the inverter could power and replace the fridge with an ac/dc unit.
Another option would be to remove/install myself and have a shop rebuild.
Oh and itís tucked in tight between the mains with a 16Ē square to access.
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Old 02-19-2019, 11:33 PM   #11
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"Back of an envelop" estimate for running an AC unit or heat pump off an inverter. /Really/ rough numbers.

Really roughly, I approximate an AC unit or heat pump as having a wattage power requirement of a little more than 10% of its BTU rating. So, for example, I'd ballpark a 16,0000btu unit at 1600W + "a bit", so maybe 1700W.

1700W is doable by many common inverters. It doesn't leave much headroom, but it is clearly doable.

But, how much battery is required? 1700W @ 12V is about 140A. That's about as much energy as one can draw from a pair of 6V golf cart batteries (parallel for 12V) in an hour at about 75% discharge. Again, really rough.

So, again really roughly, one would need 2 golf cart batteries for each hour one wants to operate a 16000btu AC unit or heat pump for heating. Want to run it for 4 hours per day? You'll need about 8 batteries. 6 hours per day? 12 golf cart batteries.

Golf cart batteries cost $150/each. A box for each pair of batteries, probably costs $60, or $30/battery. Maybe another $20/battery in wire. $200/battery in all. $2,400 for the battery bank. Maybe another $500 for the inverter. With taxes, etc, probably right around $3,000 for the set up.

If you want half as much AC capacity, you can cut that in half, 50% more, multiply by 1.5. Run it for half as long per day, cut it in half. Twice as long per day, double it. You get the idea.

But...don't forget that you need to recharge those batteries. 12 batteries might need 1200 amp-hours @ 12V. If one could dump the whole of 2x60A alternators into them, that would be 10 hours to fully charge. But, the charging efficiency might be, in really rough numbers, 50%. That would be 20 hours to charge. Not at all reasonable.

What if we just charge them to 70%. Well, then we are discharging from 70% to 30%, using 40% of the battery capacity. Before we were using 70% of the battery capacity (100% - 30%). So, we need 70/40= 1.75x as many batteries -- 22 batteries and boxes. Wildly guessing as above, $5,250 in cost.

What about the charge time? Since batteries charge ore efficiently earlier on, charging to 70% probably only takes really roughly 15hrs. Upgrade from 60A alternators to 150+A alternators, and that is down to 6 hours.

Lets say we want to charge the batteries in just 4 hours. Anything more than that would be hard on the batteries. That would be 1200 amp-hours / 4 hours = 300 amps/hour. That probably means north of 2x 175A alternators -- basically the equivalent of a 4.2kw generator! Those might be $750/alternator. Maybe $1000/alternator after making other needed adjustments. We're up to $7,750 to do this without a generator -- and the need for batteries every few years. I'd think for $7,750 one can get a rebuilt generator installed.

Even if I introduce one friendly piece of reality -- the HVAC might only have a 60% duty cycle (compressor on 60% of the time, wildly guessing), this $7,750 is still just a little shy of $5,000.

These numbers are obviously very, very, very approximate and rough and compound a bunch of error. But, my point is this. It is easy to get enough inverter to run an AC unit, even a large one. But, it takes a huge amount of battery to run one for any length of time. And, that is a much bigger expense that needs to be repeated every few years as the batteries need replaced.

But, even with that, there is just no fast way to charge that much battery from that depleted a state to a near charged state on a daily basis underway. It just takes time.

It is very reasonable to operate without a generator. But, this does involve limiting long-running major loads like HVAC. Even short bursts of loads, like a few minutes of microwave can be fine. But tings like AC? Would need to be really limited.
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Old 02-20-2019, 04:05 AM   #12
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You are not going to be able to supply an air conditioner compressor, fan and water pump with a battery/inverter setup for any useable length of time even with the main engine running. So your air would become a shore power only benefit. If you want air away from the dock, you will need a genny.
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Old 02-20-2019, 06:12 AM   #13
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"On my boat with a 8 cu ft refrigerator, one overnight at anchor sucks out about 120 Ah from the bank."


Unless you only do it once in a year , or travel every day, surely a new efficient reefer might save currency?
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Old 02-20-2019, 07:50 AM   #14
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Quote:
Originally Posted by captDJ View Post
Thanks to all, seems to have had a stuck valve which the piston hit and broke the valve rail? Plus soot in the cooling system which could point to a cracked block, estimate was 3-5k to fix.
I was thinking about replacing my a/c with one that requires less amps that the inverter could power and replace the fridge with an ac/dc unit.
Another option would be to remove/install myself and have a shop rebuild.
Oh and itís tucked in tight between the mains with a 16Ē square to access.

If you do rebuild, make sure you figure out what caused the valve to fail. Salt water back up through a poorly designed exhaust system is probably the biggest cause.


And there is no way you can run a normal 16,000 btu A/C from batteries and an inverter for very long.


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Old 02-20-2019, 08:09 AM   #15
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Thanks to all, seems to have had a stuck valve which the piston hit and broke the valve rail? Plus soot in the cooling system which could point to a cracked block, estimate was 3-5k to fix.
I was thinking about replacing my a/c with one that requires less amps that the inverter could power and replace the fridge with an ac/dc unit.
Another option would be to remove/install myself and have a shop rebuild.
Oh and itís tucked in tight between the mains with a 16Ē square to access.
With a quote of $3 to 5 to fix, plus surprises, I could argue strong for a new one. There's new ones in the 5K range for way less than $10k. Then you have a new one.
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Old 02-20-2019, 09:19 AM   #16
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You no longer need a genny for marine air conditioning. I brought this up to the northern lights dealer last week at the boat show. There are currently three major boat manufactures selling boats with dc systems that run solely off the battery bank. Average energy consumption is between 250 and 400 watts an hour for 16k btu. Depending what you use the genny for though its probably worth fixing. That unit weighs less than a set of 8ds and gives you the most options. Inverters, chargers, solar and lithium batteries combined with the new dc systems look to be the future solution but the price is still pretty high for consideration in a retrofit.
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Old 02-20-2019, 09:23 AM   #17
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Wow, you are all awesome! After your kind advice I realize I need a generator to be happy away from shore power.
First Iíll remove and then assess new unit or rebuild? Good news is I just found the shop manual online so the process begins, thanks again for the great input.
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Old 02-20-2019, 11:48 AM   #18
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If money is no object, lithium batteries totally change and arguably tip the equation. But $$$$$.
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Old 02-20-2019, 12:20 PM   #19
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I believe it was water in fuel that took out the one cylinder, original generator died because of salt water through the coffee can exhaust (PO). I installed this one w/o a raycor (my fault) and I wonít let that be the case again, which ever goes back I will put a water filter on first, costly education.
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Old 02-20-2019, 12:25 PM   #20
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You no longer need a genny for marine air conditioning. I brought this up to the northern lights dealer last week at the boat show. There are currently three major boat manufactures selling boats with dc systems that run solely off the battery bank. Average energy consumption is between 250 and 400 watts an hour for 16k btu. Depending what you use the genny for though its probably worth fixing. That unit weighs less than a set of 8ds and gives you the most options. Inverters, chargers, solar and lithium batteries combined with the new dc systems look to be the future solution but the price is still pretty high for consideration in a retrofit.

No. A 16,000 btu marine A/C system draws about 14 amps, raw water pump included. That is 1,700 watts. At a typical duty cycle of 33% which will be more like 100% on a hot sunny day, that is about 560 watts or 13,000 watt hours in 24 hours. It will take about 3,000 watts of solar to replace that on a sunny day and about 1,000 AHs of Li battery capacity or double that for AGM or FLAs to cover you at night, early morning and late afternoon when solar doesn't do much.


Like I said over on the electric boat thread: you need lots of batteries and more efficient (about 30-40% rather than the current 18%) solar panels to run A/C from batteries and solar power.


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